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/* Loop unrolling and peeling. Copyright (C) 2002, 2003, 2004, 2005, 2007, 2008, 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/>. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "tm.h" #include "rtl.h" #include "hard-reg-set.h" #include "obstack.h" #include "basic-block.h" #include "cfgloop.h" #include "cfglayout.h" #include "params.h" #include "output.h" #include "expr.h" #include "hashtab.h" #include "recog.h" /* This pass performs loop unrolling and peeling. We only perform these optimizations on innermost loops (with single exception) because the impact on performance is greatest here, and we want to avoid unnecessary code size growth. The gain is caused by greater sequentiality of code, better code to optimize for further passes and in some cases by fewer testings of exit conditions. The main problem is code growth, that impacts performance negatively due to effect of caches. What we do: -- complete peeling of once-rolling loops; this is the above mentioned exception, as this causes loop to be cancelled completely and does not cause code growth -- complete peeling of loops that roll (small) constant times. -- simple peeling of first iterations of loops that do not roll much (according to profile feedback) -- unrolling of loops that roll constant times; this is almost always win, as we get rid of exit condition tests. -- unrolling of loops that roll number of times that we can compute in runtime; we also get rid of exit condition tests here, but there is the extra expense for calculating the number of iterations -- simple unrolling of remaining loops; this is performed only if we are asked to, as the gain is questionable in this case and often it may even slow down the code For more detailed descriptions of each of those, see comments at appropriate function below. There is a lot of parameters (defined and described in params.def) that control how much we unroll/peel. ??? A great problem is that we don't have a good way how to determine how many times we should unroll the loop; the experiments I have made showed that this choice may affect performance in order of several %. */ /* Information about induction variables to split. */ struct iv_to_split { rtx insn; /* The insn in that the induction variable occurs. */ rtx base_var; /* The variable on that the values in the further iterations are based. */ rtx step; /* Step of the induction variable. */ struct iv_to_split *next; /* Next entry in walking order. */ unsigned n_loc; unsigned loc[3]; /* Location where the definition of the induction variable occurs in the insn. For example if N_LOC is 2, the expression is located at XEXP (XEXP (single_set, loc[0]), loc[1]). */ }; /* Information about accumulators to expand. */ struct var_to_expand { rtx insn; /* The insn in that the variable expansion occurs. */ rtx reg; /* The accumulator which is expanded. */ VEC(rtx,heap) *var_expansions; /* The copies of the accumulator which is expanded. */ struct var_to_expand *next; /* Next entry in walking order. */ enum rtx_code op; /* The type of the accumulation - addition, subtraction or multiplication. */ int expansion_count; /* Count the number of expansions generated so far. */ int reuse_expansion; /* The expansion we intend to reuse to expand the accumulator. If REUSE_EXPANSION is 0 reuse the original accumulator. Else use var_expansions[REUSE_EXPANSION - 1]. */ unsigned accum_pos; /* The position in which the accumulator is placed in the insn src. For example in x = x + something accum_pos is 0 while in x = something + x accum_pos is 1. */ }; /* Information about optimization applied in the unrolled loop. */ struct opt_info { htab_t insns_to_split; /* A hashtable of insns to split. */ struct iv_to_split *iv_to_split_head; /* The first iv to split. */ struct iv_to_split **iv_to_split_tail; /* Pointer to the tail of the list. */ htab_t insns_with_var_to_expand; /* A hashtable of insns with accumulators to expand. */ struct var_to_expand *var_to_expand_head; /* The first var to expand. */ struct var_to_expand **var_to_expand_tail; /* Pointer to the tail of the list. */ unsigned first_new_block; /* The first basic block that was duplicated. */ basic_block loop_exit; /* The loop exit basic block. */ basic_block loop_preheader; /* The loop preheader basic block. */ }; static void decide_unrolling_and_peeling (int); static void peel_loops_completely (int); static void decide_peel_simple (struct loop *, int); static void decide_peel_once_rolling (struct loop *, int); static void decide_peel_completely (struct loop *, int); static void decide_unroll_stupid (struct loop *, int); static void decide_unroll_constant_iterations (struct loop *, int); static void decide_unroll_runtime_iterations (struct loop *, int); static void peel_loop_simple (struct loop *); static void peel_loop_completely (struct loop *); static void unroll_loop_stupid (struct loop *); static void unroll_loop_constant_iterations (struct loop *); static void unroll_loop_runtime_iterations (struct loop *); static struct opt_info *analyze_insns_in_loop (struct loop *); static void opt_info_start_duplication (struct opt_info *); static void apply_opt_in_copies (struct opt_info *, unsigned, bool, bool); static void free_opt_info (struct opt_info *); static struct var_to_expand *analyze_insn_to_expand_var (struct loop*, rtx); static bool referenced_in_one_insn_in_loop_p (struct loop *, rtx, int *); static struct iv_to_split *analyze_iv_to_split_insn (rtx); static void expand_var_during_unrolling (struct var_to_expand *, rtx); static void insert_var_expansion_initialization (struct var_to_expand *, basic_block); static void combine_var_copies_in_loop_exit (struct var_to_expand *, basic_block); static rtx get_expansion (struct var_to_expand *); /* Unroll and/or peel (depending on FLAGS) LOOPS. */ void unroll_and_peel_loops (int flags) { struct loop *loop; bool check; loop_iterator li; /* First perform complete loop peeling (it is almost surely a win, and affects parameters for further decision a lot). */ peel_loops_completely (flags); /* Now decide rest of unrolling and peeling. */ decide_unrolling_and_peeling (flags); /* Scan the loops, inner ones first. */ FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST) { check = true; /* And perform the appropriate transformations. */ switch (loop->lpt_decision.decision) { case LPT_PEEL_COMPLETELY: /* Already done. */ gcc_unreachable (); case LPT_PEEL_SIMPLE: peel_loop_simple (loop); break; case LPT_UNROLL_CONSTANT: unroll_loop_constant_iterations (loop); break; case LPT_UNROLL_RUNTIME: unroll_loop_runtime_iterations (loop); break; case LPT_UNROLL_STUPID: unroll_loop_stupid (loop); break; case LPT_NONE: check = false; break; default: gcc_unreachable (); } if (check) { #ifdef ENABLE_CHECKING verify_dominators (CDI_DOMINATORS); verify_loop_structure (); #endif } } iv_analysis_done (); } /* Check whether exit of the LOOP is at the end of loop body. */ static bool loop_exit_at_end_p (struct loop *loop) { struct niter_desc *desc = get_simple_loop_desc (loop); rtx insn; if (desc->in_edge->dest != loop->latch) return false; /* Check that the latch is empty. */ FOR_BB_INSNS (loop->latch, insn) { if (INSN_P (insn)) return false; } return true; } /* Depending on FLAGS, check whether to peel loops completely and do so. */ static void peel_loops_completely (int flags) { struct loop *loop; loop_iterator li; /* Scan the loops, the inner ones first. */ FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST) { loop->lpt_decision.decision = LPT_NONE; if (dump_file) fprintf (dump_file, "\n;; *** Considering loop %d for complete peeling ***\n", loop->num); loop->ninsns = num_loop_insns (loop); decide_peel_once_rolling (loop, flags); if (loop->lpt_decision.decision == LPT_NONE) decide_peel_completely (loop, flags); if (loop->lpt_decision.decision == LPT_PEEL_COMPLETELY) { peel_loop_completely (loop); #ifdef ENABLE_CHECKING verify_dominators (CDI_DOMINATORS); verify_loop_structure (); #endif } } } /* Decide whether unroll or peel loops (depending on FLAGS) and how much. */ static void decide_unrolling_and_peeling (int flags) { struct loop *loop; loop_iterator li; /* Scan the loops, inner ones first. */ FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST) { loop->lpt_decision.decision = LPT_NONE; if (dump_file) fprintf (dump_file, "\n;; *** Considering loop %d ***\n", loop->num); /* Do not peel cold areas. */ if (optimize_loop_for_size_p (loop)) { if (dump_file) fprintf (dump_file, ";; Not considering loop, cold area\n"); continue; } /* Can the loop be manipulated? */ if (!can_duplicate_loop_p (loop)) { if (dump_file) fprintf (dump_file, ";; Not considering loop, cannot duplicate\n"); continue; } /* Skip non-innermost loops. */ if (loop->inner) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is not innermost\n"); continue; } loop->ninsns = num_loop_insns (loop); loop->av_ninsns = average_num_loop_insns (loop); /* Try transformations one by one in decreasing order of priority. */ decide_unroll_constant_iterations (loop, flags); if (loop->lpt_decision.decision == LPT_NONE) decide_unroll_runtime_iterations (loop, flags); if (loop->lpt_decision.decision == LPT_NONE) decide_unroll_stupid (loop, flags); if (loop->lpt_decision.decision == LPT_NONE) decide_peel_simple (loop, flags); } } /* Decide whether the LOOP is once rolling and suitable for complete peeling. */ static void decide_peel_once_rolling (struct loop *loop, int flags ATTRIBUTE_UNUSED) { struct niter_desc *desc; if (dump_file) fprintf (dump_file, "\n;; Considering peeling once rolling loop\n"); /* Is the loop small enough? */ if ((unsigned) PARAM_VALUE (PARAM_MAX_ONCE_PEELED_INSNS) < loop->ninsns) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is too big\n"); return; } /* Check for simple loops. */ desc = get_simple_loop_desc (loop); /* Check number of iterations. */ if (!desc->simple_p || desc->assumptions || desc->infinite || !desc->const_iter || desc->niter != 0) { if (dump_file) fprintf (dump_file, ";; Unable to prove that the loop rolls exactly once\n"); return; } /* Success. */ if (dump_file) fprintf (dump_file, ";; Decided to peel exactly once rolling loop\n"); loop->lpt_decision.decision = LPT_PEEL_COMPLETELY; } /* Decide whether the LOOP is suitable for complete peeling. */ static void decide_peel_completely (struct loop *loop, int flags ATTRIBUTE_UNUSED) { unsigned npeel; struct niter_desc *desc; if (dump_file) fprintf (dump_file, "\n;; Considering peeling completely\n"); /* Skip non-innermost loops. */ if (loop->inner) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is not innermost\n"); return; } /* Do not peel cold areas. */ if (optimize_loop_for_size_p (loop)) { if (dump_file) fprintf (dump_file, ";; Not considering loop, cold area\n"); return; } /* Can the loop be manipulated? */ if (!can_duplicate_loop_p (loop)) { if (dump_file) fprintf (dump_file, ";; Not considering loop, cannot duplicate\n"); return; } /* npeel = number of iterations to peel. */ npeel = PARAM_VALUE (PARAM_MAX_COMPLETELY_PEELED_INSNS) / loop->ninsns; if (npeel > (unsigned) PARAM_VALUE (PARAM_MAX_COMPLETELY_PEEL_TIMES)) npeel = PARAM_VALUE (PARAM_MAX_COMPLETELY_PEEL_TIMES); /* Is the loop small enough? */ if (!npeel) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is too big\n"); return; } /* Check for simple loops. */ desc = get_simple_loop_desc (loop); /* Check number of iterations. */ if (!desc->simple_p || desc->assumptions || !desc->const_iter || desc->infinite) { if (dump_file) fprintf (dump_file, ";; Unable to prove that the loop iterates constant times\n"); return; } if (desc->niter > npeel - 1) { if (dump_file) { fprintf (dump_file, ";; Not peeling loop completely, rolls too much ("); fprintf (dump_file, HOST_WIDEST_INT_PRINT_DEC, desc->niter); fprintf (dump_file, " iterations > %d [maximum peelings])\n", npeel); } return; } /* Success. */ if (dump_file) fprintf (dump_file, ";; Decided to peel loop completely\n"); loop->lpt_decision.decision = LPT_PEEL_COMPLETELY; } /* Peel all iterations of LOOP, remove exit edges and cancel the loop completely. The transformation done: for (i = 0; i < 4; i++) body; ==> i = 0; body; i++; body; i++; body; i++; body; i++; */ static void peel_loop_completely (struct loop *loop) { sbitmap wont_exit; unsigned HOST_WIDE_INT npeel; unsigned i; VEC (edge, heap) *remove_edges; edge ein; struct niter_desc *desc = get_simple_loop_desc (loop); struct opt_info *opt_info = NULL; npeel = desc->niter; if (npeel) { bool ok; wont_exit = sbitmap_alloc (npeel + 1); sbitmap_ones (wont_exit); RESET_BIT (wont_exit, 0); if (desc->noloop_assumptions) RESET_BIT (wont_exit, 1); remove_edges = NULL; if (flag_split_ivs_in_unroller) opt_info = analyze_insns_in_loop (loop); opt_info_start_duplication (opt_info); ok = duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop), npeel, wont_exit, desc->out_edge, &remove_edges, DLTHE_FLAG_UPDATE_FREQ | DLTHE_FLAG_COMPLETTE_PEEL | (opt_info ? DLTHE_RECORD_COPY_NUMBER : 0)); gcc_assert (ok); free (wont_exit); if (opt_info) { apply_opt_in_copies (opt_info, npeel, false, true); free_opt_info (opt_info); } /* Remove the exit edges. */ for (i = 0; VEC_iterate (edge, remove_edges, i, ein); i++) remove_path (ein); VEC_free (edge, heap, remove_edges); } ein = desc->in_edge; free_simple_loop_desc (loop); /* Now remove the unreachable part of the last iteration and cancel the loop. */ remove_path (ein); if (dump_file) fprintf (dump_file, ";; Peeled loop completely, %d times\n", (int) npeel); } /* Decide whether to unroll LOOP iterating constant number of times and how much. */ static void decide_unroll_constant_iterations (struct loop *loop, int flags) { unsigned nunroll, nunroll_by_av, best_copies, best_unroll = 0, n_copies, i; struct niter_desc *desc; if (!(flags & UAP_UNROLL)) { /* We were not asked to, just return back silently. */ return; } if (dump_file) fprintf (dump_file, "\n;; Considering unrolling loop with constant " "number of iterations\n"); /* nunroll = total number of copies of the original loop body in unrolled loop (i.e. if it is 2, we have to duplicate loop body once. */ nunroll = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / loop->ninsns; nunroll_by_av = PARAM_VALUE (PARAM_MAX_AVERAGE_UNROLLED_INSNS) / loop->av_ninsns; if (nunroll > nunroll_by_av) nunroll = nunroll_by_av; if (nunroll > (unsigned) PARAM_VALUE (PARAM_MAX_UNROLL_TIMES)) nunroll = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES); /* Skip big loops. */ if (nunroll <= 1) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is too big\n"); return; } /* Check for simple loops. */ desc = get_simple_loop_desc (loop); /* Check number of iterations. */ if (!desc->simple_p || !desc->const_iter || desc->assumptions) { if (dump_file) fprintf (dump_file, ";; Unable to prove that the loop iterates constant times\n"); return; } /* Check whether the loop rolls enough to consider. */ if (desc->niter < 2 * nunroll) { if (dump_file) fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n"); return; } /* Success; now compute number of iterations to unroll. We alter nunroll so that as few as possible copies of loop body are necessary, while still not decreasing the number of unrollings too much (at most by 1). */ best_copies = 2 * nunroll + 10; i = 2 * nunroll + 2; if (i - 1 >= desc->niter) i = desc->niter - 2; for (; i >= nunroll - 1; i--) { unsigned exit_mod = desc->niter % (i + 1); if (!loop_exit_at_end_p (loop)) n_copies = exit_mod + i + 1; else if (exit_mod != (unsigned) i || desc->noloop_assumptions != NULL_RTX) n_copies = exit_mod + i + 2; else n_copies = i + 1; if (n_copies < best_copies) { best_copies = n_copies; best_unroll = i; } } if (dump_file) fprintf (dump_file, ";; max_unroll %d (%d copies, initial %d).\n", best_unroll + 1, best_copies, nunroll); loop->lpt_decision.decision = LPT_UNROLL_CONSTANT; loop->lpt_decision.times = best_unroll; if (dump_file) fprintf (dump_file, ";; Decided to unroll the constant times rolling loop, %d times.\n", loop->lpt_decision.times); } /* Unroll LOOP with constant number of iterations LOOP->LPT_DECISION.TIMES + 1 times. The transformation does this: for (i = 0; i < 102; i++) body; ==> i = 0; body; i++; body; i++; while (i < 102) { body; i++; body; i++; body; i++; body; i++; } */ static void unroll_loop_constant_iterations (struct loop *loop) { unsigned HOST_WIDE_INT niter; unsigned exit_mod; sbitmap wont_exit; unsigned i; VEC (edge, heap) *remove_edges; edge e; unsigned max_unroll = loop->lpt_decision.times; struct niter_desc *desc = get_simple_loop_desc (loop); bool exit_at_end = loop_exit_at_end_p (loop); struct opt_info *opt_info = NULL; bool ok; niter = desc->niter; /* Should not get here (such loop should be peeled instead). */ gcc_assert (niter > max_unroll + 1); exit_mod = niter % (max_unroll + 1); wont_exit = sbitmap_alloc (max_unroll + 1); sbitmap_ones (wont_exit); remove_edges = NULL; if (flag_split_ivs_in_unroller || flag_variable_expansion_in_unroller) opt_info = analyze_insns_in_loop (loop); if (!exit_at_end) { /* The exit is not at the end of the loop; leave exit test in the first copy, so that the loops that start with test of exit condition have continuous body after unrolling. */ if (dump_file) fprintf (dump_file, ";; Condition on beginning of loop.\n"); /* Peel exit_mod iterations. */ RESET_BIT (wont_exit, 0); if (desc->noloop_assumptions) RESET_BIT (wont_exit, 1); if (exit_mod) { opt_info_start_duplication (opt_info); ok = duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop), exit_mod, wont_exit, desc->out_edge, &remove_edges, DLTHE_FLAG_UPDATE_FREQ | (opt_info && exit_mod > 1 ? DLTHE_RECORD_COPY_NUMBER : 0)); gcc_assert (ok); if (opt_info && exit_mod > 1) apply_opt_in_copies (opt_info, exit_mod, false, false); desc->noloop_assumptions = NULL_RTX; desc->niter -= exit_mod; desc->niter_max -= exit_mod; } SET_BIT (wont_exit, 1); } else { /* Leave exit test in last copy, for the same reason as above if the loop tests the condition at the end of loop body. */ if (dump_file) fprintf (dump_file, ";; Condition on end of loop.\n"); /* We know that niter >= max_unroll + 2; so we do not need to care of case when we would exit before reaching the loop. So just peel exit_mod + 1 iterations. */ if (exit_mod != max_unroll || desc->noloop_assumptions) { RESET_BIT (wont_exit, 0); if (desc->noloop_assumptions) RESET_BIT (wont_exit, 1); opt_info_start_duplication (opt_info); ok = duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop), exit_mod + 1, wont_exit, desc->out_edge, &remove_edges, DLTHE_FLAG_UPDATE_FREQ | (opt_info && exit_mod > 0 ? DLTHE_RECORD_COPY_NUMBER : 0)); gcc_assert (ok); if (opt_info && exit_mod > 0) apply_opt_in_copies (opt_info, exit_mod + 1, false, false); desc->niter -= exit_mod + 1; desc->niter_max -= exit_mod + 1; desc->noloop_assumptions = NULL_RTX; SET_BIT (wont_exit, 0); SET_BIT (wont_exit, 1); } RESET_BIT (wont_exit, max_unroll); } /* Now unroll the loop. */ opt_info_start_duplication (opt_info); ok = duplicate_loop_to_header_edge (loop, loop_latch_edge (loop), max_unroll, wont_exit, desc->out_edge, &remove_edges, DLTHE_FLAG_UPDATE_FREQ | (opt_info ? DLTHE_RECORD_COPY_NUMBER : 0)); gcc_assert (ok); if (opt_info) { apply_opt_in_copies (opt_info, max_unroll, true, true); free_opt_info (opt_info); } free (wont_exit); if (exit_at_end) { basic_block exit_block = get_bb_copy (desc->in_edge->src); /* Find a new in and out edge; they are in the last copy we have made. */ if (EDGE_SUCC (exit_block, 0)->dest == desc->out_edge->dest) { desc->out_edge = EDGE_SUCC (exit_block, 0); desc->in_edge = EDGE_SUCC (exit_block, 1); } else { desc->out_edge = EDGE_SUCC (exit_block, 1); desc->in_edge = EDGE_SUCC (exit_block, 0); } } desc->niter /= max_unroll + 1; desc->niter_max /= max_unroll + 1; desc->niter_expr = GEN_INT (desc->niter); /* Remove the edges. */ for (i = 0; VEC_iterate (edge, remove_edges, i, e); i++) remove_path (e); VEC_free (edge, heap, remove_edges); if (dump_file) fprintf (dump_file, ";; Unrolled loop %d times, constant # of iterations %i insns\n", max_unroll, num_loop_insns (loop)); } /* Decide whether to unroll LOOP iterating runtime computable number of times and how much. */ static void decide_unroll_runtime_iterations (struct loop *loop, int flags) { unsigned nunroll, nunroll_by_av, i; struct niter_desc *desc; if (!(flags & UAP_UNROLL)) { /* We were not asked to, just return back silently. */ return; } if (dump_file) fprintf (dump_file, "\n;; Considering unrolling loop with runtime " "computable number of iterations\n"); /* nunroll = total number of copies of the original loop body in unrolled loop (i.e. if it is 2, we have to duplicate loop body once. */ nunroll = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / loop->ninsns; nunroll_by_av = PARAM_VALUE (PARAM_MAX_AVERAGE_UNROLLED_INSNS) / loop->av_ninsns; if (nunroll > nunroll_by_av) nunroll = nunroll_by_av; if (nunroll > (unsigned) PARAM_VALUE (PARAM_MAX_UNROLL_TIMES)) nunroll = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES); /* Skip big loops. */ if (nunroll <= 1) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is too big\n"); return; } /* Check for simple loops. */ desc = get_simple_loop_desc (loop); /* Check simpleness. */ if (!desc->simple_p || desc->assumptions) { if (dump_file) fprintf (dump_file, ";; Unable to prove that the number of iterations " "can be counted in runtime\n"); return; } if (desc->const_iter) { if (dump_file) fprintf (dump_file, ";; Loop iterates constant times\n"); return; } /* If we have profile feedback, check whether the loop rolls. */ if (loop->header->count && expected_loop_iterations (loop) < 2 * nunroll) { if (dump_file) fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n"); return; } /* Success; now force nunroll to be power of 2, as we are unable to cope with overflows in computation of number of iterations. */ for (i = 1; 2 * i <= nunroll; i *= 2) continue; loop->lpt_decision.decision = LPT_UNROLL_RUNTIME; loop->lpt_decision.times = i - 1; if (dump_file) fprintf (dump_file, ";; Decided to unroll the runtime computable " "times rolling loop, %d times.\n", loop->lpt_decision.times); } /* Splits edge E and inserts the sequence of instructions INSNS on it, and returns the newly created block. If INSNS is NULL_RTX, nothing is changed and NULL is returned instead. */ basic_block split_edge_and_insert (edge e, rtx insns) { basic_block bb; if (!insns) return NULL; bb = split_edge (e); emit_insn_after (insns, BB_END (bb)); /* ??? We used to assume that INSNS can contain control flow insns, and that we had to try to find sub basic blocks in BB to maintain a valid CFG. For this purpose we used to set the BB_SUPERBLOCK flag on BB and call break_superblocks when going out of cfglayout mode. But it turns out that this never happens; and that if it does ever happen, the verify_flow_info call in loop_optimizer_finalize would fail. There are two reasons why we expected we could have control flow insns in INSNS. The first is when a comparison has to be done in parts, and the second is when the number of iterations is computed for loops with the number of iterations known at runtime. In both cases, test cases to get control flow in INSNS appear to be impossible to construct: * If do_compare_rtx_and_jump needs several branches to do comparison in a mode that needs comparison by parts, we cannot analyze the number of iterations of the loop, and we never get to unrolling it. * The code in expand_divmod that was suspected to cause creation of branching code seems to be only accessed for signed division. The divisions used by # of iterations analysis are always unsigned. Problems might arise on architectures that emits branching code for some operations that may appear in the unroller (especially for division), but we have no such architectures. Considering all this, it was decided that we should for now assume that INSNS can in theory contain control flow insns, but in practice it never does. So we don't handle the theoretical case, and should a real failure ever show up, we have a pretty good clue for how to fix it. */ return bb; } /* Unroll LOOP for that we are able to count number of iterations in runtime LOOP->LPT_DECISION.TIMES + 1 times. The transformation does this (with some extra care for case n < 0): for (i = 0; i < n; i++) body; ==> i = 0; mod = n % 4; switch (mod) { case 3: body; i++; case 2: body; i++; case 1: body; i++; case 0: ; } while (i < n) { body; i++; body; i++; body; i++; body; i++; } */ static void unroll_loop_runtime_iterations (struct loop *loop) { rtx old_niter, niter, init_code, branch_code, tmp; unsigned i, j, p; basic_block preheader, *body, swtch, ezc_swtch; VEC (basic_block, heap) *dom_bbs; sbitmap wont_exit; int may_exit_copy; unsigned n_peel; VEC (edge, heap) *remove_edges; edge e; bool extra_zero_check, last_may_exit; unsigned max_unroll = loop->lpt_decision.times; struct niter_desc *desc = get_simple_loop_desc (loop); bool exit_at_end = loop_exit_at_end_p (loop); struct opt_info *opt_info = NULL; bool ok; if (flag_split_ivs_in_unroller || flag_variable_expansion_in_unroller) opt_info = analyze_insns_in_loop (loop); /* Remember blocks whose dominators will have to be updated. */ dom_bbs = NULL; body = get_loop_body (loop); for (i = 0; i < loop->num_nodes; i++) { VEC (basic_block, heap) *ldom; basic_block bb; ldom = get_dominated_by (CDI_DOMINATORS, body[i]); for (j = 0; VEC_iterate (basic_block, ldom, j, bb); j++) if (!flow_bb_inside_loop_p (loop, bb)) VEC_safe_push (basic_block, heap, dom_bbs, bb); VEC_free (basic_block, heap, ldom); } free (body); if (!exit_at_end) { /* Leave exit in first copy (for explanation why see comment in unroll_loop_constant_iterations). */ may_exit_copy = 0; n_peel = max_unroll - 1; extra_zero_check = true; last_may_exit = false; } else { /* Leave exit in last copy (for explanation why see comment in unroll_loop_constant_iterations). */ may_exit_copy = max_unroll; n_peel = max_unroll; extra_zero_check = false; last_may_exit = true; } /* Get expression for number of iterations. */ start_sequence (); old_niter = niter = gen_reg_rtx (desc->mode); tmp = force_operand (copy_rtx (desc->niter_expr), niter); if (tmp != niter) emit_move_insn (niter, tmp); /* Count modulo by ANDing it with max_unroll; we use the fact that the number of unrollings is a power of two, and thus this is correct even if there is overflow in the computation. */ niter = expand_simple_binop (desc->mode, AND, niter, GEN_INT (max_unroll), NULL_RTX, 0, OPTAB_LIB_WIDEN); init_code = get_insns (); end_sequence (); unshare_all_rtl_in_chain (init_code); /* Precondition the loop. */ split_edge_and_insert (loop_preheader_edge (loop), init_code); remove_edges = NULL; wont_exit = sbitmap_alloc (max_unroll + 2); /* Peel the first copy of loop body (almost always we must leave exit test here; the only exception is when we have extra zero check and the number of iterations is reliable. Also record the place of (possible) extra zero check. */ sbitmap_zero (wont_exit); if (extra_zero_check && !desc->noloop_assumptions) SET_BIT (wont_exit, 1); ezc_swtch = loop_preheader_edge (loop)->src; ok = duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop), 1, wont_exit, desc->out_edge, &remove_edges, DLTHE_FLAG_UPDATE_FREQ); gcc_assert (ok); /* Record the place where switch will be built for preconditioning. */ swtch = split_edge (loop_preheader_edge (loop)); for (i = 0; i < n_peel; i++) { /* Peel the copy. */ sbitmap_zero (wont_exit); if (i != n_peel - 1 || !last_may_exit) SET_BIT (wont_exit, 1); ok = duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop), 1, wont_exit, desc->out_edge, &remove_edges, DLTHE_FLAG_UPDATE_FREQ); gcc_assert (ok); /* Create item for switch. */ j = n_peel - i - (extra_zero_check ? 0 : 1); p = REG_BR_PROB_BASE / (i + 2); preheader = split_edge (loop_preheader_edge (loop)); branch_code = compare_and_jump_seq (copy_rtx (niter), GEN_INT (j), EQ, block_label (preheader), p, NULL_RTX); /* We rely on the fact that the compare and jump cannot be optimized out, and hence the cfg we create is correct. */ gcc_assert (branch_code != NULL_RTX); swtch = split_edge_and_insert (single_pred_edge (swtch), branch_code); set_immediate_dominator (CDI_DOMINATORS, preheader, swtch); single_pred_edge (swtch)->probability = REG_BR_PROB_BASE - p; e = make_edge (swtch, preheader, single_succ_edge (swtch)->flags & EDGE_IRREDUCIBLE_LOOP); e->probability = p; } if (extra_zero_check) { /* Add branch for zero iterations. */ p = REG_BR_PROB_BASE / (max_unroll + 1); swtch = ezc_swtch; preheader = split_edge (loop_preheader_edge (loop)); branch_code = compare_and_jump_seq (copy_rtx (niter), const0_rtx, EQ, block_label (preheader), p, NULL_RTX); gcc_assert (branch_code != NULL_RTX); swtch = split_edge_and_insert (single_succ_edge (swtch), branch_code); set_immediate_dominator (CDI_DOMINATORS, preheader, swtch); single_succ_edge (swtch)->probability = REG_BR_PROB_BASE - p; e = make_edge (swtch, preheader, single_succ_edge (swtch)->flags & EDGE_IRREDUCIBLE_LOOP); e->probability = p; } /* Recount dominators for outer blocks. */ iterate_fix_dominators (CDI_DOMINATORS, dom_bbs, false); /* And unroll loop. */ sbitmap_ones (wont_exit); RESET_BIT (wont_exit, may_exit_copy); opt_info_start_duplication (opt_info); ok = duplicate_loop_to_header_edge (loop, loop_latch_edge (loop), max_unroll, wont_exit, desc->out_edge, &remove_edges, DLTHE_FLAG_UPDATE_FREQ | (opt_info ? DLTHE_RECORD_COPY_NUMBER : 0)); gcc_assert (ok); if (opt_info) { apply_opt_in_copies (opt_info, max_unroll, true, true); free_opt_info (opt_info); } free (wont_exit); if (exit_at_end) { basic_block exit_block = get_bb_copy (desc->in_edge->src); /* Find a new in and out edge; they are in the last copy we have made. */ if (EDGE_SUCC (exit_block, 0)->dest == desc->out_edge->dest) { desc->out_edge = EDGE_SUCC (exit_block, 0); desc->in_edge = EDGE_SUCC (exit_block, 1); } else { desc->out_edge = EDGE_SUCC (exit_block, 1); desc->in_edge = EDGE_SUCC (exit_block, 0); } } /* Remove the edges. */ for (i = 0; VEC_iterate (edge, remove_edges, i, e); i++) remove_path (e); VEC_free (edge, heap, remove_edges); /* We must be careful when updating the number of iterations due to preconditioning and the fact that the value must be valid at entry of the loop. After passing through the above code, we see that the correct new number of iterations is this: */ gcc_assert (!desc->const_iter); desc->niter_expr = simplify_gen_binary (UDIV, desc->mode, old_niter, GEN_INT (max_unroll + 1)); desc->niter_max /= max_unroll + 1; if (exit_at_end) { desc->niter_expr = simplify_gen_binary (MINUS, desc->mode, desc->niter_expr, const1_rtx); desc->noloop_assumptions = NULL_RTX; desc->niter_max--; } if (dump_file) fprintf (dump_file, ";; Unrolled loop %d times, counting # of iterations " "in runtime, %i insns\n", max_unroll, num_loop_insns (loop)); VEC_free (basic_block, heap, dom_bbs); } /* Decide whether to simply peel LOOP and how much. */ static void decide_peel_simple (struct loop *loop, int flags) { unsigned npeel; struct niter_desc *desc; if (!(flags & UAP_PEEL)) { /* We were not asked to, just return back silently. */ return; } if (dump_file) fprintf (dump_file, "\n;; Considering simply peeling loop\n"); /* npeel = number of iterations to peel. */ npeel = PARAM_VALUE (PARAM_MAX_PEELED_INSNS) / loop->ninsns; if (npeel > (unsigned) PARAM_VALUE (PARAM_MAX_PEEL_TIMES)) npeel = PARAM_VALUE (PARAM_MAX_PEEL_TIMES); /* Skip big loops. */ if (!npeel) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is too big\n"); return; } /* Check for simple loops. */ desc = get_simple_loop_desc (loop); /* Check number of iterations. */ if (desc->simple_p && !desc->assumptions && desc->const_iter) { if (dump_file) fprintf (dump_file, ";; Loop iterates constant times\n"); return; } /* Do not simply peel loops with branches inside -- it increases number of mispredicts. */ if (num_loop_branches (loop) > 1) { if (dump_file) fprintf (dump_file, ";; Not peeling, contains branches\n"); return; } if (loop->header->count) { unsigned niter = expected_loop_iterations (loop); if (niter + 1 > npeel) { if (dump_file) { fprintf (dump_file, ";; Not peeling loop, rolls too much ("); fprintf (dump_file, HOST_WIDEST_INT_PRINT_DEC, (HOST_WIDEST_INT) (niter + 1)); fprintf (dump_file, " iterations > %d [maximum peelings])\n", npeel); } return; } npeel = niter + 1; } else { /* For now we have no good heuristics to decide whether loop peeling will be effective, so disable it. */ if (dump_file) fprintf (dump_file, ";; Not peeling loop, no evidence it will be profitable\n"); return; } /* Success. */ loop->lpt_decision.decision = LPT_PEEL_SIMPLE; loop->lpt_decision.times = npeel; if (dump_file) fprintf (dump_file, ";; Decided to simply peel the loop, %d times.\n", loop->lpt_decision.times); } /* Peel a LOOP LOOP->LPT_DECISION.TIMES times. The transformation: while (cond) body; ==> if (!cond) goto end; body; if (!cond) goto end; body; while (cond) body; end: ; */ static void peel_loop_simple (struct loop *loop) { sbitmap wont_exit; unsigned npeel = loop->lpt_decision.times; struct niter_desc *desc = get_simple_loop_desc (loop); struct opt_info *opt_info = NULL; bool ok; if (flag_split_ivs_in_unroller && npeel > 1) opt_info = analyze_insns_in_loop (loop); wont_exit = sbitmap_alloc (npeel + 1); sbitmap_zero (wont_exit); opt_info_start_duplication (opt_info); ok = duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop), npeel, wont_exit, NULL, NULL, DLTHE_FLAG_UPDATE_FREQ | (opt_info ? DLTHE_RECORD_COPY_NUMBER : 0)); gcc_assert (ok); free (wont_exit); if (opt_info) { apply_opt_in_copies (opt_info, npeel, false, false); free_opt_info (opt_info); } if (desc->simple_p) { if (desc->const_iter) { desc->niter -= npeel; desc->niter_expr = GEN_INT (desc->niter); desc->noloop_assumptions = NULL_RTX; } else { /* We cannot just update niter_expr, as its value might be clobbered inside loop. We could handle this by counting the number into temporary just like we do in runtime unrolling, but it does not seem worthwhile. */ free_simple_loop_desc (loop); } } if (dump_file) fprintf (dump_file, ";; Peeling loop %d times\n", npeel); } /* Decide whether to unroll LOOP stupidly and how much. */ static void decide_unroll_stupid (struct loop *loop, int flags) { unsigned nunroll, nunroll_by_av, i; struct niter_desc *desc; if (!(flags & UAP_UNROLL_ALL)) { /* We were not asked to, just return back silently. */ return; } if (dump_file) fprintf (dump_file, "\n;; Considering unrolling loop stupidly\n"); /* nunroll = total number of copies of the original loop body in unrolled loop (i.e. if it is 2, we have to duplicate loop body once. */ nunroll = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / loop->ninsns; nunroll_by_av = PARAM_VALUE (PARAM_MAX_AVERAGE_UNROLLED_INSNS) / loop->av_ninsns; if (nunroll > nunroll_by_av) nunroll = nunroll_by_av; if (nunroll > (unsigned) PARAM_VALUE (PARAM_MAX_UNROLL_TIMES)) nunroll = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES); /* Skip big loops. */ if (nunroll <= 1) { if (dump_file) fprintf (dump_file, ";; Not considering loop, is too big\n"); return; } /* Check for simple loops. */ desc = get_simple_loop_desc (loop); /* Check simpleness. */ if (desc->simple_p && !desc->assumptions) { if (dump_file) fprintf (dump_file, ";; The loop is simple\n"); return; } /* Do not unroll loops with branches inside -- it increases number of mispredicts. */ if (num_loop_branches (loop) > 1) { if (dump_file) fprintf (dump_file, ";; Not unrolling, contains branches\n"); return; } /* If we have profile feedback, check whether the loop rolls. */ if (loop->header->count && expected_loop_iterations (loop) < 2 * nunroll) { if (dump_file) fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n"); return; } /* Success. Now force nunroll to be power of 2, as it seems that this improves results (partially because of better alignments, partially because of some dark magic). */ for (i = 1; 2 * i <= nunroll; i *= 2) continue; loop->lpt_decision.decision = LPT_UNROLL_STUPID; loop->lpt_decision.times = i - 1; if (dump_file) fprintf (dump_file, ";; Decided to unroll the loop stupidly, %d times.\n", loop->lpt_decision.times); } /* Unroll a LOOP LOOP->LPT_DECISION.TIMES times. The transformation: while (cond) body; ==> while (cond) { body; if (!cond) break; body; if (!cond) break; body; if (!cond) break; body; } */ static void unroll_loop_stupid (struct loop *loop) { sbitmap wont_exit; unsigned nunroll = loop->lpt_decision.times; struct niter_desc *desc = get_simple_loop_desc (loop); struct opt_info *opt_info = NULL; bool ok; if (flag_split_ivs_in_unroller || flag_variable_expansion_in_unroller) opt_info = analyze_insns_in_loop (loop); wont_exit = sbitmap_alloc (nunroll + 1); sbitmap_zero (wont_exit); opt_info_start_duplication (opt_info); ok = duplicate_loop_to_header_edge (loop, loop_latch_edge (loop), nunroll, wont_exit, NULL, NULL, DLTHE_FLAG_UPDATE_FREQ | (opt_info ? DLTHE_RECORD_COPY_NUMBER : 0)); gcc_assert (ok); if (opt_info) { apply_opt_in_copies (opt_info, nunroll, true, true); free_opt_info (opt_info); } free (wont_exit); if (desc->simple_p) { /* We indeed may get here provided that there are nontrivial assumptions for a loop to be really simple. We could update the counts, but the problem is that we are unable to decide which exit will be taken (not really true in case the number of iterations is constant, but noone will do anything with this information, so we do not worry about it). */ desc->simple_p = false; } if (dump_file) fprintf (dump_file, ";; Unrolled loop %d times, %i insns\n", nunroll, num_loop_insns (loop)); } /* A hash function for information about insns to split. */ static hashval_t si_info_hash (const void *ivts) { return (hashval_t) INSN_UID (((const struct iv_to_split *) ivts)->insn); } /* An equality functions for information about insns to split. */ static int si_info_eq (const void *ivts1, const void *ivts2) { const struct iv_to_split *const i1 = (const struct iv_to_split *) ivts1; const struct iv_to_split *const i2 = (const struct iv_to_split *) ivts2; return i1->insn == i2->insn; } /* Return a hash for VES, which is really a "var_to_expand *". */ static hashval_t ve_info_hash (const void *ves) { return (hashval_t) INSN_UID (((const struct var_to_expand *) ves)->insn); } /* Return true if IVTS1 and IVTS2 (which are really both of type "var_to_expand *") refer to the same instruction. */ static int ve_info_eq (const void *ivts1, const void *ivts2) { const struct var_to_expand *const i1 = (const struct var_to_expand *) ivts1; const struct var_to_expand *const i2 = (const struct var_to_expand *) ivts2; return i1->insn == i2->insn; } /* Returns true if REG is referenced in one nondebug insn in LOOP. Set *DEBUG_USES to the number of debug insns that reference the variable. */ bool referenced_in_one_insn_in_loop_p (struct loop *loop, rtx reg, int *debug_uses) { basic_block *body, bb; unsigned i; int count_ref = 0; rtx insn; body = get_loop_body (loop); for (i = 0; i < loop->num_nodes; i++) { bb = body[i]; FOR_BB_INSNS (bb, insn) if (!rtx_referenced_p (reg, insn)) continue; else if (DEBUG_INSN_P (insn)) ++*debug_uses; else if (++count_ref > 1) break; } free (body); return (count_ref == 1); } /* Reset the DEBUG_USES debug insns in LOOP that reference REG. */ static void reset_debug_uses_in_loop (struct loop *loop, rtx reg, int debug_uses) { basic_block *body, bb; unsigned i; rtx insn; body = get_loop_body (loop); for (i = 0; debug_uses && i < loop->num_nodes; i++) { bb = body[i]; FOR_BB_INSNS (bb, insn) if (!DEBUG_INSN_P (insn) || !rtx_referenced_p (reg, insn)) continue; else { validate_change (insn, &INSN_VAR_LOCATION_LOC (insn), gen_rtx_UNKNOWN_VAR_LOC (), 0); if (!--debug_uses) break; } } free (body); } /* Determine whether INSN contains an accumulator which can be expanded into separate copies, one for each copy of the LOOP body. for (i = 0 ; i < n; i++) sum += a[i]; ==> sum += a[i] .... i = i+1; sum1 += a[i] .... i = i+1 sum2 += a[i]; .... Return NULL if INSN contains no opportunity for expansion of accumulator. Otherwise, allocate a VAR_TO_EXPAND structure, fill it with the relevant information and return a pointer to it. */ static struct var_to_expand * analyze_insn_to_expand_var (struct loop *loop, rtx insn) { rtx set, dest, src, op1, op2, something; struct var_to_expand *ves; enum machine_mode mode1, mode2; unsigned accum_pos; int debug_uses = 0; set = single_set (insn); if (!set) return NULL; dest = SET_DEST (set); src = SET_SRC (set); if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS && GET_CODE (src) != MULT) return NULL; /* Hmm, this is a bit paradoxical. We know that INSN is a valid insn in MD. But if there is no optab to generate the insn, we can not perform the variable expansion. This can happen if an MD provides an insn but not a named pattern to generate it, for example to avoid producing code that needs additional mode switches like for x87/mmx. So we check have_insn_for which looks for an optab for the operation in SRC. If it doesn't exist, we can't perform the expansion even though INSN is valid. */ if (!have_insn_for (GET_CODE (src), GET_MODE (src))) return NULL; op1 = XEXP (src, 0); op2 = XEXP (src, 1); if (!REG_P (dest) && !(GET_CODE (dest) == SUBREG && REG_P (SUBREG_REG (dest)))) return NULL; if (rtx_equal_p (dest, op1)) accum_pos = 0; else if (rtx_equal_p (dest, op2)) accum_pos = 1; else return NULL; /* The method of expansion that we are using; which includes the initialization of the expansions with zero and the summation of the expansions at the end of the computation will yield wrong results for (x = something - x) thus avoid using it in that case. */ if (accum_pos == 1 && GET_CODE (src) == MINUS) return NULL; something = (accum_pos == 0) ? op2 : op1; if (rtx_referenced_p (dest, something)) return NULL; if (!referenced_in_one_insn_in_loop_p (loop, dest, &debug_uses)) return NULL; mode1 = GET_MODE (dest); mode2 = GET_MODE (something); if ((FLOAT_MODE_P (mode1) || FLOAT_MODE_P (mode2)) && !flag_associative_math) return NULL; if (dump_file) { fprintf (dump_file, "\n;; Expanding Accumulator "); print_rtl (dump_file, dest); fprintf (dump_file, "\n"); } if (debug_uses) /* Instead of resetting the debug insns, we could replace each debug use in the loop with the sum or product of all expanded accummulators. Since we'll only know of all expansions at the end, we'd have to keep track of which vars_to_expand a debug insn in the loop references, take note of each copy of the debug insn during unrolling, and when it's all done, compute the sum or product of each variable and adjust the original debug insn and each copy thereof. What a pain! */ reset_debug_uses_in_loop (loop, dest, debug_uses); /* Record the accumulator to expand. */ ves = XNEW (struct var_to_expand); ves->insn = insn; ves->reg = copy_rtx (dest); ves->var_expansions = VEC_alloc (rtx, heap, 1); ves->next = NULL; ves->op = GET_CODE (src); ves->expansion_count = 0; ves->reuse_expansion = 0; ves->accum_pos = accum_pos; return ves; } /* Determine whether there is an induction variable in INSN that we would like to split during unrolling. I.e. replace i = i + 1; ... i = i + 1; ... i = i + 1; ... type chains by i0 = i + 1 ... i = i0 + 1 ... i = i0 + 2 ... Return NULL if INSN contains no interesting IVs. Otherwise, allocate an IV_TO_SPLIT structure, fill it with the relevant information and return a pointer to it. */ static struct iv_to_split * analyze_iv_to_split_insn (rtx insn) { rtx set, dest; struct rtx_iv iv; struct iv_to_split *ivts; bool ok; /* For now we just split the basic induction variables. Later this may be extended for example by selecting also addresses of memory references. */ set = single_set (insn); if (!set) return NULL; dest = SET_DEST (set); if (!REG_P (dest)) return NULL; if (!biv_p (insn, dest)) return NULL; ok = iv_analyze_result (insn, dest, &iv); /* This used to be an assert under the assumption that if biv_p returns true that iv_analyze_result must also return true. However, that assumption is not strictly correct as evidenced by pr25569. Returning NULL when iv_analyze_result returns false is safe and avoids the problems in pr25569 until the iv_analyze_* routines can be fixed, which is apparently hard and time consuming according to their author. */ if (! ok) return NULL; if (iv.step == const0_rtx || iv.mode != iv.extend_mode) return NULL; /* Record the insn to split. */ ivts = XNEW (struct iv_to_split); ivts->insn = insn; ivts->base_var = NULL_RTX; ivts->step = iv.step; ivts->next = NULL; ivts->n_loc = 1; ivts->loc[0] = 1; return ivts; } /* Determines which of insns in LOOP can be optimized. Return a OPT_INFO struct with the relevant hash tables filled with all insns to be optimized. The FIRST_NEW_BLOCK field is undefined for the return value. */ static struct opt_info * analyze_insns_in_loop (struct loop *loop) { basic_block *body, bb; unsigned i; struct opt_info *opt_info = XCNEW (struct opt_info); rtx insn; struct iv_to_split *ivts = NULL; struct var_to_expand *ves = NULL; PTR *slot1; PTR *slot2; VEC (edge, heap) *edges = get_loop_exit_edges (loop); edge exit; bool can_apply = false; iv_analysis_loop_init (loop); body = get_loop_body (loop); if (flag_split_ivs_in_unroller) { opt_info->insns_to_split = htab_create (5 * loop->num_nodes, si_info_hash, si_info_eq, free); opt_info->iv_to_split_head = NULL; opt_info->iv_to_split_tail = &opt_info->iv_to_split_head; } /* Record the loop exit bb and loop preheader before the unrolling. */ opt_info->loop_preheader = loop_preheader_edge (loop)->src; if (VEC_length (edge, edges) == 1) { exit = VEC_index (edge, edges, 0); if (!(exit->flags & EDGE_COMPLEX)) { opt_info->loop_exit = split_edge (exit); can_apply = true; } } if (flag_variable_expansion_in_unroller && can_apply) { opt_info->insns_with_var_to_expand = htab_create (5 * loop->num_nodes, ve_info_hash, ve_info_eq, free); opt_info->var_to_expand_head = NULL; opt_info->var_to_expand_tail = &opt_info->var_to_expand_head; } for (i = 0; i < loop->num_nodes; i++) { bb = body[i]; if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb)) continue; FOR_BB_INSNS (bb, insn) { if (!INSN_P (insn)) continue; if (opt_info->insns_to_split) ivts = analyze_iv_to_split_insn (insn); if (ivts) { slot1 = htab_find_slot (opt_info->insns_to_split, ivts, INSERT); gcc_assert (*slot1 == NULL); *slot1 = ivts; *opt_info->iv_to_split_tail = ivts; opt_info->iv_to_split_tail = &ivts->next; continue; } if (opt_info->insns_with_var_to_expand) ves = analyze_insn_to_expand_var (loop, insn); if (ves) { slot2 = htab_find_slot (opt_info->insns_with_var_to_expand, ves, INSERT); gcc_assert (*slot2 == NULL); *slot2 = ves; *opt_info->var_to_expand_tail = ves; opt_info->var_to_expand_tail = &ves->next; } } } VEC_free (edge, heap, edges); free (body); return opt_info; } /* Called just before loop duplication. Records start of duplicated area to OPT_INFO. */ static void opt_info_start_duplication (struct opt_info *opt_info) { if (opt_info) opt_info->first_new_block = last_basic_block; } /* Determine the number of iterations between initialization of the base variable and the current copy (N_COPY). N_COPIES is the total number of newly created copies. UNROLLING is true if we are unrolling (not peeling) the loop. */ static unsigned determine_split_iv_delta (unsigned n_copy, unsigned n_copies, bool unrolling) { if (unrolling) { /* If we are unrolling, initialization is done in the original loop body (number 0). */ return n_copy; } else { /* If we are peeling, the copy in that the initialization occurs has number 1. The original loop (number 0) is the last. */ if (n_copy) return n_copy - 1; else return n_copies; } } /* Locate in EXPR the expression corresponding to the location recorded in IVTS, and return a pointer to the RTX for this location. */ static rtx * get_ivts_expr (rtx expr, struct iv_to_split *ivts) { unsigned i; rtx *ret = &expr; for (i = 0; i < ivts->n_loc; i++) ret = &XEXP (*ret, ivts->loc[i]); return ret; } /* Allocate basic variable for the induction variable chain. */ static void allocate_basic_variable (struct iv_to_split *ivts) { rtx expr = *get_ivts_expr (single_set (ivts->insn), ivts); ivts->base_var = gen_reg_rtx (GET_MODE (expr)); } /* Insert initialization of basic variable of IVTS before INSN, taking the initial value from INSN. */ static void insert_base_initialization (struct iv_to_split *ivts, rtx insn) { rtx expr = copy_rtx (*get_ivts_expr (single_set (insn), ivts)); rtx seq; start_sequence (); expr = force_operand (expr, ivts->base_var); if (expr != ivts->base_var) emit_move_insn (ivts->base_var, expr); seq = get_insns (); end_sequence (); emit_insn_before (seq, insn); } /* Replace the use of induction variable described in IVTS in INSN by base variable + DELTA * step. */ static void split_iv (struct iv_to_split *ivts, rtx insn, unsigned delta) { rtx expr, *loc, seq, incr, var; enum machine_mode mode = GET_MODE (ivts->base_var); rtx src, dest, set; /* Construct base + DELTA * step. */ if (!delta) expr = ivts->base_var; else { incr = simplify_gen_binary (MULT, mode, ivts->step, gen_int_mode (delta, mode)); expr = simplify_gen_binary (PLUS, GET_MODE (ivts->base_var), ivts->base_var, incr); } /* Figure out where to do the replacement. */ loc = get_ivts_expr (single_set (insn), ivts); /* If we can make the replacement right away, we're done. */ if (validate_change (insn, loc, expr, 0)) return; /* Otherwise, force EXPR into a register and try again. */ start_sequence (); var = gen_reg_rtx (mode); expr = force_operand (expr, var); if (expr != var) emit_move_insn (var, expr); seq = get_insns (); end_sequence (); emit_insn_before (seq, insn); if (validate_change (insn, loc, var, 0)) return; /* The last chance. Try recreating the assignment in insn completely from scratch. */ set = single_set (insn); gcc_assert (set); start_sequence (); *loc = var; src = copy_rtx (SET_SRC (set)); dest = copy_rtx (SET_DEST (set)); src = force_operand (src, dest); if (src != dest) emit_move_insn (dest, src); seq = get_insns (); end_sequence (); emit_insn_before (seq, insn); delete_insn (insn); } /* Return one expansion of the accumulator recorded in struct VE. */ static rtx get_expansion (struct var_to_expand *ve) { rtx reg; if (ve->reuse_expansion == 0) reg = ve->reg; else reg = VEC_index (rtx, ve->var_expansions, ve->reuse_expansion - 1); if (VEC_length (rtx, ve->var_expansions) == (unsigned) ve->reuse_expansion) ve->reuse_expansion = 0; else ve->reuse_expansion++; return reg; } /* Given INSN replace the uses of the accumulator recorded in VE with a new register. */ static void expand_var_during_unrolling (struct var_to_expand *ve, rtx insn) { rtx new_reg, set; bool really_new_expansion = false; set = single_set (insn); gcc_assert (set); /* Generate a new register only if the expansion limit has not been reached. Else reuse an already existing expansion. */ if (PARAM_VALUE (PARAM_MAX_VARIABLE_EXPANSIONS) > ve->expansion_count) { really_new_expansion = true; new_reg = gen_reg_rtx (GET_MODE (ve->reg)); } else new_reg = get_expansion (ve); validate_change (insn, &SET_DEST (set), new_reg, 1); validate_change (insn, &XEXP (SET_SRC (set), ve->accum_pos), new_reg, 1); if (apply_change_group ()) if (really_new_expansion) { VEC_safe_push (rtx, heap, ve->var_expansions, new_reg); ve->expansion_count++; } } /* Initialize the variable expansions in loop preheader. PLACE is the loop-preheader basic block where the initialization of the expansions should take place. The expansions are initialized with (-0) when the operation is plus or minus to honor sign zero. This way we can prevent cases where the sign of the final result is effected by the sign of the expansion. Here is an example to demonstrate this: for (i = 0 ; i < n; i++) sum += something; ==> sum += something .... i = i+1; sum1 += something .... i = i+1 sum2 += something; .... When SUM is initialized with -zero and SOMETHING is also -zero; the final result of sum should be -zero thus the expansions sum1 and sum2 should be initialized with -zero as well (otherwise we will get +zero as the final result). */ static void insert_var_expansion_initialization (struct var_to_expand *ve, basic_block place) { rtx seq, var, zero_init, insn; unsigned i; enum machine_mode mode = GET_MODE (ve->reg); bool honor_signed_zero_p = HONOR_SIGNED_ZEROS (mode); if (VEC_length (rtx, ve->var_expansions) == 0) return; start_sequence (); if (ve->op == PLUS || ve->op == MINUS) for (i = 0; VEC_iterate (rtx, ve->var_expansions, i, var); i++) { if (honor_signed_zero_p) zero_init = simplify_gen_unary (NEG, mode, CONST0_RTX (mode), mode); else zero_init = CONST0_RTX (mode); emit_move_insn (var, zero_init); } else if (ve->op == MULT) for (i = 0; VEC_iterate (rtx, ve->var_expansions, i, var); i++) { zero_init = CONST1_RTX (GET_MODE (var)); emit_move_insn (var, zero_init); } seq = get_insns (); end_sequence (); insn = BB_HEAD (place); while (!NOTE_INSN_BASIC_BLOCK_P (insn)) insn = NEXT_INSN (insn); emit_insn_after (seq, insn); } /* Combine the variable expansions at the loop exit. PLACE is the loop exit basic block where the summation of the expansions should take place. */ static void combine_var_copies_in_loop_exit (struct var_to_expand *ve, basic_block place) { rtx sum = ve->reg; rtx expr, seq, var, insn; unsigned i; if (VEC_length (rtx, ve->var_expansions) == 0) return; start_sequence (); if (ve->op == PLUS || ve->op == MINUS) for (i = 0; VEC_iterate (rtx, ve->var_expansions, i, var); i++) { sum = simplify_gen_binary (PLUS, GET_MODE (ve->reg), var, sum); } else if (ve->op == MULT) for (i = 0; VEC_iterate (rtx, ve->var_expansions, i, var); i++) { sum = simplify_gen_binary (MULT, GET_MODE (ve->reg), var, sum); } expr = force_operand (sum, ve->reg); if (expr != ve->reg) emit_move_insn (ve->reg, expr); seq = get_insns (); end_sequence (); insn = BB_HEAD (place); while (!NOTE_INSN_BASIC_BLOCK_P (insn)) insn = NEXT_INSN (insn); emit_insn_after (seq, insn); } /* Apply loop optimizations in loop copies using the data which gathered during the unrolling. Structure OPT_INFO record that data. UNROLLING is true if we unrolled (not peeled) the loop. REWRITE_ORIGINAL_BODY is true if we should also rewrite the original body of the loop (as it should happen in complete unrolling, but not in ordinary peeling of the loop). */ static void apply_opt_in_copies (struct opt_info *opt_info, unsigned n_copies, bool unrolling, bool rewrite_original_loop) { unsigned i, delta; basic_block bb, orig_bb; rtx insn, orig_insn, next; struct iv_to_split ivts_templ, *ivts; struct var_to_expand ve_templ, *ves; /* Sanity check -- we need to put initialization in the original loop body. */ gcc_assert (!unrolling || rewrite_original_loop); /* Allocate the basic variables (i0). */ if (opt_info->insns_to_split) for (ivts = opt_info->iv_to_split_head; ivts; ivts = ivts->next) allocate_basic_variable (ivts); for (i = opt_info->first_new_block; i < (unsigned) last_basic_block; i++) { bb = BASIC_BLOCK (i); orig_bb = get_bb_original (bb); /* bb->aux holds position in copy sequence initialized by duplicate_loop_to_header_edge. */ delta = determine_split_iv_delta ((size_t)bb->aux, n_copies, unrolling); bb->aux = 0; orig_insn = BB_HEAD (orig_bb); for (insn = BB_HEAD (bb); insn != NEXT_INSN (BB_END (bb)); insn = next) { next = NEXT_INSN (insn); if (!INSN_P (insn)) continue; while (!INSN_P (orig_insn)) orig_insn = NEXT_INSN (orig_insn); ivts_templ.insn = orig_insn; ve_templ.insn = orig_insn; /* Apply splitting iv optimization. */ if (opt_info->insns_to_split) { ivts = (struct iv_to_split *) htab_find (opt_info->insns_to_split, &ivts_templ); if (ivts) { gcc_assert (GET_CODE (PATTERN (insn)) == GET_CODE (PATTERN (orig_insn))); if (!delta) insert_base_initialization (ivts, insn); split_iv (ivts, insn, delta); } } /* Apply variable expansion optimization. */ if (unrolling && opt_info->insns_with_var_to_expand) { ves = (struct var_to_expand *) htab_find (opt_info->insns_with_var_to_expand, &ve_templ); if (ves) { gcc_assert (GET_CODE (PATTERN (insn)) == GET_CODE (PATTERN (orig_insn))); expand_var_during_unrolling (ves, insn); } } orig_insn = NEXT_INSN (orig_insn); } } if (!rewrite_original_loop) return; /* Initialize the variable expansions in the loop preheader and take care of combining them at the loop exit. */ if (opt_info->insns_with_var_to_expand) { for (ves = opt_info->var_to_expand_head; ves; ves = ves->next) insert_var_expansion_initialization (ves, opt_info->loop_preheader); for (ves = opt_info->var_to_expand_head; ves; ves = ves->next) combine_var_copies_in_loop_exit (ves, opt_info->loop_exit); } /* Rewrite also the original loop body. Find them as originals of the blocks in the last copied iteration, i.e. those that have get_bb_copy (get_bb_original (bb)) == bb. */ for (i = opt_info->first_new_block; i < (unsigned) last_basic_block; i++) { bb = BASIC_BLOCK (i); orig_bb = get_bb_original (bb); if (get_bb_copy (orig_bb) != bb) continue; delta = determine_split_iv_delta (0, n_copies, unrolling); for (orig_insn = BB_HEAD (orig_bb); orig_insn != NEXT_INSN (BB_END (bb)); orig_insn = next) { next = NEXT_INSN (orig_insn); if (!INSN_P (orig_insn)) continue; ivts_templ.insn = orig_insn; if (opt_info->insns_to_split) { ivts = (struct iv_to_split *) htab_find (opt_info->insns_to_split, &ivts_templ); if (ivts) { if (!delta) insert_base_initialization (ivts, orig_insn); split_iv (ivts, orig_insn, delta); continue; } } } } } /* Release OPT_INFO. */ static void free_opt_info (struct opt_info *opt_info) { if (opt_info->insns_to_split) htab_delete (opt_info->insns_to_split); if (opt_info->insns_with_var_to_expand) { struct var_to_expand *ves; for (ves = opt_info->var_to_expand_head; ves; ves = ves->next) VEC_free (rtx, heap, ves->var_expansions); htab_delete (opt_info->insns_with_var_to_expand); } free (opt_info); }
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