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/* Callgraph based analysis of static variables. Copyright (C) 2004, 2005, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. Contributed by Kenneth Zadeck <zadeck@naturalbridge.com> 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/>. */ /* This file marks functions as being either const (TREE_READONLY) or pure (DECL_PURE_P). It can also set a variant of these that are allowed to loop indefinitely (DECL_LOOPING_CONST_PURE_P). This must be run after inlining decisions have been made since otherwise, the local sets will not contain information that is consistent with post inlined state. The global sets are not prone to this problem since they are by definition transitive. */ /* The code in this module is called by the ipa pass manager. It should be one of the later passes since it's information is used by the rest of the compilation. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "tree.h" #include "tree-flow.h" #include "tree-inline.h" #include "tree-pass.h" #include "langhooks.h" #include "pointer-set.h" #include "ggc.h" #include "ipa-utils.h" #include "gimple.h" #include "cgraph.h" #include "output.h" #include "flags.h" #include "timevar.h" #include "diagnostic.h" #include "gimple-pretty-print.h" #include "langhooks.h" #include "target.h" #include "lto-streamer.h" #include "data-streamer.h" #include "tree-streamer.h" #include "cfgloop.h" #include "tree-scalar-evolution.h" #include "intl.h" #include "opts.h" static struct pointer_set_t *visited_nodes; /* Lattice values for const and pure functions. Everything starts out being const, then may drop to pure and then neither depending on what is found. */ enum pure_const_state_e { IPA_CONST, IPA_PURE, IPA_NEITHER }; const char *pure_const_names[3] = {"const", "pure", "neither"}; /* Holder for the const_state. There is one of these per function decl. */ struct funct_state_d { /* See above. */ enum pure_const_state_e pure_const_state; /* What user set here; we can be always sure about this. */ enum pure_const_state_e state_previously_known; bool looping_previously_known; /* True if the function could possibly infinite loop. There are a lot of ways that this could be determined. We are pretty conservative here. While it is possible to cse pure and const calls, it is not legal to have dce get rid of the call if there is a possibility that the call could infinite loop since this is a behavioral change. */ bool looping; bool can_throw; }; /* State used when we know nothing about function. */ static struct funct_state_d varying_state = { IPA_NEITHER, IPA_NEITHER, true, true, true }; typedef struct funct_state_d * funct_state; /* The storage of the funct_state is abstracted because there is the possibility that it may be desirable to move this to the cgraph local info. */ /* Array, indexed by cgraph node uid, of function states. */ DEF_VEC_P (funct_state); DEF_VEC_ALLOC_P (funct_state, heap); static VEC (funct_state, heap) *funct_state_vec; /* Holders of ipa cgraph hooks: */ static struct cgraph_node_hook_list *function_insertion_hook_holder; static struct cgraph_2node_hook_list *node_duplication_hook_holder; static struct cgraph_node_hook_list *node_removal_hook_holder; /* Try to guess if function body will always be visible to compiler when compiling the call and whether compiler will be able to propagate the information by itself. */ static bool function_always_visible_to_compiler_p (tree decl) { return (!TREE_PUBLIC (decl) || DECL_DECLARED_INLINE_P (decl)); } /* Emit suggestion about attribute ATTRIB_NAME for DECL. KNOWN_FINITE is true if the function is known to be finite. The diagnostic is controlled by OPTION. WARNED_ABOUT is a pointer_set unique for OPTION, this function may initialize it and it is always returned by the function. */ static struct pointer_set_t * suggest_attribute (int option, tree decl, bool known_finite, struct pointer_set_t *warned_about, const char * attrib_name) { if (!option_enabled (option, &global_options)) return warned_about; if (TREE_THIS_VOLATILE (decl) || (known_finite && function_always_visible_to_compiler_p (decl))) return warned_about; if (!warned_about) warned_about = pointer_set_create (); if (pointer_set_contains (warned_about, decl)) return warned_about; pointer_set_insert (warned_about, decl); warning_at (DECL_SOURCE_LOCATION (decl), option, known_finite ? _("function might be candidate for attribute %<%s%>") : _("function might be candidate for attribute %<%s%>" " if it is known to return normally"), attrib_name); return warned_about; } /* Emit suggestion about __attribute_((pure)) for DECL. KNOWN_FINITE is true if the function is known to be finite. */ static void warn_function_pure (tree decl, bool known_finite) { static struct pointer_set_t *warned_about; warned_about = suggest_attribute (OPT_Wsuggest_attribute_pure, decl, known_finite, warned_about, "pure"); } /* Emit suggestion about __attribute_((const)) for DECL. KNOWN_FINITE is true if the function is known to be finite. */ static void warn_function_const (tree decl, bool known_finite) { static struct pointer_set_t *warned_about; warned_about = suggest_attribute (OPT_Wsuggest_attribute_const, decl, known_finite, warned_about, "const"); } void warn_function_noreturn (tree decl) { static struct pointer_set_t *warned_about; if (!lang_hooks.missing_noreturn_ok_p (decl)) warned_about = suggest_attribute (OPT_Wsuggest_attribute_noreturn, decl, true, warned_about, "noreturn"); } /* Init the function state. */ static void finish_state (void) { free (funct_state_vec); } /* Return true if we have a function state for NODE. */ static inline bool has_function_state (struct cgraph_node *node) { if (!funct_state_vec || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid) return false; return VEC_index (funct_state, funct_state_vec, node->uid) != NULL; } /* Return the function state from NODE. */ static inline funct_state get_function_state (struct cgraph_node *node) { if (!funct_state_vec || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid || !VEC_index (funct_state, funct_state_vec, node->uid)) /* We might want to put correct previously_known state into varying. */ return &varying_state; return VEC_index (funct_state, funct_state_vec, node->uid); } /* Set the function state S for NODE. */ static inline void set_function_state (struct cgraph_node *node, funct_state s) { if (!funct_state_vec || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid) VEC_safe_grow_cleared (funct_state, heap, funct_state_vec, node->uid + 1); VEC_replace (funct_state, funct_state_vec, node->uid, s); } /* Check to see if the use (or definition when CHECKING_WRITE is true) variable T is legal in a function that is either pure or const. */ static inline void check_decl (funct_state local, tree t, bool checking_write, bool ipa) { /* Do not want to do anything with volatile except mark any function that uses one to be not const or pure. */ if (TREE_THIS_VOLATILE (t)) { local->pure_const_state = IPA_NEITHER; if (dump_file) fprintf (dump_file, " Volatile operand is not const/pure"); return; } /* Do not care about a local automatic that is not static. */ if (!TREE_STATIC (t) && !DECL_EXTERNAL (t)) return; /* If the variable has the "used" attribute, treat it as if it had a been touched by the devil. */ if (DECL_PRESERVE_P (t)) { local->pure_const_state = IPA_NEITHER; if (dump_file) fprintf (dump_file, " Used static/global variable is not const/pure\n"); return; } /* In IPA mode we are not interested in checking actual loads and stores; they will be processed at propagation time using ipa_ref. */ if (ipa) return; /* Since we have dealt with the locals and params cases above, if we are CHECKING_WRITE, this cannot be a pure or constant function. */ if (checking_write) { local->pure_const_state = IPA_NEITHER; if (dump_file) fprintf (dump_file, " static/global memory write is not const/pure\n"); return; } if (DECL_EXTERNAL (t) || TREE_PUBLIC (t)) { /* Readonly reads are safe. */ if (TREE_READONLY (t) && !TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (t))) return; /* Read of a constant, do not change the function state. */ else { if (dump_file) fprintf (dump_file, " global memory read is not const\n"); /* Just a regular read. */ if (local->pure_const_state == IPA_CONST) local->pure_const_state = IPA_PURE; } } else { /* Compilation level statics can be read if they are readonly variables. */ if (TREE_READONLY (t)) return; if (dump_file) fprintf (dump_file, " static memory read is not const\n"); /* Just a regular read. */ if (local->pure_const_state == IPA_CONST) local->pure_const_state = IPA_PURE; } } /* Check to see if the use (or definition when CHECKING_WRITE is true) variable T is legal in a function that is either pure or const. */ static inline void check_op (funct_state local, tree t, bool checking_write) { t = get_base_address (t); if (t && TREE_THIS_VOLATILE (t)) { local->pure_const_state = IPA_NEITHER; if (dump_file) fprintf (dump_file, " Volatile indirect ref is not const/pure\n"); return; } else if (t && (INDIRECT_REF_P (t) || TREE_CODE (t) == MEM_REF) && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME && !ptr_deref_may_alias_global_p (TREE_OPERAND (t, 0))) { if (dump_file) fprintf (dump_file, " Indirect ref to local memory is OK\n"); return; } else if (checking_write) { local->pure_const_state = IPA_NEITHER; if (dump_file) fprintf (dump_file, " Indirect ref write is not const/pure\n"); return; } else { if (dump_file) fprintf (dump_file, " Indirect ref read is not const\n"); if (local->pure_const_state == IPA_CONST) local->pure_const_state = IPA_PURE; } } /* compute state based on ECF FLAGS and store to STATE and LOOPING. */ static void state_from_flags (enum pure_const_state_e *state, bool *looping, int flags, bool cannot_lead_to_return) { *looping = false; if (flags & ECF_LOOPING_CONST_OR_PURE) { *looping = true; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " looping"); } if (flags & ECF_CONST) { *state = IPA_CONST; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " const\n"); } else if (flags & ECF_PURE) { *state = IPA_PURE; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " pure\n"); } else if (cannot_lead_to_return) { *state = IPA_PURE; *looping = true; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " ignoring side effects->pure looping\n"); } else { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " neihter\n"); *state = IPA_NEITHER; *looping = true; } } /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store into STATE and LOOPING better of the two variants. Be sure to merge looping correctly. IPA_NEITHER functions have looping 0 even if they don't have to return. */ static inline void better_state (enum pure_const_state_e *state, bool *looping, enum pure_const_state_e state2, bool looping2) { if (state2 < *state) { if (*state == IPA_NEITHER) *looping = looping2; else *looping = MIN (*looping, looping2); } else if (state2 != IPA_NEITHER) *looping = MIN (*looping, looping2); } /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store into STATE and LOOPING worse of the two variants. */ static inline void worse_state (enum pure_const_state_e *state, bool *looping, enum pure_const_state_e state2, bool looping2) { *state = MAX (*state, state2); *looping = MAX (*looping, looping2); } /* Recognize special cases of builtins that are by themselves not pure or const but function using them is. */ static bool special_builtin_state (enum pure_const_state_e *state, bool *looping, tree callee) { if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL) switch (DECL_FUNCTION_CODE (callee)) { case BUILT_IN_RETURN: case BUILT_IN_UNREACHABLE: case BUILT_IN_ALLOCA: case BUILT_IN_ALLOCA_WITH_ALIGN: case BUILT_IN_STACK_SAVE: case BUILT_IN_STACK_RESTORE: case BUILT_IN_EH_POINTER: case BUILT_IN_EH_FILTER: case BUILT_IN_UNWIND_RESUME: case BUILT_IN_CXA_END_CLEANUP: case BUILT_IN_EH_COPY_VALUES: case BUILT_IN_FRAME_ADDRESS: case BUILT_IN_APPLY: case BUILT_IN_APPLY_ARGS: *looping = false; *state = IPA_CONST; return true; case BUILT_IN_PREFETCH: *looping = true; *state = IPA_CONST; return true; } return false; } /* Check the parameters of a function call to CALL_EXPR to see if there are any references in the parameters that are not allowed for pure or const functions. Also check to see if this is either an indirect call, a call outside the compilation unit, or has special attributes that may also effect the purity. The CALL_EXPR node for the entire call expression. */ static void check_call (funct_state local, gimple call, bool ipa) { int flags = gimple_call_flags (call); tree callee_t = gimple_call_fndecl (call); bool possibly_throws = stmt_could_throw_p (call); bool possibly_throws_externally = (possibly_throws && stmt_can_throw_external (call)); if (possibly_throws) { unsigned int i; for (i = 0; i < gimple_num_ops (call); i++) if (gimple_op (call, i) && tree_could_throw_p (gimple_op (call, i))) { if (possibly_throws && cfun->can_throw_non_call_exceptions) { if (dump_file) fprintf (dump_file, " operand can throw; looping\n"); local->looping = true; } if (possibly_throws_externally) { if (dump_file) fprintf (dump_file, " operand can throw externally\n"); local->can_throw = true; } } } /* The const and pure flags are set by a variety of places in the compiler (including here). If someone has already set the flags for the callee, (such as for some of the builtins) we will use them, otherwise we will compute our own information. Const and pure functions have less clobber effects than other functions so we process these first. Otherwise if it is a call outside the compilation unit or an indirect call we punt. This leaves local calls which will be processed by following the call graph. */ if (callee_t) { enum pure_const_state_e call_state; bool call_looping; if (special_builtin_state (&call_state, &call_looping, callee_t)) { worse_state (&local->pure_const_state, &local->looping, call_state, call_looping); return; } /* When bad things happen to bad functions, they cannot be const or pure. */ if (setjmp_call_p (callee_t)) { if (dump_file) fprintf (dump_file, " setjmp is not const/pure\n"); local->looping = true; local->pure_const_state = IPA_NEITHER; } if (DECL_BUILT_IN_CLASS (callee_t) == BUILT_IN_NORMAL) switch (DECL_FUNCTION_CODE (callee_t)) { case BUILT_IN_LONGJMP: case BUILT_IN_NONLOCAL_GOTO: if (dump_file) fprintf (dump_file, " longjmp and nonlocal goto is not const/pure\n"); local->pure_const_state = IPA_NEITHER; local->looping = true; break; default: break; } } /* When not in IPA mode, we can still handle self recursion. */ if (!ipa && callee_t == current_function_decl) { if (dump_file) fprintf (dump_file, " Recursive call can loop.\n"); local->looping = true; } /* Either callee is unknown or we are doing local analysis. Look to see if there are any bits available for the callee (such as by declaration or because it is builtin) and process solely on the basis of those bits. */ else if (!ipa) { enum pure_const_state_e call_state; bool call_looping; if (possibly_throws && cfun->can_throw_non_call_exceptions) { if (dump_file) fprintf (dump_file, " can throw; looping\n"); local->looping = true; } if (possibly_throws_externally) { if (dump_file) { fprintf (dump_file, " can throw externally to lp %i\n", lookup_stmt_eh_lp (call)); if (callee_t) fprintf (dump_file, " callee:%s\n", IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (callee_t))); } local->can_throw = true; } if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " checking flags for call:"); state_from_flags (&call_state, &call_looping, flags, ((flags & (ECF_NORETURN | ECF_NOTHROW)) == (ECF_NORETURN | ECF_NOTHROW)) || (!flag_exceptions && (flags & ECF_NORETURN))); worse_state (&local->pure_const_state, &local->looping, call_state, call_looping); } /* Direct functions calls are handled by IPA propagation. */ } /* Wrapper around check_decl for loads in local more. */ static bool check_load (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data) { if (DECL_P (op)) check_decl ((funct_state)data, op, false, false); else check_op ((funct_state)data, op, false); return false; } /* Wrapper around check_decl for stores in local more. */ static bool check_store (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data) { if (DECL_P (op)) check_decl ((funct_state)data, op, true, false); else check_op ((funct_state)data, op, true); return false; } /* Wrapper around check_decl for loads in ipa mode. */ static bool check_ipa_load (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data) { if (DECL_P (op)) check_decl ((funct_state)data, op, false, true); else check_op ((funct_state)data, op, false); return false; } /* Wrapper around check_decl for stores in ipa mode. */ static bool check_ipa_store (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data) { if (DECL_P (op)) check_decl ((funct_state)data, op, true, true); else check_op ((funct_state)data, op, true); return false; } /* Look into pointer pointed to by GSIP and figure out what interesting side effects it has. */ static void check_stmt (gimple_stmt_iterator *gsip, funct_state local, bool ipa) { gimple stmt = gsi_stmt (*gsip); if (is_gimple_debug (stmt)) return; if (dump_file) { fprintf (dump_file, " scanning: "); print_gimple_stmt (dump_file, stmt, 0, 0); } if (gimple_has_volatile_ops (stmt) && !gimple_clobber_p (stmt)) { local->pure_const_state = IPA_NEITHER; if (dump_file) fprintf (dump_file, " Volatile stmt is not const/pure\n"); } /* Look for loads and stores. */ walk_stmt_load_store_ops (stmt, local, ipa ? check_ipa_load : check_load, ipa ? check_ipa_store : check_store); if (gimple_code (stmt) != GIMPLE_CALL && stmt_could_throw_p (stmt)) { if (cfun->can_throw_non_call_exceptions) { if (dump_file) fprintf (dump_file, " can throw; looping"); local->looping = true; } if (stmt_can_throw_external (stmt)) { if (dump_file) fprintf (dump_file, " can throw externally"); local->can_throw = true; } } switch (gimple_code (stmt)) { case GIMPLE_CALL: check_call (local, stmt, ipa); break; case GIMPLE_LABEL: if (DECL_NONLOCAL (gimple_label_label (stmt))) /* Target of long jump. */ { if (dump_file) fprintf (dump_file, " nonlocal label is not const/pure"); local->pure_const_state = IPA_NEITHER; } break; case GIMPLE_ASM: if (gimple_asm_clobbers_memory_p (stmt)) { if (dump_file) fprintf (dump_file, " memory asm clobber is not const/pure"); /* Abandon all hope, ye who enter here. */ local->pure_const_state = IPA_NEITHER; } if (gimple_asm_volatile_p (stmt)) { if (dump_file) fprintf (dump_file, " volatile is not const/pure"); /* Abandon all hope, ye who enter here. */ local->pure_const_state = IPA_NEITHER; local->looping = true; } return; default: break; } } /* This is the main routine for finding the reference patterns for global variables within a function FN. */ static funct_state analyze_function (struct cgraph_node *fn, bool ipa) { tree decl = fn->decl; tree old_decl = current_function_decl; funct_state l; basic_block this_block; l = XCNEW (struct funct_state_d); l->pure_const_state = IPA_CONST; l->state_previously_known = IPA_NEITHER; l->looping_previously_known = true; l->looping = false; l->can_throw = false; state_from_flags (&l->state_previously_known, &l->looping_previously_known, flags_from_decl_or_type (fn->decl), cgraph_node_cannot_return (fn)); if (fn->thunk.thunk_p || fn->alias) { /* Thunk gets propagated through, so nothing interesting happens. */ gcc_assert (ipa); return l; } if (dump_file) { fprintf (dump_file, "\n\n local analysis of %s\n ", cgraph_node_name (fn)); } push_cfun (DECL_STRUCT_FUNCTION (decl)); current_function_decl = decl; FOR_EACH_BB (this_block) { gimple_stmt_iterator gsi; struct walk_stmt_info wi; memset (&wi, 0, sizeof(wi)); for (gsi = gsi_start_bb (this_block); !gsi_end_p (gsi); gsi_next (&gsi)) { check_stmt (&gsi, l, ipa); if (l->pure_const_state == IPA_NEITHER && l->looping && l->can_throw) goto end; } } end: if (l->pure_const_state != IPA_NEITHER) { /* Const functions cannot have back edges (an indication of possible infinite loop side effect. */ if (mark_dfs_back_edges ()) { /* Preheaders are needed for SCEV to work. Simple latches and recorded exits improve chances that loop will proved to be finite in testcases such as in loop-15.c and loop-24.c */ loop_optimizer_init (LOOPS_NORMAL | LOOPS_HAVE_RECORDED_EXITS); if (dump_file && (dump_flags & TDF_DETAILS)) flow_loops_dump (dump_file, NULL, 0); if (mark_irreducible_loops ()) { if (dump_file) fprintf (dump_file, " has irreducible loops\n"); l->looping = true; } else { loop_iterator li; struct loop *loop; scev_initialize (); FOR_EACH_LOOP (li, loop, 0) if (!finite_loop_p (loop)) { if (dump_file) fprintf (dump_file, " can not prove finiteness of loop %i\n", loop->num); l->looping =true; break; } scev_finalize (); } loop_optimizer_finalize (); } } if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " checking previously known:"); better_state (&l->pure_const_state, &l->looping, l->state_previously_known, l->looping_previously_known); if (TREE_NOTHROW (decl)) l->can_throw = false; pop_cfun (); current_function_decl = old_decl; if (dump_file) { if (l->looping) fprintf (dump_file, "Function is locally looping.\n"); if (l->can_throw) fprintf (dump_file, "Function is locally throwing.\n"); if (l->pure_const_state == IPA_CONST) fprintf (dump_file, "Function is locally const.\n"); if (l->pure_const_state == IPA_PURE) fprintf (dump_file, "Function is locally pure.\n"); } return l; } /* Called when new function is inserted to callgraph late. */ static void add_new_function (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED) { if (cgraph_function_body_availability (node) < AVAIL_OVERWRITABLE) return; /* There are some shared nodes, in particular the initializers on static declarations. We do not need to scan them more than once since all we would be interested in are the addressof operations. */ visited_nodes = pointer_set_create (); if (cgraph_function_body_availability (node) > AVAIL_OVERWRITABLE) set_function_state (node, analyze_function (node, true)); pointer_set_destroy (visited_nodes); visited_nodes = NULL; } /* Called when new clone is inserted to callgraph late. */ static void duplicate_node_data (struct cgraph_node *src, struct cgraph_node *dst, void *data ATTRIBUTE_UNUSED) { if (has_function_state (src)) { funct_state l = XNEW (struct funct_state_d); gcc_assert (!has_function_state (dst)); memcpy (l, get_function_state (src), sizeof (*l)); set_function_state (dst, l); } } /* Called when new clone is inserted to callgraph late. */ static void remove_node_data (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED) { if (has_function_state (node)) { funct_state l = get_function_state (node); if (l != &varying_state) free (l); set_function_state (node, NULL); } } static void register_hooks (void) { static bool init_p = false; if (init_p) return; init_p = true; node_removal_hook_holder = cgraph_add_node_removal_hook (&remove_node_data, NULL); node_duplication_hook_holder = cgraph_add_node_duplication_hook (&duplicate_node_data, NULL); function_insertion_hook_holder = cgraph_add_function_insertion_hook (&add_new_function, NULL); } /* Analyze each function in the cgraph to see if it is locally PURE or CONST. */ static void generate_summary (void) { struct cgraph_node *node; register_hooks (); /* There are some shared nodes, in particular the initializers on static declarations. We do not need to scan them more than once since all we would be interested in are the addressof operations. */ visited_nodes = pointer_set_create (); /* Process all of the functions. We process AVAIL_OVERWRITABLE functions. We can not use the results by default, but the info can be used at LTO with -fwhole-program or when function got cloned and the clone is AVAILABLE. */ for (node = cgraph_nodes; node; node = node->next) if (cgraph_function_body_availability (node) >= AVAIL_OVERWRITABLE) set_function_state (node, analyze_function (node, true)); pointer_set_destroy (visited_nodes); visited_nodes = NULL; } /* Serialize the ipa info for lto. */ static void pure_const_write_summary (cgraph_node_set set, varpool_node_set vset ATTRIBUTE_UNUSED) { struct cgraph_node *node; struct lto_simple_output_block *ob = lto_create_simple_output_block (LTO_section_ipa_pure_const); unsigned int count = 0; cgraph_node_set_iterator csi; for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi)) { node = csi_node (csi); if (node->analyzed && has_function_state (node)) count++; } streamer_write_uhwi_stream (ob->main_stream, count); /* Process all of the functions. */ for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi)) { node = csi_node (csi); if (node->analyzed && has_function_state (node)) { struct bitpack_d bp; funct_state fs; int node_ref; lto_cgraph_encoder_t encoder; fs = get_function_state (node); encoder = ob->decl_state->cgraph_node_encoder; node_ref = lto_cgraph_encoder_encode (encoder, node); streamer_write_uhwi_stream (ob->main_stream, node_ref); /* Note that flags will need to be read in the opposite order as we are pushing the bitflags into FLAGS. */ bp = bitpack_create (ob->main_stream); bp_pack_value (&bp, fs->pure_const_state, 2); bp_pack_value (&bp, fs->state_previously_known, 2); bp_pack_value (&bp, fs->looping_previously_known, 1); bp_pack_value (&bp, fs->looping, 1); bp_pack_value (&bp, fs->can_throw, 1); streamer_write_bitpack (&bp); } } lto_destroy_simple_output_block (ob); } /* Deserialize the ipa info for lto. */ static void pure_const_read_summary (void) { struct lto_file_decl_data **file_data_vec = lto_get_file_decl_data (); struct lto_file_decl_data *file_data; unsigned int j = 0; register_hooks (); while ((file_data = file_data_vec[j++])) { const char *data; size_t len; struct lto_input_block *ib = lto_create_simple_input_block (file_data, LTO_section_ipa_pure_const, &data, &len); if (ib) { unsigned int i; unsigned int count = streamer_read_uhwi (ib); for (i = 0; i < count; i++) { unsigned int index; struct cgraph_node *node; struct bitpack_d bp; funct_state fs; lto_cgraph_encoder_t encoder; fs = XCNEW (struct funct_state_d); index = streamer_read_uhwi (ib); encoder = file_data->cgraph_node_encoder; node = lto_cgraph_encoder_deref (encoder, index); set_function_state (node, fs); /* Note that the flags must be read in the opposite order in which they were written (the bitflags were pushed into FLAGS). */ bp = streamer_read_bitpack (ib); fs->pure_const_state = (enum pure_const_state_e) bp_unpack_value (&bp, 2); fs->state_previously_known = (enum pure_const_state_e) bp_unpack_value (&bp, 2); fs->looping_previously_known = bp_unpack_value (&bp, 1); fs->looping = bp_unpack_value (&bp, 1); fs->can_throw = bp_unpack_value (&bp, 1); if (dump_file) { int flags = flags_from_decl_or_type (node->decl); fprintf (dump_file, "Read info for %s/%i ", cgraph_node_name (node), node->uid); if (flags & ECF_CONST) fprintf (dump_file, " const"); if (flags & ECF_PURE) fprintf (dump_file, " pure"); if (flags & ECF_NOTHROW) fprintf (dump_file, " nothrow"); fprintf (dump_file, "\n pure const state: %s\n", pure_const_names[fs->pure_const_state]); fprintf (dump_file, " previously known state: %s\n", pure_const_names[fs->looping_previously_known]); if (fs->looping) fprintf (dump_file," function is locally looping\n"); if (fs->looping_previously_known) fprintf (dump_file," function is previously known looping\n"); if (fs->can_throw) fprintf (dump_file," function is locally throwing\n"); } } lto_destroy_simple_input_block (file_data, LTO_section_ipa_pure_const, ib, data, len); } } } static bool ignore_edge (struct cgraph_edge *e) { return (!e->can_throw_external); } /* Return true if NODE is self recursive function. ??? self recursive and indirectly recursive funcions should be the same, so this function seems unnecesary. */ static bool self_recursive_p (struct cgraph_node *node) { struct cgraph_edge *e; for (e = node->callees; e; e = e->next_callee) if (cgraph_function_node (e->callee, NULL) == node) return true; return false; } /* Produce transitive closure over the callgraph and compute pure/const attributes. */ static void propagate_pure_const (void) { struct cgraph_node *node; struct cgraph_node *w; struct cgraph_node **order = XCNEWVEC (struct cgraph_node *, cgraph_n_nodes); int order_pos; int i; struct ipa_dfs_info * w_info; order_pos = ipa_reduced_postorder (order, true, false, NULL); if (dump_file) { dump_cgraph (dump_file); ipa_print_order(dump_file, "reduced", order, order_pos); } /* Propagate the local information thru the call graph to produce the global information. All the nodes within a cycle will have the same info so we collapse cycles first. Then we can do the propagation in one pass from the leaves to the roots. */ for (i = 0; i < order_pos; i++ ) { enum pure_const_state_e pure_const_state = IPA_CONST; bool looping = false; int count = 0; node = order[i]; if (node->alias) continue; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Starting cycle\n"); /* Find the worst state for any node in the cycle. */ w = node; while (w && pure_const_state != IPA_NEITHER) { struct cgraph_edge *e; struct cgraph_edge *ie; int i; struct ipa_ref *ref; funct_state w_l = get_function_state (w); if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " Visiting %s/%i state:%s looping %i\n", cgraph_node_name (w), w->uid, pure_const_names[w_l->pure_const_state], w_l->looping); /* First merge in function body properties. */ worse_state (&pure_const_state, &looping, w_l->pure_const_state, w_l->looping); if (pure_const_state == IPA_NEITHER) break; /* For overwritable nodes we can not assume anything. */ if (cgraph_function_body_availability (w) == AVAIL_OVERWRITABLE) { worse_state (&pure_const_state, &looping, w_l->state_previously_known, w_l->looping_previously_known); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " Overwritable. state %s looping %i\n", pure_const_names[w_l->state_previously_known], w_l->looping_previously_known); } break; } count++; /* We consider recursive cycles as possibly infinite. This might be relaxed since infinite recursion leads to stack overflow. */ if (count > 1) looping = true; /* Now walk the edges and merge in callee properties. */ for (e = w->callees; e; e = e->next_callee) { enum availability avail; struct cgraph_node *y = cgraph_function_node (e->callee, &avail); enum pure_const_state_e edge_state = IPA_CONST; bool edge_looping = false; if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " Call to %s/%i", cgraph_node_name (e->callee), e->callee->uid); } if (avail > AVAIL_OVERWRITABLE) { funct_state y_l = get_function_state (y); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " state:%s looping:%i\n", pure_const_names[y_l->pure_const_state], y_l->looping); } if (y_l->pure_const_state > IPA_PURE && cgraph_edge_cannot_lead_to_return (e)) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " Ignoring side effects" " -> pure, looping\n"); edge_state = IPA_PURE; edge_looping = true; } else { edge_state = y_l->pure_const_state; edge_looping = y_l->looping; } } else if (special_builtin_state (&edge_state, &edge_looping, y->decl)) ; else state_from_flags (&edge_state, &edge_looping, flags_from_decl_or_type (y->decl), cgraph_edge_cannot_lead_to_return (e)); /* Merge the results with what we already know. */ better_state (&edge_state, &edge_looping, w_l->state_previously_known, w_l->looping_previously_known); worse_state (&pure_const_state, &looping, edge_state, edge_looping); if (pure_const_state == IPA_NEITHER) break; } if (pure_const_state == IPA_NEITHER) break; /* Now process the indirect call. */ for (ie = w->indirect_calls; ie; ie = ie->next_callee) { enum pure_const_state_e edge_state = IPA_CONST; bool edge_looping = false; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " Indirect call"); state_from_flags (&edge_state, &edge_looping, ie->indirect_info->ecf_flags, cgraph_edge_cannot_lead_to_return (ie)); /* Merge the results with what we already know. */ better_state (&edge_state, &edge_looping, w_l->state_previously_known, w_l->looping_previously_known); worse_state (&pure_const_state, &looping, edge_state, edge_looping); if (pure_const_state == IPA_NEITHER) break; } if (pure_const_state == IPA_NEITHER) break; /* And finally all loads and stores. */ for (i = 0; ipa_ref_list_reference_iterate (&w->ref_list, i, ref); i++) { enum pure_const_state_e ref_state = IPA_CONST; bool ref_looping = false; switch (ref->use) { case IPA_REF_LOAD: /* readonly reads are safe. */ if (TREE_READONLY (ipa_ref_varpool_node (ref)->decl)) break; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " nonreadonly global var read\n"); ref_state = IPA_PURE; break; case IPA_REF_STORE: if (ipa_ref_cannot_lead_to_return (ref)) break; ref_state = IPA_NEITHER; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, " global var write\n"); break; case IPA_REF_ADDR: break; } better_state (&ref_state, &ref_looping, w_l->state_previously_known, w_l->looping_previously_known); worse_state (&pure_const_state, &looping, ref_state, ref_looping); if (pure_const_state == IPA_NEITHER) break; } w_info = (struct ipa_dfs_info *) w->aux; w = w_info->next_cycle; } if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Result %s looping %i\n", pure_const_names [pure_const_state], looping); /* Copy back the region's pure_const_state which is shared by all nodes in the region. */ w = node; while (w) { funct_state w_l = get_function_state (w); enum pure_const_state_e this_state = pure_const_state; bool this_looping = looping; if (w_l->state_previously_known != IPA_NEITHER && this_state > w_l->state_previously_known) { this_state = w_l->state_previously_known; this_looping |= w_l->looping_previously_known; } if (!this_looping && self_recursive_p (w)) this_looping = true; if (!w_l->looping_previously_known) this_looping = false; /* All nodes within a cycle share the same info. */ w_l->pure_const_state = this_state; w_l->looping = this_looping; switch (this_state) { case IPA_CONST: if (!TREE_READONLY (w->decl)) { warn_function_const (w->decl, !this_looping); if (dump_file) fprintf (dump_file, "Function found to be %sconst: %s\n", this_looping ? "looping " : "", cgraph_node_name (w)); } cgraph_set_const_flag (w, true, this_looping); break; case IPA_PURE: if (!DECL_PURE_P (w->decl)) { warn_function_pure (w->decl, !this_looping); if (dump_file) fprintf (dump_file, "Function found to be %spure: %s\n", this_looping ? "looping " : "", cgraph_node_name (w)); } cgraph_set_pure_flag (w, true, this_looping); break; default: break; } w_info = (struct ipa_dfs_info *) w->aux; w = w_info->next_cycle; } } ipa_free_postorder_info (); free (order); } /* Produce transitive closure over the callgraph and compute nothrow attributes. */ static void propagate_nothrow (void) { struct cgraph_node *node; struct cgraph_node *w; struct cgraph_node **order = XCNEWVEC (struct cgraph_node *, cgraph_n_nodes); int order_pos; int i; struct ipa_dfs_info * w_info; order_pos = ipa_reduced_postorder (order, true, false, ignore_edge); if (dump_file) { dump_cgraph (dump_file); ipa_print_order (dump_file, "reduced for nothrow", order, order_pos); } /* Propagate the local information thru the call graph to produce the global information. All the nodes within a cycle will have the same info so we collapse cycles first. Then we can do the propagation in one pass from the leaves to the roots. */ for (i = 0; i < order_pos; i++ ) { bool can_throw = false; node = order[i]; if (node->alias) continue; /* Find the worst state for any node in the cycle. */ w = node; while (w) { struct cgraph_edge *e, *ie; funct_state w_l = get_function_state (w); if (w_l->can_throw || cgraph_function_body_availability (w) == AVAIL_OVERWRITABLE) can_throw = true; if (can_throw) break; for (e = w->callees; e; e = e->next_callee) { enum availability avail; struct cgraph_node *y = cgraph_function_node (e->callee, &avail); if (avail > AVAIL_OVERWRITABLE) { funct_state y_l = get_function_state (y); if (can_throw) break; if (y_l->can_throw && !TREE_NOTHROW (w->decl) && e->can_throw_external) can_throw = true; } else if (e->can_throw_external && !TREE_NOTHROW (y->decl)) can_throw = true; } for (ie = node->indirect_calls; ie; ie = ie->next_callee) if (ie->can_throw_external) can_throw = true; w_info = (struct ipa_dfs_info *) w->aux; w = w_info->next_cycle; } /* Copy back the region's pure_const_state which is shared by all nodes in the region. */ w = node; while (w) { funct_state w_l = get_function_state (w); if (!can_throw && !TREE_NOTHROW (w->decl)) { cgraph_set_nothrow_flag (w, true); if (dump_file) fprintf (dump_file, "Function found to be nothrow: %s\n", cgraph_node_name (w)); } else if (can_throw && !TREE_NOTHROW (w->decl)) w_l->can_throw = true; w_info = (struct ipa_dfs_info *) w->aux; w = w_info->next_cycle; } } ipa_free_postorder_info (); free (order); } /* Produce the global information by preforming a transitive closure on the local information that was produced by generate_summary. */ static unsigned int propagate (void) { struct cgraph_node *node; cgraph_remove_function_insertion_hook (function_insertion_hook_holder); cgraph_remove_node_duplication_hook (node_duplication_hook_holder); cgraph_remove_node_removal_hook (node_removal_hook_holder); /* Nothrow makes more function to not lead to return and improve later analysis. */ propagate_nothrow (); propagate_pure_const (); /* Cleanup. */ for (node = cgraph_nodes; node; node = node->next) if (has_function_state (node)) free (get_function_state (node)); VEC_free (funct_state, heap, funct_state_vec); finish_state (); return 0; } static bool gate_pure_const (void) { return (flag_ipa_pure_const /* Don't bother doing anything if the program has errors. */ && !seen_error ()); } struct ipa_opt_pass_d pass_ipa_pure_const = { { IPA_PASS, "pure-const", /* name */ gate_pure_const, /* gate */ propagate, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_IPA_PURE_CONST, /* tv_id */ 0, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ 0 /* todo_flags_finish */ }, generate_summary, /* generate_summary */ pure_const_write_summary, /* write_summary */ pure_const_read_summary, /* read_summary */ NULL, /* write_optimization_summary */ NULL, /* read_optimization_summary */ NULL, /* stmt_fixup */ 0, /* TODOs */ NULL, /* function_transform */ NULL /* variable_transform */ }; /* Return true if function should be skipped for local pure const analysis. */ static bool skip_function_for_local_pure_const (struct cgraph_node *node) { /* Because we do not schedule pass_fixup_cfg over whole program after early optimizations we must not promote functions that are called by already processed functions. */ if (function_called_by_processed_nodes_p ()) { if (dump_file) fprintf (dump_file, "Function called in recursive cycle; ignoring\n"); return true; } if (cgraph_function_body_availability (node) <= AVAIL_OVERWRITABLE) { if (dump_file) fprintf (dump_file, "Function is not available or overwritable; not analyzing.\n"); return true; } return false; } /* Simple local pass for pure const discovery reusing the analysis from ipa_pure_const. This pass is effective when executed together with other optimization passes in early optimization pass queue. */ static unsigned int local_pure_const (void) { bool changed = false; funct_state l; bool skip; struct cgraph_node *node; node = cgraph_get_node (current_function_decl); skip = skip_function_for_local_pure_const (node); if (!warn_suggest_attribute_const && !warn_suggest_attribute_pure && skip) return 0; l = analyze_function (node, false); /* Do NORETURN discovery. */ if (!skip && !TREE_THIS_VOLATILE (current_function_decl) && EDGE_COUNT (EXIT_BLOCK_PTR->preds) == 0) { warn_function_noreturn (cfun->decl); if (dump_file) fprintf (dump_file, "Function found to be noreturn: %s\n", lang_hooks.decl_printable_name (current_function_decl, 2)); /* Update declaration and reduce profile to executed once. */ TREE_THIS_VOLATILE (current_function_decl) = 1; if (node->frequency > NODE_FREQUENCY_EXECUTED_ONCE) node->frequency = NODE_FREQUENCY_EXECUTED_ONCE; changed = true; } switch (l->pure_const_state) { case IPA_CONST: if (!TREE_READONLY (current_function_decl)) { warn_function_const (current_function_decl, !l->looping); if (!skip) { cgraph_set_const_flag (node, true, l->looping); changed = true; } if (dump_file) fprintf (dump_file, "Function found to be %sconst: %s\n", l->looping ? "looping " : "", lang_hooks.decl_printable_name (current_function_decl, 2)); } else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl) && !l->looping) { if (!skip) { cgraph_set_const_flag (node, true, false); changed = true; } if (dump_file) fprintf (dump_file, "Function found to be non-looping: %s\n", lang_hooks.decl_printable_name (current_function_decl, 2)); } break; case IPA_PURE: if (!DECL_PURE_P (current_function_decl)) { if (!skip) { cgraph_set_pure_flag (node, true, l->looping); changed = true; } warn_function_pure (current_function_decl, !l->looping); if (dump_file) fprintf (dump_file, "Function found to be %spure: %s\n", l->looping ? "looping " : "", lang_hooks.decl_printable_name (current_function_decl, 2)); } else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl) && !l->looping) { if (!skip) { cgraph_set_pure_flag (node, true, false); changed = true; } if (dump_file) fprintf (dump_file, "Function found to be non-looping: %s\n", lang_hooks.decl_printable_name (current_function_decl, 2)); } break; default: break; } if (!l->can_throw && !TREE_NOTHROW (current_function_decl)) { cgraph_set_nothrow_flag (node, true); changed = true; if (dump_file) fprintf (dump_file, "Function found to be nothrow: %s\n", lang_hooks.decl_printable_name (current_function_decl, 2)); } free (l); if (changed) return execute_fixup_cfg (); else return 0; } struct gimple_opt_pass pass_local_pure_const = { { GIMPLE_PASS, "local-pure-const", /* name */ gate_pure_const, /* gate */ local_pure_const, /* execute */ NULL, /* sub */ NULL, /* next */ 0, /* static_pass_number */ TV_IPA_PURE_CONST, /* tv_id */ 0, /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ 0 /* todo_flags_finish */ } };
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