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/* Global common subexpression elimination/Partial redundancy elimination and global constant/copy propagation for GNU compiler. Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see <http://www.gnu.org/licenses/>. */ /* TODO - reordering of memory allocation and freeing to be more space efficient - do rough calc of how many regs are needed in each block, and a rough calc of how many regs are available in each class and use that to throttle back the code in cases where RTX_COST is minimal. - a store to the same address as a load does not kill the load if the source of the store is also the destination of the load. Handling this allows more load motion, particularly out of loops. */ /* References searched while implementing this. Compilers Principles, Techniques and Tools Aho, Sethi, Ullman Addison-Wesley, 1988 Global Optimization by Suppression of Partial Redundancies E. Morel, C. Renvoise communications of the acm, Vol. 22, Num. 2, Feb. 1979 A Portable Machine-Independent Global Optimizer - Design and Measurements Frederick Chow Stanford Ph.D. thesis, Dec. 1983 A Fast Algorithm for Code Movement Optimization D.M. Dhamdhere SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988 A Solution to a Problem with Morel and Renvoise's Global Optimization by Suppression of Partial Redundancies K-H Drechsler, M.P. Stadel ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988 Practical Adaptation of the Global Optimization Algorithm of Morel and Renvoise D.M. Dhamdhere ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991 Efficiently Computing Static Single Assignment Form and the Control Dependence Graph R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991 Lazy Code Motion J. Knoop, O. Ruthing, B. Steffen ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI What's In a Region? Or Computing Control Dependence Regions in Near-Linear Time for Reducible Flow Control Thomas Ball ACM Letters on Programming Languages and Systems, Vol. 2, Num. 1-4, Mar-Dec 1993 An Efficient Representation for Sparse Sets Preston Briggs, Linda Torczon ACM Letters on Programming Languages and Systems, Vol. 2, Num. 1-4, Mar-Dec 1993 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion K-H Drechsler, M.P. Stadel ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993 Partial Dead Code Elimination J. Knoop, O. Ruthing, B. Steffen ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994 Effective Partial Redundancy Elimination P. Briggs, K.D. Cooper ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994 The Program Structure Tree: Computing Control Regions in Linear Time R. Johnson, D. Pearson, K. Pingali ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994 Optimal Code Motion: Theory and Practice J. Knoop, O. Ruthing, B. Steffen ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994 The power of assignment motion J. Knoop, O. Ruthing, B. Steffen ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI Global code motion / global value numbering C. Click ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI Value Driven Redundancy Elimination L.T. Simpson Rice University Ph.D. thesis, Apr. 1996 Value Numbering L.T. Simpson Massively Scalar Compiler Project, Rice University, Sep. 1996 High Performance Compilers for Parallel Computing Michael Wolfe Addison-Wesley, 1996 Advanced Compiler Design and Implementation Steven Muchnick Morgan Kaufmann, 1997 Building an Optimizing Compiler Robert Morgan Digital Press, 1998 People wishing to speed up the code here should read: Elimination Algorithms for Data Flow Analysis B.G. Ryder, M.C. Paull ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986 How to Analyze Large Programs Efficiently and Informatively D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI People wishing to do something different can find various possibilities in the above papers and elsewhere. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "toplev.h" #include "rtl.h" #include "tree.h" #include "tm_p.h" #include "regs.h" #include "hard-reg-set.h" #include "flags.h" #include "real.h" #include "insn-config.h" #include "recog.h" #include "basic-block.h" #include "output.h" #include "function.h" #include "expr.h" #include "except.h" #include "ggc.h" #include "params.h" #include "cselib.h" #include "intl.h" #include "obstack.h" #include "timevar.h" #include "tree-pass.h" #include "hashtab.h" #include "df.h" #include "dbgcnt.h" #include "target.h" /* We support GCSE via Partial Redundancy Elimination. PRE optimizations are a superset of those done by classic GCSE. We perform the following steps: 1) Compute table of places where registers are set. 2) Perform copy/constant propagation. 3) Perform global cse using lazy code motion if not optimizing for size, or code hoisting if we are. 4) Perform another pass of copy/constant propagation. Try to bypass conditional jumps if the condition can be computed from a value of an incoming edge. Two passes of copy/constant propagation are done because the first one enables more GCSE and the second one helps to clean up the copies that GCSE creates. This is needed more for PRE than for Classic because Classic GCSE will try to use an existing register containing the common subexpression rather than create a new one. This is harder to do for PRE because of the code motion (which Classic GCSE doesn't do). Expressions we are interested in GCSE-ing are of the form (set (pseudo-reg) (expression)). Function want_to_gcse_p says what these are. In addition, expressions in REG_EQUAL notes are candidates for GCSE-ing. This allows PRE to hoist expressions that are expressed in multiple insns, such as complex address calculations (e.g. for PIC code, or loads with a high part and a low part). PRE handles moving invariant expressions out of loops (by treating them as partially redundant). ********************** We used to support multiple passes but there are diminishing returns in doing so. The first pass usually makes 90% of the changes that are doable. A second pass can make a few more changes made possible by the first pass. Experiments show any further passes don't make enough changes to justify the expense. A study of spec92 using an unlimited number of passes: [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83, [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2, [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1 It was found doing copy propagation between each pass enables further substitutions. This study was done before expressions in REG_EQUAL notes were added as candidate expressions for optimization, and before the GIMPLE optimizers were added. Probably, multiple passes is even less efficient now than at the time when the study was conducted. PRE is quite expensive in complicated functions because the DFA can take a while to converge. Hence we only perform one pass. ********************** The steps for PRE are: 1) Build the hash table of expressions we wish to GCSE (expr_hash_table). 2) Perform the data flow analysis for PRE. 3) Delete the redundant instructions 4) Insert the required copies [if any] that make the partially redundant instructions fully redundant. 5) For other reaching expressions, insert an instruction to copy the value to a newly created pseudo that will reach the redundant instruction. The deletion is done first so that when we do insertions we know which pseudo reg to use. Various papers have argued that PRE DFA is expensive (O(n^2)) and others argue it is not. The number of iterations for the algorithm to converge is typically 2-4 so I don't view it as that expensive (relatively speaking). PRE GCSE depends heavily on the second CPROP pass to clean up the copies we create. To make an expression reach the place where it's redundant, the result of the expression is copied to a new register, and the redundant expression is deleted by replacing it with this new register. Classic GCSE doesn't have this problem as much as it computes the reaching defs of each register in each block and thus can try to use an existing register. */ /* GCSE global vars. */ /* Set to non-zero if CSE should run after all GCSE optimizations are done. */ int flag_rerun_cse_after_global_opts; /* An obstack for our working variables. */ static struct obstack gcse_obstack; struct reg_use {rtx reg_rtx; }; /* Hash table of expressions. */ struct expr { /* The expression (SET_SRC for expressions, PATTERN for assignments). */ rtx expr; /* Index in the available expression bitmaps. */ int bitmap_index; /* Next entry with the same hash. */ struct expr *next_same_hash; /* List of anticipatable occurrences in basic blocks in the function. An "anticipatable occurrence" is one that is the first occurrence in the basic block, the operands are not modified in the basic block prior to the occurrence and the output is not used between the start of the block and the occurrence. */ struct occr *antic_occr; /* List of available occurrence in basic blocks in the function. An "available occurrence" is one that is the last occurrence in the basic block and the operands are not modified by following statements in the basic block [including this insn]. */ struct occr *avail_occr; /* Non-null if the computation is PRE redundant. The value is the newly created pseudo-reg to record a copy of the expression in all the places that reach the redundant copy. */ rtx reaching_reg; }; /* Occurrence of an expression. There is one per basic block. If a pattern appears more than once the last appearance is used [or first for anticipatable expressions]. */ struct occr { /* Next occurrence of this expression. */ struct occr *next; /* The insn that computes the expression. */ rtx insn; /* Nonzero if this [anticipatable] occurrence has been deleted. */ char deleted_p; /* Nonzero if this [available] occurrence has been copied to reaching_reg. */ /* ??? This is mutually exclusive with deleted_p, so they could share the same byte. */ char copied_p; }; /* Expression and copy propagation hash tables. Each hash table is an array of buckets. ??? It is known that if it were an array of entries, structure elements `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is not clear whether in the final analysis a sufficient amount of memory would be saved as the size of the available expression bitmaps would be larger [one could build a mapping table without holes afterwards though]. Someday I'll perform the computation and figure it out. */ struct hash_table_d { /* The table itself. This is an array of `expr_hash_table_size' elements. */ struct expr **table; /* Size of the hash table, in elements. */ unsigned int size; /* Number of hash table elements. */ unsigned int n_elems; /* Whether the table is expression of copy propagation one. */ int set_p; }; /* Expression hash table. */ static struct hash_table_d expr_hash_table; /* Copy propagation hash table. */ static struct hash_table_d set_hash_table; /* This is a list of expressions which are MEMs and will be used by load or store motion. Load motion tracks MEMs which aren't killed by anything except itself. (i.e., loads and stores to a single location). We can then allow movement of these MEM refs with a little special allowance. (all stores copy the same value to the reaching reg used for the loads). This means all values used to store into memory must have no side effects so we can re-issue the setter value. Store Motion uses this structure as an expression table to track stores which look interesting, and might be moveable towards the exit block. */ struct ls_expr { struct expr * expr; /* Gcse expression reference for LM. */ rtx pattern; /* Pattern of this mem. */ rtx pattern_regs; /* List of registers mentioned by the mem. */ rtx loads; /* INSN list of loads seen. */ rtx stores; /* INSN list of stores seen. */ struct ls_expr * next; /* Next in the list. */ int invalid; /* Invalid for some reason. */ int index; /* If it maps to a bitmap index. */ unsigned int hash_index; /* Index when in a hash table. */ rtx reaching_reg; /* Register to use when re-writing. */ }; /* Array of implicit set patterns indexed by basic block index. */ static rtx *implicit_sets; /* Head of the list of load/store memory refs. */ static struct ls_expr * pre_ldst_mems = NULL; /* Hashtable for the load/store memory refs. */ static htab_t pre_ldst_table = NULL; /* Bitmap containing one bit for each register in the program. Used when performing GCSE to track which registers have been set since the start of the basic block. */ static regset reg_set_bitmap; /* Array, indexed by basic block number for a list of insns which modify memory within that block. */ static rtx * modify_mem_list; static bitmap modify_mem_list_set; /* This array parallels modify_mem_list, but is kept canonicalized. */ static rtx * canon_modify_mem_list; /* Bitmap indexed by block numbers to record which blocks contain function calls. */ static bitmap blocks_with_calls; /* Various variables for statistics gathering. */ /* Memory used in a pass. This isn't intended to be absolutely precise. Its intent is only to keep an eye on memory usage. */ static int bytes_used; /* GCSE substitutions made. */ static int gcse_subst_count; /* Number of copy instructions created. */ static int gcse_create_count; /* Number of local constants propagated. */ static int local_const_prop_count; /* Number of local copies propagated. */ static int local_copy_prop_count; /* Number of global constants propagated. */ static int global_const_prop_count; /* Number of global copies propagated. */ static int global_copy_prop_count; /* For available exprs */ static sbitmap *ae_kill; static void compute_can_copy (void); static void *gmalloc (size_t) ATTRIBUTE_MALLOC; static void *gcalloc (size_t, size_t) ATTRIBUTE_MALLOC; static void *gcse_alloc (unsigned long); static void alloc_gcse_mem (void); static void free_gcse_mem (void); static void hash_scan_insn (rtx, struct hash_table_d *); static void hash_scan_set (rtx, rtx, struct hash_table_d *); static void hash_scan_clobber (rtx, rtx, struct hash_table_d *); static void hash_scan_call (rtx, rtx, struct hash_table_d *); static int want_to_gcse_p (rtx); static bool gcse_constant_p (const_rtx); static int oprs_unchanged_p (const_rtx, const_rtx, int); static int oprs_anticipatable_p (const_rtx, const_rtx); static int oprs_available_p (const_rtx, const_rtx); static void insert_expr_in_table (rtx, enum machine_mode, rtx, int, int, struct hash_table_d *); static void insert_set_in_table (rtx, rtx, struct hash_table_d *); static unsigned int hash_expr (const_rtx, enum machine_mode, int *, int); static unsigned int hash_set (int, int); static int expr_equiv_p (const_rtx, const_rtx); static void record_last_reg_set_info (rtx, int); static void record_last_mem_set_info (rtx); static void record_last_set_info (rtx, const_rtx, void *); static void compute_hash_table (struct hash_table_d *); static void alloc_hash_table (struct hash_table_d *, int); static void free_hash_table (struct hash_table_d *); static void compute_hash_table_work (struct hash_table_d *); static void dump_hash_table (FILE *, const char *, struct hash_table_d *); static struct expr *lookup_set (unsigned int, struct hash_table_d *); static struct expr *next_set (unsigned int, struct expr *); static void reset_opr_set_tables (void); static int oprs_not_set_p (const_rtx, const_rtx); static void mark_call (rtx); static void mark_set (rtx, rtx); static void mark_clobber (rtx, rtx); static void mark_oprs_set (rtx); static void alloc_cprop_mem (int, int); static void free_cprop_mem (void); static void compute_transp (const_rtx, int, sbitmap *, int); static void compute_transpout (void); static void compute_local_properties (sbitmap *, sbitmap *, sbitmap *, struct hash_table_d *); static void compute_cprop_data (void); static void find_used_regs (rtx *, void *); static int try_replace_reg (rtx, rtx, rtx); static struct expr *find_avail_set (int, rtx); static int cprop_jump (basic_block, rtx, rtx, rtx, rtx); static void mems_conflict_for_gcse_p (rtx, const_rtx, void *); static int load_killed_in_block_p (const_basic_block, int, const_rtx, int); static void canon_list_insert (rtx, const_rtx, void *); static int cprop_insn (rtx); static void find_implicit_sets (void); static int one_cprop_pass (void); static bool constprop_register (rtx, rtx, rtx); static struct expr *find_bypass_set (int, int); static bool reg_killed_on_edge (const_rtx, const_edge); static int bypass_block (basic_block, rtx, rtx); static int bypass_conditional_jumps (void); static void alloc_pre_mem (int, int); static void free_pre_mem (void); static void compute_pre_data (void); static int pre_expr_reaches_here_p (basic_block, struct expr *, basic_block); static void insert_insn_end_basic_block (struct expr *, basic_block, int); static void pre_insert_copy_insn (struct expr *, rtx); static void pre_insert_copies (void); static int pre_delete (void); static int pre_gcse (void); static int one_pre_gcse_pass (void); static void add_label_notes (rtx, rtx); static void alloc_code_hoist_mem (int, int); static void free_code_hoist_mem (void); static void compute_code_hoist_vbeinout (void); static void compute_code_hoist_data (void); static int hoist_expr_reaches_here_p (basic_block, int, basic_block, char *); static int hoist_code (void); static int one_code_hoisting_pass (void); static rtx process_insert_insn (struct expr *); static int pre_edge_insert (struct edge_list *, struct expr **); static int pre_expr_reaches_here_p_work (basic_block, struct expr *, basic_block, char *); static struct ls_expr * ldst_entry (rtx); static void free_ldst_entry (struct ls_expr *); static void free_ldst_mems (void); static void print_ldst_list (FILE *); static struct ls_expr * find_rtx_in_ldst (rtx); static inline struct ls_expr * first_ls_expr (void); static inline struct ls_expr * next_ls_expr (struct ls_expr *); static int simple_mem (const_rtx); static void invalidate_any_buried_refs (rtx); static void compute_ld_motion_mems (void); static void trim_ld_motion_mems (void); static void update_ld_motion_stores (struct expr *); static void free_insn_expr_list_list (rtx *); static void clear_modify_mem_tables (void); static void free_modify_mem_tables (void); static rtx gcse_emit_move_after (rtx, rtx, rtx); static void local_cprop_find_used_regs (rtx *, void *); static bool do_local_cprop (rtx, rtx); static int local_cprop_pass (void); static bool is_too_expensive (const char *); #define GNEW(T) ((T *) gmalloc (sizeof (T))) #define GCNEW(T) ((T *) gcalloc (1, sizeof (T))) #define GNEWVEC(T, N) ((T *) gmalloc (sizeof (T) * (N))) #define GCNEWVEC(T, N) ((T *) gcalloc ((N), sizeof (T))) #define GNEWVAR(T, S) ((T *) gmalloc ((S))) #define GCNEWVAR(T, S) ((T *) gcalloc (1, (S))) #define GOBNEW(T) ((T *) gcse_alloc (sizeof (T))) #define GOBNEWVAR(T, S) ((T *) gcse_alloc ((S))) /* Misc. utilities. */ /* Nonzero for each mode that supports (set (reg) (reg)). This is trivially true for integer and floating point values. It may or may not be true for condition codes. */ static char can_copy[(int) NUM_MACHINE_MODES]; /* Compute which modes support reg/reg copy operations. */ static void compute_can_copy (void) { int i; #ifndef AVOID_CCMODE_COPIES rtx reg, insn; #endif memset (can_copy, 0, NUM_MACHINE_MODES); start_sequence (); for (i = 0; i < NUM_MACHINE_MODES; i++) if (GET_MODE_CLASS (i) == MODE_CC) { #ifdef AVOID_CCMODE_COPIES can_copy[i] = 0; #else reg = gen_rtx_REG ((enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1); insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg)); if (recog (PATTERN (insn), insn, NULL) >= 0) can_copy[i] = 1; #endif } else can_copy[i] = 1; end_sequence (); } /* Returns whether the mode supports reg/reg copy operations. */ bool can_copy_p (enum machine_mode mode) { static bool can_copy_init_p = false; if (! can_copy_init_p) { compute_can_copy (); can_copy_init_p = true; } return can_copy[mode] != 0; } /* Cover function to xmalloc to record bytes allocated. */ static void * gmalloc (size_t size) { bytes_used += size; return xmalloc (size); } /* Cover function to xcalloc to record bytes allocated. */ static void * gcalloc (size_t nelem, size_t elsize) { bytes_used += nelem * elsize; return xcalloc (nelem, elsize); } /* Cover function to obstack_alloc. */ static void * gcse_alloc (unsigned long size) { bytes_used += size; return obstack_alloc (&gcse_obstack, size); } /* Allocate memory for the reg/memory set tracking tables. This is called at the start of each pass. */ static void alloc_gcse_mem (void) { /* Allocate vars to track sets of regs. */ reg_set_bitmap = BITMAP_ALLOC (NULL); /* Allocate array to keep a list of insns which modify memory in each basic block. */ modify_mem_list = GCNEWVEC (rtx, last_basic_block); canon_modify_mem_list = GCNEWVEC (rtx, last_basic_block); modify_mem_list_set = BITMAP_ALLOC (NULL); blocks_with_calls = BITMAP_ALLOC (NULL); } /* Free memory allocated by alloc_gcse_mem. */ static void free_gcse_mem (void) { free_modify_mem_tables (); BITMAP_FREE (modify_mem_list_set); BITMAP_FREE (blocks_with_calls); } /* Compute the local properties of each recorded expression. Local properties are those that are defined by the block, irrespective of other blocks. An expression is transparent in a block if its operands are not modified in the block. An expression is computed (locally available) in a block if it is computed at least once and expression would contain the same value if the computation was moved to the end of the block. An expression is locally anticipatable in a block if it is computed at least once and expression would contain the same value if the computation was moved to the beginning of the block. We call this routine for cprop, pre and code hoisting. They all compute basically the same information and thus can easily share this code. TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local properties. If NULL, then it is not necessary to compute or record that particular property. TABLE controls which hash table to look at. If it is set hash table, additionally, TRANSP is computed as ~TRANSP, since this is really cprop's ABSALTERED. */ static void compute_local_properties (sbitmap *transp, sbitmap *comp, sbitmap *antloc, struct hash_table_d *table) { unsigned int i; /* Initialize any bitmaps that were passed in. */ if (transp) { if (table->set_p) sbitmap_vector_zero (transp, last_basic_block); else sbitmap_vector_ones (transp, last_basic_block); } if (comp) sbitmap_vector_zero (comp, last_basic_block); if (antloc) sbitmap_vector_zero (antloc, last_basic_block); for (i = 0; i < table->size; i++) { struct expr *expr; for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash) { int indx = expr->bitmap_index; struct occr *occr; /* The expression is transparent in this block if it is not killed. We start by assuming all are transparent [none are killed], and then reset the bits for those that are. */ if (transp) compute_transp (expr->expr, indx, transp, table->set_p); /* The occurrences recorded in antic_occr are exactly those that we want to set to nonzero in ANTLOC. */ if (antloc) for (occr = expr->antic_occr; occr != NULL; occr = occr->next) { SET_BIT (antloc[BLOCK_FOR_INSN (occr->insn)->index], indx); /* While we're scanning the table, this is a good place to initialize this. */ occr->deleted_p = 0; } /* The occurrences recorded in avail_occr are exactly those that we want to set to nonzero in COMP. */ if (comp) for (occr = expr->avail_occr; occr != NULL; occr = occr->next) { SET_BIT (comp[BLOCK_FOR_INSN (occr->insn)->index], indx); /* While we're scanning the table, this is a good place to initialize this. */ occr->copied_p = 0; } /* While we're scanning the table, this is a good place to initialize this. */ expr->reaching_reg = 0; } } } /* Hash table support. */ struct reg_avail_info { basic_block last_bb; int first_set; int last_set; }; static struct reg_avail_info *reg_avail_info; static basic_block current_bb; /* See whether X, the source of a set, is something we want to consider for GCSE. */ static int want_to_gcse_p (rtx x) { #ifdef STACK_REGS /* On register stack architectures, don't GCSE constants from the constant pool, as the benefits are often swamped by the overhead of shuffling the register stack between basic blocks. */ if (IS_STACK_MODE (GET_MODE (x))) x = avoid_constant_pool_reference (x); #endif switch (GET_CODE (x)) { case REG: case SUBREG: case CONST_INT: case CONST_DOUBLE: case CONST_FIXED: case CONST_VECTOR: case CALL: return 0; default: return can_assign_to_reg_without_clobbers_p (x); } } /* Used internally by can_assign_to_reg_without_clobbers_p. */ static GTY(()) rtx test_insn; /* Return true if we can assign X to a pseudo register such that the resulting insn does not result in clobbering a hard register as a side-effect. Additionally, if the target requires it, check that the resulting insn can be copied. If it cannot, this means that X is special and probably has hidden side-effects we don't want to mess with. This function is typically used by code motion passes, to verify that it is safe to insert an insn without worrying about clobbering maybe live hard regs. */ bool can_assign_to_reg_without_clobbers_p (rtx x) { int num_clobbers = 0; int icode; /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */ if (general_operand (x, GET_MODE (x))) return 1; else if (GET_MODE (x) == VOIDmode) return 0; /* Otherwise, check if we can make a valid insn from it. First initialize our test insn if we haven't already. */ if (test_insn == 0) { test_insn = make_insn_raw (gen_rtx_SET (VOIDmode, gen_rtx_REG (word_mode, FIRST_PSEUDO_REGISTER * 2), const0_rtx)); NEXT_INSN (test_insn) = PREV_INSN (test_insn) = 0; } /* Now make an insn like the one we would make when GCSE'ing and see if valid. */ PUT_MODE (SET_DEST (PATTERN (test_insn)), GET_MODE (x)); SET_SRC (PATTERN (test_insn)) = x; icode = recog (PATTERN (test_insn), test_insn, &num_clobbers); if (icode < 0) return false; if (num_clobbers > 0 && added_clobbers_hard_reg_p (icode)) return false; if (targetm.cannot_copy_insn_p && targetm.cannot_copy_insn_p (test_insn)) return false; return true; } /* Return nonzero if the operands of expression X are unchanged from the start of INSN's basic block up to but not including INSN (if AVAIL_P == 0), or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */ static int oprs_unchanged_p (const_rtx x, const_rtx insn, int avail_p) { int i, j; enum rtx_code code; const char *fmt; if (x == 0) return 1; code = GET_CODE (x); switch (code) { case REG: { struct reg_avail_info *info = ®_avail_info[REGNO (x)]; if (info->last_bb != current_bb) return 1; if (avail_p) return info->last_set < DF_INSN_LUID (insn); else return info->first_set >= DF_INSN_LUID (insn); } case MEM: if (load_killed_in_block_p (current_bb, DF_INSN_LUID (insn), x, avail_p)) return 0; else return oprs_unchanged_p (XEXP (x, 0), insn, avail_p); case PRE_DEC: case PRE_INC: case POST_DEC: case POST_INC: case PRE_MODIFY: case POST_MODIFY: return 0; case PC: case CC0: /*FIXME*/ case CONST: case CONST_INT: case CONST_DOUBLE: case CONST_FIXED: case CONST_VECTOR: case SYMBOL_REF: case LABEL_REF: case ADDR_VEC: case ADDR_DIFF_VEC: return 1; default: break; } for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--) { if (fmt[i] == 'e') { /* If we are about to do the last recursive call needed at this level, change it into iteration. This function is called enough to be worth it. */ if (i == 0) return oprs_unchanged_p (XEXP (x, i), insn, avail_p); else if (! oprs_unchanged_p (XEXP (x, i), insn, avail_p)) return 0; } else if (fmt[i] == 'E') for (j = 0; j < XVECLEN (x, i); j++) if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p)) return 0; } return 1; } /* Used for communication between mems_conflict_for_gcse_p and load_killed_in_block_p. Nonzero if mems_conflict_for_gcse_p finds a conflict between two memory references. */ static int gcse_mems_conflict_p; /* Used for communication between mems_conflict_for_gcse_p and load_killed_in_block_p. A memory reference for a load instruction, mems_conflict_for_gcse_p will see if a memory store conflicts with this memory load. */ static const_rtx gcse_mem_operand; /* DEST is the output of an instruction. If it is a memory reference, and possibly conflicts with the load found in gcse_mem_operand, then set gcse_mems_conflict_p to a nonzero value. */ static void mems_conflict_for_gcse_p (rtx dest, const_rtx setter ATTRIBUTE_UNUSED, void *data ATTRIBUTE_UNUSED) { while (GET_CODE (dest) == SUBREG || GET_CODE (dest) == ZERO_EXTRACT || GET_CODE (dest) == STRICT_LOW_PART) dest = XEXP (dest, 0); /* If DEST is not a MEM, then it will not conflict with the load. Note that function calls are assumed to clobber memory, but are handled elsewhere. */ if (! MEM_P (dest)) return; /* If we are setting a MEM in our list of specially recognized MEMs, don't mark as killed this time. */ if (expr_equiv_p (dest, gcse_mem_operand) && pre_ldst_mems != NULL) { if (!find_rtx_in_ldst (dest)) gcse_mems_conflict_p = 1; return; } if (true_dependence (dest, GET_MODE (dest), gcse_mem_operand, rtx_addr_varies_p)) gcse_mems_conflict_p = 1; } /* Return nonzero if the expression in X (a memory reference) is killed in block BB before or after the insn with the LUID in UID_LIMIT. AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills before UID_LIMIT. To check the entire block, set UID_LIMIT to max_uid + 1 and AVAIL_P to 0. */ static int load_killed_in_block_p (const_basic_block bb, int uid_limit, const_rtx x, int avail_p) { rtx list_entry = modify_mem_list[bb->index]; /* If this is a readonly then we aren't going to be changing it. */ if (MEM_READONLY_P (x)) return 0; while (list_entry) { rtx setter; /* Ignore entries in the list that do not apply. */ if ((avail_p && DF_INSN_LUID (XEXP (list_entry, 0)) < uid_limit) || (! avail_p && DF_INSN_LUID (XEXP (list_entry, 0)) > uid_limit)) { list_entry = XEXP (list_entry, 1); continue; } setter = XEXP (list_entry, 0); /* If SETTER is a call everything is clobbered. Note that calls to pure functions are never put on the list, so we need not worry about them. */ if (CALL_P (setter)) return 1; /* SETTER must be an INSN of some kind that sets memory. Call note_stores to examine each hunk of memory that is modified. The note_stores interface is pretty limited, so we have to communicate via global variables. Yuk. */ gcse_mem_operand = x; gcse_mems_conflict_p = 0; note_stores (PATTERN (setter), mems_conflict_for_gcse_p, NULL); if (gcse_mems_conflict_p) return 1; list_entry = XEXP (list_entry, 1); } return 0; } /* Return nonzero if the operands of expression X are unchanged from the start of INSN's basic block up to but not including INSN. */ static int oprs_anticipatable_p (const_rtx x, const_rtx insn) { return oprs_unchanged_p (x, insn, 0); } /* Return nonzero if the operands of expression X are unchanged from INSN to the end of INSN's basic block. */ static int oprs_available_p (const_rtx x, const_rtx insn) { return oprs_unchanged_p (x, insn, 1); } /* Hash expression X. MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean indicating if a volatile operand is found or if the expression contains something we don't want to insert in the table. HASH_TABLE_SIZE is the current size of the hash table to be probed. */ static unsigned int hash_expr (const_rtx x, enum machine_mode mode, int *do_not_record_p, int hash_table_size) { unsigned int hash; *do_not_record_p = 0; hash = hash_rtx (x, mode, do_not_record_p, NULL, /*have_reg_qty=*/false); return hash % hash_table_size; } /* Hash a set of register REGNO. Sets are hashed on the register that is set. This simplifies the PRE copy propagation code. ??? May need to make things more elaborate. Later, as necessary. */ static unsigned int hash_set (int regno, int hash_table_size) { unsigned int hash; hash = regno; return hash % hash_table_size; } /* Return nonzero if exp1 is equivalent to exp2. */ static int expr_equiv_p (const_rtx x, const_rtx y) { return exp_equiv_p (x, y, 0, true); } /* Insert expression X in INSN in the hash TABLE. If it is already present, record it as the last occurrence in INSN's basic block. MODE is the mode of the value X is being stored into. It is only used if X is a CONST_INT. ANTIC_P is nonzero if X is an anticipatable expression. AVAIL_P is nonzero if X is an available expression. */ static void insert_expr_in_table (rtx x, enum machine_mode mode, rtx insn, int antic_p, int avail_p, struct hash_table_d *table) { int found, do_not_record_p; unsigned int hash; struct expr *cur_expr, *last_expr = NULL; struct occr *antic_occr, *avail_occr; hash = hash_expr (x, mode, &do_not_record_p, table->size); /* Do not insert expression in table if it contains volatile operands, or if hash_expr determines the expression is something we don't want to or can't handle. */ if (do_not_record_p) return; cur_expr = table->table[hash]; found = 0; while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x))) { /* If the expression isn't found, save a pointer to the end of the list. */ last_expr = cur_expr; cur_expr = cur_expr->next_same_hash; } if (! found) { cur_expr = GOBNEW (struct expr); bytes_used += sizeof (struct expr); if (table->table[hash] == NULL) /* This is the first pattern that hashed to this index. */ table->table[hash] = cur_expr; else /* Add EXPR to end of this hash chain. */ last_expr->next_same_hash = cur_expr; /* Set the fields of the expr element. */ cur_expr->expr = x; cur_expr->bitmap_index = table->n_elems++; cur_expr->next_same_hash = NULL; cur_expr->antic_occr = NULL; cur_expr->avail_occr = NULL; } /* Now record the occurrence(s). */ if (antic_p) { antic_occr = cur_expr->antic_occr; if (antic_occr && BLOCK_FOR_INSN (antic_occr->insn) != BLOCK_FOR_INSN (insn)) antic_occr = NULL; if (antic_occr) /* Found another instance of the expression in the same basic block. Prefer the currently recorded one. We want the first one in the block and the block is scanned from start to end. */ ; /* nothing to do */ else { /* First occurrence of this expression in this basic block. */ antic_occr = GOBNEW (struct occr); bytes_used += sizeof (struct occr); antic_occr->insn = insn; antic_occr->next = cur_expr->antic_occr; antic_occr->deleted_p = 0; cur_expr->antic_occr = antic_occr; } } if (avail_p) { avail_occr = cur_expr->avail_occr; if (avail_occr && BLOCK_FOR_INSN (avail_occr->insn) == BLOCK_FOR_INSN (insn)) { /* Found another instance of the expression in the same basic block. Prefer this occurrence to the currently recorded one. We want the last one in the block and the block is scanned from start to end. */ avail_occr->insn = insn; } else { /* First occurrence of this expression in this basic block. */ avail_occr = GOBNEW (struct occr); bytes_used += sizeof (struct occr); avail_occr->insn = insn; avail_occr->next = cur_expr->avail_occr; avail_occr->deleted_p = 0; cur_expr->avail_occr = avail_occr; } } } /* Insert pattern X in INSN in the hash table. X is a SET of a reg to either another reg or a constant. If it is already present, record it as the last occurrence in INSN's basic block. */ static void insert_set_in_table (rtx x, rtx insn, struct hash_table_d *table) { int found; unsigned int hash; struct expr *cur_expr, *last_expr = NULL; struct occr *cur_occr; gcc_assert (GET_CODE (x) == SET && REG_P (SET_DEST (x))); hash = hash_set (REGNO (SET_DEST (x)), table->size); cur_expr = table->table[hash]; found = 0; while (cur_expr && 0 == (found = expr_equiv_p (cur_expr->expr, x))) { /* If the expression isn't found, save a pointer to the end of the list. */ last_expr = cur_expr; cur_expr = cur_expr->next_same_hash; } if (! found) { cur_expr = GOBNEW (struct expr); bytes_used += sizeof (struct expr); if (table->table[hash] == NULL) /* This is the first pattern that hashed to this index. */ table->table[hash] = cur_expr; else /* Add EXPR to end of this hash chain. */ last_expr->next_same_hash = cur_expr; /* Set the fields of the expr element. We must copy X because it can be modified when copy propagation is performed on its operands. */ cur_expr->expr = copy_rtx (x); cur_expr->bitmap_index = table->n_elems++; cur_expr->next_same_hash = NULL; cur_expr->antic_occr = NULL; cur_expr->avail_occr = NULL; } /* Now record the occurrence. */ cur_occr = cur_expr->avail_occr; if (cur_occr && BLOCK_FOR_INSN (cur_occr->insn) == BLOCK_FOR_INSN (insn)) { /* Found another instance of the expression in the same basic block. Prefer this occurrence to the currently recorded one. We want the last one in the block and the block is scanned from start to end. */ cur_occr->insn = insn; } else { /* First occurrence of this expression in this basic block. */ cur_occr = GOBNEW (struct occr); bytes_used += sizeof (struct occr); cur_occr->insn = insn; cur_occr->next = cur_expr->avail_occr; cur_occr->deleted_p = 0; cur_expr->avail_occr = cur_occr; } } /* Determine whether the rtx X should be treated as a constant for the purposes of GCSE's constant propagation. */ static bool gcse_constant_p (const_rtx x) { /* Consider a COMPARE of two integers constant. */ if (GET_CODE (x) == COMPARE && CONST_INT_P (XEXP (x, 0)) && CONST_INT_P (XEXP (x, 1))) return true; /* Consider a COMPARE of the same registers is a constant if they are not floating point registers. */ if (GET_CODE(x) == COMPARE && REG_P (XEXP (x, 0)) && REG_P (XEXP (x, 1)) && REGNO (XEXP (x, 0)) == REGNO (XEXP (x, 1)) && ! FLOAT_MODE_P (GET_MODE (XEXP (x, 0))) && ! FLOAT_MODE_P (GET_MODE (XEXP (x, 1)))) return true; /* Since X might be inserted more than once we have to take care that it is sharable. */ return CONSTANT_P (x) && (GET_CODE (x) != CONST || shared_const_p (x)); } /* Scan pattern PAT of INSN and add an entry to the hash TABLE (set or expression one). */ static void hash_scan_set (rtx pat, rtx insn, struct hash_table_d *table) { rtx src = SET_SRC (pat); rtx dest = SET_DEST (pat); rtx note; if (GET_CODE (src) == CALL) hash_scan_call (src, insn, table); else if (REG_P (dest)) { unsigned int regno = REGNO (dest); rtx tmp; /* See if a REG_EQUAL note shows this equivalent to a simpler expression. This allows us to do a single GCSE pass and still eliminate redundant constants, addresses or other expressions that are constructed with multiple instructions. However, keep the original SRC if INSN is a simple reg-reg move. In In this case, there will almost always be a REG_EQUAL note on the insn that sets SRC. By recording the REG_EQUAL value here as SRC for INSN, we miss copy propagation opportunities and we perform the same PRE GCSE operation repeatedly on the same REG_EQUAL value if we do more than one PRE GCSE pass. Note that this does not impede profitable constant propagations. We "look through" reg-reg sets in lookup_avail_set. */ note = find_reg_equal_equiv_note (insn); if (note != 0 && REG_NOTE_KIND (note) == REG_EQUAL && !REG_P (src) && (table->set_p ? gcse_constant_p (XEXP (note, 0)) : want_to_gcse_p (XEXP (note, 0)))) src = XEXP (note, 0), pat = gen_rtx_SET (VOIDmode, dest, src); /* Only record sets of pseudo-regs in the hash table. */ if (! table->set_p && regno >= FIRST_PSEUDO_REGISTER /* Don't GCSE something if we can't do a reg/reg copy. */ && can_copy_p (GET_MODE (dest)) /* GCSE commonly inserts instruction after the insn. We can't do that easily for EH edges so disable GCSE on these for now. */ /* ??? We can now easily create new EH landing pads at the gimple level, for splitting edges; there's no reason we can't do the same thing at the rtl level. */ && !can_throw_internal (insn) /* Is SET_SRC something we want to gcse? */ && want_to_gcse_p (src) /* Don't CSE a nop. */ && ! set_noop_p (pat) /* Don't GCSE if it has attached REG_EQUIV note. At this point this only function parameters should have REG_EQUIV notes and if the argument slot is used somewhere explicitly, it means address of parameter has been taken, so we should not extend the lifetime of the pseudo. */ && (note == NULL_RTX || ! MEM_P (XEXP (note, 0)))) { /* An expression is not anticipatable if its operands are modified before this insn or if this is not the only SET in this insn. The latter condition does not have to mean that SRC itself is not anticipatable, but we just will not be able to handle code motion of insns with multiple sets. */ int antic_p = oprs_anticipatable_p (src, insn) && !multiple_sets (insn); /* An expression is not available if its operands are subsequently modified, including this insn. It's also not available if this is a branch, because we can't insert a set after the branch. */ int avail_p = (oprs_available_p (src, insn) && ! JUMP_P (insn)); insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p, table); } /* Record sets for constant/copy propagation. */ else if (table->set_p && regno >= FIRST_PSEUDO_REGISTER && ((REG_P (src) && REGNO (src) >= FIRST_PSEUDO_REGISTER && can_copy_p (GET_MODE (dest)) && REGNO (src) != regno) || gcse_constant_p (src)) /* A copy is not available if its src or dest is subsequently modified. Here we want to search from INSN+1 on, but oprs_available_p searches from INSN on. */ && (insn == BB_END (BLOCK_FOR_INSN (insn)) || (tmp = next_nonnote_insn (insn)) == NULL_RTX || BLOCK_FOR_INSN (tmp) != BLOCK_FOR_INSN (insn) || oprs_available_p (pat, tmp))) insert_set_in_table (pat, insn, table); } /* In case of store we want to consider the memory value as available in the REG stored in that memory. This makes it possible to remove redundant loads from due to stores to the same location. */ else if (flag_gcse_las && REG_P (src) && MEM_P (dest)) { unsigned int regno = REGNO (src); /* Do not do this for constant/copy propagation. */ if (! table->set_p /* Only record sets of pseudo-regs in the hash table. */ && regno >= FIRST_PSEUDO_REGISTER /* Don't GCSE something if we can't do a reg/reg copy. */ && can_copy_p (GET_MODE (src)) /* GCSE commonly inserts instruction after the insn. We can't do that easily for EH edges so disable GCSE on these for now. */ && !can_throw_internal (insn) /* Is SET_DEST something we want to gcse? */ && want_to_gcse_p (dest) /* Don't CSE a nop. */ && ! set_noop_p (pat) /* Don't GCSE if it has attached REG_EQUIV note. At this point this only function parameters should have REG_EQUIV notes and if the argument slot is used somewhere explicitly, it means address of parameter has been taken, so we should not extend the lifetime of the pseudo. */ && ((note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) == 0 || ! MEM_P (XEXP (note, 0)))) { /* Stores are never anticipatable. */ int antic_p = 0; /* An expression is not available if its operands are subsequently modified, including this insn. It's also not available if this is a branch, because we can't insert a set after the branch. */ int avail_p = oprs_available_p (dest, insn) && ! JUMP_P (insn); /* Record the memory expression (DEST) in the hash table. */ insert_expr_in_table (dest, GET_MODE (dest), insn, antic_p, avail_p, table); } } } static void hash_scan_clobber (rtx x ATTRIBUTE_UNUSED, rtx insn ATTRIBUTE_UNUSED, struct hash_table_d *table ATTRIBUTE_UNUSED) { /* Currently nothing to do. */ } static void hash_scan_call (rtx x ATTRIBUTE_UNUSED, rtx insn ATTRIBUTE_UNUSED, struct hash_table_d *table ATTRIBUTE_UNUSED) { /* Currently nothing to do. */ } /* Process INSN and add hash table entries as appropriate. Only available expressions that set a single pseudo-reg are recorded. Single sets in a PARALLEL could be handled, but it's an extra complication that isn't dealt with right now. The trick is handling the CLOBBERs that are also in the PARALLEL. Later. If SET_P is nonzero, this is for the assignment hash table, otherwise it is for the expression hash table. */ static void hash_scan_insn (rtx insn, struct hash_table_d *table) { rtx pat = PATTERN (insn); int i; /* Pick out the sets of INSN and for other forms of instructions record what's been modified. */ if (GET_CODE (pat) == SET) hash_scan_set (pat, insn, table); else if (GET_CODE (pat) == PARALLEL) for (i = 0; i < XVECLEN (pat, 0); i++) { rtx x = XVECEXP (pat, 0, i); if (GET_CODE (x) == SET) hash_scan_set (x, insn, table); else if (GET_CODE (x) == CLOBBER) hash_scan_clobber (x, insn, table); else if (GET_CODE (x) == CALL) hash_scan_call (x, insn, table); } else if (GET_CODE (pat) == CLOBBER) hash_scan_clobber (pat, insn, table); else if (GET_CODE (pat) == CALL) hash_scan_call (pat, insn, table); } static void dump_hash_table (FILE *file, const char *name, struct hash_table_d *table) { int i; /* Flattened out table, so it's printed in proper order. */ struct expr **flat_table; unsigned int *hash_val; struct expr *expr; flat_table = XCNEWVEC (struct expr *, table->n_elems); hash_val = XNEWVEC (unsigned int, table->n_elems); for (i = 0; i < (int) table->size; i++) for (expr = table->table[i]; expr != NULL; expr = expr->next_same_hash) { flat_table[expr->bitmap_index] = expr; hash_val[expr->bitmap_index] = i; } fprintf (file, "%s hash table (%d buckets, %d entries)\n", name, table->size, table->n_elems); for (i = 0; i < (int) table->n_elems; i++) if (flat_table[i] != 0) { expr = flat_table[i]; fprintf (file, "Index %d (hash value %d)\n ", expr->bitmap_index, hash_val[i]); print_rtl (file, expr->expr); fprintf (file, "\n"); } fprintf (file, "\n"); free (flat_table); free (hash_val); } /* Record register first/last/block set information for REGNO in INSN. first_set records the first place in the block where the register is set and is used to compute "anticipatability". last_set records the last place in the block where the register is set and is used to compute "availability". last_bb records the block for which first_set and last_set are valid, as a quick test to invalidate them. */ static void record_last_reg_set_info (rtx insn, int regno) { struct reg_avail_info *info = ®_avail_info[regno]; int luid = DF_INSN_LUID (insn); info->last_set = luid; if (info->last_bb != current_bb) { info->last_bb = current_bb; info->first_set = luid; } } /* Record all of the canonicalized MEMs of record_last_mem_set_info's insn. Note we store a pair of elements in the list, so they have to be taken off pairwise. */ static void canon_list_insert (rtx dest ATTRIBUTE_UNUSED, const_rtx unused1 ATTRIBUTE_UNUSED, void * v_insn) { rtx dest_addr, insn; int bb; while (GET_CODE (dest) == SUBREG || GET_CODE (dest) == ZERO_EXTRACT || GET_CODE (dest) == STRICT_LOW_PART) dest = XEXP (dest, 0); /* If DEST is not a MEM, then it will not conflict with a load. Note that function calls are assumed to clobber memory, but are handled elsewhere. */ if (! MEM_P (dest)) return; dest_addr = get_addr (XEXP (dest, 0)); dest_addr = canon_rtx (dest_addr); insn = (rtx) v_insn; bb = BLOCK_FOR_INSN (insn)->index; canon_modify_mem_list[bb] = alloc_EXPR_LIST (VOIDmode, dest_addr, canon_modify_mem_list[bb]); canon_modify_mem_list[bb] = alloc_EXPR_LIST (VOIDmode, dest, canon_modify_mem_list[bb]); } /* Record memory modification information for INSN. We do not actually care about the memory location(s) that are set, or even how they are set (consider a CALL_INSN). We merely need to record which insns modify memory. */ static void record_last_mem_set_info (rtx insn) { int bb = BLOCK_FOR_INSN (insn)->index; /* load_killed_in_block_p will handle the case of calls clobbering everything. */ modify_mem_list[bb] = alloc_INSN_LIST (insn, modify_mem_list[bb]); bitmap_set_bit (modify_mem_list_set, bb); if (CALL_P (insn)) { /* Note that traversals of this loop (other than for free-ing) will break after encountering a CALL_INSN. So, there's no need to insert a pair of items, as canon_list_insert does. */ canon_modify_mem_list[bb] = alloc_INSN_LIST (insn, canon_modify_mem_list[bb]); bitmap_set_bit (blocks_with_calls, bb); } else note_stores (PATTERN (insn), canon_list_insert, (void*) insn); } /* Called from compute_hash_table via note_stores to handle one SET or CLOBBER in an insn. DATA is really the instruction in which the SET is taking place. */ static void record_last_set_info (rtx dest, const_rtx setter ATTRIBUTE_UNUSED, void *data) { rtx last_set_insn = (rtx) data; if (GET_CODE (dest) == SUBREG) dest = SUBREG_REG (dest); if (REG_P (dest)) record_last_reg_set_info (last_set_insn, REGNO (dest)); else if (MEM_P (dest) /* Ignore pushes, they clobber nothing. */ && ! push_operand (dest, GET_MODE (dest))) record_last_mem_set_info (last_set_insn); } /* Top level function to create an expression or assignment hash table. Expression entries are placed in the hash table if - they are of the form (set (pseudo-reg) src), - src is something we want to perform GCSE on, - none of the operands are subsequently modified in the block Assignment entries are placed in the hash table if - they are of the form (set (pseudo-reg) src), - src is something we want to perform const/copy propagation on, - none of the operands or target are subsequently modified in the block Currently src must be a pseudo-reg or a const_int. TABLE is the table computed. */ static void compute_hash_table_work (struct hash_table_d *table) { int i; /* re-Cache any INSN_LIST nodes we have allocated. */ clear_modify_mem_tables (); /* Some working arrays used to track first and last set in each block. */ reg_avail_info = GNEWVEC (struct reg_avail_info, max_reg_num ()); for (i = 0; i < max_reg_num (); ++i) reg_avail_info[i].last_bb = NULL; FOR_EACH_BB (current_bb) { rtx insn; unsigned int regno; /* First pass over the instructions records information used to determine when registers and memory are first and last set. */ FOR_BB_INSNS (current_bb, insn) { if (! INSN_P (insn)) continue; if (CALL_P (insn)) { for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++) if (TEST_HARD_REG_BIT (regs_invalidated_by_call, regno)) record_last_reg_set_info (insn, regno); mark_call (insn); } note_stores (PATTERN (insn), record_last_set_info, insn); } /* Insert implicit sets in the hash table. */ if (table->set_p && implicit_sets[current_bb->index] != NULL_RTX) hash_scan_set (implicit_sets[current_bb->index], BB_HEAD (current_bb), table); /* The next pass builds the hash table. */ FOR_BB_INSNS (current_bb, insn) if (INSN_P (insn)) hash_scan_insn (insn, table); } free (reg_avail_info); reg_avail_info = NULL; } /* Allocate space for the set/expr hash TABLE. It is used to determine the number of buckets to use. SET_P determines whether set or expression table will be created. */ static void alloc_hash_table (struct hash_table_d *table, int set_p) { int n; n = get_max_insn_count (); table->size = n / 4; if (table->size < 11) table->size = 11; /* Attempt to maintain efficient use of hash table. Making it an odd number is simplest for now. ??? Later take some measurements. */ table->size |= 1; n = table->size * sizeof (struct expr *); table->table = GNEWVAR (struct expr *, n); table->set_p = set_p; } /* Free things allocated by alloc_hash_table. */ static void free_hash_table (struct hash_table_d *table) { free (table->table); } /* Compute the hash TABLE for doing copy/const propagation or expression hash table. */ static void compute_hash_table (struct hash_table_d *table) { /* Initialize count of number of entries in hash table. */ table->n_elems = 0; memset (table->table, 0, table->size * sizeof (struct expr *)); compute_hash_table_work (table); } /* Expression tracking support. */ /* Lookup REGNO in the set TABLE. The result is a pointer to the table entry, or NULL if not found. */ static struct expr * lookup_set (unsigned int regno, struct hash_table_d *table) { unsigned int hash = hash_set (regno, table->size); struct expr *expr; expr = table->table[hash]; while (expr && REGNO (SET_DEST (expr->expr)) != regno) expr = expr->next_same_hash; return expr; } /* Return the next entry for REGNO in list EXPR. */ static struct expr * next_set (unsigned int regno, struct expr *expr) { do expr = expr->next_same_hash; while (expr && REGNO (SET_DEST (expr->expr)) != regno); return expr; } /* Like free_INSN_LIST_list or free_EXPR_LIST_list, except that the node types may be mixed. */ static void free_insn_expr_list_list (rtx *listp) { rtx list, next; for (list = *listp; list ; list = next) { next = XEXP (list, 1); if (GET_CODE (list) == EXPR_LIST) free_EXPR_LIST_node (list); else free_INSN_LIST_node (list); } *listp = NULL; } /* Clear canon_modify_mem_list and modify_mem_list tables. */ static void clear_modify_mem_tables (void) { unsigned i; bitmap_iterator bi; EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set, 0, i, bi) { free_INSN_LIST_list (modify_mem_list + i); free_insn_expr_list_list (canon_modify_mem_list + i); } bitmap_clear (modify_mem_list_set); bitmap_clear (blocks_with_calls); } /* Release memory used by modify_mem_list_set. */ static void free_modify_mem_tables (void) { clear_modify_mem_tables (); free (modify_mem_list); free (canon_modify_mem_list); modify_mem_list = 0; canon_modify_mem_list = 0; } /* Reset tables used to keep track of what's still available [since the start of the block]. */ static void reset_opr_set_tables (void) { /* Maintain a bitmap of which regs have been set since beginning of the block. */ CLEAR_REG_SET (reg_set_bitmap); /* Also keep a record of the last instruction to modify memory. For now this is very trivial, we only record whether any memory location has been modified. */ clear_modify_mem_tables (); } /* Return nonzero if the operands of X are not set before INSN in INSN's basic block. */ static int oprs_not_set_p (const_rtx x, const_rtx insn) { int i, j; enum rtx_code code; const char *fmt; if (x == 0) return 1; code = GET_CODE (x); switch (code) { case PC: case CC0: case CONST: case CONST_INT: case CONST_DOUBLE: case CONST_FIXED: case CONST_VECTOR: case SYMBOL_REF: case LABEL_REF: case ADDR_VEC: case ADDR_DIFF_VEC: return 1; case MEM: if (load_killed_in_block_p (BLOCK_FOR_INSN (insn), DF_INSN_LUID (insn), x, 0)) return 0; else return oprs_not_set_p (XEXP (x, 0), insn); case REG: return ! REGNO_REG_SET_P (reg_set_bitmap, REGNO (x)); default: break; } for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--) { if (fmt[i] == 'e') { /* If we are about to do the last recursive call needed at this level, change it into iteration. This function is called enough to be worth it. */ if (i == 0) return oprs_not_set_p (XEXP (x, i), insn); if (! oprs_not_set_p (XEXP (x, i), insn)) return 0; } else if (fmt[i] == 'E') for (j = 0; j < XVECLEN (x, i); j++) if (! oprs_not_set_p (XVECEXP (x, i, j), insn)) return 0; } return 1; } /* Mark things set by a CALL. */ static void mark_call (rtx insn) { if (! RTL_CONST_OR_PURE_CALL_P (insn)) record_last_mem_set_info (insn); } /* Mark things set by a SET. */ static void mark_set (rtx pat, rtx insn) { rtx dest = SET_DEST (pat); while (GET_CODE (dest) == SUBREG || GET_CODE (dest) == ZERO_EXTRACT || GET_CODE (dest) == STRICT_LOW_PART) dest = XEXP (dest, 0); if (REG_P (dest)) SET_REGNO_REG_SET (reg_set_bitmap, REGNO (dest)); else if (MEM_P (dest)) record_last_mem_set_info (insn); if (GET_CODE (SET_SRC (pat)) == CALL) mark_call (insn); } /* Record things set by a CLOBBER. */ static void mark_clobber (rtx pat, rtx insn) { rtx clob = XEXP (pat, 0); while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART) clob = XEXP (clob, 0); if (REG_P (clob)) SET_REGNO_REG_SET (reg_set_bitmap, REGNO (clob)); else record_last_mem_set_info (insn); } /* Record things set by INSN. This data is used by oprs_not_set_p. */ static void mark_oprs_set (rtx insn) { rtx pat = PATTERN (insn); int i; if (GET_CODE (pat) == SET) mark_set (pat, insn); else if (GET_CODE (pat) == PARALLEL) for (i = 0; i < XVECLEN (pat, 0); i++) { rtx x = XVECEXP (pat, 0, i); if (GET_CODE (x) == SET) mark_set (x, insn); else if (GET_CODE (x) == CLOBBER) mark_clobber (x, insn); else if (GET_CODE (x) == CALL) mark_call (insn); } else if (GET_CODE (pat) == CLOBBER) mark_clobber (pat, insn); else if (GET_CODE (pat) == CALL) mark_call (insn); } /* Compute copy/constant propagation working variables. */ /* Local properties of assignments. */ static sbitmap *cprop_pavloc; static sbitmap *cprop_absaltered; /* Global properties of assignments (computed from the local properties). */ static sbitmap *cprop_avin; static sbitmap *cprop_avout; /* Allocate vars used for copy/const propagation. N_BLOCKS is the number of basic blocks. N_SETS is the number of sets. */ static void alloc_cprop_mem (int n_blocks, int n_sets) { cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets); cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets); cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets); cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets); } /* Free vars used by copy/const propagation. */ static void free_cprop_mem (void) { sbitmap_vector_free (cprop_pavloc); sbitmap_vector_free (cprop_absaltered); sbitmap_vector_free (cprop_avin); sbitmap_vector_free (cprop_avout); } /* For each block, compute whether X is transparent. X is either an expression or an assignment [though we don't care which, for this context an assignment is treated as an expression]. For each block where an element of X is modified, set (SET_P == 1) or reset (SET_P == 0) the INDX bit in BMAP. */ static void compute_transp (const_rtx x, int indx, sbitmap *bmap, int set_p) { int i, j; enum rtx_code code; const char *fmt; /* repeat is used to turn tail-recursion into iteration since GCC can't do it when there's no return value. */ repeat: if (x == 0) return; code = GET_CODE (x); switch (code) { case REG: if (set_p) { df_ref def; for (def = DF_REG_DEF_CHAIN (REGNO (x)); def; def = DF_REF_NEXT_REG (def)) SET_BIT (bmap[DF_REF_BB (def)->index], indx); } else { df_ref def; for (def = DF_REG_DEF_CHAIN (REGNO (x)); def; def = DF_REF_NEXT_REG (def)) RESET_BIT (bmap[DF_REF_BB (def)->index], indx); } return; case MEM: if (! MEM_READONLY_P (x)) { bitmap_iterator bi; unsigned bb_index; /* First handle all the blocks with calls. We don't need to do any list walking for them. */ EXECUTE_IF_SET_IN_BITMAP (blocks_with_calls, 0, bb_index, bi) { if (set_p) SET_BIT (bmap[bb_index], indx); else RESET_BIT (bmap[bb_index], indx); } /* Now iterate over the blocks which have memory modifications but which do not have any calls. */ EXECUTE_IF_AND_COMPL_IN_BITMAP (modify_mem_list_set, blocks_with_calls, 0, bb_index, bi) { rtx list_entry = canon_modify_mem_list[bb_index]; while (list_entry) { rtx dest, dest_addr; /* LIST_ENTRY must be an INSN of some kind that sets memory. Examine each hunk of memory that is modified. */ dest = XEXP (list_entry, 0); list_entry = XEXP (list_entry, 1); dest_addr = XEXP (list_entry, 0); if (canon_true_dependence (dest, GET_MODE (dest), dest_addr, x, NULL_RTX, rtx_addr_varies_p)) { if (set_p) SET_BIT (bmap[bb_index], indx); else RESET_BIT (bmap[bb_index], indx); break; } list_entry = XEXP (list_entry, 1); } } } x = XEXP (x, 0); goto repeat; case PC: case CC0: /*FIXME*/ case CONST: case CONST_INT: case CONST_DOUBLE: case CONST_FIXED: case CONST_VECTOR: case SYMBOL_REF: case LABEL_REF: case ADDR_VEC: case ADDR_DIFF_VEC: return; default: break; } for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--) { if (fmt[i] == 'e') { /* If we are about to do the last recursive call needed at this level, change it into iteration. This function is called enough to be worth it. */ if (i == 0) { x = XEXP (x, i); goto repeat; } compute_transp (XEXP (x, i), indx, bmap, set_p); } else if (fmt[i] == 'E') for (j = 0; j < XVECLEN (x, i); j++) compute_transp (XVECEXP (x, i, j), indx, bmap, set_p); } } /* Top level routine to do the dataflow analysis needed by copy/const propagation. */ static void compute_cprop_data (void) { compute_local_properties (cprop_absaltered, cprop_pavloc, NULL, &set_hash_table); compute_available (cprop_pavloc, cprop_absaltered, cprop_avout, cprop_avin); } /* Copy/constant propagation. */ /* Maximum number of register uses in an insn that we handle. */ #define MAX_USES 8 /* Table of uses found in an insn. Allocated statically to avoid alloc/free complexity and overhead. */ static struct reg_use reg_use_table[MAX_USES]; /* Index into `reg_use_table' while building it. */ static int reg_use_count; /* Set up a list of register numbers used in INSN. The found uses are stored in `reg_use_table'. `reg_use_count' is initialized to zero before entry, and contains the number of uses in the table upon exit. ??? If a register appears multiple times we will record it multiple times. This doesn't hurt anything but it will slow things down. */ static void find_used_regs (rtx *xptr, void *data ATTRIBUTE_UNUSED) { int i, j; enum rtx_code code; const char *fmt; rtx x = *xptr; /* repeat is used to turn tail-recursion into iteration since GCC can't do it when there's no return value. */ repeat: if (x == 0) return; code = GET_CODE (x); if (REG_P (x)) { if (reg_use_count == MAX_USES) return; reg_use_table[reg_use_count].reg_rtx = x; reg_use_count++; } /* Recursively scan the operands of this expression. */ for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--) { if (fmt[i] == 'e') { /* If we are about to do the last recursive call needed at this level, change it into iteration. This function is called enough to be worth it. */ if (i == 0) { x = XEXP (x, 0); goto repeat; } find_used_regs (&XEXP (x, i), data); } else if (fmt[i] == 'E') for (j = 0; j < XVECLEN (x, i); j++) find_used_regs (&XVECEXP (x, i, j), data); } } /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO. Returns nonzero is successful. */ static int try_replace_reg (rtx from, rtx to, rtx insn) { rtx note = find_reg_equal_equiv_note (insn); rtx src = 0; int success = 0; rtx set = single_set (insn); /* Usually we substitute easy stuff, so we won't copy everything. We however need to take care to not duplicate non-trivial CONST expressions. */ to = copy_rtx (to); validate_replace_src_group (from, to, insn); if (num_changes_pending () && apply_change_group ()) success = 1; /* Try to simplify SET_SRC if we have substituted a constant. */ if (success && set && CONSTANT_P (to)) { src = simplify_rtx (SET_SRC (set)); if (src) validate_change (insn, &SET_SRC (set), src, 0); } /* If there is already a REG_EQUAL note, update the expression in it with our replacement. */ if (note != 0 && REG_NOTE_KIND (note) == REG_EQUAL) set_unique_reg_note (insn, REG_EQUAL, simplify_replace_rtx (XEXP (note, 0), from, to)); if (!success && set && reg_mentioned_p (from, SET_SRC (set))) { /* If above failed and this is a single set, try to simplify the source of the set given our substitution. We could perhaps try this for multiple SETs, but it probably won't buy us anything. */ src = simplify_replace_rtx (SET_SRC (set), from, to); if (!rtx_equal_p (src, SET_SRC (set)) && validate_change (insn, &SET_SRC (set), src, 0)) success = 1; /* If we've failed to do replacement, have a single SET, don't already have a note, and have no special SET, add a REG_EQUAL note to not lose information. */ if (!success && note == 0 && set != 0 && GET_CODE (SET_DEST (set)) != ZERO_EXTRACT && GET_CODE (SET_DEST (set)) != STRICT_LOW_PART) note = set_unique_reg_note (insn, REG_EQUAL, copy_rtx (src)); } /* REG_EQUAL may get simplified into register. We don't allow that. Remove that note. This code ought not to happen, because previous code ought to synthesize reg-reg move, but be on the safe side. */ if (note && REG_NOTE_KIND (note) == REG_EQUAL && REG_P (XEXP (note, 0))) remove_note (insn, note); return success; } /* Find a set of REGNOs that are available on entry to INSN's block. Returns NULL no such set is found. */ static struct expr * find_avail_set (int regno, rtx insn) { /* SET1 contains the last set found that can be returned to the caller for use in a substitution. */ struct expr *set1 = 0; /* Loops are not possible here. To get a loop we would need two sets available at the start of the block containing INSN. i.e. we would need two sets like this available at the start of the block: (set (reg X) (reg Y)) (set (reg Y) (reg X)) This can not happen since the set of (reg Y) would have killed the set of (reg X) making it unavailable at the start of this block. */ while (1) { rtx src; struct expr *set = lookup_set (regno, &set_hash_table); /* Find a set that is available at the start of the block which contains INSN. */ while (set) { if (TEST_BIT (cprop_avin[BLOCK_FOR_INSN (insn)->index], set->bitmap_index)) break; set = next_set (regno, set); } /* If no available set was found we've reached the end of the (possibly empty) copy chain. */ if (set == 0) break; gcc_assert (GET_CODE (set->expr) == SET); src = SET_SRC (set->expr); /* We know the set is available. Now check that SRC is ANTLOC (i.e. none of the source operands have changed since the start of the block). If the source operand changed, we may still use it for the next iteration of this loop, but we may not use it for substitutions. */ if (gcse_constant_p (src) || oprs_not_set_p (src, insn)) set1 = set; /* If the source of the set is anything except a register, then we have reached the end of the copy chain. */ if (! REG_P (src)) break; /* Follow the copy chain, i.e. start another iteration of the loop and see if we have an available copy into SRC. */ regno = REGNO (src); } /* SET1 holds the last set that was available and anticipatable at INSN. */ return set1; } /* Subroutine of cprop_insn that tries to propagate constants into JUMP_INSNS. JUMP must be a conditional jump. If SETCC is non-NULL it is the instruction that immediately precedes JUMP, and must be a single SET of a register. FROM is what we will try to replace, SRC is the constant we will try to substitute for it. Returns nonzero if a change was made. */ static int cprop_jump (basic_block bb, rtx setcc, rtx jump, rtx from, rtx src) { rtx new_rtx, set_src, note_src; rtx set = pc_set (jump); rtx note = find_reg_equal_equiv_note (jump); if (note) { note_src = XEXP (note, 0); if (GET_CODE (note_src) == EXPR_LIST) note_src = NULL_RTX; } else note_src = NULL_RTX; /* Prefer REG_EQUAL notes except those containing EXPR_LISTs. */ set_src = note_src ? note_src : SET_SRC (set); /* First substitute the SETCC condition into the JUMP instruction, then substitute that given values into this expanded JUMP. */ if (setcc != NULL_RTX && !modified_between_p (from, setcc, jump) && !modified_between_p (src, setcc, jump)) { rtx setcc_src; rtx setcc_set = single_set (setcc); rtx setcc_note = find_reg_equal_equiv_note (setcc); setcc_src = (setcc_note && GET_CODE (XEXP (setcc_note, 0)) != EXPR_LIST) ? XEXP (setcc_note, 0) : SET_SRC (setcc_set); set_src = simplify_replace_rtx (set_src, SET_DEST (setcc_set), setcc_src); } else setcc = NULL_RTX; new_rtx = simplify_replace_rtx (set_src, from, src); /* If no simplification can be made, then try the next register. */ if (rtx_equal_p (new_rtx, SET_SRC (set))) return 0; /* If this is now a no-op delete it, otherwise this must be a valid insn. */ if (new_rtx == pc_rtx) delete_insn (jump); else { /* Ensure the value computed inside the jump insn to be equivalent to one computed by setcc. */ if (setcc && modified_in_p (new_rtx, setcc)) return 0; if (! validate_unshare_change (jump, &SET_SRC (set), new_rtx, 0)) { /* When (some) constants are not valid in a comparison, and there are two registers to be replaced by constants before the entire comparison can be folded into a constant, we need to keep intermediate information in REG_EQUAL notes. For targets with separate compare insns, such notes are added by try_replace_reg. When we have a combined compare-and-branch instruction, however, we need to attach a note to the branch itself to make this optimization work. */ if (!rtx_equal_p (new_rtx, note_src)) set_unique_reg_note (jump, REG_EQUAL, copy_rtx (new_rtx)); return 0; } /* Remove REG_EQUAL note after simplification. */ if (note_src) remove_note (jump, note); } #ifdef HAVE_cc0 /* Delete the cc0 setter. */ if (setcc != NULL && CC0_P (SET_DEST (single_set (setcc)))) delete_insn (setcc); #endif global_const_prop_count++; if (dump_file != NULL) { fprintf (dump_file, "GLOBAL CONST-PROP: Replacing reg %d in jump_insn %d with constant ", REGNO (from), INSN_UID (jump)); print_rtl (dump_file, src); fprintf (dump_file, "\n"); } purge_dead_edges (bb); /* If a conditional jump has been changed into unconditional jump, remove the jump and make the edge fallthru - this is always called in cfglayout mode. */ if (new_rtx != pc_rtx && simplejump_p (jump)) { edge e; edge_iterator ei; for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ei_next (&ei)) if (e->dest != EXIT_BLOCK_PTR && BB_HEAD (e->dest) == JUMP_LABEL (jump)) { e->flags |= EDGE_FALLTHRU; break; } delete_insn (jump); } return 1; } static bool constprop_register (rtx insn, rtx from, rtx to) { rtx sset; /* Check for reg or cc0 setting instructions followed by conditional branch instructions first. */ if ((sset = single_set (insn)) != NULL && NEXT_INSN (insn) && any_condjump_p (NEXT_INSN (insn)) && onlyjump_p (NEXT_INSN (insn))) { rtx dest = SET_DEST (sset); if ((REG_P (dest) || CC0_P (dest)) && cprop_jump (BLOCK_FOR_INSN (insn), insn, NEXT_INSN (insn), from, to)) return 1; } /* Handle normal insns next. */ if (NONJUMP_INSN_P (insn) && try_replace_reg (from, to, insn)) return 1; /* Try to propagate a CONST_INT into a conditional jump. We're pretty specific about what we will handle in this code, we can extend this as necessary over time. Right now the insn in question must look like (set (pc) (if_then_else ...)) */ else if (any_condjump_p (insn) && onlyjump_p (insn)) return cprop_jump (BLOCK_FOR_INSN (insn), NULL, insn, from, to); return 0; } /* Perform constant and copy propagation on INSN. The result is nonzero if a change was made. */ static int cprop_insn (rtx insn) { struct reg_use *reg_used; int changed = 0; rtx note; if (!INSN_P (insn)) return 0; reg_use_count = 0; note_uses (&PATTERN (insn), find_used_regs, NULL); note = find_reg_equal_equiv_note (insn); /* We may win even when propagating constants into notes. */ if (note) find_used_regs (&XEXP (note, 0), NULL); for (reg_used = ®_use_table[0]; reg_use_count > 0; reg_used++, reg_use_count--) { unsigned int regno = REGNO (reg_used->reg_rtx); rtx pat, src; struct expr *set; /* If the register has already been set in this block, there's nothing we can do. */ if (! oprs_not_set_p (reg_used->reg_rtx, insn)) continue; /* Find an assignment that sets reg_used and is available at the start of the block. */ set = find_avail_set (regno, insn); if (! set) continue; pat = set->expr; /* ??? We might be able to handle PARALLELs. Later. */ gcc_assert (GET_CODE (pat) == SET); src = SET_SRC (pat); /* Constant propagation. */ if (gcse_constant_p (src)) { if (constprop_register (insn, reg_used->reg_rtx, src)) { changed = 1; global_const_prop_count++; if (dump_file != NULL) { fprintf (dump_file, "GLOBAL CONST-PROP: Replacing reg %d in ", regno); fprintf (dump_file, "insn %d with constant ", INSN_UID (insn)); print_rtl (dump_file, src); fprintf (dump_file, "\n"); } if (INSN_DELETED_P (insn)) return 1; } } else if (REG_P (src) && REGNO (src) >= FIRST_PSEUDO_REGISTER && REGNO (src) != regno) { if (try_replace_reg (reg_used->reg_rtx, src, insn)) { changed = 1; global_copy_prop_count++; if (dump_file != NULL) { fprintf (dump_file, "GLOBAL COPY-PROP: Replacing reg %d in insn %d", regno, INSN_UID (insn)); fprintf (dump_file, " with reg %d\n", REGNO (src)); } /* The original insn setting reg_used may or may not now be deletable. We leave the deletion to flow. */ /* FIXME: If it turns out that the insn isn't deletable, then we may have unnecessarily extended register lifetimes and made things worse. */ } } } if (changed && DEBUG_INSN_P (insn)) return 0; return changed; } /* Like find_used_regs, but avoid recording uses that appear in input-output contexts such as zero_extract or pre_dec. This restricts the cases we consider to those for which local cprop can legitimately make replacements. */ static void local_cprop_find_used_regs (rtx *xptr, void *data) { rtx x = *xptr; if (x == 0) return; switch (GET_CODE (x)) { case ZERO_EXTRACT: case SIGN_EXTRACT: case STRICT_LOW_PART: return; case PRE_DEC: case PRE_INC: case POST_DEC: case POST_INC: case PRE_MODIFY: case POST_MODIFY: /* Can only legitimately appear this early in the context of stack pushes for function arguments, but handle all of the codes nonetheless. */ return; case SUBREG: /* Setting a subreg of a register larger than word_mode leaves the non-written words unchanged. */ if (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))) > BITS_PER_WORD) return; break; default: break; } find_used_regs (xptr, data); } /* Try to perform local const/copy propagation on X in INSN. */ static bool do_local_cprop (rtx x, rtx insn) { rtx newreg = NULL, newcnst = NULL; /* Rule out USE instructions and ASM statements as we don't want to change the hard registers mentioned. */ if (REG_P (x) && (REGNO (x) >= FIRST_PSEUDO_REGISTER || (GET_CODE (PATTERN (insn)) != USE && asm_noperands (PATTERN (insn)) < 0))) { cselib_val *val = cselib_lookup (x, GET_MODE (x), 0); struct elt_loc_list *l; if (!val) return false; for (l = val->locs; l; l = l->next) { rtx this_rtx = l->loc; rtx note; if (gcse_constant_p (this_rtx)) newcnst = this_rtx; if (REG_P (this_rtx) && REGNO (this_rtx) >= FIRST_PSEUDO_REGISTER /* Don't copy propagate if it has attached REG_EQUIV note. At this point this only function parameters should have REG_EQUIV notes and if the argument slot is used somewhere explicitly, it means address of parameter has been taken, so we should not extend the lifetime of the pseudo. */ && (!(note = find_reg_note (l->setting_insn, REG_EQUIV, NULL_RTX)) || ! MEM_P (XEXP (note, 0)))) newreg = this_rtx; } if (newcnst && constprop_register (insn, x, newcnst)) { if (dump_file != NULL) { fprintf (dump_file, "LOCAL CONST-PROP: Replacing reg %d in ", REGNO (x)); fprintf (dump_file, "insn %d with constant ", INSN_UID (insn)); print_rtl (dump_file, newcnst); fprintf (dump_file, "\n"); } local_const_prop_count++; return true; } else if (newreg && newreg != x && try_replace_reg (x, newreg, insn)) { if (dump_file != NULL) { fprintf (dump_file, "LOCAL COPY-PROP: Replacing reg %d in insn %d", REGNO (x), INSN_UID (insn)); fprintf (dump_file, " with reg %d\n", REGNO (newreg)); } local_copy_prop_count++; return true; } } return false; } /* Do local const/copy propagation (i.e. within each basic block). */ static int local_cprop_pass (void) { basic_block bb; rtx insn; struct reg_use *reg_used; bool changed = false; cselib_init (0); FOR_EACH_BB (bb) { FOR_BB_INSNS (bb, insn) { if (INSN_P (insn)) { rtx note = find_reg_equal_equiv_note (insn); do { reg_use_count = 0; note_uses (&PATTERN (insn), local_cprop_find_used_regs, NULL); if (note) local_cprop_find_used_regs (&XEXP (note, 0), NULL); for (reg_used = ®_use_table[0]; reg_use_count > 0; reg_used++, reg_use_count--) { if (do_local_cprop (reg_used->reg_rtx, insn)) { changed = true; break; } } if (INSN_DELETED_P (insn)) break; } while (reg_use_count); } cselib_process_insn (insn); } /* Forget everything at the end of a basic block. */ cselib_clear_table (); } cselib_finish (); return changed; } /* Similar to get_condition, only the resulting condition must be valid at JUMP, instead of at EARLIEST. This differs from noce_get_condition in ifcvt.c in that we prefer not to settle for the condition variable in the jump instruction being integral. We prefer to be able to record the value of a user variable, rather than the value of a temporary used in a condition. This could be solved by recording the value of *every* register scanned by canonicalize_condition, but this would require some code reorganization. */ rtx fis_get_condition (rtx jump) { return get_condition (jump, NULL, false, true); } /* Check the comparison COND to see if we can safely form an implicit set from it. COND is either an EQ or NE comparison. */ static bool implicit_set_cond_p (const_rtx cond) { const enum machine_mode mode = GET_MODE (XEXP (cond, 0)); const_rtx cst = XEXP (cond, 1); /* We can't perform this optimization if either operand might be or might contain a signed zero. */ if (HONOR_SIGNED_ZEROS (mode)) { /* It is sufficient to check if CST is or contains a zero. We must handle float, complex, and vector. If any subpart is a zero, then the optimization can't be performed. */ /* ??? The complex and vector checks are not implemented yet. We just always return zero for them. */ if (GET_CODE (cst) == CONST_DOUBLE) { REAL_VALUE_TYPE d; REAL_VALUE_FROM_CONST_DOUBLE (d, cst); if (REAL_VALUES_EQUAL (d, dconst0)) return 0; } else return 0; } return gcse_constant_p (cst); } /* Find the implicit sets of a function. An "implicit set" is a constraint on the value of a variable, implied by a conditional jump. For example, following "if (x == 2)", the then branch may be optimized as though the conditional performed an "explicit set", in this example, "x = 2". This function records the set patterns that are implicit at the start of each basic block. FIXME: This would be more effective if critical edges are pre-split. As it is now, we can't record implicit sets for blocks that have critical successor edges. This results in missed optimizations and in more (unnecessary) work in cfgcleanup.c:thread_jump(). */ static void find_implicit_sets (void) { basic_block bb, dest; unsigned int count; rtx cond, new_rtx; count = 0; FOR_EACH_BB (bb) /* Check for more than one successor. */ if (EDGE_COUNT (bb->succs) > 1) { cond = fis_get_condition (BB_END (bb)); if (cond && (GET_CODE (cond) == EQ || GET_CODE (cond) == NE) && REG_P (XEXP (cond, 0)) && REGNO (XEXP (cond, 0)) >= FIRST_PSEUDO_REGISTER && implicit_set_cond_p (cond)) { dest = GET_CODE (cond) == EQ ? BRANCH_EDGE (bb)->dest : FALLTHRU_EDGE (bb)->dest; if (dest /* Record nothing for a critical edge. */ && single_pred_p (dest) && dest != EXIT_BLOCK_PTR) { new_rtx = gen_rtx_SET (VOIDmode, XEXP (cond, 0), XEXP (cond, 1)); implicit_sets[dest->index] = new_rtx; if (dump_file) { fprintf(dump_file, "Implicit set of reg %d in ", REGNO (XEXP (cond, 0))); fprintf(dump_file, "basic block %d\n", dest->index); } count++; } } } if (dump_file) fprintf (dump_file, "Found %d implicit sets\n", count); } /* Bypass conditional jumps. */ /* The value of last_basic_block at the beginning of the jump_bypass pass. The use of redirect_edge_and_branch_force may introduce new basic blocks, but the data flow analysis is only valid for basic block indices less than bypass_last_basic_block. */ static int bypass_last_basic_block; /* Find a set of REGNO to a constant that is available at the end of basic block BB. Returns NULL if no such set is found. Based heavily upon find_avail_set. */ static struct expr * find_bypass_set (int regno, int bb) { struct expr *result = 0; for (;;) { rtx src; struct expr *set = lookup_set (regno, &set_hash_table); while (set) { if (TEST_BIT (cprop_avout[bb], set->bitmap_index)) break; set = next_set (regno, set); } if (set == 0) break; gcc_assert (GET_CODE (set->expr) == SET); src = SET_SRC (set->expr); if (gcse_constant_p (src)) result = set; if (! REG_P (src)) break; regno = REGNO (src); } return result; } /* Subroutine of bypass_block that checks whether a pseudo is killed by any of the instructions inserted on an edge. Jump bypassing places condition code setters on CFG edges using insert_insn_on_edge. This function is required to check that our data flow analysis is still valid prior to commit_edge_insertions. */ static bool reg_killed_on_edge (const_rtx reg, const_edge e) { rtx insn; for (insn = e->insns.r; insn; insn = NEXT_INSN (insn)) if (INSN_P (insn) && reg_set_p (reg, insn)) return true; return false; } /* Subroutine of bypass_conditional_jumps that attempts to bypass the given basic block BB which has more than one predecessor. If not NULL, SETCC is the first instruction of BB, which is immediately followed by JUMP_INSN JUMP. Otherwise, SETCC is NULL, and JUMP is the first insn of BB. Returns nonzero if a change was made. During the jump bypassing pass, we may place copies of SETCC instructions on CFG edges. The following routine must be careful to pay attention to these inserted insns when performing its transformations. */ static int bypass_block (basic_block bb, rtx setcc, rtx jump) { rtx insn, note; edge e, edest; int i, change; int may_be_loop_header; unsigned removed_p; edge_iterator ei; insn = (setcc != NULL) ? setcc : jump; /* Determine set of register uses in INSN. */ reg_use_count = 0; note_uses (&PATTERN (insn), find_used_regs, NULL); note = find_reg_equal_equiv_note (insn); if (note) find_used_regs (&XEXP (note, 0), NULL); may_be_loop_header = false; FOR_EACH_EDGE (e, ei, bb->preds) if (e->flags & EDGE_DFS_BACK) { may_be_loop_header = true; break; } change = 0; for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) { removed_p = 0; if (e->flags & EDGE_COMPLEX) { ei_next (&ei); continue; } /* We can't redirect edges from new basic blocks. */ if (e->src->index >= bypass_last_basic_block) { ei_next (&ei); continue; } /* The irreducible loops created by redirecting of edges entering the loop from outside would decrease effectiveness of some of the following optimizations, so prevent this. */ if (may_be_loop_header && !(e->flags & EDGE_DFS_BACK)) { ei_next (&ei); continue; } for (i = 0; i < reg_use_count; i++) { struct reg_use *reg_used = ®_use_table[i]; unsigned int regno = REGNO (reg_used->reg_rtx); basic_block dest, old_dest; struct expr *set; rtx src, new_rtx; set = find_bypass_set (regno, e->src->index); if (! set) continue; /* Check the data flow is valid after edge insertions. */ if (e->insns.r && reg_killed_on_edge (reg_used->reg_rtx, e)) continue; src = SET_SRC (pc_set (jump)); if (setcc != NULL) src = simplify_replace_rtx (src, SET_DEST (PATTERN (setcc)), SET_SRC (PATTERN (setcc))); new_rtx = simplify_replace_rtx (src, reg_used->reg_rtx, SET_SRC (set->expr)); /* Jump bypassing may have already placed instructions on edges of the CFG. We can't bypass an outgoing edge that has instructions associated with it, as these insns won't get executed if the incoming edge is redirected. */ if (new_rtx == pc_rtx) { edest = FALLTHRU_EDGE (bb); dest = edest->insns.r ? NULL : edest->dest; } else if (GET_CODE (new_rtx) == LABEL_REF) { dest = BLOCK_FOR_INSN (XEXP (new_rtx, 0)); /* Don't bypass edges containing instructions. */ edest = find_edge (bb, dest); if (edest && edest->insns.r) dest = NULL; } else dest = NULL; /* Avoid unification of the edge with other edges from original branch. We would end up emitting the instruction on "both" edges. */ if (dest && setcc && !CC0_P (SET_DEST (PATTERN (setcc))) && find_edge (e->src, dest)) dest = NULL; old_dest = e->dest; if (dest != NULL && dest != old_dest && dest != EXIT_BLOCK_PTR) { redirect_edge_and_branch_force (e, dest); /* Copy the register setter to the redirected edge. Don't copy CC0 setters, as CC0 is dead after jump. */ if (setcc) { rtx pat = PATTERN (setcc); if (!CC0_P (SET_DEST (pat))) insert_insn_on_edge (copy_insn (pat), e); } if (dump_file != NULL) { fprintf (dump_file, "JUMP-BYPASS: Proved reg %d " "in jump_insn %d equals constant ", regno, INSN_UID (jump)); print_rtl (dump_file, SET_SRC (set->expr)); fprintf (dump_file, "\nBypass edge from %d->%d to %d\n", e->src->index, old_dest->index, dest->index); } change = 1; removed_p = 1; break; } } if (!removed_p) ei_next (&ei); } return change; } /* Find basic blocks with more than one predecessor that only contain a single conditional jump. If the result of the comparison is known at compile-time from any incoming edge, redirect that edge to the appropriate target. Returns nonzero if a change was made. This function is now mis-named, because we also handle indirect jumps. */ static int bypass_conditional_jumps (void) { basic_block bb; int changed; rtx setcc; rtx insn; rtx dest; /* Note we start at block 1. */ if (ENTRY_BLOCK_PTR->next_bb == EXIT_BLOCK_PTR) return 0; bypass_last_basic_block = last_basic_block; mark_dfs_back_edges (); changed = 0; FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb->next_bb, EXIT_BLOCK_PTR, next_bb) { /* Check for more than one predecessor. */ if (!single_pred_p (bb)) { setcc = NULL_RTX; FOR_BB_INSNS (bb, insn) if (DEBUG_INSN_P (insn)) continue; else if (NONJUMP_INSN_P (insn)) { if (setcc) break; if (GET_CODE (PATTERN (insn)) != SET) break; dest = SET_DEST (PATTERN (insn)); if (REG_P (dest) || CC0_P (dest)) setcc = insn; else break; } else if (JUMP_P (insn)) { if ((any_condjump_p (insn) || computed_jump_p (insn)) && onlyjump_p (insn)) changed |= bypass_block (bb, setcc, insn); break; } else if (INSN_P (insn)) break; } } /* If we bypassed any register setting insns, we inserted a copy on the redirected edge. These need to be committed. */ if (changed) commit_edge_insertions (); return changed; } /* Compute PRE+LCM working variables. */ /* Local properties of expressions. */ /* Nonzero for expressions that are transparent in the block. */ static sbitmap *transp; /* Nonzero for expressions that are transparent at the end of the block. This is only zero for expressions killed by abnormal critical edge created by a calls. */ static sbitmap *transpout; /* Nonzero for expressions that are computed (available) in the block. */ static sbitmap *comp; /* Nonzero for expressions that are locally anticipatable in the block. */ static sbitmap *antloc; /* Nonzero for expressions where this block is an optimal computation point. */ static sbitmap *pre_optimal; /* Nonzero for expressions which are redundant in a particular block. */ static sbitmap *pre_redundant; /* Nonzero for expressions which should be inserted on a specific edge. */ static sbitmap *pre_insert_map; /* Nonzero for expressions which should be deleted in a specific block. */ static sbitmap *pre_delete_map; /* Contains the edge_list returned by pre_edge_lcm. */ static struct edge_list *edge_list; /* Allocate vars used for PRE analysis. */ static void alloc_pre_mem (int n_blocks, int n_exprs) { transp = sbitmap_vector_alloc (n_blocks, n_exprs); comp = sbitmap_vector_alloc (n_blocks, n_exprs); antloc = sbitmap_vector_alloc (n_blocks, n_exprs); pre_optimal = NULL; pre_redundant = NULL; pre_insert_map = NULL; pre_delete_map = NULL; ae_kill = sbitmap_vector_alloc (n_blocks, n_exprs); /* pre_insert and pre_delete are allocated later. */ } /* Free vars used for PRE analysis. */ static void free_pre_mem (void) { sbitmap_vector_free (transp); sbitmap_vector_free (comp); /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */ if (pre_optimal) sbitmap_vector_free (pre_optimal); if (pre_redundant) sbitmap_vector_free (pre_redundant); if (pre_insert_map) sbitmap_vector_free (pre_insert_map); if (pre_delete_map) sbitmap_vector_free (pre_delete_map); transp = comp = NULL; pre_optimal = pre_redundant = pre_insert_map = pre_delete_map = NULL; } /* Top level routine to do the dataflow analysis needed by PRE. */ static void compute_pre_data (void) { sbitmap trapping_expr; basic_block bb; unsigned int ui; compute_local_properties (transp, comp, antloc, &expr_hash_table); sbitmap_vector_zero (ae_kill, last_basic_block); /* Collect expressions which might trap. */ trapping_expr = sbitmap_alloc (expr_hash_table.n_elems); sbitmap_zero (trapping_expr); for (ui = 0; ui < expr_hash_table.size; ui++) { struct expr *e; for (e = expr_hash_table.table[ui]; e != NULL; e = e->next_same_hash) if (may_trap_p (e->expr)) SET_BIT (trapping_expr, e->bitmap_index); } /* Compute ae_kill for each basic block using: ~(TRANSP | COMP) */ FOR_EACH_BB (bb) { edge e; edge_iterator ei; /* If the current block is the destination of an abnormal edge, we kill all trapping expressions because we won't be able to properly place the instruction on the edge. So make them neither anticipatable nor transparent. This is fairly conservative. */ FOR_EACH_EDGE (e, ei, bb->preds) if (e->flags & EDGE_ABNORMAL) { sbitmap_difference (antloc[bb->index], antloc[bb->index], trapping_expr); sbitmap_difference (transp[bb->index], transp[bb->index], trapping_expr); break; } sbitmap_a_or_b (ae_kill[bb->index], transp[bb->index], comp[bb->index]); sbitmap_not (ae_kill[bb->index], ae_kill[bb->index]); } edge_list = pre_edge_lcm (expr_hash_table.n_elems, transp, comp, antloc, ae_kill, &pre_insert_map, &pre_delete_map); sbitmap_vector_free (antloc); antloc = NULL; sbitmap_vector_free (ae_kill); ae_kill = NULL; sbitmap_free (trapping_expr); } /* PRE utilities */ /* Return nonzero if an occurrence of expression EXPR in OCCR_BB would reach block BB. VISITED is a pointer to a working buffer for tracking which BB's have been visited. It is NULL for the top-level call. We treat reaching expressions that go through blocks containing the same reaching expression as "not reaching". E.g. if EXPR is generated in blocks 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block 2 as not reaching. The intent is to improve the probability of finding only one reaching expression and to reduce register lifetimes by picking the closest such expression. */ static int pre_expr_reaches_here_p_work (basic_block occr_bb, struct expr *expr, basic_block bb, char *visited) { edge pred; edge_iterator ei; FOR_EACH_EDGE (pred, ei, bb->preds) { basic_block pred_bb = pred->src; if (pred->src == ENTRY_BLOCK_PTR /* Has predecessor has already been visited? */ || visited[pred_bb->index]) ;/* Nothing to do. */ /* Does this predecessor generate this expression? */ else if (TEST_BIT (comp[pred_bb->index], expr->bitmap_index)) { /* Is this the occurrence we're looking for? Note that there's only one generating occurrence per block so we just need to check the block number. */ if (occr_bb == pred_bb) return 1; visited[pred_bb->index] = 1; } /* Ignore this predecessor if it kills the expression. */ else if (! TEST_BIT (transp[pred_bb->index], expr->bitmap_index)) visited[pred_bb->index] = 1; /* Neither gen nor kill. */ else { visited[pred_bb->index] = 1; if (pre_expr_reaches_here_p_work (occr_bb, expr, pred_bb, visited)) return 1; } } /* All paths have been checked. */ return 0; } /* The wrapper for pre_expr_reaches_here_work that ensures that any memory allocated for that function is returned. */ static int pre_expr_reaches_here_p (basic_block occr_bb, struct expr *expr, basic_block bb) { int rval; char *visited = XCNEWVEC (char, last_basic_block); rval = pre_expr_reaches_here_p_work (occr_bb, expr, bb, visited); free (visited); return rval; } /* Given an expr, generate RTL which we can insert at the end of a BB, or on an edge. Set the block number of any insns generated to the value of BB. */ static rtx process_insert_insn (struct expr *expr) { rtx reg = expr->reaching_reg; rtx exp = copy_rtx (expr->expr); rtx pat; start_sequence (); /* If the expression is something that's an operand, like a constant, just copy it to a register. */ if (general_operand (exp, GET_MODE (reg))) emit_move_insn (reg, exp); /* Otherwise, make a new insn to compute this expression and make sure the insn will be recognized (this also adds any needed CLOBBERs). Copy the expression to make sure we don't have any sharing issues. */ else { rtx insn = emit_insn (gen_rtx_SET (VOIDmode, reg, exp)); if (insn_invalid_p (insn)) gcc_unreachable (); } pat = get_insns (); end_sequence (); return pat; } /* Add EXPR to the end of basic block BB. This is used by both the PRE and code hoisting. For PRE, we want to verify that the expr is either transparent or locally anticipatable in the target block. This check makes no sense for code hoisting. */ static void insert_insn_end_basic_block (struct expr *expr, basic_block bb, int pre) { rtx insn = BB_END (bb); rtx new_insn; rtx reg = expr->reaching_reg; int regno = REGNO (reg); rtx pat, pat_end; pat = process_insert_insn (expr); gcc_assert (pat && INSN_P (pat)); pat_end = pat; while (NEXT_INSN (pat_end) != NULL_RTX) pat_end = NEXT_INSN (pat_end); /* If the last insn is a jump, insert EXPR in front [taking care to handle cc0, etc. properly]. Similarly we need to care trapping instructions in presence of non-call exceptions. */ if (JUMP_P (insn) || (NONJUMP_INSN_P (insn) && (!single_succ_p (bb) || single_succ_edge (bb)->flags & EDGE_ABNORMAL))) { #ifdef HAVE_cc0 rtx note; #endif /* It should always be the case that we can put these instructions anywhere in the basic block with performing PRE optimizations. Check this. */ gcc_assert (!NONJUMP_INSN_P (insn) || !pre || TEST_BIT (antloc[bb->index], expr->bitmap_index) || TEST_BIT (transp[bb->index], expr->bitmap_index)); /* If this is a jump table, then we can't insert stuff here. Since we know the previous real insn must be the tablejump, we insert the new instruction just before the tablejump. */ if (GET_CODE (PATTERN (insn)) == ADDR_VEC || GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC) insn = prev_real_insn (insn); #ifdef HAVE_cc0 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts if cc0 isn't set. */ note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX); if (note) insn = XEXP (note, 0); else { rtx maybe_cc0_setter = prev_nonnote_insn (insn); if (maybe_cc0_setter && INSN_P (maybe_cc0_setter) && sets_cc0_p (PATTERN (maybe_cc0_setter))) insn = maybe_cc0_setter; } #endif /* FIXME: What if something in cc0/jump uses value set in new insn? */ new_insn = emit_insn_before_noloc (pat, insn, bb); } /* Likewise if the last insn is a call, as will happen in the presence of exception handling. */ else if (CALL_P (insn) && (!single_succ_p (bb) || single_succ_edge (bb)->flags & EDGE_ABNORMAL)) { /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers, we search backward and place the instructions before the first parameter is loaded. Do this for everyone for consistency and a presumption that we'll get better code elsewhere as well. It should always be the case that we can put these instructions anywhere in the basic block with performing PRE optimizations. Check this. */ gcc_assert (!pre || TEST_BIT (antloc[bb->index], expr->bitmap_index) || TEST_BIT (transp[bb->index], expr->bitmap_index)); /* Since different machines initialize their parameter registers in different orders, assume nothing. Collect the set of all parameter registers. */ insn = find_first_parameter_load (insn, BB_HEAD (bb)); /* If we found all the parameter loads, then we want to insert before the first parameter load. If we did not find all the parameter loads, then we might have stopped on the head of the block, which could be a CODE_LABEL. If we inserted before the CODE_LABEL, then we would be putting the insn in the wrong basic block. In that case, put the insn after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */ while (LABEL_P (insn) || NOTE_INSN_BASIC_BLOCK_P (insn)) insn = NEXT_INSN (insn); new_insn = emit_insn_before_noloc (pat, insn, bb); } else new_insn = emit_insn_after_noloc (pat, insn, bb); while (1) { if (INSN_P (pat)) add_label_notes (PATTERN (pat), new_insn); if (pat == pat_end) break; pat = NEXT_INSN (pat); } gcse_create_count++; if (dump_file) { fprintf (dump_file, "PRE/HOIST: end of bb %d, insn %d, ", bb->index, INSN_UID (new_insn)); fprintf (dump_file, "copying expression %d to reg %d\n", expr->bitmap_index, regno); } } /* Insert partially redundant expressions on edges in the CFG to make the expressions fully redundant. */ static int pre_edge_insert (struct edge_list *edge_list, struct expr **index_map) { int e, i, j, num_edges, set_size, did_insert = 0; sbitmap *inserted; /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge if it reaches any of the deleted expressions. */ set_size = pre_insert_map[0]->size; num_edges = NUM_EDGES (edge_list); inserted = sbitmap_vector_alloc (num_edges, expr_hash_table.n_elems); sbitmap_vector_zero (inserted, num_edges); for (e = 0; e < num_edges; e++) { int indx; basic_block bb = INDEX_EDGE_PRED_BB (edge_list, e); for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS) { SBITMAP_ELT_TYPE insert = pre_insert_map[e]->elms[i]; for (j = indx; insert && j < (int) expr_hash_table.n_elems; j++, insert >>= 1) if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX) { struct expr *expr = index_map[j]; struct occr *occr; /* Now look at each deleted occurrence of this expression. */ for (occr = expr->antic_occr; occr != NULL; occr = occr->next) { if (! occr->deleted_p) continue; /* Insert this expression on this edge if it would reach the deleted occurrence in BB. */ if (!TEST_BIT (inserted[e], j)) { rtx insn; edge eg = INDEX_EDGE (edge_list, e); /* We can't insert anything on an abnormal and critical edge, so we insert the insn at the end of the previous block. There are several alternatives detailed in Morgans book P277 (sec 10.5) for handling this situation. This one is easiest for now. */ if (eg->flags & EDGE_ABNORMAL) insert_insn_end_basic_block (index_map[j], bb, 0); else { insn = process_insert_insn (index_map[j]); insert_insn_on_edge (insn, eg); } if (dump_file) { fprintf (dump_file, "PRE: edge (%d,%d), ", bb->index, INDEX_EDGE_SUCC_BB (edge_list, e)->index); fprintf (dump_file, "copy expression %d\n", expr->bitmap_index); } update_ld_motion_stores (expr); SET_BIT (inserted[e], j); did_insert = 1; gcse_create_count++; } } } } } sbitmap_vector_free (inserted); return did_insert; } /* Copy the result of EXPR->EXPR generated by INSN to EXPR->REACHING_REG. Given "old_reg <- expr" (INSN), instead of adding after it reaching_reg <- old_reg it's better to do the following: reaching_reg <- expr old_reg <- reaching_reg because this way copy propagation can discover additional PRE opportunities. But if this fails, we try the old way. When "expr" is a store, i.e. given "MEM <- old_reg", instead of adding after it reaching_reg <- old_reg it's better to add it before as follows: reaching_reg <- old_reg MEM <- reaching_reg. */ static void pre_insert_copy_insn (struct expr *expr, rtx insn) { rtx reg = expr->reaching_reg; int regno = REGNO (reg); int indx = expr->bitmap_index; rtx pat = PATTERN (insn); rtx set, first_set, new_insn; rtx old_reg; int i; /* This block matches the logic in hash_scan_insn. */ switch (GET_CODE (pat)) { case SET: set = pat; break; case PARALLEL: /* Search through the parallel looking for the set whose source was the expression that we're interested in. */ first_set = NULL_RTX; set = NULL_RTX; for (i = 0; i < XVECLEN (pat, 0); i++) { rtx x = XVECEXP (pat, 0, i); if (GET_CODE (x) == SET) { /* If the source was a REG_EQUAL or REG_EQUIV note, we may not find an equivalent expression, but in this case the PARALLEL will have a single set. */ if (first_set == NULL_RTX) first_set = x; if (expr_equiv_p (SET_SRC (x), expr->expr)) { set = x; break; } } } gcc_assert (first_set); if (set == NULL_RTX) set = first_set; break; default: gcc_unreachable (); } if (REG_P (SET_DEST (set))) { old_reg = SET_DEST (set); /* Check if we can modify the set destination in the original insn. */ if (validate_change (insn, &SET_DEST (set), reg, 0)) { new_insn = gen_move_insn (old_reg, reg); new_insn = emit_insn_after (new_insn, insn); } else { new_insn = gen_move_insn (reg, old_reg); new_insn = emit_insn_after (new_insn, insn); } } else /* This is possible only in case of a store to memory. */ { old_reg = SET_SRC (set); new_insn = gen_move_insn (reg, old_reg); /* Check if we can modify the set source in the original insn. */ if (validate_change (insn, &SET_SRC (set), reg, 0)) new_insn = emit_insn_before (new_insn, insn); else new_insn = emit_insn_after (new_insn, insn); } gcse_create_count++; if (dump_file) fprintf (dump_file, "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n", BLOCK_FOR_INSN (insn)->index, INSN_UID (new_insn), indx, INSN_UID (insn), regno); } /* Copy available expressions that reach the redundant expression to `reaching_reg'. */ static void pre_insert_copies (void) { unsigned int i, added_copy; struct expr *expr; struct occr *occr; struct occr *avail; /* For each available expression in the table, copy the result to `reaching_reg' if the expression reaches a deleted one. ??? The current algorithm is rather brute force. Need to do some profiling. */ for (i = 0; i < expr_hash_table.size; i++) for (expr = expr_hash_table.table[i]; expr != NULL; expr = expr->next_same_hash) { /* If the basic block isn't reachable, PPOUT will be TRUE. However, we don't want to insert a copy here because the expression may not really be redundant. So only insert an insn if the expression was deleted. This test also avoids further processing if the expression wasn't deleted anywhere. */ if (expr->reaching_reg == NULL) continue; /* Set when we add a copy for that expression. */ added_copy = 0; for (occr = expr->antic_occr; occr != NULL; occr = occr->next) { if (! occr->deleted_p) continue; for (avail = expr->avail_occr; avail != NULL; avail = avail->next) { rtx insn = avail->insn; /* No need to handle this one if handled already. */ if (avail->copied_p) continue; /* Don't handle this one if it's a redundant one. */ if (INSN_DELETED_P (insn)) continue; /* Or if the expression doesn't reach the deleted one. */ if (! pre_expr_reaches_here_p (BLOCK_FOR_INSN (avail->insn), expr, BLOCK_FOR_INSN (occr->insn))) continue; added_copy = 1; /* Copy the result of avail to reaching_reg. */ pre_insert_copy_insn (expr, insn); avail->copied_p = 1; } } if (added_copy) update_ld_motion_stores (expr); } } /* Emit move from SRC to DEST noting the equivalence with expression computed in INSN. */ static rtx gcse_emit_move_after (rtx src, rtx dest, rtx insn) { rtx new_rtx; rtx set = single_set (insn), set2; rtx note; rtx eqv; /* This should never fail since we're creating a reg->reg copy we've verified to be valid. */ new_rtx = emit_insn_after (gen_move_insn (dest, src), insn); /* Note the equivalence for local CSE pass. */ set2 = single_set (new_rtx); if (!set2 || !rtx_equal_p (SET_DEST (set2), dest)) return new_rtx; if ((note = find_reg_equal_equiv_note (insn))) eqv = XEXP (note, 0); else eqv = SET_SRC (set); set_unique_reg_note (new_rtx, REG_EQUAL, copy_insn_1 (eqv)); return new_rtx; } /* Delete redundant computations. Deletion is done by changing the insn to copy the `reaching_reg' of the expression into the result of the SET. It is left to later passes (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it. Returns nonzero if a change is made. */ static int pre_delete (void) { unsigned int i; int changed; struct expr *expr; struct occr *occr; changed = 0; for (i = 0; i < expr_hash_table.size; i++) for (expr = expr_hash_table.table[i]; expr != NULL; expr = expr->next_same_hash) { int indx = expr->bitmap_index; /* We only need to search antic_occr since we require ANTLOC != 0. */ for (occr = expr->antic_occr; occr != NULL; occr = occr->next) { rtx insn = occr->insn; rtx set; basic_block bb = BLOCK_FOR_INSN (insn); /* We only delete insns that have a single_set. */ if (TEST_BIT (pre_delete_map[bb->index], indx) && (set = single_set (insn)) != 0 && dbg_cnt (pre_insn)) { /* Create a pseudo-reg to store the result of reaching expressions into. Get the mode for the new pseudo from the mode of the original destination pseudo. */ if (expr->reaching_reg == NULL) expr->reaching_reg = gen_reg_rtx_and_attrs (SET_DEST (set)); gcse_emit_move_after (expr->reaching_reg, SET_DEST (set), insn); delete_insn (insn); occr->deleted_p = 1; changed = 1; gcse_subst_count++; if (dump_file) { fprintf (dump_file, "PRE: redundant insn %d (expression %d) in ", INSN_UID (insn), indx); fprintf (dump_file, "bb %d, reaching reg is %d\n", bb->index, REGNO (expr->reaching_reg)); } } } } return changed; } /* Perform GCSE optimizations using PRE. This is called by one_pre_gcse_pass after all the dataflow analysis has been done. This is based on the original Morel-Renvoise paper Fred Chow's thesis, and lazy code motion from Knoop, Ruthing and Steffen as described in Advanced Compiler Design and Implementation. ??? A new pseudo reg is created to hold the reaching expression. The nice thing about the classical approach is that it would try to use an existing reg. If the register can't be adequately optimized [i.e. we introduce reload problems], one could add a pass here to propagate the new register through the block. ??? We don't handle single sets in PARALLELs because we're [currently] not able to copy the rest of the parallel when we insert copies to create full redundancies from partial redundancies. However, there's no reason why we can't handle PARALLELs in the cases where there are no partial redundancies. */ static int pre_gcse (void) { unsigned int i; int did_insert, changed; struct expr **index_map; struct expr *expr; /* Compute a mapping from expression number (`bitmap_index') to hash table entry. */ index_map = XCNEWVEC (struct expr *, expr_hash_table.n_elems); for (i = 0; i < expr_hash_table.size; i++) for (expr = expr_hash_table.table[i]; expr != NULL; expr = expr->next_same_hash) index_map[expr->bitmap_index] = expr; /* Delete the redundant insns first so that - we know what register to use for the new insns and for the other ones with reaching expressions - we know which insns are redundant when we go to create copies */ changed = pre_delete (); did_insert = pre_edge_insert (edge_list, index_map); /* In other places with reaching expressions, copy the expression to the specially allocated pseudo-reg that reaches the redundant expr. */ pre_insert_copies (); if (did_insert) { commit_edge_insertions (); changed = 1; } free (index_map); return changed; } /* Top level routine to perform one PRE GCSE pass. Return nonzero if a change was made. */ static int one_pre_gcse_pass (void) { int changed = 0; gcse_subst_count = 0; gcse_create_count = 0; /* Return if there's nothing to do, or it is too expensive. */ if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1 || is_too_expensive (_("PRE disabled"))) return 0; /* We need alias. */ init_alias_analysis (); bytes_used = 0; gcc_obstack_init (&gcse_obstack); alloc_gcse_mem (); alloc_hash_table (&expr_hash_table, 0); add_noreturn_fake_exit_edges (); if (flag_gcse_lm) compute_ld_motion_mems (); compute_hash_table (&expr_hash_table); trim_ld_motion_mems (); if (dump_file) dump_hash_table (dump_file, "Expression", &expr_hash_table); if (expr_hash_table.n_elems > 0) { alloc_pre_mem (last_basic_block, expr_hash_table.n_elems); compute_pre_data (); changed |= pre_gcse (); free_edge_list (edge_list); free_pre_mem (); } free_ldst_mems (); remove_fake_exit_edges (); free_hash_table (&expr_hash_table); free_gcse_mem (); obstack_free (&gcse_obstack, NULL); /* We are finished with alias. */ end_alias_analysis (); if (dump_file) { fprintf (dump_file, "PRE GCSE of %s, %d basic blocks, %d bytes needed, ", current_function_name (), n_basic_blocks, bytes_used); fprintf (dump_file, "%d substs, %d insns created\n", gcse_subst_count, gcse_create_count); } return changed; } /* If X contains any LABEL_REF's, add REG_LABEL_OPERAND notes for them to INSN. If such notes are added to an insn which references a CODE_LABEL, the LABEL_NUSES count is incremented. We have to add that note, because the following loop optimization pass requires them. */ /* ??? If there was a jump optimization pass after gcse and before loop, then we would not need to do this here, because jump would add the necessary REG_LABEL_OPERAND and REG_LABEL_TARGET notes. */ static void add_label_notes (rtx x, rtx insn) { enum rtx_code code = GET_CODE (x); int i, j; const char *fmt; if (code == LABEL_REF && !LABEL_REF_NONLOCAL_P (x)) { /* This code used to ignore labels that referred to dispatch tables to avoid flow generating (slightly) worse code. We no longer ignore such label references (see LABEL_REF handling in mark_jump_label for additional information). */ /* There's no reason for current users to emit jump-insns with such a LABEL_REF, so we don't have to handle REG_LABEL_TARGET notes. */ gcc_assert (!JUMP_P (insn)); add_reg_note (insn, REG_LABEL_OPERAND, XEXP (x, 0)); if (LABEL_P (XEXP (x, 0))) LABEL_NUSES (XEXP (x, 0))++; return; } for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--) { if (fmt[i] == 'e') add_label_notes (XEXP (x, i), insn); else if (fmt[i] == 'E') for (j = XVECLEN (x, i) - 1; j >= 0; j--) add_label_notes (XVECEXP (x, i, j), insn); } } /* Compute transparent outgoing information for each block. An expression is transparent to an edge unless it is killed by the edge itself. This can only happen with abnormal control flow, when the edge is traversed through a call. This happens with non-local labels and exceptions. This would not be necessary if we split the edge. While this is normally impossible for abnormal critical edges, with some effort it should be possible with exception handling, since we still have control over which handler should be invoked. But due to increased EH table sizes, this may not be worthwhile. */ static void compute_transpout (void) { basic_block bb; unsigned int i; struct expr *expr; sbitmap_vector_ones (transpout, last_basic_block); FOR_EACH_BB (bb) { /* Note that flow inserted a nop at the end of basic blocks that end in call instructions for reasons other than abnormal control flow. */ if (! CALL_P (BB_END (bb))) continue; for (i = 0; i < expr_hash_table.size; i++) for (expr = expr_hash_table.table[i]; expr ; expr = expr->next_same_hash) if (MEM_P (expr->expr)) { if (GET_CODE (XEXP (expr->expr, 0)) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (XEXP (expr->expr, 0))) continue; /* ??? Optimally, we would use interprocedural alias analysis to determine if this mem is actually killed by this call. */ RESET_BIT (transpout[bb->index], expr->bitmap_index); } } } /* Code Hoisting variables and subroutines. */ /* Very busy expressions. */ static sbitmap *hoist_vbein; static sbitmap *hoist_vbeout; /* Hoistable expressions. */ static sbitmap *hoist_exprs; /* ??? We could compute post dominators and run this algorithm in reverse to perform tail merging, doing so would probably be more effective than the tail merging code in jump.c. It's unclear if tail merging could be run in parallel with code hoisting. It would be nice. */ /* Allocate vars used for code hoisting analysis. */ static void alloc_code_hoist_mem (int n_blocks, int n_exprs) { antloc = sbitmap_vector_alloc (n_blocks, n_exprs); transp = sbitmap_vector_alloc (n_blocks, n_exprs); comp = sbitmap_vector_alloc (n_blocks, n_exprs); hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs); hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs); hoist_exprs = sbitmap_vector_alloc (n_blocks, n_exprs); transpout = sbitmap_vector_alloc (n_blocks, n_exprs); } /* Free vars used for code hoisting analysis. */ static void free_code_hoist_mem (void) { sbitmap_vector_free (antloc); sbitmap_vector_free (transp); sbitmap_vector_free (comp); sbitmap_vector_free (hoist_vbein); sbitmap_vector_free (hoist_vbeout); sbitmap_vector_free (hoist_exprs); sbitmap_vector_free (transpout); free_dominance_info (CDI_DOMINATORS); } /* Compute the very busy expressions at entry/exit from each block. An expression is very busy if all paths from a given point compute the expression. */ static void compute_code_hoist_vbeinout (void) { int changed, passes; basic_block bb; sbitmap_vector_zero (hoist_vbeout, last_basic_block); sbitmap_vector_zero (hoist_vbein, last_basic_block); passes = 0; changed = 1; while (changed) { changed = 0; /* We scan the blocks in the reverse order to speed up the convergence. */ FOR_EACH_BB_REVERSE (bb) { if (bb->next_bb != EXIT_BLOCK_PTR) sbitmap_intersection_of_succs (hoist_vbeout[bb->index], hoist_vbein, bb->index); changed |= sbitmap_a_or_b_and_c_cg (hoist_vbein[bb->index], antloc[bb->index], hoist_vbeout[bb->index], transp[bb->index]); } passes++; } if (dump_file) fprintf (dump_file, "hoisting vbeinout computation: %d passes\n", passes); } /* Top level routine to do the dataflow analysis needed by code hoisting. */ static void compute_code_hoist_data (void) { compute_local_properties (transp, comp, antloc, &expr_hash_table); compute_transpout (); compute_code_hoist_vbeinout (); calculate_dominance_info (CDI_DOMINATORS); if (dump_file) fprintf (dump_file, "\n"); } /* Determine if the expression identified by EXPR_INDEX would reach BB unimpared if it was placed at the end of EXPR_BB. It's unclear exactly what Muchnick meant by "unimpared". It seems to me that the expression must either be computed or transparent in *every* block in the path(s) from EXPR_BB to BB. Any other definition would allow the expression to be hoisted out of loops, even if the expression wasn't a loop invariant. Contrast this to reachability for PRE where an expression is considered reachable if *any* path reaches instead of *all* paths. */ static int hoist_expr_reaches_here_p (basic_block expr_bb, int expr_index, basic_block bb, char *visited) { edge pred; edge_iterator ei; int visited_allocated_locally = 0; if (visited == NULL) { visited_allocated_locally = 1; visited = XCNEWVEC (char, last_basic_block); } FOR_EACH_EDGE (pred, ei, bb->preds) { basic_block pred_bb = pred->src; if (pred->src == ENTRY_BLOCK_PTR) break; else if (pred_bb == expr_bb) continue; else if (visited[pred_bb->index]) continue; /* Does this predecessor generate this expression? */ else if (TEST_BIT (comp[pred_bb->index], expr_index)) break; else if (! TEST_BIT (transp[pred_bb->index], expr_index)) break; /* Not killed. */ else { visited[pred_bb->index] = 1; if (! hoist_expr_reaches_here_p (expr_bb, expr_index, pred_bb, visited)) break; } } if (visited_allocated_locally) free (visited); return (pred == NULL); } /* Actually perform code hoisting. */ static int hoist_code (void) { basic_block bb, dominated; VEC (basic_block, heap) *domby; unsigned int i,j; struct expr **index_map; struct expr *expr; int changed = 0; sbitmap_vector_zero (hoist_exprs, last_basic_block); /* Compute a mapping from expression number (`bitmap_index') to hash table entry. */ index_map = XCNEWVEC (struct expr *, expr_hash_table.n_elems); for (i = 0; i < expr_hash_table.size; i++) for (expr = expr_hash_table.table[i]; expr != NULL; expr = expr->next_same_hash) index_map[expr->bitmap_index] = expr; /* Walk over each basic block looking for potentially hoistable expressions, nothing gets hoisted from the entry block. */ FOR_EACH_BB (bb) { int found = 0; int insn_inserted_p; domby = get_dominated_by (CDI_DOMINATORS, bb); /* Examine each expression that is very busy at the exit of this block. These are the potentially hoistable expressions. */ for (i = 0; i < hoist_vbeout[bb->index]->n_bits; i++) { int hoistable = 0; if (TEST_BIT (hoist_vbeout[bb->index], i) && TEST_BIT (transpout[bb->index], i)) { /* We've found a potentially hoistable expression, now we look at every block BB dominates to see if it computes the expression. */ for (j = 0; VEC_iterate (basic_block, domby, j, dominated); j++) { /* Ignore self dominance. */ if (bb == dominated) continue; /* We've found a dominated block, now see if it computes the busy expression and whether or not moving that expression to the "beginning" of that block is safe. */ if (!TEST_BIT (antloc[dominated->index], i)) continue; /* Note if the expression would reach the dominated block unimpared if it was placed at the end of BB. Keep track of how many times this expression is hoistable from a dominated block into BB. */ if (hoist_expr_reaches_here_p (bb, i, dominated, NULL)) hoistable++; } /* If we found more than one hoistable occurrence of this expression, then note it in the bitmap of expressions to hoist. It makes no sense to hoist things which are computed in only one BB, and doing so tends to pessimize register allocation. One could increase this value to try harder to avoid any possible code expansion due to register allocation issues; however experiments have shown that the vast majority of hoistable expressions are only movable from two successors, so raising this threshold is likely to nullify any benefit we get from code hoisting. */ if (hoistable > 1) { SET_BIT (hoist_exprs[bb->index], i); found = 1; } } } /* If we found nothing to hoist, then quit now. */ if (! found) { VEC_free (basic_block, heap, domby); continue; } /* Loop over all the hoistable expressions. */ for (i = 0; i < hoist_exprs[bb->index]->n_bits; i++) { /* We want to insert the expression into BB only once, so note when we've inserted it. */ insn_inserted_p = 0; /* These tests should be the same as the tests above. */ if (TEST_BIT (hoist_exprs[bb->index], i)) { /* We've found a potentially hoistable expression, now we look at every block BB dominates to see if it computes the expression. */ for (j = 0; VEC_iterate (basic_block, domby, j, dominated); j++) { /* Ignore self dominance. */ if (bb == dominated) continue; /* We've found a dominated block, now see if it computes the busy expression and whether or not moving that expression to the "beginning" of that block is safe. */ if (!TEST_BIT (antloc[dominated->index], i)) continue; /* The expression is computed in the dominated block and it would be safe to compute it at the start of the dominated block. Now we have to determine if the expression would reach the dominated block if it was placed at the end of BB. */ if (hoist_expr_reaches_here_p (bb, i, dominated, NULL)) { struct expr *expr = index_map[i]; struct occr *occr = expr->antic_occr; rtx insn; rtx set; /* Find the right occurrence of this expression. */ while (BLOCK_FOR_INSN (occr->insn) != dominated && occr) occr = occr->next; gcc_assert (occr); insn = occr->insn; set = single_set (insn); gcc_assert (set); /* Create a pseudo-reg to store the result of reaching expressions into. Get the mode for the new pseudo from the mode of the original destination pseudo. */ if (expr->reaching_reg == NULL) expr->reaching_reg = gen_reg_rtx_and_attrs (SET_DEST (set)); gcse_emit_move_after (expr->reaching_reg, SET_DEST (set), insn); delete_insn (insn); occr->deleted_p = 1; changed = 1; gcse_subst_count++; if (!insn_inserted_p) { insert_insn_end_basic_block (index_map[i], bb, 0); insn_inserted_p = 1; } } } } } VEC_free (basic_block, heap, domby); } free (index_map); return changed; } /* Top level routine to perform one code hoisting (aka unification) pass Return nonzero if a change was made. */ static int one_code_hoisting_pass (void) { int changed = 0; gcse_subst_count = 0; gcse_create_count = 0; /* Return if there's nothing to do, or it is too expensive. */ if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1 || is_too_expensive (_("GCSE disabled"))) return 0; /* We need alias. */ init_alias_analysis (); bytes_used = 0; gcc_obstack_init (&gcse_obstack); alloc_gcse_mem (); alloc_hash_table (&expr_hash_table, 0); compute_hash_table (&expr_hash_table); if (dump_file) dump_hash_table (dump_file, "Code Hosting Expressions", &expr_hash_table); if (expr_hash_table.n_elems > 0) { alloc_code_hoist_mem (last_basic_block, expr_hash_table.n_elems); compute_code_hoist_data (); changed = hoist_code (); free_code_hoist_mem (); } free_hash_table (&expr_hash_table); free_gcse_mem (); obstack_free (&gcse_obstack, NULL); /* We are finished with alias. */ end_alias_analysis (); if (dump_file) { fprintf (dump_file, "HOIST of %s, %d basic blocks, %d bytes needed, ", current_function_name (), n_basic_blocks, bytes_used); fprintf (dump_file, "%d substs, %d insns created\n", gcse_subst_count, gcse_create_count); } return changed; } /* Here we provide the things required to do store motion towards the exit. In order for this to be effective, gcse also needed to be taught how to move a load when it is kill only by a store to itself. int i; float a[10]; void foo(float scale) { for (i=0; i<10; i++) a[i] *= scale; } 'i' is both loaded and stored to in the loop. Normally, gcse cannot move the load out since its live around the loop, and stored at the bottom of the loop. The 'Load Motion' referred to and implemented in this file is an enhancement to gcse which when using edge based lcm, recognizes this situation and allows gcse to move the load out of the loop. Once gcse has hoisted the load, store motion can then push this load towards the exit, and we end up with no loads or stores of 'i' in the loop. */ static hashval_t pre_ldst_expr_hash (const void *p) { int do_not_record_p = 0; const struct ls_expr *const x = (const struct ls_expr *) p; return hash_rtx (x->pattern, GET_MODE (x->pattern), &do_not_record_p, NULL, false); } static int pre_ldst_expr_eq (const void *p1, const void *p2) { const struct ls_expr *const ptr1 = (const struct ls_expr *) p1, *const ptr2 = (const struct ls_expr *) p2; return expr_equiv_p (ptr1->pattern, ptr2->pattern); } /* This will search the ldst list for a matching expression. If it doesn't find one, we create one and initialize it. */ static struct ls_expr * ldst_entry (rtx x) { int do_not_record_p = 0; struct ls_expr * ptr; unsigned int hash; void **slot; struct ls_expr e; hash = hash_rtx (x, GET_MODE (x), &do_not_record_p, NULL, /*have_reg_qty=*/false); e.pattern = x; slot = htab_find_slot_with_hash (pre_ldst_table, &e, hash, INSERT); if (*slot) return (struct ls_expr *)*slot; ptr = XNEW (struct ls_expr); ptr->next = pre_ldst_mems; ptr->expr = NULL; ptr->pattern = x; ptr->pattern_regs = NULL_RTX; ptr->loads = NULL_RTX; ptr->stores = NULL_RTX; ptr->reaching_reg = NULL_RTX; ptr->invalid = 0; ptr->index = 0; ptr->hash_index = hash; pre_ldst_mems = ptr; *slot = ptr; return ptr; } /* Free up an individual ldst entry. */ static void free_ldst_entry (struct ls_expr * ptr) { free_INSN_LIST_list (& ptr->loads); free_INSN_LIST_list (& ptr->stores); free (ptr); } /* Free up all memory associated with the ldst list. */ static void free_ldst_mems (void) { if (pre_ldst_table) htab_delete (pre_ldst_table); pre_ldst_table = NULL; while (pre_ldst_mems) { struct ls_expr * tmp = pre_ldst_mems; pre_ldst_mems = pre_ldst_mems->next; free_ldst_entry (tmp); } pre_ldst_mems = NULL; } /* Dump debugging info about the ldst list. */ static void print_ldst_list (FILE * file) { struct ls_expr * ptr; fprintf (file, "LDST list: \n"); for (ptr = first_ls_expr (); ptr != NULL; ptr = next_ls_expr (ptr)) { fprintf (file, " Pattern (%3d): ", ptr->index); print_rtl (file, ptr->pattern); fprintf (file, "\n Loads : "); if (ptr->loads) print_rtl (file, ptr->loads); else fprintf (file, "(nil)"); fprintf (file, "\n Stores : "); if (ptr->stores) print_rtl (file, ptr->stores); else fprintf (file, "(nil)"); fprintf (file, "\n\n"); } fprintf (file, "\n"); } /* Returns 1 if X is in the list of ldst only expressions. */ static struct ls_expr * find_rtx_in_ldst (rtx x) { struct ls_expr e; void **slot; if (!pre_ldst_table) return NULL; e.pattern = x; slot = htab_find_slot (pre_ldst_table, &e, NO_INSERT); if (!slot || ((struct ls_expr *)*slot)->invalid) return NULL; return (struct ls_expr *) *slot; } /* Return first item in the list. */ static inline struct ls_expr * first_ls_expr (void) { return pre_ldst_mems; } /* Return the next item in the list after the specified one. */ static inline struct ls_expr * next_ls_expr (struct ls_expr * ptr) { return ptr->next; } /* Load Motion for loads which only kill themselves. */ /* Return true if x is a simple MEM operation, with no registers or side effects. These are the types of loads we consider for the ld_motion list, otherwise we let the usual aliasing take care of it. */ static int simple_mem (const_rtx x) { if (! MEM_P (x)) return 0; if (MEM_VOLATILE_P (x)) return 0; if (GET_MODE (x) == BLKmode) return 0; /* If we are handling exceptions, we must be careful with memory references that may trap. If we are not, the behavior is undefined, so we may just continue. */ if (flag_non_call_exceptions && may_trap_p (x)) return 0; if (side_effects_p (x)) return 0; /* Do not consider function arguments passed on stack. */ if (reg_mentioned_p (stack_pointer_rtx, x)) return 0; if (flag_float_store && FLOAT_MODE_P (GET_MODE (x))) return 0; return 1; } /* Make sure there isn't a buried reference in this pattern anywhere. If there is, invalidate the entry for it since we're not capable of fixing it up just yet.. We have to be sure we know about ALL loads since the aliasing code will allow all entries in the ld_motion list to not-alias itself. If we miss a load, we will get the wrong value since gcse might common it and we won't know to fix it up. */ static void invalidate_any_buried_refs (rtx x) { const char * fmt; int i, j; struct ls_expr * ptr; /* Invalidate it in the list. */ if (MEM_P (x) && simple_mem (x)) { ptr = ldst_entry (x); ptr->invalid = 1; } /* Recursively process the insn. */ fmt = GET_RTX_FORMAT (GET_CODE (x)); for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--) { if (fmt[i] == 'e') invalidate_any_buried_refs (XEXP (x, i)); else if (fmt[i] == 'E') for (j = XVECLEN (x, i) - 1; j >= 0; j--) invalidate_any_buried_refs (XVECEXP (x, i, j)); } } /* Find all the 'simple' MEMs which are used in LOADs and STORES. Simple being defined as MEM loads and stores to symbols, with no side effects and no registers in the expression. For a MEM destination, we also check that the insn is still valid if we replace the destination with a REG, as is done in update_ld_motion_stores. If there are any uses/defs which don't match this criteria, they are invalidated and trimmed out later. */ static void compute_ld_motion_mems (void) { struct ls_expr * ptr; basic_block bb; rtx insn; pre_ldst_mems = NULL; pre_ldst_table = htab_create (13, pre_ldst_expr_hash, pre_ldst_expr_eq, NULL); FOR_EACH_BB (bb) { FOR_BB_INSNS (bb, insn) { if (NONDEBUG_INSN_P (insn)) { if (GET_CODE (PATTERN (insn)) == SET) { rtx src = SET_SRC (PATTERN (insn)); rtx dest = SET_DEST (PATTERN (insn)); /* Check for a simple LOAD... */ if (MEM_P (src) && simple_mem (src)) { ptr = ldst_entry (src); if (REG_P (dest)) ptr->loads = alloc_INSN_LIST (insn, ptr->loads); else ptr->invalid = 1; } else { /* Make sure there isn't a buried load somewhere. */ invalidate_any_buried_refs (src); } /* Check for stores. Don't worry about aliased ones, they will block any movement we might do later. We only care about this exact pattern since those are the only circumstance that we will ignore the aliasing info. */ if (MEM_P (dest) && simple_mem (dest)) { ptr = ldst_entry (dest); if (! MEM_P (src) && GET_CODE (src) != ASM_OPERANDS /* Check for REG manually since want_to_gcse_p returns 0 for all REGs. */ && can_assign_to_reg_without_clobbers_p (src)) ptr->stores = alloc_INSN_LIST (insn, ptr->stores); else ptr->invalid = 1; } } else invalidate_any_buried_refs (PATTERN (insn)); } } } } /* Remove any references that have been either invalidated or are not in the expression list for pre gcse. */ static void trim_ld_motion_mems (void) { struct ls_expr * * last = & pre_ldst_mems; struct ls_expr * ptr = pre_ldst_mems; while (ptr != NULL) { struct expr * expr; /* Delete if entry has been made invalid. */ if (! ptr->invalid) { /* Delete if we cannot find this mem in the expression list. */ unsigned int hash = ptr->hash_index % expr_hash_table.size; for (expr = expr_hash_table.table[hash]; expr != NULL; expr = expr->next_same_hash) if (expr_equiv_p (expr->expr, ptr->pattern)) break; } else expr = (struct expr *) 0; if (expr) { /* Set the expression field if we are keeping it. */ ptr->expr = expr; last = & ptr->next; ptr = ptr->next; } else { *last = ptr->next; htab_remove_elt_with_hash (pre_ldst_table, ptr, ptr->hash_index); free_ldst_entry (ptr); ptr = * last; } } /* Show the world what we've found. */ if (dump_file && pre_ldst_mems != NULL) print_ldst_list (dump_file); } /* This routine will take an expression which we are replacing with a reaching register, and update any stores that are needed if that expression is in the ld_motion list. Stores are updated by copying their SRC to the reaching register, and then storing the reaching register into the store location. These keeps the correct value in the reaching register for the loads. */ static void update_ld_motion_stores (struct expr * expr) { struct ls_expr * mem_ptr; if ((mem_ptr = find_rtx_in_ldst (expr->expr))) { /* We can try to find just the REACHED stores, but is shouldn't matter to set the reaching reg everywhere... some might be dead and should be eliminated later. */ /* We replace (set mem expr) with (set reg expr) (set mem reg) where reg is the reaching reg used in the load. We checked in compute_ld_motion_mems that we can replace (set mem expr) with (set reg expr) in that insn. */ rtx list = mem_ptr->stores; for ( ; list != NULL_RTX; list = XEXP (list, 1)) { rtx insn = XEXP (list, 0); rtx pat = PATTERN (insn); rtx src = SET_SRC (pat); rtx reg = expr->reaching_reg; rtx copy; /* If we've already copied it, continue. */ if (expr->reaching_reg == src) continue; if (dump_file) { fprintf (dump_file, "PRE: store updated with reaching reg "); print_rtl (dump_file, expr->reaching_reg); fprintf (dump_file, ":\n "); print_inline_rtx (dump_file, insn, 8); fprintf (dump_file, "\n"); } copy = gen_move_insn (reg, copy_rtx (SET_SRC (pat))); emit_insn_before (copy, insn); SET_SRC (pat) = reg; df_insn_rescan (insn); /* un-recognize this pattern since it's probably different now. */ INSN_CODE (insn) = -1; gcse_create_count++; } } } /* Return true if the graph is too expensive to optimize. PASS is the optimization about to be performed. */ static bool is_too_expensive (const char *pass) { /* Trying to perform global optimizations on flow graphs which have a high connectivity will take a long time and is unlikely to be particularly useful. In normal circumstances a cfg should have about twice as many edges as blocks. But we do not want to punish small functions which have a couple switch statements. Rather than simply threshold the number of blocks, uses something with a more graceful degradation. */ if (n_edges > 20000 + n_basic_blocks * 4) { warning (OPT_Wdisabled_optimization, "%s: %d basic blocks and %d edges/basic block", pass, n_basic_blocks, n_edges / n_basic_blocks); return true; } /* If allocating memory for the cprop bitmap would take up too much storage it's better just to disable the optimization. */ if ((n_basic_blocks * SBITMAP_SET_SIZE (max_reg_num ()) * sizeof (SBITMAP_ELT_TYPE)) > MAX_GCSE_MEMORY) { warning (OPT_Wdisabled_optimization, "%s: %d basic blocks and %d registers", pass, n_basic_blocks, max_reg_num ()); return true; } return false; } /* Main function for the CPROP pass. */ static int one_cprop_pass (void) { int changed = 0; /* Return if there's nothing to do, or it is too expensive. */ if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1 || is_too_expensive (_ ("const/copy propagation disabled"))) return 0; global_const_prop_count = local_const_prop_count = 0; global_copy_prop_count = local_copy_prop_count = 0; bytes_used = 0; gcc_obstack_init (&gcse_obstack); alloc_gcse_mem (); /* Do a local const/copy propagation pass first. The global pass only handles global opportunities. If the local pass changes something, remove any unreachable blocks because the CPROP global dataflow analysis may get into infinite loops for CFGs with unreachable blocks. FIXME: This local pass should not be necessary after CSE (but for some reason it still is). It is also (proven) not necessary to run the local pass right after FWPWOP. FIXME: The global analysis would not get into infinite loops if it would use the DF solver (via df_simple_dataflow) instead of the solver implemented in this file. */ if (local_cprop_pass ()) { delete_unreachable_blocks (); df_analyze (); } /* Determine implicit sets. */ implicit_sets = XCNEWVEC (rtx, last_basic_block); find_implicit_sets (); alloc_hash_table (&set_hash_table, 1); compute_hash_table (&set_hash_table); /* Free implicit_sets before peak usage. */ free (implicit_sets); implicit_sets = NULL; if (dump_file) dump_hash_table (dump_file, "SET", &set_hash_table); if (set_hash_table.n_elems > 0) { basic_block bb; rtx insn; alloc_cprop_mem (last_basic_block, set_hash_table.n_elems); compute_cprop_data (); FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb->next_bb, EXIT_BLOCK_PTR, next_bb) { /* Reset tables used to keep track of what's still valid [since the start of the block]. */ reset_opr_set_tables (); FOR_BB_INSNS (bb, insn) if (INSN_P (insn)) { changed |= cprop_insn (insn); /* Keep track of everything modified by this insn. */ /* ??? Need to be careful w.r.t. mods done to INSN. Don't call mark_oprs_set if we turned the insn into a NOTE. */ if (! NOTE_P (insn)) mark_oprs_set (insn); } } changed |= bypass_conditional_jumps (); free_cprop_mem (); } free_hash_table (&set_hash_table); free_gcse_mem (); obstack_free (&gcse_obstack, NULL); if (dump_file) { fprintf (dump_file, "CPROP of %s, %d basic blocks, %d bytes needed, ", current_function_name (), n_basic_blocks, bytes_used); fprintf (dump_file, "%d local const props, %d local copy props, ", local_const_prop_count, local_copy_prop_count); fprintf (dump_file, "%d global const props, %d global copy props\n\n", global_const_prop_count, global_copy_prop_count); } return changed; } /* All the passes implemented in this file. Each pass has its own gate and execute function, and at the end of the file a pass definition for passes.c. We do not construct an accurate cfg in functions which call setjmp, so none of these passes runs if the function calls setjmp. FIXME: Should just handle setjmp via REG_SETJMP notes. */ static bool gate_rtl_cprop (void) { return optimize > 0 && flag_gcse && !cfun->calls_setjmp && dbg_cnt (cprop); } static unsigned int execute_rtl_cprop (void) { delete_unreachable_blocks (); df_set_flags (DF_LR_RUN_DCE); df_analyze (); flag_rerun_cse_after_global_opts |= one_cprop_pass (); return 0; } static bool gate_rtl_pre (void) { return optimize > 0 && flag_gcse && !cfun->calls_setjmp && optimize_function_for_speed_p (cfun) && dbg_cnt (pre); } static unsigned int execute_rtl_pre (void) { delete_unreachable_blocks (); df_analyze (); flag_rerun_cse_after_global_opts |= one_pre_gcse_pass (); return 0; } static bool gate_rtl_hoist (void) { return optimize > 0 && flag_gcse && !cfun->calls_setjmp /* It does not make sense to run code hoisting unless we are optimizing for code size -- it rarely makes programs faster, and can make then bigger if we did PRE (when optimizing for space, we don't run PRE). */ && optimize_function_for_size_p (cfun) && dbg_cnt (hoist); } static unsigned int execute_rtl_hoist (void) { delete_unreachable_blocks (); df_analyze (); flag_rerun_cse_after_global_opts |= one_code_hoisting_pass (); return 0; } struct rtl_opt_pass pass_rtl_cprop = { { RTL_PASS, "cprop", /* name */ gate_rtl_cprop, /* gate */ execute_rtl_cprop, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_CPROP, /* tv_id */ PROP_cfglayout, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_df_finish | TODO_verify_rtl_sharing | TODO_dump_func | TODO_verify_flow | TODO_ggc_collect /* todo_flags_finish */ } }; struct rtl_opt_pass pass_rtl_pre = { { RTL_PASS, "rtl pre", /* name */ gate_rtl_pre, /* gate */ execute_rtl_pre, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_PRE, /* tv_id */ PROP_cfglayout, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_df_finish | TODO_verify_rtl_sharing | TODO_dump_func | TODO_verify_flow | TODO_ggc_collect /* todo_flags_finish */ } }; struct rtl_opt_pass pass_rtl_hoist = { { RTL_PASS, "hoist", /* name */ gate_rtl_hoist, /* gate */ execute_rtl_hoist, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_HOIST, /* tv_id */ PROP_cfglayout, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ TODO_df_finish | TODO_verify_rtl_sharing | TODO_dump_func | TODO_verify_flow | TODO_ggc_collect /* todo_flags_finish */ } }; #include "gt-gcse.h"
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