| /* Branch prediction routines for the GNU compiler. |
| Copyright (C) 2000-2021 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/>. */ |
| |
| /* References: |
| |
| [1] "Branch Prediction for Free" |
| Ball and Larus; PLDI '93. |
| [2] "Static Branch Frequency and Program Profile Analysis" |
| Wu and Larus; MICRO-27. |
| [3] "Corpus-based Static Branch Prediction" |
| Calder, Grunwald, Lindsay, Martin, Mozer, and Zorn; PLDI '95. */ |
| |
| |
| #include "config.h" |
| #include "system.h" |
| #include "coretypes.h" |
| #include "backend.h" |
| #include "rtl.h" |
| #include "tree.h" |
| #include "gimple.h" |
| #include "cfghooks.h" |
| #include "tree-pass.h" |
| #include "ssa.h" |
| #include "memmodel.h" |
| #include "emit-rtl.h" |
| #include "cgraph.h" |
| #include "coverage.h" |
| #include "diagnostic-core.h" |
| #include "gimple-predict.h" |
| #include "fold-const.h" |
| #include "calls.h" |
| #include "cfganal.h" |
| #include "profile.h" |
| #include "sreal.h" |
| #include "cfgloop.h" |
| #include "gimple-iterator.h" |
| #include "tree-cfg.h" |
| #include "tree-ssa-loop-niter.h" |
| #include "tree-ssa-loop.h" |
| #include "tree-scalar-evolution.h" |
| #include "ipa-utils.h" |
| #include "gimple-pretty-print.h" |
| #include "selftest.h" |
| #include "cfgrtl.h" |
| #include "stringpool.h" |
| #include "attribs.h" |
| |
| /* Enum with reasons why a predictor is ignored. */ |
| |
| enum predictor_reason |
| { |
| REASON_NONE, |
| REASON_IGNORED, |
| REASON_SINGLE_EDGE_DUPLICATE, |
| REASON_EDGE_PAIR_DUPLICATE |
| }; |
| |
| /* String messages for the aforementioned enum. */ |
| |
| static const char *reason_messages[] = {"", " (ignored)", |
| " (single edge duplicate)", " (edge pair duplicate)"}; |
| |
| |
| static void combine_predictions_for_insn (rtx_insn *, basic_block); |
| static void dump_prediction (FILE *, enum br_predictor, int, basic_block, |
| enum predictor_reason, edge); |
| static void predict_paths_leading_to (basic_block, enum br_predictor, |
| enum prediction, |
| class loop *in_loop = NULL); |
| static void predict_paths_leading_to_edge (edge, enum br_predictor, |
| enum prediction, |
| class loop *in_loop = NULL); |
| static bool can_predict_insn_p (const rtx_insn *); |
| static HOST_WIDE_INT get_predictor_value (br_predictor, HOST_WIDE_INT); |
| static void determine_unlikely_bbs (); |
| |
| /* Information we hold about each branch predictor. |
| Filled using information from predict.def. */ |
| |
| struct predictor_info |
| { |
| const char *const name; /* Name used in the debugging dumps. */ |
| const int hitrate; /* Expected hitrate used by |
| predict_insn_def call. */ |
| const int flags; |
| }; |
| |
| /* Use given predictor without Dempster-Shaffer theory if it matches |
| using first_match heuristics. */ |
| #define PRED_FLAG_FIRST_MATCH 1 |
| |
| /* Recompute hitrate in percent to our representation. */ |
| |
| #define HITRATE(VAL) ((int) ((VAL) * REG_BR_PROB_BASE + 50) / 100) |
| |
| #define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) {NAME, HITRATE, FLAGS}, |
| static const struct predictor_info predictor_info[]= { |
| #include "predict.def" |
| |
| /* Upper bound on predictors. */ |
| {NULL, 0, 0} |
| }; |
| #undef DEF_PREDICTOR |
| |
| static gcov_type min_count = -1; |
| |
| /* Determine the threshold for hot BB counts. */ |
| |
| gcov_type |
| get_hot_bb_threshold () |
| { |
| if (min_count == -1) |
| { |
| const int hot_frac = param_hot_bb_count_fraction; |
| const gcov_type min_hot_count |
| = hot_frac |
| ? profile_info->sum_max / hot_frac |
| : (gcov_type)profile_count::max_count; |
| set_hot_bb_threshold (min_hot_count); |
| if (dump_file) |
| fprintf (dump_file, "Setting hotness threshold to %" PRId64 ".\n", |
| min_hot_count); |
| } |
| return min_count; |
| } |
| |
| /* Set the threshold for hot BB counts. */ |
| |
| void |
| set_hot_bb_threshold (gcov_type min) |
| { |
| min_count = min; |
| } |
| |
| /* Return TRUE if COUNT is considered to be hot in function FUN. */ |
| |
| bool |
| maybe_hot_count_p (struct function *fun, profile_count count) |
| { |
| if (!count.initialized_p ()) |
| return true; |
| if (count.ipa () == profile_count::zero ()) |
| return false; |
| if (!count.ipa_p ()) |
| { |
| struct cgraph_node *node = cgraph_node::get (fun->decl); |
| if (!profile_info || profile_status_for_fn (fun) != PROFILE_READ) |
| { |
| if (node->frequency == NODE_FREQUENCY_UNLIKELY_EXECUTED) |
| return false; |
| if (node->frequency == NODE_FREQUENCY_HOT) |
| return true; |
| } |
| if (profile_status_for_fn (fun) == PROFILE_ABSENT) |
| return true; |
| if (node->frequency == NODE_FREQUENCY_EXECUTED_ONCE |
| && count < (ENTRY_BLOCK_PTR_FOR_FN (fun)->count.apply_scale (2, 3))) |
| return false; |
| if (count.apply_scale (param_hot_bb_frequency_fraction, 1) |
| < ENTRY_BLOCK_PTR_FOR_FN (fun)->count) |
| return false; |
| return true; |
| } |
| /* Code executed at most once is not hot. */ |
| if (count <= MAX (profile_info ? profile_info->runs : 1, 1)) |
| return false; |
| return (count >= get_hot_bb_threshold ()); |
| } |
| |
| /* Return true if basic block BB of function FUN can be CPU intensive |
| and should thus be optimized for maximum performance. */ |
| |
| bool |
| maybe_hot_bb_p (struct function *fun, const_basic_block bb) |
| { |
| gcc_checking_assert (fun); |
| return maybe_hot_count_p (fun, bb->count); |
| } |
| |
| /* Return true if edge E can be CPU intensive and should thus be optimized |
| for maximum performance. */ |
| |
| bool |
| maybe_hot_edge_p (edge e) |
| { |
| return maybe_hot_count_p (cfun, e->count ()); |
| } |
| |
| /* Return true if COUNT is considered to be never executed in function FUN |
| or if function FUN is considered so in the static profile. */ |
| |
| static bool |
| probably_never_executed (struct function *fun, profile_count count) |
| { |
| gcc_checking_assert (fun); |
| if (count.ipa () == profile_count::zero ()) |
| return true; |
| /* Do not trust adjusted counts. This will make us to drop int cold section |
| code with low execution count as a result of inlining. These low counts |
| are not safe even with read profile and may lead us to dropping |
| code which actually gets executed into cold section of binary that is not |
| desirable. */ |
| if (count.precise_p () && profile_status_for_fn (fun) == PROFILE_READ) |
| { |
| const int unlikely_frac = param_unlikely_bb_count_fraction; |
| if (count.apply_scale (unlikely_frac, 1) >= profile_info->runs) |
| return false; |
| return true; |
| } |
| if ((!profile_info || profile_status_for_fn (fun) != PROFILE_READ) |
| && (cgraph_node::get (fun->decl)->frequency |
| == NODE_FREQUENCY_UNLIKELY_EXECUTED)) |
| return true; |
| return false; |
| } |
| |
| /* Return true if basic block BB of function FUN is probably never executed. */ |
| |
| bool |
| probably_never_executed_bb_p (struct function *fun, const_basic_block bb) |
| { |
| return probably_never_executed (fun, bb->count); |
| } |
| |
| /* Return true if edge E is unlikely executed for obvious reasons. */ |
| |
| static bool |
| unlikely_executed_edge_p (edge e) |
| { |
| return (e->src->count == profile_count::zero () |
| || e->probability == profile_probability::never ()) |
| || (e->flags & (EDGE_EH | EDGE_FAKE)); |
| } |
| |
| /* Return true if edge E of function FUN is probably never executed. */ |
| |
| bool |
| probably_never_executed_edge_p (struct function *fun, edge e) |
| { |
| if (unlikely_executed_edge_p (e)) |
| return true; |
| return probably_never_executed (fun, e->count ()); |
| } |
| |
| /* Return true if function FUN should always be optimized for size. */ |
| |
| optimize_size_level |
| optimize_function_for_size_p (struct function *fun) |
| { |
| if (!fun || !fun->decl) |
| return optimize_size ? OPTIMIZE_SIZE_MAX : OPTIMIZE_SIZE_NO; |
| cgraph_node *n = cgraph_node::get (fun->decl); |
| if (n) |
| return n->optimize_for_size_p (); |
| return OPTIMIZE_SIZE_NO; |
| } |
| |
| /* Return true if function FUN should always be optimized for speed. */ |
| |
| bool |
| optimize_function_for_speed_p (struct function *fun) |
| { |
| return !optimize_function_for_size_p (fun); |
| } |
| |
| /* Return the optimization type that should be used for function FUN. */ |
| |
| optimization_type |
| function_optimization_type (struct function *fun) |
| { |
| return (optimize_function_for_speed_p (fun) |
| ? OPTIMIZE_FOR_SPEED |
| : OPTIMIZE_FOR_SIZE); |
| } |
| |
| /* Return TRUE if basic block BB should be optimized for size. */ |
| |
| optimize_size_level |
| optimize_bb_for_size_p (const_basic_block bb) |
| { |
| enum optimize_size_level ret = optimize_function_for_size_p (cfun); |
| |
| if (bb && ret < OPTIMIZE_SIZE_MAX && bb->count == profile_count::zero ()) |
| ret = OPTIMIZE_SIZE_MAX; |
| if (bb && ret < OPTIMIZE_SIZE_BALANCED && !maybe_hot_bb_p (cfun, bb)) |
| ret = OPTIMIZE_SIZE_BALANCED; |
| return ret; |
| } |
| |
| /* Return TRUE if basic block BB should be optimized for speed. */ |
| |
| bool |
| optimize_bb_for_speed_p (const_basic_block bb) |
| { |
| return !optimize_bb_for_size_p (bb); |
| } |
| |
| /* Return the optimization type that should be used for basic block BB. */ |
| |
| optimization_type |
| bb_optimization_type (const_basic_block bb) |
| { |
| return (optimize_bb_for_speed_p (bb) |
| ? OPTIMIZE_FOR_SPEED |
| : OPTIMIZE_FOR_SIZE); |
| } |
| |
| /* Return TRUE if edge E should be optimized for size. */ |
| |
| optimize_size_level |
| optimize_edge_for_size_p (edge e) |
| { |
| enum optimize_size_level ret = optimize_function_for_size_p (cfun); |
| |
| if (ret < OPTIMIZE_SIZE_MAX && unlikely_executed_edge_p (e)) |
| ret = OPTIMIZE_SIZE_MAX; |
| if (ret < OPTIMIZE_SIZE_BALANCED && !maybe_hot_edge_p (e)) |
| ret = OPTIMIZE_SIZE_BALANCED; |
| return ret; |
| } |
| |
| /* Return TRUE if edge E should be optimized for speed. */ |
| |
| bool |
| optimize_edge_for_speed_p (edge e) |
| { |
| return !optimize_edge_for_size_p (e); |
| } |
| |
| /* Return TRUE if the current function is optimized for size. */ |
| |
| optimize_size_level |
| optimize_insn_for_size_p (void) |
| { |
| enum optimize_size_level ret = optimize_function_for_size_p (cfun); |
| if (ret < OPTIMIZE_SIZE_BALANCED && !crtl->maybe_hot_insn_p) |
| ret = OPTIMIZE_SIZE_BALANCED; |
| return ret; |
| } |
| |
| /* Return TRUE if the current function is optimized for speed. */ |
| |
| bool |
| optimize_insn_for_speed_p (void) |
| { |
| return !optimize_insn_for_size_p (); |
| } |
| |
| /* Return TRUE if LOOP should be optimized for size. */ |
| |
| optimize_size_level |
| optimize_loop_for_size_p (class loop *loop) |
| { |
| return optimize_bb_for_size_p (loop->header); |
| } |
| |
| /* Return TRUE if LOOP should be optimized for speed. */ |
| |
| bool |
| optimize_loop_for_speed_p (class loop *loop) |
| { |
| return optimize_bb_for_speed_p (loop->header); |
| } |
| |
| /* Return TRUE if nest rooted at LOOP should be optimized for speed. */ |
| |
| bool |
| optimize_loop_nest_for_speed_p (class loop *loop) |
| { |
| class loop *l = loop; |
| if (optimize_loop_for_speed_p (loop)) |
| return true; |
| l = loop->inner; |
| while (l && l != loop) |
| { |
| if (optimize_loop_for_speed_p (l)) |
| return true; |
| if (l->inner) |
| l = l->inner; |
| else if (l->next) |
| l = l->next; |
| else |
| { |
| while (l != loop && !l->next) |
| l = loop_outer (l); |
| if (l != loop) |
| l = l->next; |
| } |
| } |
| return false; |
| } |
| |
| /* Return TRUE if nest rooted at LOOP should be optimized for size. */ |
| |
| optimize_size_level |
| optimize_loop_nest_for_size_p (class loop *loop) |
| { |
| enum optimize_size_level ret = optimize_loop_for_size_p (loop); |
| class loop *l = loop; |
| |
| l = loop->inner; |
| while (l && l != loop) |
| { |
| if (ret == OPTIMIZE_SIZE_NO) |
| break; |
| ret = MIN (optimize_loop_for_size_p (l), ret); |
| if (l->inner) |
| l = l->inner; |
| else if (l->next) |
| l = l->next; |
| else |
| { |
| while (l != loop && !l->next) |
| l = loop_outer (l); |
| if (l != loop) |
| l = l->next; |
| } |
| } |
| return ret; |
| } |
| |
| /* Return true if edge E is likely to be well predictable by branch |
| predictor. */ |
| |
| bool |
| predictable_edge_p (edge e) |
| { |
| if (!e->probability.initialized_p ()) |
| return false; |
| if ((e->probability.to_reg_br_prob_base () |
| <= param_predictable_branch_outcome * REG_BR_PROB_BASE / 100) |
| || (REG_BR_PROB_BASE - e->probability.to_reg_br_prob_base () |
| <= param_predictable_branch_outcome * REG_BR_PROB_BASE / 100)) |
| return true; |
| return false; |
| } |
| |
| |
| /* Set RTL expansion for BB profile. */ |
| |
| void |
| rtl_profile_for_bb (basic_block bb) |
| { |
| crtl->maybe_hot_insn_p = maybe_hot_bb_p (cfun, bb); |
| } |
| |
| /* Set RTL expansion for edge profile. */ |
| |
| void |
| rtl_profile_for_edge (edge e) |
| { |
| crtl->maybe_hot_insn_p = maybe_hot_edge_p (e); |
| } |
| |
| /* Set RTL expansion to default mode (i.e. when profile info is not known). */ |
| void |
| default_rtl_profile (void) |
| { |
| crtl->maybe_hot_insn_p = true; |
| } |
| |
| /* Return true if the one of outgoing edges is already predicted by |
| PREDICTOR. */ |
| |
| bool |
| rtl_predicted_by_p (const_basic_block bb, enum br_predictor predictor) |
| { |
| rtx note; |
| if (!INSN_P (BB_END (bb))) |
| return false; |
| for (note = REG_NOTES (BB_END (bb)); note; note = XEXP (note, 1)) |
| if (REG_NOTE_KIND (note) == REG_BR_PRED |
| && INTVAL (XEXP (XEXP (note, 0), 0)) == (int)predictor) |
| return true; |
| return false; |
| } |
| |
| /* Structure representing predictions in tree level. */ |
| |
| struct edge_prediction { |
| struct edge_prediction *ep_next; |
| edge ep_edge; |
| enum br_predictor ep_predictor; |
| int ep_probability; |
| }; |
| |
| /* This map contains for a basic block the list of predictions for the |
| outgoing edges. */ |
| |
| static hash_map<const_basic_block, edge_prediction *> *bb_predictions; |
| |
| /* Return true if the one of outgoing edges is already predicted by |
| PREDICTOR. */ |
| |
| bool |
| gimple_predicted_by_p (const_basic_block bb, enum br_predictor predictor) |
| { |
| struct edge_prediction *i; |
| edge_prediction **preds = bb_predictions->get (bb); |
| |
| if (!preds) |
| return false; |
| |
| for (i = *preds; i; i = i->ep_next) |
| if (i->ep_predictor == predictor) |
| return true; |
| return false; |
| } |
| |
| /* Return true if the one of outgoing edges is already predicted by |
| PREDICTOR for edge E predicted as TAKEN. */ |
| |
| bool |
| edge_predicted_by_p (edge e, enum br_predictor predictor, bool taken) |
| { |
| struct edge_prediction *i; |
| basic_block bb = e->src; |
| edge_prediction **preds = bb_predictions->get (bb); |
| if (!preds) |
| return false; |
| |
| int probability = predictor_info[(int) predictor].hitrate; |
| |
| if (taken != TAKEN) |
| probability = REG_BR_PROB_BASE - probability; |
| |
| for (i = *preds; i; i = i->ep_next) |
| if (i->ep_predictor == predictor |
| && i->ep_edge == e |
| && i->ep_probability == probability) |
| return true; |
| return false; |
| } |
| |
| /* Same predicate as above, working on edges. */ |
| bool |
| edge_probability_reliable_p (const_edge e) |
| { |
| return e->probability.probably_reliable_p (); |
| } |
| |
| /* Same predicate as edge_probability_reliable_p, working on notes. */ |
| bool |
| br_prob_note_reliable_p (const_rtx note) |
| { |
| gcc_assert (REG_NOTE_KIND (note) == REG_BR_PROB); |
| return profile_probability::from_reg_br_prob_note |
| (XINT (note, 0)).probably_reliable_p (); |
| } |
| |
| static void |
| predict_insn (rtx_insn *insn, enum br_predictor predictor, int probability) |
| { |
| gcc_assert (any_condjump_p (insn)); |
| if (!flag_guess_branch_prob) |
| return; |
| |
| add_reg_note (insn, REG_BR_PRED, |
| gen_rtx_CONCAT (VOIDmode, |
| GEN_INT ((int) predictor), |
| GEN_INT ((int) probability))); |
| } |
| |
| /* Predict insn by given predictor. */ |
| |
| void |
| predict_insn_def (rtx_insn *insn, enum br_predictor predictor, |
| enum prediction taken) |
| { |
| int probability = predictor_info[(int) predictor].hitrate; |
| gcc_assert (probability != PROB_UNINITIALIZED); |
| |
| if (taken != TAKEN) |
| probability = REG_BR_PROB_BASE - probability; |
| |
| predict_insn (insn, predictor, probability); |
| } |
| |
| /* Predict edge E with given probability if possible. */ |
| |
| void |
| rtl_predict_edge (edge e, enum br_predictor predictor, int probability) |
| { |
| rtx_insn *last_insn; |
| last_insn = BB_END (e->src); |
| |
| /* We can store the branch prediction information only about |
| conditional jumps. */ |
| if (!any_condjump_p (last_insn)) |
| return; |
| |
| /* We always store probability of branching. */ |
| if (e->flags & EDGE_FALLTHRU) |
| probability = REG_BR_PROB_BASE - probability; |
| |
| predict_insn (last_insn, predictor, probability); |
| } |
| |
| /* Predict edge E with the given PROBABILITY. */ |
| void |
| gimple_predict_edge (edge e, enum br_predictor predictor, int probability) |
| { |
| if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun) |
| && EDGE_COUNT (e->src->succs) > 1 |
| && flag_guess_branch_prob |
| && optimize) |
| { |
| struct edge_prediction *i = XNEW (struct edge_prediction); |
| edge_prediction *&preds = bb_predictions->get_or_insert (e->src); |
| |
| i->ep_next = preds; |
| preds = i; |
| i->ep_probability = probability; |
| i->ep_predictor = predictor; |
| i->ep_edge = e; |
| } |
| } |
| |
| /* Filter edge predictions PREDS by a function FILTER: if FILTER return false |
| the prediction is removed. |
| DATA are passed to the filter function. */ |
| |
| static void |
| filter_predictions (edge_prediction **preds, |
| bool (*filter) (edge_prediction *, void *), void *data) |
| { |
| if (!bb_predictions) |
| return; |
| |
| if (preds) |
| { |
| struct edge_prediction **prediction = preds; |
| struct edge_prediction *next; |
| |
| while (*prediction) |
| { |
| if ((*filter) (*prediction, data)) |
| prediction = &((*prediction)->ep_next); |
| else |
| { |
| next = (*prediction)->ep_next; |
| free (*prediction); |
| *prediction = next; |
| } |
| } |
| } |
| } |
| |
| /* Filter function predicate that returns true for a edge predicate P |
| if its edge is equal to DATA. */ |
| |
| static bool |
| not_equal_edge_p (edge_prediction *p, void *data) |
| { |
| return p->ep_edge != (edge)data; |
| } |
| |
| /* Remove all predictions on given basic block that are attached |
| to edge E. */ |
| void |
| remove_predictions_associated_with_edge (edge e) |
| { |
| if (!bb_predictions) |
| return; |
| |
| edge_prediction **preds = bb_predictions->get (e->src); |
| filter_predictions (preds, not_equal_edge_p, e); |
| } |
| |
| /* Clears the list of predictions stored for BB. */ |
| |
| static void |
| clear_bb_predictions (basic_block bb) |
| { |
| edge_prediction **preds = bb_predictions->get (bb); |
| struct edge_prediction *pred, *next; |
| |
| if (!preds) |
| return; |
| |
| for (pred = *preds; pred; pred = next) |
| { |
| next = pred->ep_next; |
| free (pred); |
| } |
| *preds = NULL; |
| } |
| |
| /* Return true when we can store prediction on insn INSN. |
| At the moment we represent predictions only on conditional |
| jumps, not at computed jump or other complicated cases. */ |
| static bool |
| can_predict_insn_p (const rtx_insn *insn) |
| { |
| return (JUMP_P (insn) |
| && any_condjump_p (insn) |
| && EDGE_COUNT (BLOCK_FOR_INSN (insn)->succs) >= 2); |
| } |
| |
| /* Predict edge E by given predictor if possible. */ |
| |
| void |
| predict_edge_def (edge e, enum br_predictor predictor, |
| enum prediction taken) |
| { |
| int probability = predictor_info[(int) predictor].hitrate; |
| |
| if (taken != TAKEN) |
| probability = REG_BR_PROB_BASE - probability; |
| |
| predict_edge (e, predictor, probability); |
| } |
| |
| /* Invert all branch predictions or probability notes in the INSN. This needs |
| to be done each time we invert the condition used by the jump. */ |
| |
| void |
| invert_br_probabilities (rtx insn) |
| { |
| rtx note; |
| |
| for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) |
| if (REG_NOTE_KIND (note) == REG_BR_PROB) |
| XINT (note, 0) = profile_probability::from_reg_br_prob_note |
| (XINT (note, 0)).invert ().to_reg_br_prob_note (); |
| else if (REG_NOTE_KIND (note) == REG_BR_PRED) |
| XEXP (XEXP (note, 0), 1) |
| = GEN_INT (REG_BR_PROB_BASE - INTVAL (XEXP (XEXP (note, 0), 1))); |
| } |
| |
| /* Dump information about the branch prediction to the output file. */ |
| |
| static void |
| dump_prediction (FILE *file, enum br_predictor predictor, int probability, |
| basic_block bb, enum predictor_reason reason = REASON_NONE, |
| edge ep_edge = NULL) |
| { |
| edge e = ep_edge; |
| edge_iterator ei; |
| |
| if (!file) |
| return; |
| |
| if (e == NULL) |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (! (e->flags & EDGE_FALLTHRU)) |
| break; |
| |
| char edge_info_str[128]; |
| if (ep_edge) |
| sprintf (edge_info_str, " of edge %d->%d", ep_edge->src->index, |
| ep_edge->dest->index); |
| else |
| edge_info_str[0] = '\0'; |
| |
| fprintf (file, " %s heuristics%s%s: %.2f%%", |
| predictor_info[predictor].name, |
| edge_info_str, reason_messages[reason], |
| probability * 100.0 / REG_BR_PROB_BASE); |
| |
| if (bb->count.initialized_p ()) |
| { |
| fprintf (file, " exec "); |
| bb->count.dump (file); |
| if (e) |
| { |
| fprintf (file, " hit "); |
| e->count ().dump (file); |
| fprintf (file, " (%.1f%%)", e->count ().to_gcov_type() * 100.0 |
| / bb->count.to_gcov_type ()); |
| } |
| } |
| |
| fprintf (file, "\n"); |
| |
| /* Print output that be easily read by analyze_brprob.py script. We are |
| interested only in counts that are read from GCDA files. */ |
| if (dump_file && (dump_flags & TDF_DETAILS) |
| && bb->count.precise_p () |
| && reason == REASON_NONE) |
| { |
| fprintf (file, ";;heuristics;%s;%" PRId64 ";%" PRId64 ";%.1f;\n", |
| predictor_info[predictor].name, |
| bb->count.to_gcov_type (), e->count ().to_gcov_type (), |
| probability * 100.0 / REG_BR_PROB_BASE); |
| } |
| } |
| |
| /* Return true if STMT is known to be unlikely executed. */ |
| |
| static bool |
| unlikely_executed_stmt_p (gimple *stmt) |
| { |
| if (!is_gimple_call (stmt)) |
| return false; |
| /* NORETURN attribute alone is not strong enough: exit() may be quite |
| likely executed once during program run. */ |
| if (gimple_call_fntype (stmt) |
| && lookup_attribute ("cold", |
| TYPE_ATTRIBUTES (gimple_call_fntype (stmt))) |
| && !lookup_attribute ("cold", DECL_ATTRIBUTES (current_function_decl))) |
| return true; |
| tree decl = gimple_call_fndecl (stmt); |
| if (!decl) |
| return false; |
| if (lookup_attribute ("cold", DECL_ATTRIBUTES (decl)) |
| && !lookup_attribute ("cold", DECL_ATTRIBUTES (current_function_decl))) |
| return true; |
| |
| cgraph_node *n = cgraph_node::get (decl); |
| if (!n) |
| return false; |
| |
| availability avail; |
| n = n->ultimate_alias_target (&avail); |
| if (avail < AVAIL_AVAILABLE) |
| return false; |
| if (!n->analyzed |
| || n->decl == current_function_decl) |
| return false; |
| return n->frequency == NODE_FREQUENCY_UNLIKELY_EXECUTED; |
| } |
| |
| /* Return true if BB is unlikely executed. */ |
| |
| static bool |
| unlikely_executed_bb_p (basic_block bb) |
| { |
| if (bb->count == profile_count::zero ()) |
| return true; |
| if (bb == ENTRY_BLOCK_PTR_FOR_FN (cfun) || bb == EXIT_BLOCK_PTR_FOR_FN (cfun)) |
| return false; |
| for (gimple_stmt_iterator gsi = gsi_start_bb (bb); |
| !gsi_end_p (gsi); gsi_next (&gsi)) |
| { |
| if (unlikely_executed_stmt_p (gsi_stmt (gsi))) |
| return true; |
| if (stmt_can_terminate_bb_p (gsi_stmt (gsi))) |
| return false; |
| } |
| return false; |
| } |
| |
| /* We cannot predict the probabilities of outgoing edges of bb. Set them |
| evenly and hope for the best. If UNLIKELY_EDGES is not null, distribute |
| even probability for all edges not mentioned in the set. These edges |
| are given PROB_VERY_UNLIKELY probability. Similarly for LIKELY_EDGES, |
| if we have exactly one likely edge, make the other edges predicted |
| as not probable. */ |
| |
| static void |
| set_even_probabilities (basic_block bb, |
| hash_set<edge> *unlikely_edges = NULL, |
| hash_set<edge_prediction *> *likely_edges = NULL) |
| { |
| unsigned nedges = 0, unlikely_count = 0; |
| edge e = NULL; |
| edge_iterator ei; |
| profile_probability all = profile_probability::always (); |
| |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (e->probability.initialized_p ()) |
| all -= e->probability; |
| else if (!unlikely_executed_edge_p (e)) |
| { |
| nedges++; |
| if (unlikely_edges != NULL && unlikely_edges->contains (e)) |
| { |
| all -= profile_probability::very_unlikely (); |
| unlikely_count++; |
| } |
| } |
| |
| /* Make the distribution even if all edges are unlikely. */ |
| unsigned likely_count = likely_edges ? likely_edges->elements () : 0; |
| if (unlikely_count == nedges) |
| { |
| unlikely_edges = NULL; |
| unlikely_count = 0; |
| } |
| |
| /* If we have one likely edge, then use its probability and distribute |
| remaining probabilities as even. */ |
| if (likely_count == 1) |
| { |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (e->probability.initialized_p ()) |
| ; |
| else if (!unlikely_executed_edge_p (e)) |
| { |
| edge_prediction *prediction = *likely_edges->begin (); |
| int p = prediction->ep_probability; |
| profile_probability prob |
| = profile_probability::from_reg_br_prob_base (p); |
| |
| if (prediction->ep_edge == e) |
| e->probability = prob; |
| else if (unlikely_edges != NULL && unlikely_edges->contains (e)) |
| e->probability = profile_probability::very_unlikely (); |
| else |
| { |
| profile_probability remainder = prob.invert (); |
| remainder -= profile_probability::very_unlikely () |
| .apply_scale (unlikely_count, 1); |
| int count = nedges - unlikely_count - 1; |
| gcc_assert (count >= 0); |
| |
| e->probability = remainder.apply_scale (1, count); |
| } |
| } |
| else |
| e->probability = profile_probability::never (); |
| } |
| else |
| { |
| /* Make all unlikely edges unlikely and the rest will have even |
| probability. */ |
| unsigned scale = nedges - unlikely_count; |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (e->probability.initialized_p ()) |
| ; |
| else if (!unlikely_executed_edge_p (e)) |
| { |
| if (unlikely_edges != NULL && unlikely_edges->contains (e)) |
| e->probability = profile_probability::very_unlikely (); |
| else |
| e->probability = all.apply_scale (1, scale); |
| } |
| else |
| e->probability = profile_probability::never (); |
| } |
| } |
| |
| /* Add REG_BR_PROB note to JUMP with PROB. */ |
| |
| void |
| add_reg_br_prob_note (rtx_insn *jump, profile_probability prob) |
| { |
| gcc_checking_assert (JUMP_P (jump) && !find_reg_note (jump, REG_BR_PROB, 0)); |
| add_int_reg_note (jump, REG_BR_PROB, prob.to_reg_br_prob_note ()); |
| } |
| |
| /* Combine all REG_BR_PRED notes into single probability and attach REG_BR_PROB |
| note if not already present. Remove now useless REG_BR_PRED notes. */ |
| |
| static void |
| combine_predictions_for_insn (rtx_insn *insn, basic_block bb) |
| { |
| rtx prob_note; |
| rtx *pnote; |
| rtx note; |
| int best_probability = PROB_EVEN; |
| enum br_predictor best_predictor = END_PREDICTORS; |
| int combined_probability = REG_BR_PROB_BASE / 2; |
| int d; |
| bool first_match = false; |
| bool found = false; |
| |
| if (!can_predict_insn_p (insn)) |
| { |
| set_even_probabilities (bb); |
| return; |
| } |
| |
| prob_note = find_reg_note (insn, REG_BR_PROB, 0); |
| pnote = ®_NOTES (insn); |
| if (dump_file) |
| fprintf (dump_file, "Predictions for insn %i bb %i\n", INSN_UID (insn), |
| bb->index); |
| |
| /* We implement "first match" heuristics and use probability guessed |
| by predictor with smallest index. */ |
| for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) |
| if (REG_NOTE_KIND (note) == REG_BR_PRED) |
| { |
| enum br_predictor predictor = ((enum br_predictor) |
| INTVAL (XEXP (XEXP (note, 0), 0))); |
| int probability = INTVAL (XEXP (XEXP (note, 0), 1)); |
| |
| found = true; |
| if (best_predictor > predictor |
| && predictor_info[predictor].flags & PRED_FLAG_FIRST_MATCH) |
| best_probability = probability, best_predictor = predictor; |
| |
| d = (combined_probability * probability |
| + (REG_BR_PROB_BASE - combined_probability) |
| * (REG_BR_PROB_BASE - probability)); |
| |
| /* Use FP math to avoid overflows of 32bit integers. */ |
| if (d == 0) |
| /* If one probability is 0% and one 100%, avoid division by zero. */ |
| combined_probability = REG_BR_PROB_BASE / 2; |
| else |
| combined_probability = (((double) combined_probability) * probability |
| * REG_BR_PROB_BASE / d + 0.5); |
| } |
| |
| /* Decide which heuristic to use. In case we didn't match anything, |
| use no_prediction heuristic, in case we did match, use either |
| first match or Dempster-Shaffer theory depending on the flags. */ |
| |
| if (best_predictor != END_PREDICTORS) |
| first_match = true; |
| |
| if (!found) |
| dump_prediction (dump_file, PRED_NO_PREDICTION, |
| combined_probability, bb); |
| else |
| { |
| if (!first_match) |
| dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, |
| bb, !first_match ? REASON_NONE : REASON_IGNORED); |
| else |
| dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, |
| bb, first_match ? REASON_NONE : REASON_IGNORED); |
| } |
| |
| if (first_match) |
| combined_probability = best_probability; |
| dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb); |
| |
| while (*pnote) |
| { |
| if (REG_NOTE_KIND (*pnote) == REG_BR_PRED) |
| { |
| enum br_predictor predictor = ((enum br_predictor) |
| INTVAL (XEXP (XEXP (*pnote, 0), 0))); |
| int probability = INTVAL (XEXP (XEXP (*pnote, 0), 1)); |
| |
| dump_prediction (dump_file, predictor, probability, bb, |
| (!first_match || best_predictor == predictor) |
| ? REASON_NONE : REASON_IGNORED); |
| *pnote = XEXP (*pnote, 1); |
| } |
| else |
| pnote = &XEXP (*pnote, 1); |
| } |
| |
| if (!prob_note) |
| { |
| profile_probability p |
| = profile_probability::from_reg_br_prob_base (combined_probability); |
| add_reg_br_prob_note (insn, p); |
| |
| /* Save the prediction into CFG in case we are seeing non-degenerated |
| conditional jump. */ |
| if (!single_succ_p (bb)) |
| { |
| BRANCH_EDGE (bb)->probability = p; |
| FALLTHRU_EDGE (bb)->probability |
| = BRANCH_EDGE (bb)->probability.invert (); |
| } |
| } |
| else if (!single_succ_p (bb)) |
| { |
| profile_probability prob = profile_probability::from_reg_br_prob_note |
| (XINT (prob_note, 0)); |
| |
| BRANCH_EDGE (bb)->probability = prob; |
| FALLTHRU_EDGE (bb)->probability = prob.invert (); |
| } |
| else |
| single_succ_edge (bb)->probability = profile_probability::always (); |
| } |
| |
| /* Edge prediction hash traits. */ |
| |
| struct predictor_hash: pointer_hash <edge_prediction> |
| { |
| |
| static inline hashval_t hash (const edge_prediction *); |
| static inline bool equal (const edge_prediction *, const edge_prediction *); |
| }; |
| |
| /* Calculate hash value of an edge prediction P based on predictor and |
| normalized probability. */ |
| |
| inline hashval_t |
| predictor_hash::hash (const edge_prediction *p) |
| { |
| inchash::hash hstate; |
| hstate.add_int (p->ep_predictor); |
| |
| int prob = p->ep_probability; |
| if (prob > REG_BR_PROB_BASE / 2) |
| prob = REG_BR_PROB_BASE - prob; |
| |
| hstate.add_int (prob); |
| |
| return hstate.end (); |
| } |
| |
| /* Return true whether edge predictions P1 and P2 use the same predictor and |
| have equal (or opposed probability). */ |
| |
| inline bool |
| predictor_hash::equal (const edge_prediction *p1, const edge_prediction *p2) |
| { |
| return (p1->ep_predictor == p2->ep_predictor |
| && (p1->ep_probability == p2->ep_probability |
| || p1->ep_probability == REG_BR_PROB_BASE - p2->ep_probability)); |
| } |
| |
| struct predictor_hash_traits: predictor_hash, |
| typed_noop_remove <edge_prediction *> {}; |
| |
| /* Return true if edge prediction P is not in DATA hash set. */ |
| |
| static bool |
| not_removed_prediction_p (edge_prediction *p, void *data) |
| { |
| hash_set<edge_prediction *> *remove = (hash_set<edge_prediction *> *) data; |
| return !remove->contains (p); |
| } |
| |
| /* Prune predictions for a basic block BB. Currently we do following |
| clean-up steps: |
| |
| 1) remove duplicate prediction that is guessed with the same probability |
| (different than 1/2) to both edge |
| 2) remove duplicates for a prediction that belongs with the same probability |
| to a single edge |
| |
| */ |
| |
| static void |
| prune_predictions_for_bb (basic_block bb) |
| { |
| edge_prediction **preds = bb_predictions->get (bb); |
| |
| if (preds) |
| { |
| hash_table <predictor_hash_traits> s (13); |
| hash_set <edge_prediction *> remove; |
| |
| /* Step 1: identify predictors that should be removed. */ |
| for (edge_prediction *pred = *preds; pred; pred = pred->ep_next) |
| { |
| edge_prediction *existing = s.find (pred); |
| if (existing) |
| { |
| if (pred->ep_edge == existing->ep_edge |
| && pred->ep_probability == existing->ep_probability) |
| { |
| /* Remove a duplicate predictor. */ |
| dump_prediction (dump_file, pred->ep_predictor, |
| pred->ep_probability, bb, |
| REASON_SINGLE_EDGE_DUPLICATE, pred->ep_edge); |
| |
| remove.add (pred); |
| } |
| else if (pred->ep_edge != existing->ep_edge |
| && pred->ep_probability == existing->ep_probability |
| && pred->ep_probability != REG_BR_PROB_BASE / 2) |
| { |
| /* Remove both predictors as they predict the same |
| for both edges. */ |
| dump_prediction (dump_file, existing->ep_predictor, |
| pred->ep_probability, bb, |
| REASON_EDGE_PAIR_DUPLICATE, |
| existing->ep_edge); |
| dump_prediction (dump_file, pred->ep_predictor, |
| pred->ep_probability, bb, |
| REASON_EDGE_PAIR_DUPLICATE, |
| pred->ep_edge); |
| |
| remove.add (existing); |
| remove.add (pred); |
| } |
| } |
| |
| edge_prediction **slot2 = s.find_slot (pred, INSERT); |
| *slot2 = pred; |
| } |
| |
| /* Step 2: Remove predictors. */ |
| filter_predictions (preds, not_removed_prediction_p, &remove); |
| } |
| } |
| |
| /* Combine predictions into single probability and store them into CFG. |
| Remove now useless prediction entries. |
| If DRY_RUN is set, only produce dumps and do not modify profile. */ |
| |
| static void |
| combine_predictions_for_bb (basic_block bb, bool dry_run) |
| { |
| int best_probability = PROB_EVEN; |
| enum br_predictor best_predictor = END_PREDICTORS; |
| int combined_probability = REG_BR_PROB_BASE / 2; |
| int d; |
| bool first_match = false; |
| bool found = false; |
| struct edge_prediction *pred; |
| int nedges = 0; |
| edge e, first = NULL, second = NULL; |
| edge_iterator ei; |
| int nzero = 0; |
| int nunknown = 0; |
| |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| { |
| if (!unlikely_executed_edge_p (e)) |
| { |
| nedges ++; |
| if (first && !second) |
| second = e; |
| if (!first) |
| first = e; |
| } |
| else if (!e->probability.initialized_p ()) |
| e->probability = profile_probability::never (); |
| if (!e->probability.initialized_p ()) |
| nunknown++; |
| else if (e->probability == profile_probability::never ()) |
| nzero++; |
| } |
| |
| /* When there is no successor or only one choice, prediction is easy. |
| |
| When we have a basic block with more than 2 successors, the situation |
| is more complicated as DS theory cannot be used literally. |
| More precisely, let's assume we predicted edge e1 with probability p1, |
| thus: m1({b1}) = p1. As we're going to combine more than 2 edges, we |
| need to find probability of e.g. m1({b2}), which we don't know. |
| The only approximation is to equally distribute 1-p1 to all edges |
| different from b1. |
| |
| According to numbers we've got from SPEC2006 benchark, there's only |
| one interesting reliable predictor (noreturn call), which can be |
| handled with a bit easier approach. */ |
| if (nedges != 2) |
| { |
| hash_set<edge> unlikely_edges (4); |
| hash_set<edge_prediction *> likely_edges (4); |
| |
| /* Identify all edges that have a probability close to very unlikely. |
| Doing the approach for very unlikely doesn't worth for doing as |
| there's no such probability in SPEC2006 benchmark. */ |
| edge_prediction **preds = bb_predictions->get (bb); |
| if (preds) |
| for (pred = *preds; pred; pred = pred->ep_next) |
| { |
| if (pred->ep_probability <= PROB_VERY_UNLIKELY |
| || pred->ep_predictor == PRED_COLD_LABEL) |
| unlikely_edges.add (pred->ep_edge); |
| else if (pred->ep_probability >= PROB_VERY_LIKELY |
| || pred->ep_predictor == PRED_BUILTIN_EXPECT |
| || pred->ep_predictor == PRED_HOT_LABEL) |
| likely_edges.add (pred); |
| } |
| |
| /* It can happen that an edge is both in likely_edges and unlikely_edges. |
| Clear both sets in that situation. */ |
| for (hash_set<edge_prediction *>::iterator it = likely_edges.begin (); |
| it != likely_edges.end (); ++it) |
| if (unlikely_edges.contains ((*it)->ep_edge)) |
| { |
| likely_edges.empty (); |
| unlikely_edges.empty (); |
| break; |
| } |
| |
| if (!dry_run) |
| set_even_probabilities (bb, &unlikely_edges, &likely_edges); |
| clear_bb_predictions (bb); |
| if (dump_file) |
| { |
| fprintf (dump_file, "Predictions for bb %i\n", bb->index); |
| if (unlikely_edges.is_empty ()) |
| fprintf (dump_file, |
| "%i edges in bb %i predicted to even probabilities\n", |
| nedges, bb->index); |
| else |
| { |
| fprintf (dump_file, |
| "%i edges in bb %i predicted with some unlikely edges\n", |
| nedges, bb->index); |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (!unlikely_executed_edge_p (e)) |
| dump_prediction (dump_file, PRED_COMBINED, |
| e->probability.to_reg_br_prob_base (), bb, REASON_NONE, e); |
| } |
| } |
| return; |
| } |
| |
| if (dump_file) |
| fprintf (dump_file, "Predictions for bb %i\n", bb->index); |
| |
| prune_predictions_for_bb (bb); |
| |
| edge_prediction **preds = bb_predictions->get (bb); |
| |
| if (preds) |
| { |
| /* We implement "first match" heuristics and use probability guessed |
| by predictor with smallest index. */ |
| for (pred = *preds; pred; pred = pred->ep_next) |
| { |
| enum br_predictor predictor = pred->ep_predictor; |
| int probability = pred->ep_probability; |
| |
| if (pred->ep_edge != first) |
| probability = REG_BR_PROB_BASE - probability; |
| |
| found = true; |
| /* First match heuristics would be widly confused if we predicted |
| both directions. */ |
| if (best_predictor > predictor |
| && predictor_info[predictor].flags & PRED_FLAG_FIRST_MATCH) |
| { |
| struct edge_prediction *pred2; |
| int prob = probability; |
| |
| for (pred2 = (struct edge_prediction *) *preds; |
| pred2; pred2 = pred2->ep_next) |
| if (pred2 != pred && pred2->ep_predictor == pred->ep_predictor) |
| { |
| int probability2 = pred2->ep_probability; |
| |
| if (pred2->ep_edge != first) |
| probability2 = REG_BR_PROB_BASE - probability2; |
| |
| if ((probability < REG_BR_PROB_BASE / 2) != |
| (probability2 < REG_BR_PROB_BASE / 2)) |
| break; |
| |
| /* If the same predictor later gave better result, go for it! */ |
| if ((probability >= REG_BR_PROB_BASE / 2 && (probability2 > probability)) |
| || (probability <= REG_BR_PROB_BASE / 2 && (probability2 < probability))) |
| prob = probability2; |
| } |
| if (!pred2) |
| best_probability = prob, best_predictor = predictor; |
| } |
| |
| d = (combined_probability * probability |
| + (REG_BR_PROB_BASE - combined_probability) |
| * (REG_BR_PROB_BASE - probability)); |
| |
| /* Use FP math to avoid overflows of 32bit integers. */ |
| if (d == 0) |
| /* If one probability is 0% and one 100%, avoid division by zero. */ |
| combined_probability = REG_BR_PROB_BASE / 2; |
| else |
| combined_probability = (((double) combined_probability) |
| * probability |
| * REG_BR_PROB_BASE / d + 0.5); |
| } |
| } |
| |
| /* Decide which heuristic to use. In case we didn't match anything, |
| use no_prediction heuristic, in case we did match, use either |
| first match or Dempster-Shaffer theory depending on the flags. */ |
| |
| if (best_predictor != END_PREDICTORS) |
| first_match = true; |
| |
| if (!found) |
| dump_prediction (dump_file, PRED_NO_PREDICTION, combined_probability, bb); |
| else |
| { |
| if (!first_match) |
| dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, bb, |
| !first_match ? REASON_NONE : REASON_IGNORED); |
| else |
| dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, bb, |
| first_match ? REASON_NONE : REASON_IGNORED); |
| } |
| |
| if (first_match) |
| combined_probability = best_probability; |
| dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb); |
| |
| if (preds) |
| { |
| for (pred = (struct edge_prediction *) *preds; pred; pred = pred->ep_next) |
| { |
| enum br_predictor predictor = pred->ep_predictor; |
| int probability = pred->ep_probability; |
| |
| dump_prediction (dump_file, predictor, probability, bb, |
| (!first_match || best_predictor == predictor) |
| ? REASON_NONE : REASON_IGNORED, pred->ep_edge); |
| } |
| } |
| clear_bb_predictions (bb); |
| |
| |
| /* If we have only one successor which is unknown, we can compute missing |
| probability. */ |
| if (nunknown == 1) |
| { |
| profile_probability prob = profile_probability::always (); |
| edge missing = NULL; |
| |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (e->probability.initialized_p ()) |
| prob -= e->probability; |
| else if (missing == NULL) |
| missing = e; |
| else |
| gcc_unreachable (); |
| missing->probability = prob; |
| } |
| /* If nothing is unknown, we have nothing to update. */ |
| else if (!nunknown && nzero != (int)EDGE_COUNT (bb->succs)) |
| ; |
| else if (!dry_run) |
| { |
| first->probability |
| = profile_probability::from_reg_br_prob_base (combined_probability); |
| second->probability = first->probability.invert (); |
| } |
| } |
| |
| /* Check if T1 and T2 satisfy the IV_COMPARE condition. |
| Return the SSA_NAME if the condition satisfies, NULL otherwise. |
| |
| T1 and T2 should be one of the following cases: |
| 1. T1 is SSA_NAME, T2 is NULL |
| 2. T1 is SSA_NAME, T2 is INTEGER_CST between [-4, 4] |
| 3. T2 is SSA_NAME, T1 is INTEGER_CST between [-4, 4] */ |
| |
| static tree |
| strips_small_constant (tree t1, tree t2) |
| { |
| tree ret = NULL; |
| int value = 0; |
| |
| if (!t1) |
| return NULL; |
| else if (TREE_CODE (t1) == SSA_NAME) |
| ret = t1; |
| else if (tree_fits_shwi_p (t1)) |
| value = tree_to_shwi (t1); |
| else |
| return NULL; |
| |
| if (!t2) |
| return ret; |
| else if (tree_fits_shwi_p (t2)) |
| value = tree_to_shwi (t2); |
| else if (TREE_CODE (t2) == SSA_NAME) |
| { |
| if (ret) |
| return NULL; |
| else |
| ret = t2; |
| } |
| |
| if (value <= 4 && value >= -4) |
| return ret; |
| else |
| return NULL; |
| } |
| |
| /* Return the SSA_NAME in T or T's operands. |
| Return NULL if SSA_NAME cannot be found. */ |
| |
| static tree |
| get_base_value (tree t) |
| { |
| if (TREE_CODE (t) == SSA_NAME) |
| return t; |
| |
| if (!BINARY_CLASS_P (t)) |
| return NULL; |
| |
| switch (TREE_OPERAND_LENGTH (t)) |
| { |
| case 1: |
| return strips_small_constant (TREE_OPERAND (t, 0), NULL); |
| case 2: |
| return strips_small_constant (TREE_OPERAND (t, 0), |
| TREE_OPERAND (t, 1)); |
| default: |
| return NULL; |
| } |
| } |
| |
| /* Check the compare STMT in LOOP. If it compares an induction |
| variable to a loop invariant, return true, and save |
| LOOP_INVARIANT, COMPARE_CODE and LOOP_STEP. |
| Otherwise return false and set LOOP_INVAIANT to NULL. */ |
| |
| static bool |
| is_comparison_with_loop_invariant_p (gcond *stmt, class loop *loop, |
| tree *loop_invariant, |
| enum tree_code *compare_code, |
| tree *loop_step, |
| tree *loop_iv_base) |
| { |
| tree op0, op1, bound, base; |
| affine_iv iv0, iv1; |
| enum tree_code code; |
| tree step; |
| |
| code = gimple_cond_code (stmt); |
| *loop_invariant = NULL; |
| |
| switch (code) |
| { |
| case GT_EXPR: |
| case GE_EXPR: |
| case NE_EXPR: |
| case LT_EXPR: |
| case LE_EXPR: |
| case EQ_EXPR: |
| break; |
| |
| default: |
| return false; |
| } |
| |
| op0 = gimple_cond_lhs (stmt); |
| op1 = gimple_cond_rhs (stmt); |
| |
| if ((TREE_CODE (op0) != SSA_NAME && TREE_CODE (op0) != INTEGER_CST) |
| || (TREE_CODE (op1) != SSA_NAME && TREE_CODE (op1) != INTEGER_CST)) |
| return false; |
| if (!simple_iv (loop, loop_containing_stmt (stmt), op0, &iv0, true)) |
| return false; |
| if (!simple_iv (loop, loop_containing_stmt (stmt), op1, &iv1, true)) |
| return false; |
| if (TREE_CODE (iv0.step) != INTEGER_CST |
| || TREE_CODE (iv1.step) != INTEGER_CST) |
| return false; |
| if ((integer_zerop (iv0.step) && integer_zerop (iv1.step)) |
| || (!integer_zerop (iv0.step) && !integer_zerop (iv1.step))) |
| return false; |
| |
| if (integer_zerop (iv0.step)) |
| { |
| if (code != NE_EXPR && code != EQ_EXPR) |
| code = invert_tree_comparison (code, false); |
| bound = iv0.base; |
| base = iv1.base; |
| if (tree_fits_shwi_p (iv1.step)) |
| step = iv1.step; |
| else |
| return false; |
| } |
| else |
| { |
| bound = iv1.base; |
| base = iv0.base; |
| if (tree_fits_shwi_p (iv0.step)) |
| step = iv0.step; |
| else |
| return false; |
| } |
| |
| if (TREE_CODE (bound) != INTEGER_CST) |
| bound = get_base_value (bound); |
| if (!bound) |
| return false; |
| if (TREE_CODE (base) != INTEGER_CST) |
| base = get_base_value (base); |
| if (!base) |
| return false; |
| |
| *loop_invariant = bound; |
| *compare_code = code; |
| *loop_step = step; |
| *loop_iv_base = base; |
| return true; |
| } |
| |
| /* Compare two SSA_NAMEs: returns TRUE if T1 and T2 are value coherent. */ |
| |
| static bool |
| expr_coherent_p (tree t1, tree t2) |
| { |
| gimple *stmt; |
| tree ssa_name_1 = NULL; |
| tree ssa_name_2 = NULL; |
| |
| gcc_assert (TREE_CODE (t1) == SSA_NAME || TREE_CODE (t1) == INTEGER_CST); |
| gcc_assert (TREE_CODE (t2) == SSA_NAME || TREE_CODE (t2) == INTEGER_CST); |
| |
| if (t1 == t2) |
| return true; |
| |
| if (TREE_CODE (t1) == INTEGER_CST && TREE_CODE (t2) == INTEGER_CST) |
| return true; |
| if (TREE_CODE (t1) == INTEGER_CST || TREE_CODE (t2) == INTEGER_CST) |
| return false; |
| |
| /* Check to see if t1 is expressed/defined with t2. */ |
| stmt = SSA_NAME_DEF_STMT (t1); |
| gcc_assert (stmt != NULL); |
| if (is_gimple_assign (stmt)) |
| { |
| ssa_name_1 = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE); |
| if (ssa_name_1 && ssa_name_1 == t2) |
| return true; |
| } |
| |
| /* Check to see if t2 is expressed/defined with t1. */ |
| stmt = SSA_NAME_DEF_STMT (t2); |
| gcc_assert (stmt != NULL); |
| if (is_gimple_assign (stmt)) |
| { |
| ssa_name_2 = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE); |
| if (ssa_name_2 && ssa_name_2 == t1) |
| return true; |
| } |
| |
| /* Compare if t1 and t2's def_stmts are identical. */ |
| if (ssa_name_2 != NULL && ssa_name_1 == ssa_name_2) |
| return true; |
| else |
| return false; |
| } |
| |
| /* Return true if E is predicted by one of loop heuristics. */ |
| |
| static bool |
| predicted_by_loop_heuristics_p (basic_block bb) |
| { |
| struct edge_prediction *i; |
| edge_prediction **preds = bb_predictions->get (bb); |
| |
| if (!preds) |
| return false; |
| |
| for (i = *preds; i; i = i->ep_next) |
| if (i->ep_predictor == PRED_LOOP_ITERATIONS_GUESSED |
| || i->ep_predictor == PRED_LOOP_ITERATIONS_MAX |
| || i->ep_predictor == PRED_LOOP_ITERATIONS |
| || i->ep_predictor == PRED_LOOP_EXIT |
| || i->ep_predictor == PRED_LOOP_EXIT_WITH_RECURSION |
| || i->ep_predictor == PRED_LOOP_EXTRA_EXIT) |
| return true; |
| return false; |
| } |
| |
| /* Predict branch probability of BB when BB contains a branch that compares |
| an induction variable in LOOP with LOOP_IV_BASE_VAR to LOOP_BOUND_VAR. The |
| loop exit is compared using LOOP_BOUND_CODE, with step of LOOP_BOUND_STEP. |
| |
| E.g. |
| for (int i = 0; i < bound; i++) { |
| if (i < bound - 2) |
| computation_1(); |
| else |
| computation_2(); |
| } |
| |
| In this loop, we will predict the branch inside the loop to be taken. */ |
| |
| static void |
| predict_iv_comparison (class loop *loop, basic_block bb, |
| tree loop_bound_var, |
| tree loop_iv_base_var, |
| enum tree_code loop_bound_code, |
| int loop_bound_step) |
| { |
| gimple *stmt; |
| tree compare_var, compare_base; |
| enum tree_code compare_code; |
| tree compare_step_var; |
| edge then_edge; |
| edge_iterator ei; |
| |
| if (predicted_by_loop_heuristics_p (bb)) |
| return; |
| |
| stmt = last_stmt (bb); |
| if (!stmt || gimple_code (stmt) != GIMPLE_COND) |
| return; |
| if (!is_comparison_with_loop_invariant_p (as_a <gcond *> (stmt), |
| loop, &compare_var, |
| &compare_code, |
| &compare_step_var, |
| &compare_base)) |
| return; |
| |
| /* Find the taken edge. */ |
| FOR_EACH_EDGE (then_edge, ei, bb->succs) |
| if (then_edge->flags & EDGE_TRUE_VALUE) |
| break; |
| |
| /* When comparing an IV to a loop invariant, NE is more likely to be |
| taken while EQ is more likely to be not-taken. */ |
| if (compare_code == NE_EXPR) |
| { |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN); |
| return; |
| } |
| else if (compare_code == EQ_EXPR) |
| { |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, NOT_TAKEN); |
| return; |
| } |
| |
| if (!expr_coherent_p (loop_iv_base_var, compare_base)) |
| return; |
| |
| /* If loop bound, base and compare bound are all constants, we can |
| calculate the probability directly. */ |
| if (tree_fits_shwi_p (loop_bound_var) |
| && tree_fits_shwi_p (compare_var) |
| && tree_fits_shwi_p (compare_base)) |
| { |
| int probability; |
| wi::overflow_type overflow; |
| bool overall_overflow = false; |
| widest_int compare_count, tem; |
| |
| /* (loop_bound - base) / compare_step */ |
| tem = wi::sub (wi::to_widest (loop_bound_var), |
| wi::to_widest (compare_base), SIGNED, &overflow); |
| overall_overflow |= overflow; |
| widest_int loop_count = wi::div_trunc (tem, |
| wi::to_widest (compare_step_var), |
| SIGNED, &overflow); |
| overall_overflow |= overflow; |
| |
| if (!wi::neg_p (wi::to_widest (compare_step_var)) |
| ^ (compare_code == LT_EXPR || compare_code == LE_EXPR)) |
| { |
| /* (loop_bound - compare_bound) / compare_step */ |
| tem = wi::sub (wi::to_widest (loop_bound_var), |
| wi::to_widest (compare_var), SIGNED, &overflow); |
| overall_overflow |= overflow; |
| compare_count = wi::div_trunc (tem, wi::to_widest (compare_step_var), |
| SIGNED, &overflow); |
| overall_overflow |= overflow; |
| } |
| else |
| { |
| /* (compare_bound - base) / compare_step */ |
| tem = wi::sub (wi::to_widest (compare_var), |
| wi::to_widest (compare_base), SIGNED, &overflow); |
| overall_overflow |= overflow; |
| compare_count = wi::div_trunc (tem, wi::to_widest (compare_step_var), |
| SIGNED, &overflow); |
| overall_overflow |= overflow; |
| } |
| if (compare_code == LE_EXPR || compare_code == GE_EXPR) |
| ++compare_count; |
| if (loop_bound_code == LE_EXPR || loop_bound_code == GE_EXPR) |
| ++loop_count; |
| if (wi::neg_p (compare_count)) |
| compare_count = 0; |
| if (wi::neg_p (loop_count)) |
| loop_count = 0; |
| if (loop_count == 0) |
| probability = 0; |
| else if (wi::cmps (compare_count, loop_count) == 1) |
| probability = REG_BR_PROB_BASE; |
| else |
| { |
| tem = compare_count * REG_BR_PROB_BASE; |
| tem = wi::udiv_trunc (tem, loop_count); |
| probability = tem.to_uhwi (); |
| } |
| |
| /* FIXME: The branch prediction seems broken. It has only 20% hitrate. */ |
| if (!overall_overflow) |
| predict_edge (then_edge, PRED_LOOP_IV_COMPARE, probability); |
| |
| return; |
| } |
| |
| if (expr_coherent_p (loop_bound_var, compare_var)) |
| { |
| if ((loop_bound_code == LT_EXPR || loop_bound_code == LE_EXPR) |
| && (compare_code == LT_EXPR || compare_code == LE_EXPR)) |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN); |
| else if ((loop_bound_code == GT_EXPR || loop_bound_code == GE_EXPR) |
| && (compare_code == GT_EXPR || compare_code == GE_EXPR)) |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN); |
| else if (loop_bound_code == NE_EXPR) |
| { |
| /* If the loop backedge condition is "(i != bound)", we do |
| the comparison based on the step of IV: |
| * step < 0 : backedge condition is like (i > bound) |
| * step > 0 : backedge condition is like (i < bound) */ |
| gcc_assert (loop_bound_step != 0); |
| if (loop_bound_step > 0 |
| && (compare_code == LT_EXPR |
| || compare_code == LE_EXPR)) |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN); |
| else if (loop_bound_step < 0 |
| && (compare_code == GT_EXPR |
| || compare_code == GE_EXPR)) |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN); |
| else |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, NOT_TAKEN); |
| } |
| else |
| /* The branch is predicted not-taken if loop_bound_code is |
| opposite with compare_code. */ |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, NOT_TAKEN); |
| } |
| else if (expr_coherent_p (loop_iv_base_var, compare_var)) |
| { |
| /* For cases like: |
| for (i = s; i < h; i++) |
| if (i > s + 2) .... |
| The branch should be predicted taken. */ |
| if (loop_bound_step > 0 |
| && (compare_code == GT_EXPR || compare_code == GE_EXPR)) |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN); |
| else if (loop_bound_step < 0 |
| && (compare_code == LT_EXPR || compare_code == LE_EXPR)) |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, TAKEN); |
| else |
| predict_edge_def (then_edge, PRED_LOOP_IV_COMPARE_GUESS, NOT_TAKEN); |
| } |
| } |
| |
| /* Predict for extra loop exits that will lead to EXIT_EDGE. The extra loop |
| exits are resulted from short-circuit conditions that will generate an |
| if_tmp. E.g.: |
| |
| if (foo() || global > 10) |
| break; |
| |
| This will be translated into: |
| |
| BB3: |
| loop header... |
| BB4: |
| if foo() goto BB6 else goto BB5 |
| BB5: |
| if global > 10 goto BB6 else goto BB7 |
| BB6: |
| goto BB7 |
| BB7: |
| iftmp = (PHI 0(BB5), 1(BB6)) |
| if iftmp == 1 goto BB8 else goto BB3 |
| BB8: |
| outside of the loop... |
| |
| The edge BB7->BB8 is loop exit because BB8 is outside of the loop. |
| From the dataflow, we can infer that BB4->BB6 and BB5->BB6 are also loop |
| exits. This function takes BB7->BB8 as input, and finds out the extra loop |
| exits to predict them using PRED_LOOP_EXTRA_EXIT. */ |
| |
| static void |
| predict_extra_loop_exits (edge exit_edge) |
| { |
| unsigned i; |
| bool check_value_one; |
| gimple *lhs_def_stmt; |
| gphi *phi_stmt; |
| tree cmp_rhs, cmp_lhs; |
| gimple *last; |
| gcond *cmp_stmt; |
| |
| last = last_stmt (exit_edge->src); |
| if (!last) |
| return; |
| cmp_stmt = dyn_cast <gcond *> (last); |
| if (!cmp_stmt) |
| return; |
| |
| cmp_rhs = gimple_cond_rhs (cmp_stmt); |
| cmp_lhs = gimple_cond_lhs (cmp_stmt); |
| if (!TREE_CONSTANT (cmp_rhs) |
| || !(integer_zerop (cmp_rhs) || integer_onep (cmp_rhs))) |
| return; |
| if (TREE_CODE (cmp_lhs) != SSA_NAME) |
| return; |
| |
| /* If check_value_one is true, only the phi_args with value '1' will lead |
| to loop exit. Otherwise, only the phi_args with value '0' will lead to |
| loop exit. */ |
| check_value_one = (((integer_onep (cmp_rhs)) |
| ^ (gimple_cond_code (cmp_stmt) == EQ_EXPR)) |
| ^ ((exit_edge->flags & EDGE_TRUE_VALUE) != 0)); |
| |
| lhs_def_stmt = SSA_NAME_DEF_STMT (cmp_lhs); |
| if (!lhs_def_stmt) |
| return; |
| |
| phi_stmt = dyn_cast <gphi *> (lhs_def_stmt); |
| if (!phi_stmt) |
| return; |
| |
| for (i = 0; i < gimple_phi_num_args (phi_stmt); i++) |
| { |
| edge e1; |
| edge_iterator ei; |
| tree val = gimple_phi_arg_def (phi_stmt, i); |
| edge e = gimple_phi_arg_edge (phi_stmt, i); |
| |
| if (!TREE_CONSTANT (val) || !(integer_zerop (val) || integer_onep (val))) |
| continue; |
| if ((check_value_one ^ integer_onep (val)) == 1) |
| continue; |
| if (EDGE_COUNT (e->src->succs) != 1) |
| { |
| predict_paths_leading_to_edge (e, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN); |
| continue; |
| } |
| |
| FOR_EACH_EDGE (e1, ei, e->src->preds) |
| predict_paths_leading_to_edge (e1, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN); |
| } |
| } |
| |
| |
| /* Predict edge probabilities by exploiting loop structure. */ |
| |
| static void |
| predict_loops (void) |
| { |
| class loop *loop; |
| basic_block bb; |
| hash_set <class loop *> with_recursion(10); |
| |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| gimple_stmt_iterator gsi; |
| tree decl; |
| |
| for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
| if (is_gimple_call (gsi_stmt (gsi)) |
| && (decl = gimple_call_fndecl (gsi_stmt (gsi))) != NULL |
| && recursive_call_p (current_function_decl, decl)) |
| { |
| loop = bb->loop_father; |
| while (loop && !with_recursion.add (loop)) |
| loop = loop_outer (loop); |
| } |
| } |
| |
| /* Try to predict out blocks in a loop that are not part of a |
| natural loop. */ |
| for (auto loop : loops_list (cfun, LI_FROM_INNERMOST)) |
| { |
| basic_block bb, *bbs; |
| unsigned j, n_exits = 0; |
| class tree_niter_desc niter_desc; |
| edge ex; |
| class nb_iter_bound *nb_iter; |
| enum tree_code loop_bound_code = ERROR_MARK; |
| tree loop_bound_step = NULL; |
| tree loop_bound_var = NULL; |
| tree loop_iv_base = NULL; |
| gcond *stmt = NULL; |
| bool recursion = with_recursion.contains (loop); |
| |
| auto_vec<edge> exits = get_loop_exit_edges (loop); |
| FOR_EACH_VEC_ELT (exits, j, ex) |
| if (!unlikely_executed_edge_p (ex) && !(ex->flags & EDGE_ABNORMAL_CALL)) |
| n_exits ++; |
| if (!n_exits) |
| continue; |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "Predicting loop %i%s with %i exits.\n", |
| loop->num, recursion ? " (with recursion)":"", n_exits); |
| if (dump_file && (dump_flags & TDF_DETAILS) |
| && max_loop_iterations_int (loop) >= 0) |
| { |
| fprintf (dump_file, |
| "Loop %d iterates at most %i times.\n", loop->num, |
| (int)max_loop_iterations_int (loop)); |
| } |
| if (dump_file && (dump_flags & TDF_DETAILS) |
| && likely_max_loop_iterations_int (loop) >= 0) |
| { |
| fprintf (dump_file, "Loop %d likely iterates at most %i times.\n", |
| loop->num, (int)likely_max_loop_iterations_int (loop)); |
| } |
| |
| FOR_EACH_VEC_ELT (exits, j, ex) |
| { |
| tree niter = NULL; |
| HOST_WIDE_INT nitercst; |
| int max = param_max_predicted_iterations; |
| int probability; |
| enum br_predictor predictor; |
| widest_int nit; |
| |
| if (unlikely_executed_edge_p (ex) |
| || (ex->flags & EDGE_ABNORMAL_CALL)) |
| continue; |
| /* Loop heuristics do not expect exit conditional to be inside |
| inner loop. We predict from innermost to outermost loop. */ |
| if (predicted_by_loop_heuristics_p (ex->src)) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "Skipping exit %i->%i because " |
| "it is already predicted.\n", |
| ex->src->index, ex->dest->index); |
| continue; |
| } |
| predict_extra_loop_exits (ex); |
| |
| if (number_of_iterations_exit (loop, ex, &niter_desc, false, false)) |
| niter = niter_desc.niter; |
| if (!niter || TREE_CODE (niter_desc.niter) != INTEGER_CST) |
| niter = loop_niter_by_eval (loop, ex); |
| if (dump_file && (dump_flags & TDF_DETAILS) |
| && TREE_CODE (niter) == INTEGER_CST) |
| { |
| fprintf (dump_file, "Exit %i->%i %d iterates ", |
| ex->src->index, ex->dest->index, |
| loop->num); |
| print_generic_expr (dump_file, niter, TDF_SLIM); |
| fprintf (dump_file, " times.\n"); |
| } |
| |
| if (TREE_CODE (niter) == INTEGER_CST) |
| { |
| if (tree_fits_uhwi_p (niter) |
| && max |
| && compare_tree_int (niter, max - 1) == -1) |
| nitercst = tree_to_uhwi (niter) + 1; |
| else |
| nitercst = max; |
| predictor = PRED_LOOP_ITERATIONS; |
| } |
| /* If we have just one exit and we can derive some information about |
| the number of iterations of the loop from the statements inside |
| the loop, use it to predict this exit. */ |
| else if (n_exits == 1 |
| && estimated_stmt_executions (loop, &nit)) |
| { |
| if (wi::gtu_p (nit, max)) |
| nitercst = max; |
| else |
| nitercst = nit.to_shwi (); |
| predictor = PRED_LOOP_ITERATIONS_GUESSED; |
| } |
| /* If we have likely upper bound, trust it for very small iteration |
| counts. Such loops would otherwise get mispredicted by standard |
| LOOP_EXIT heuristics. */ |
| else if (n_exits == 1 |
| && likely_max_stmt_executions (loop, &nit) |
| && wi::ltu_p (nit, |
| RDIV (REG_BR_PROB_BASE, |
| REG_BR_PROB_BASE |
| - predictor_info |
| [recursion |
| ? PRED_LOOP_EXIT_WITH_RECURSION |
| : PRED_LOOP_EXIT].hitrate))) |
| { |
| nitercst = nit.to_shwi (); |
| predictor = PRED_LOOP_ITERATIONS_MAX; |
| } |
| else |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "Nothing known about exit %i->%i.\n", |
| ex->src->index, ex->dest->index); |
| continue; |
| } |
| |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "Recording prediction to %i iterations by %s.\n", |
| (int)nitercst, predictor_info[predictor].name); |
| /* If the prediction for number of iterations is zero, do not |
| predict the exit edges. */ |
| if (nitercst == 0) |
| continue; |
| |
| probability = RDIV (REG_BR_PROB_BASE, nitercst); |
| predict_edge (ex, predictor, probability); |
| } |
| |
| /* Find information about loop bound variables. */ |
| for (nb_iter = loop->bounds; nb_iter; |
| nb_iter = nb_iter->next) |
| if (nb_iter->stmt |
| && gimple_code (nb_iter->stmt) == GIMPLE_COND) |
| { |
| stmt = as_a <gcond *> (nb_iter->stmt); |
| break; |
| } |
| if (!stmt && last_stmt (loop->header) |
| && gimple_code (last_stmt (loop->header)) == GIMPLE_COND) |
| stmt = as_a <gcond *> (last_stmt (loop->header)); |
| if (stmt) |
| is_comparison_with_loop_invariant_p (stmt, loop, |
| &loop_bound_var, |
| &loop_bound_code, |
| &loop_bound_step, |
| &loop_iv_base); |
| |
| bbs = get_loop_body (loop); |
| |
| for (j = 0; j < loop->num_nodes; j++) |
| { |
| edge e; |
| edge_iterator ei; |
| |
| bb = bbs[j]; |
| |
| /* Bypass loop heuristics on continue statement. These |
| statements construct loops via "non-loop" constructs |
| in the source language and are better to be handled |
| separately. */ |
| if (predicted_by_p (bb, PRED_CONTINUE)) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, "BB %i predicted by continue.\n", |
| bb->index); |
| continue; |
| } |
| |
| /* If we already used more reliable loop exit predictors, do not |
| bother with PRED_LOOP_EXIT. */ |
| if (!predicted_by_loop_heuristics_p (bb)) |
| { |
| /* For loop with many exits we don't want to predict all exits |
| with the pretty large probability, because if all exits are |
| considered in row, the loop would be predicted to iterate |
| almost never. The code to divide probability by number of |
| exits is very rough. It should compute the number of exits |
| taken in each patch through function (not the overall number |
| of exits that might be a lot higher for loops with wide switch |
| statements in them) and compute n-th square root. |
| |
| We limit the minimal probability by 2% to avoid |
| EDGE_PROBABILITY_RELIABLE from trusting the branch prediction |
| as this was causing regression in perl benchmark containing such |
| a wide loop. */ |
| |
| int probability = ((REG_BR_PROB_BASE |
| - predictor_info |
| [recursion |
| ? PRED_LOOP_EXIT_WITH_RECURSION |
| : PRED_LOOP_EXIT].hitrate) |
| / n_exits); |
| if (probability < HITRATE (2)) |
| probability = HITRATE (2); |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| if (e->dest->index < NUM_FIXED_BLOCKS |
| || !flow_bb_inside_loop_p (loop, e->dest)) |
| { |
| if (dump_file && (dump_flags & TDF_DETAILS)) |
| fprintf (dump_file, |
| "Predicting exit %i->%i with prob %i.\n", |
| e->src->index, e->dest->index, probability); |
| predict_edge (e, |
| recursion ? PRED_LOOP_EXIT_WITH_RECURSION |
| : PRED_LOOP_EXIT, probability); |
| } |
| } |
| if (loop_bound_var) |
| predict_iv_comparison (loop, bb, loop_bound_var, loop_iv_base, |
| loop_bound_code, |
| tree_to_shwi (loop_bound_step)); |
| } |
| |
| /* In the following code |
| for (loop1) |
| if (cond) |
| for (loop2) |
| body; |
| guess that cond is unlikely. */ |
| if (loop_outer (loop)->num) |
| { |
| basic_block bb = NULL; |
| edge preheader_edge = loop_preheader_edge (loop); |
| |
| if (single_pred_p (preheader_edge->src) |
| && single_succ_p (preheader_edge->src)) |
| preheader_edge = single_pred_edge (preheader_edge->src); |
| |
| gimple *stmt = last_stmt (preheader_edge->src); |
| /* Pattern match fortran loop preheader: |
| _16 = BUILTIN_EXPECT (_15, 1, PRED_FORTRAN_LOOP_PREHEADER); |
| _17 = (logical(kind=4)) _16; |
| if (_17 != 0) |
| goto <bb 11>; |
| else |
| goto <bb 13>; |
| |
| Loop guard branch prediction says nothing about duplicated loop |
| headers produced by fortran frontend and in this case we want |
| to predict paths leading to this preheader. */ |
| |
| if (stmt |
| && gimple_code (stmt) == GIMPLE_COND |
| && gimple_cond_code (stmt) == NE_EXPR |
| && TREE_CODE (gimple_cond_lhs (stmt)) == SSA_NAME |
| && integer_zerop (gimple_cond_rhs (stmt))) |
| { |
| gimple *call_stmt = SSA_NAME_DEF_STMT (gimple_cond_lhs (stmt)); |
| if (gimple_code (call_stmt) == GIMPLE_ASSIGN |
| && CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (call_stmt)) |
| && TREE_CODE (gimple_assign_rhs1 (call_stmt)) == SSA_NAME) |
| call_stmt = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (call_stmt)); |
| if (gimple_call_internal_p (call_stmt, IFN_BUILTIN_EXPECT) |
| && TREE_CODE (gimple_call_arg (call_stmt, 2)) == INTEGER_CST |
| && tree_fits_uhwi_p (gimple_call_arg (call_stmt, 2)) |
| && tree_to_uhwi (gimple_call_arg (call_stmt, 2)) |
| == PRED_FORTRAN_LOOP_PREHEADER) |
| bb = preheader_edge->src; |
| } |
| if (!bb) |
| { |
| if (!dominated_by_p (CDI_DOMINATORS, |
| loop_outer (loop)->latch, loop->header)) |
| predict_paths_leading_to_edge (loop_preheader_edge (loop), |
| recursion |
| ? PRED_LOOP_GUARD_WITH_RECURSION |
| : PRED_LOOP_GUARD, |
| NOT_TAKEN, |
| loop_outer (loop)); |
| } |
| else |
| { |
| if (!dominated_by_p (CDI_DOMINATORS, |
| loop_outer (loop)->latch, bb)) |
| predict_paths_leading_to (bb, |
| recursion |
| ? PRED_LOOP_GUARD_WITH_RECURSION |
| : PRED_LOOP_GUARD, |
| NOT_TAKEN, |
| loop_outer (loop)); |
| } |
| } |
| |
| /* Free basic blocks from get_loop_body. */ |
| free (bbs); |
| } |
| } |
| |
| /* Attempt to predict probabilities of BB outgoing edges using local |
| properties. */ |
| static void |
| bb_estimate_probability_locally (basic_block bb) |
| { |
| rtx_insn *last_insn = BB_END (bb); |
| rtx cond; |
| |
| if (! can_predict_insn_p (last_insn)) |
| return; |
| cond = get_condition (last_insn, NULL, false, false); |
| if (! cond) |
| return; |
| |
| /* Try "pointer heuristic." |
| A comparison ptr == 0 is predicted as false. |
| Similarly, a comparison ptr1 == ptr2 is predicted as false. */ |
| if (COMPARISON_P (cond) |
| && ((REG_P (XEXP (cond, 0)) && REG_POINTER (XEXP (cond, 0))) |
| || (REG_P (XEXP (cond, 1)) && REG_POINTER (XEXP (cond, 1))))) |
| { |
| if (GET_CODE (cond) == EQ) |
| predict_insn_def (last_insn, PRED_POINTER, NOT_TAKEN); |
| else if (GET_CODE (cond) == NE) |
| predict_insn_def (last_insn, PRED_POINTER, TAKEN); |
| } |
| else |
| |
| /* Try "opcode heuristic." |
| EQ tests are usually false and NE tests are usually true. Also, |
| most quantities are positive, so we can make the appropriate guesses |
| about signed comparisons against zero. */ |
| switch (GET_CODE (cond)) |
| { |
| case CONST_INT: |
| /* Unconditional branch. */ |
| predict_insn_def (last_insn, PRED_UNCONDITIONAL, |
| cond == const0_rtx ? NOT_TAKEN : TAKEN); |
| break; |
| |
| case EQ: |
| case UNEQ: |
| /* Floating point comparisons appears to behave in a very |
| unpredictable way because of special role of = tests in |
| FP code. */ |
| if (FLOAT_MODE_P (GET_MODE (XEXP (cond, 0)))) |
| ; |
| /* Comparisons with 0 are often used for booleans and there is |
| nothing useful to predict about them. */ |
| else if (XEXP (cond, 1) == const0_rtx |
| || XEXP (cond, 0) == const0_rtx) |
| ; |
| else |
| predict_insn_def (last_insn, PRED_OPCODE_NONEQUAL, NOT_TAKEN); |
| break; |
| |
| case NE: |
| case LTGT: |
| /* Floating point comparisons appears to behave in a very |
| unpredictable way because of special role of = tests in |
| FP code. */ |
| if (FLOAT_MODE_P (GET_MODE (XEXP (cond, 0)))) |
| ; |
| /* Comparisons with 0 are often used for booleans and there is |
| nothing useful to predict about them. */ |
| else if (XEXP (cond, 1) == const0_rtx |
| || XEXP (cond, 0) == const0_rtx) |
| ; |
| else |
| predict_insn_def (last_insn, PRED_OPCODE_NONEQUAL, TAKEN); |
| break; |
| |
| case ORDERED: |
| predict_insn_def (last_insn, PRED_FPOPCODE, TAKEN); |
| break; |
| |
| case UNORDERED: |
| predict_insn_def (last_insn, PRED_FPOPCODE, NOT_TAKEN); |
| break; |
| |
| case LE: |
| case LT: |
| if (XEXP (cond, 1) == const0_rtx || XEXP (cond, 1) == const1_rtx |
| || XEXP (cond, 1) == constm1_rtx) |
| predict_insn_def (last_insn, PRED_OPCODE_POSITIVE, NOT_TAKEN); |
| break; |
| |
| case GE: |
| case GT: |
| if (XEXP (cond, 1) == const0_rtx || XEXP (cond, 1) == const1_rtx |
| || XEXP (cond, 1) == constm1_rtx) |
| predict_insn_def (last_insn, PRED_OPCODE_POSITIVE, TAKEN); |
| break; |
| |
| default: |
| break; |
| } |
| } |
| |
| /* Set edge->probability for each successor edge of BB. */ |
| void |
| guess_outgoing_edge_probabilities (basic_block bb) |
| { |
| bb_estimate_probability_locally (bb); |
| combine_predictions_for_insn (BB_END (bb), bb); |
| } |
| |
| static tree expr_expected_value (tree, bitmap, enum br_predictor *predictor, |
| HOST_WIDE_INT *probability); |
| |
| /* Helper function for expr_expected_value. */ |
| |
| static tree |
| expr_expected_value_1 (tree type, tree op0, enum tree_code code, |
| tree op1, bitmap visited, enum br_predictor *predictor, |
| HOST_WIDE_INT *probability) |
| { |
| gimple *def; |
| |
| /* Reset returned probability value. */ |
| *probability = -1; |
| *predictor = PRED_UNCONDITIONAL; |
| |
| if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS) |
| { |
| if (TREE_CONSTANT (op0)) |
| return op0; |
| |
| if (code == IMAGPART_EXPR) |
| { |
| if (TREE_CODE (TREE_OPERAND (op0, 0)) == SSA_NAME) |
| { |
| def = SSA_NAME_DEF_STMT (TREE_OPERAND (op0, 0)); |
| if (is_gimple_call (def) |
| && gimple_call_internal_p (def) |
| && (gimple_call_internal_fn (def) |
| == IFN_ATOMIC_COMPARE_EXCHANGE)) |
| { |
| /* Assume that any given atomic operation has low contention, |
| and thus the compare-and-swap operation succeeds. */ |
| *predictor = PRED_COMPARE_AND_SWAP; |
| return build_one_cst (TREE_TYPE (op0)); |
| } |
| } |
| } |
| |
| if (code != SSA_NAME) |
| return NULL_TREE; |
| |
| def = SSA_NAME_DEF_STMT (op0); |
| |
| /* If we were already here, break the infinite cycle. */ |
| if (!bitmap_set_bit (visited, SSA_NAME_VERSION (op0))) |
| return NULL; |
| |
| if (gimple_code (def) == GIMPLE_PHI) |
| { |
| /* All the arguments of the PHI node must have the same constant |
| length. */ |
| int i, n = gimple_phi_num_args (def); |
| tree val = NULL, new_val; |
| |
| for (i = 0; i < n; i++) |
| { |
| tree arg = PHI_ARG_DEF (def, i); |
| enum br_predictor predictor2; |
| |
| /* If this PHI has itself as an argument, we cannot |
| determine the string length of this argument. However, |
| if we can find an expected constant value for the other |
| PHI args then we can still be sure that this is |
| likely a constant. So be optimistic and just |
| continue with the next argument. */ |
| if (arg == PHI_RESULT (def)) |
| continue; |
| |
| HOST_WIDE_INT probability2; |
| new_val = expr_expected_value (arg, visited, &predictor2, |
| &probability2); |
| |
| /* It is difficult to combine value predictors. Simply assume |
| that later predictor is weaker and take its prediction. */ |
| if (*predictor < predictor2) |
| { |
| *predictor = predictor2; |
| *probability = probability2; |
| } |
| if (!new_val) |
| return NULL; |
| if (!val) |
| val = new_val; |
| else if (!operand_equal_p (val, new_val, false)) |
| return NULL; |
| } |
| return val; |
| } |
| if (is_gimple_assign (def)) |
| { |
| if (gimple_assign_lhs (def) != op0) |
| return NULL; |
| |
| return expr_expected_value_1 (TREE_TYPE (gimple_assign_lhs (def)), |
| gimple_assign_rhs1 (def), |
| gimple_assign_rhs_code (def), |
| gimple_assign_rhs2 (def), |
| visited, predictor, probability); |
| } |
| |
| if (is_gimple_call (def)) |
| { |
| tree decl = gimple_call_fndecl (def); |
| if (!decl) |
| { |
| if (gimple_call_internal_p (def) |
| && gimple_call_internal_fn (def) == IFN_BUILTIN_EXPECT) |
| { |
| gcc_assert (gimple_call_num_args (def) == 3); |
| tree val = gimple_call_arg (def, 0); |
| if (TREE_CONSTANT (val)) |
| return val; |
| tree val2 = gimple_call_arg (def, 2); |
| gcc_assert (TREE_CODE (val2) == INTEGER_CST |
| && tree_fits_uhwi_p (val2) |
| && tree_to_uhwi (val2) < END_PREDICTORS); |
| *predictor = (enum br_predictor) tree_to_uhwi (val2); |
| if (*predictor == PRED_BUILTIN_EXPECT) |
| *probability |
| = HITRATE (param_builtin_expect_probability); |
| return gimple_call_arg (def, 1); |
| } |
| return NULL; |
| } |
| |
| if (DECL_IS_MALLOC (decl) || DECL_IS_OPERATOR_NEW_P (decl)) |
| { |
| if (predictor) |
| *predictor = PRED_MALLOC_NONNULL; |
| return boolean_true_node; |
| } |
| |
| if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL) |
| switch (DECL_FUNCTION_CODE (decl)) |
| { |
| case BUILT_IN_EXPECT: |
| { |
| tree val; |
| if (gimple_call_num_args (def) != 2) |
| return NULL; |
| val = gimple_call_arg (def, 0); |
| if (TREE_CONSTANT (val)) |
| return val; |
| *predictor = PRED_BUILTIN_EXPECT; |
| *probability |
| = HITRATE (param_builtin_expect_probability); |
| return gimple_call_arg (def, 1); |
| } |
| case BUILT_IN_EXPECT_WITH_PROBABILITY: |
| { |
| tree val; |
| if (gimple_call_num_args (def) != 3) |
| return NULL; |
| val = gimple_call_arg (def, 0); |
| if (TREE_CONSTANT (val)) |
| return val; |
| /* Compute final probability as: |
| probability * REG_BR_PROB_BASE. */ |
| tree prob = gimple_call_arg (def, 2); |
| tree t = TREE_TYPE (prob); |
| tree base = build_int_cst (integer_type_node, |
| REG_BR_PROB_BASE); |
| base = build_real_from_int_cst (t, base); |
| tree r = fold_build2_initializer_loc (UNKNOWN_LOCATION, |
| MULT_EXPR, t, prob, base); |
| if (TREE_CODE (r) != REAL_CST) |
| { |
| error_at (gimple_location (def), |
| "probability %qE must be " |
| "constant floating-point expression", prob); |
| return NULL; |
| } |
| HOST_WIDE_INT probi |
| = real_to_integer (TREE_REAL_CST_PTR (r)); |
| if (probi >= 0 && probi <= REG_BR_PROB_BASE) |
| { |
| *predictor = PRED_BUILTIN_EXPECT_WITH_PROBABILITY; |
| *probability = probi; |
| } |
| else |
| error_at (gimple_location (def), |
| "probability %qE is outside " |
| "the range [0.0, 1.0]", prob); |
| |
| return gimple_call_arg (def, 1); |
| } |
| |
| case BUILT_IN_SYNC_BOOL_COMPARE_AND_SWAP_N: |
| case BUILT_IN_SYNC_BOOL_COMPARE_AND_SWAP_1: |
| case BUILT_IN_SYNC_BOOL_COMPARE_AND_SWAP_2: |
| case BUILT_IN_SYNC_BOOL_COMPARE_AND_SWAP_4: |
| case BUILT_IN_SYNC_BOOL_COMPARE_AND_SWAP_8: |
| case BUILT_IN_SYNC_BOOL_COMPARE_AND_SWAP_16: |
| case BUILT_IN_ATOMIC_COMPARE_EXCHANGE: |
| case BUILT_IN_ATOMIC_COMPARE_EXCHANGE_N: |
| case BUILT_IN_ATOMIC_COMPARE_EXCHANGE_1: |
| case BUILT_IN_ATOMIC_COMPARE_EXCHANGE_2: |
| case BUILT_IN_ATOMIC_COMPARE_EXCHANGE_4: |
| case BUILT_IN_ATOMIC_COMPARE_EXCHANGE_8: |
| case BUILT_IN_ATOMIC_COMPARE_EXCHANGE_16: |
| /* Assume that any given atomic operation has low contention, |
| and thus the compare-and-swap operation succeeds. */ |
| *predictor = PRED_COMPARE_AND_SWAP; |
| return boolean_true_node; |
| case BUILT_IN_REALLOC: |
| if (predictor) |
| *predictor = PRED_MALLOC_NONNULL; |
| return boolean_true_node; |
| default: |
| break; |
| } |
| } |
| |
| return NULL; |
| } |
| |
| if (get_gimple_rhs_class (code) == GIMPLE_BINARY_RHS) |
| { |
| tree res; |
| enum br_predictor predictor2; |
| HOST_WIDE_INT probability2; |
| op0 = expr_expected_value (op0, visited, predictor, probability); |
| if (!op0) |
| return NULL; |
| op1 = expr_expected_value (op1, visited, &predictor2, &probability2); |
| if (!op1) |
| return NULL; |
| res = fold_build2 (code, type, op0, op1); |
| if (TREE_CODE (res) == INTEGER_CST |
| && TREE_CODE (op0) == INTEGER_CST |
| && TREE_CODE (op1) == INTEGER_CST) |
| { |
| /* Combine binary predictions. */ |
| if (*probability != -1 || probability2 != -1) |
| { |
| HOST_WIDE_INT p1 = get_predictor_value (*predictor, *probability); |
| HOST_WIDE_INT p2 = get_predictor_value (predictor2, probability2); |
| *probability = RDIV (p1 * p2, REG_BR_PROB_BASE); |
| } |
| |
| if (*predictor < predictor2) |
| *predictor = predictor2; |
| |
| return res; |
| } |
| return NULL; |
| } |
| if (get_gimple_rhs_class (code) == GIMPLE_UNARY_RHS) |
| { |
| tree res; |
| op0 = expr_expected_value (op0, visited, predictor, probability); |
| if (!op0) |
| return NULL; |
| res = fold_build1 (code, type, op0); |
| if (TREE_CONSTANT (res)) |
| return res; |
| return NULL; |
| } |
| return NULL; |
| } |
| |
| /* Return constant EXPR will likely have at execution time, NULL if unknown. |
| The function is used by builtin_expect branch predictor so the evidence |
| must come from this construct and additional possible constant folding. |
| |
| We may want to implement more involved value guess (such as value range |
| propagation based prediction), but such tricks shall go to new |
| implementation. */ |
| |
| static tree |
| expr_expected_value (tree expr, bitmap visited, |
| enum br_predictor *predictor, |
| HOST_WIDE_INT *probability) |
| { |
| enum tree_code code; |
| tree op0, op1; |
| |
| if (TREE_CONSTANT (expr)) |
| { |
| *predictor = PRED_UNCONDITIONAL; |
| *probability = -1; |
| return expr; |
| } |
| |
| extract_ops_from_tree (expr, &code, &op0, &op1); |
| return expr_expected_value_1 (TREE_TYPE (expr), |
| op0, code, op1, visited, predictor, |
| probability); |
| } |
| |
| |
| /* Return probability of a PREDICTOR. If the predictor has variable |
| probability return passed PROBABILITY. */ |
| |
| static HOST_WIDE_INT |
| get_predictor_value (br_predictor predictor, HOST_WIDE_INT probability) |
| { |
| switch (predictor) |
| { |
| case PRED_BUILTIN_EXPECT: |
| case PRED_BUILTIN_EXPECT_WITH_PROBABILITY: |
| gcc_assert (probability != -1); |
| return probability; |
| default: |
| gcc_assert (probability == -1); |
| return predictor_info[(int) predictor].hitrate; |
| } |
| } |
| |
| /* Predict using opcode of the last statement in basic block. */ |
| static void |
| tree_predict_by_opcode (basic_block bb) |
| { |
| gimple *stmt = last_stmt (bb); |
| edge then_edge; |
| tree op0, op1; |
| tree type; |
| tree val; |
| enum tree_code cmp; |
| edge_iterator ei; |
| enum br_predictor predictor; |
| HOST_WIDE_INT probability; |
| |
| if (!stmt) |
| return; |
| |
| if (gswitch *sw = dyn_cast <gswitch *> (stmt)) |
| { |
| tree index = gimple_switch_index (sw); |
| tree val = expr_expected_value (index, auto_bitmap (), |
| &predictor, &probability); |
| if (val && TREE_CODE (val) == INTEGER_CST) |
| { |
| edge e = find_taken_edge_switch_expr (sw, val); |
| if (predictor == PRED_BUILTIN_EXPECT) |
| { |
| int percent = param_builtin_expect_probability; |
| gcc_assert (percent >= 0 && percent <= 100); |
| predict_edge (e, PRED_BUILTIN_EXPECT, |
| HITRATE (percent)); |
| } |
| else |
| predict_edge_def (e, predictor, TAKEN); |
| } |
| } |
| |
| if (gimple_code (stmt) != GIMPLE_COND) |
| return; |
| FOR_EACH_EDGE (then_edge, ei, bb->succs) |
| if (then_edge->flags & EDGE_TRUE_VALUE) |
| break; |
| op0 = gimple_cond_lhs (stmt); |
| op1 = gimple_cond_rhs (stmt); |
| cmp = gimple_cond_code (stmt); |
| type = TREE_TYPE (op0); |
| val = expr_expected_value_1 (boolean_type_node, op0, cmp, op1, auto_bitmap (), |
| &predictor, &probability); |
| if (val && TREE_CODE (val) == INTEGER_CST) |
| { |
| HOST_WIDE_INT prob = get_predictor_value (predictor, probability); |
| if (integer_zerop (val)) |
| prob = REG_BR_PROB_BASE - prob; |
| predict_edge (then_edge, predictor, prob); |
| } |
| /* Try "pointer heuristic." |
| A comparison ptr == 0 is predicted as false. |
| Similarly, a comparison ptr1 == ptr2 is predicted as false. */ |
| if (POINTER_TYPE_P (type)) |
| { |
| if (cmp == EQ_EXPR) |
| predict_edge_def (then_edge, PRED_TREE_POINTER, NOT_TAKEN); |
| else if (cmp == NE_EXPR) |
| predict_edge_def (then_edge, PRED_TREE_POINTER, TAKEN); |
| } |
| else |
| |
| /* Try "opcode heuristic." |
| EQ tests are usually false and NE tests are usually true. Also, |
| most quantities are positive, so we can make the appropriate guesses |
| about signed comparisons against zero. */ |
| switch (cmp) |
| { |
| case EQ_EXPR: |
| case UNEQ_EXPR: |
| /* Floating point comparisons appears to behave in a very |
| unpredictable way because of special role of = tests in |
| FP code. */ |
| if (FLOAT_TYPE_P (type)) |
| ; |
| /* Comparisons with 0 are often used for booleans and there is |
| nothing useful to predict about them. */ |
| else if (integer_zerop (op0) || integer_zerop (op1)) |
| ; |
| else |
| predict_edge_def (then_edge, PRED_TREE_OPCODE_NONEQUAL, NOT_TAKEN); |
| break; |
| |
| case NE_EXPR: |
| case LTGT_EXPR: |
| /* Floating point comparisons appears to behave in a very |
| unpredictable way because of special role of = tests in |
| FP code. */ |
| if (FLOAT_TYPE_P (type)) |
| ; |
| /* Comparisons with 0 are often used for booleans and there is |
| nothing useful to predict about them. */ |
| else if (integer_zerop (op0) |
| || integer_zerop (op1)) |
| ; |
| else |
| predict_edge_def (then_edge, PRED_TREE_OPCODE_NONEQUAL, TAKEN); |
| break; |
| |
| case ORDERED_EXPR: |
| predict_edge_def (then_edge, PRED_TREE_FPOPCODE, TAKEN); |
| break; |
| |
| case UNORDERED_EXPR: |
| predict_edge_def (then_edge, PRED_TREE_FPOPCODE, NOT_TAKEN); |
| break; |
| |
| case LE_EXPR: |
| case LT_EXPR: |
| if (integer_zerop (op1) |
| || integer_onep (op1) |
| || integer_all_onesp (op1) |
| || real_zerop (op1) |
| || real_onep (op1) |
| || real_minus_onep (op1)) |
| predict_edge_def (then_edge, PRED_TREE_OPCODE_POSITIVE, NOT_TAKEN); |
| break; |
| |
| case GE_EXPR: |
| case GT_EXPR: |
| if (integer_zerop (op1) |
| || integer_onep (op1) |
| || integer_all_onesp (op1) |
| || real_zerop (op1) |
| || real_onep (op1) |
| || real_minus_onep (op1)) |
| predict_edge_def (then_edge, PRED_TREE_OPCODE_POSITIVE, TAKEN); |
| break; |
| |
| default: |
| break; |
| } |
| } |
| |
| /* Returns TRUE if the STMT is exit(0) like statement. */ |
| |
| static bool |
| is_exit_with_zero_arg (const gimple *stmt) |
| { |
| /* This is not exit, _exit or _Exit. */ |
| if (!gimple_call_builtin_p (stmt, BUILT_IN_EXIT) |
| && !gimple_call_builtin_p (stmt, BUILT_IN__EXIT) |
| && !gimple_call_builtin_p (stmt, BUILT_IN__EXIT2)) |
| return false; |
| |
| /* Argument is an interger zero. */ |
| return integer_zerop (gimple_call_arg (stmt, 0)); |
| } |
| |
| /* Try to guess whether the value of return means error code. */ |
| |
| static enum br_predictor |
| return_prediction (tree val, enum prediction *prediction) |
| { |
| /* VOID. */ |
| if (!val) |
| return PRED_NO_PREDICTION; |
| /* Different heuristics for pointers and scalars. */ |
| if (POINTER_TYPE_P (TREE_TYPE (val))) |
| { |
| /* NULL is usually not returned. */ |
| if (integer_zerop (val)) |
| { |
| *prediction = NOT_TAKEN; |
| return PRED_NULL_RETURN; |
| } |
| } |
| else if (INTEGRAL_TYPE_P (TREE_TYPE (val))) |
| { |
| /* Negative return values are often used to indicate |
| errors. */ |
| if (TREE_CODE (val) == INTEGER_CST |
| && tree_int_cst_sgn (val) < 0) |
| { |
| *prediction = NOT_TAKEN; |
| return PRED_NEGATIVE_RETURN; |
| } |
| /* Constant return values seems to be commonly taken. |
| Zero/one often represent booleans so exclude them from the |
| heuristics. */ |
| if (TREE_CONSTANT (val) |
| && (!integer_zerop (val) && !integer_onep (val))) |
| { |
| *prediction = NOT_TAKEN; |
| return PRED_CONST_RETURN; |
| } |
| } |
| return PRED_NO_PREDICTION; |
| } |
| |
| /* Return zero if phi result could have values other than -1, 0 or 1, |
| otherwise return a bitmask, with bits 0, 1 and 2 set if -1, 0 and 1 |
| values are used or likely. */ |
| |
| static int |
| zero_one_minusone (gphi *phi, int limit) |
| { |
| int phi_num_args = gimple_phi_num_args (phi); |
| int ret = 0; |
| for (int i = 0; i < phi_num_args; i++) |
| { |
| tree t = PHI_ARG_DEF (phi, i); |
| if (TREE_CODE (t) != INTEGER_CST) |
| continue; |
| wide_int w = wi::to_wide (t); |
| if (w == -1) |
| ret |= 1; |
| else if (w == 0) |
| ret |= 2; |
| else if (w == 1) |
| ret |= 4; |
| else |
| return 0; |
| } |
| for (int i = 0; i < phi_num_args; i++) |
| { |
| tree t = PHI_ARG_DEF (phi, i); |
| if (TREE_CODE (t) == INTEGER_CST) |
| continue; |
| if (TREE_CODE (t) != SSA_NAME) |
| return 0; |
| gimple *g = SSA_NAME_DEF_STMT (t); |
| if (gimple_code (g) == GIMPLE_PHI && limit > 0) |
| if (int r = zero_one_minusone (as_a <gphi *> (g), limit - 1)) |
| { |
| ret |= r; |
| continue; |
| } |
| if (!is_gimple_assign (g)) |
| return 0; |
| if (gimple_assign_cast_p (g)) |
| { |
| tree rhs1 = gimple_assign_rhs1 (g); |
| if (TREE_CODE (rhs1) != SSA_NAME |
| || !INTEGRAL_TYPE_P (TREE_TYPE (rhs1)) |
| || TYPE_PRECISION (TREE_TYPE (rhs1)) != 1 |
| || !TYPE_UNSIGNED (TREE_TYPE (rhs1))) |
| return 0; |
| ret |= (2 | 4); |
| continue; |
| } |
| if (TREE_CODE_CLASS (gimple_assign_rhs_code (g)) != tcc_comparison) |
| return 0; |
| ret |= (2 | 4); |
| } |
| return ret; |
| } |
| |
| /* Find the basic block with return expression and look up for possible |
| return value trying to apply RETURN_PREDICTION heuristics. */ |
| static void |
| apply_return_prediction (void) |
| { |
| greturn *return_stmt = NULL; |
| tree return_val; |
| edge e; |
| gphi *phi; |
| int phi_num_args, i; |
| enum br_predictor pred; |
| enum prediction direction; |
| edge_iterator ei; |
| |
| FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds) |
| { |
| gimple *last = last_stmt (e->src); |
| if (last |
| && gimple_code (last) == GIMPLE_RETURN) |
| { |
| return_stmt = as_a <greturn *> (last); |
| break; |
| } |
| } |
| if (!e) |
| return; |
| return_val = gimple_return_retval (return_stmt); |
| if (!return_val) |
| return; |
| if (TREE_CODE (return_val) != SSA_NAME |
| || !SSA_NAME_DEF_STMT (return_val) |
| || gimple_code (SSA_NAME_DEF_STMT (return_val)) != GIMPLE_PHI) |
| return; |
| phi = as_a <gphi *> (SSA_NAME_DEF_STMT (return_val)); |
| phi_num_args = gimple_phi_num_args (phi); |
| pred = return_prediction (PHI_ARG_DEF (phi, 0), &direction); |
| |
| /* Avoid the case where the function returns -1, 0 and 1 values and |
| nothing else. Those could be qsort etc. comparison functions |
| where the negative return isn't less probable than positive. |
| For this require that the function returns at least -1 or 1 |
| or -1 and a boolean value or comparison result, so that functions |
| returning just -1 and 0 are treated as if -1 represents error value. */ |
| if (INTEGRAL_TYPE_P (TREE_TYPE (return_val)) |
| && !TYPE_UNSIGNED (TREE_TYPE (return_val)) |
| && TYPE_PRECISION (TREE_TYPE (return_val)) > 1) |
| if (int r = zero_one_minusone (phi, 3)) |
| if ((r & (1 | 4)) == (1 | 4)) |
| return; |
| |
| /* Avoid the degenerate case where all return values form the function |
| belongs to same category (ie they are all positive constants) |
| so we can hardly say something about them. */ |
| for (i = 1; i < phi_num_args; i++) |
| if (pred != return_prediction (PHI_ARG_DEF (phi, i), &direction)) |
| break; |
| if (i != phi_num_args) |
| for (i = 0; i < phi_num_args; i++) |
| { |
| pred = return_prediction (PHI_ARG_DEF (phi, i), &direction); |
| if (pred != PRED_NO_PREDICTION) |
| predict_paths_leading_to_edge (gimple_phi_arg_edge (phi, i), pred, |
| direction); |
| } |
| } |
| |
| /* Look for basic block that contains unlikely to happen events |
| (such as noreturn calls) and mark all paths leading to execution |
| of this basic blocks as unlikely. */ |
| |
| static void |
| tree_bb_level_predictions (void) |
| { |
| basic_block bb; |
| bool has_return_edges = false; |
| edge e; |
| edge_iterator ei; |
| |
| FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds) |
| if (!unlikely_executed_edge_p (e) && !(e->flags & EDGE_ABNORMAL_CALL)) |
| { |
| has_return_edges = true; |
| break; |
| } |
| |
| apply_return_prediction (); |
| |
| FOR_EACH_BB_FN (bb, cfun) |
| { |
| gimple_stmt_iterator gsi; |
| |
| for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) |
| { |
| gimple *stmt = gsi_stmt (gsi); |
| tree decl; |
| |
| if (is_gimple_call (stmt)) |
| { |
| if (gimple_call_noreturn_p (stmt) |
| && has_return_edges |
| && !is_exit_with_zero_arg (stmt)) |
| predict_paths_leading_to (bb, PRED_NORETURN, |
| NOT_TAKEN); |
| decl = gimple_call_fndecl (stmt); |
| if (decl |
| && lookup_attribute ("cold", |
| DECL_ATTRIBUTES (decl))) |
| predict_paths_leading_to (bb, PRED_COLD_FUNCTION, |
| NOT_TAKEN); |
| if (decl && recursive_call_p (current_function_decl, decl)) |
| predict_paths_leading_to (bb, PRED_RECURSIVE_CALL, |
| NOT_TAKEN); |
| } |
| else if (gimple_code (stmt) == GIMPLE_PREDICT) |
| { |
| predict_paths_leading_to (bb, gimple_predict_predictor (stmt), |
| gimple_predict_outcome (stmt)); |
| /* Keep GIMPLE_PREDICT around so early inlining will propagate |
| hints to callers. */ |
| } |
| } |
| } |
| } |
| |
| /* Callback for hash_map::traverse, asserts that the pointer map is |
| empty. */ |
| |
| bool |
| assert_is_empty (const_basic_block const &, edge_prediction *const &value, |
| void *) |
| { |
| gcc_assert (!value); |
| return false; |
| } |
| |
| /* Predict branch probabilities and estimate profile for basic block BB. |
| When LOCAL_ONLY is set do not use any global properties of CFG. */ |
| |
| static void |
| tree_estimate_probability_bb (basic_block bb, bool local_only) |
| { |
| edge e; |
| edge_iterator ei; |
| |
| FOR_EACH_EDGE (e, ei, bb->succs) |
| { |
| /* Look for block we are guarding (ie we dominate it, |
| but it doesn't postdominate us). */ |
| if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun) && e->dest != bb |
| && !local_only |
| && dominated_by_p (CDI_DOMINATORS, e->dest, e->src) |
| && !dominated_by_p (CDI_POST_DOMINATORS, e->src, e->dest)) |
| { |
| gimple_stmt_iterator bi; |
| |
| /* The call heuristic claims that a guarded function call |
| is improbable. This is because such calls are often used |
| to signal exceptional situations such as printing error |
| messages. */ |
| for (bi = gsi_start_bb (e->dest); !gsi_end_p (bi); |
| gsi_next (&bi)) |
| { |
| gimple *stmt = gsi_stmt (bi); |
| if (is_gimple_call (stmt) |
| && !gimple_inexpensive_call_p (as_a <gcall *> (stmt)) |
| /* Constant and pure calls are hardly used to signalize |
| something exceptional. */ |
| && gimple_has_side_effects (stmt)) |
| { |
| if (gimple_call_fndecl (stmt)) |
| predict_edge_def (e, PRED_CALL, NOT_TAKEN); |
| else if (virtual_method_call_p (gimple_call_fn (stmt))) |
| predict_edge_def (e, PRED_POLYMORPHIC_CALL, NOT_TAKEN); |
| else |
| predict_edge_def (e, PRED_INDIR_CALL, TAKEN); |
| break; |
| } |
| } |
| } |
| } |
| tree_predict_by_opcode (bb); |
| } |
| |
| /* Predict branch probabilities and estimate profile of the tree CFG. |
| This function can be called from the loop optimizers to recompute |
| the profile information. |
| If DRY_RUN is set, do not modify CFG and only produce dump files. */ |
| |
| void |
| tree_estimate_probability (bool dry_run) |
| { |
| basic_block bb; |
| |
| connect_infinite_loops_to_exit (); |
| /* We use loop_niter_by_eval, which requires that the loops have |
| preheaders. */ |
| create_preheaders (CP_SIMPLE_PREHEADERS); |
| calculate_dominance_info (CDI_POST_DOMINATORS); |
| /* Decide which edges are known to be unlikely. This improves later |
| branch prediction. */ |
| determine_unlikely_bbs (); |
| |
| bb_predictions = new hash_map<const_basic_block, edge_prediction *>; |
| tree_bb_level_predictions (); |
| record_loop_exits (); |
| |
| if (number_of_loops (cfun) > 1) |
| predict_loops (); |
| |
| FOR_EACH_BB_FN (bb, cfun) |
| tree_estimate_probability_bb (bb, false); |
| |
| FOR_EACH_BB_FN (bb, cfun) |
| combine_predictions_for_bb (bb, dry_run); |
| |
| if (flag_checking) |
| bb_predictions->traverse<void *, assert_is_empty> (NULL); |
| |
| delete bb_predictions; |
| bb_predictions = NULL; |
| |
| if (!dry_run) |
| estimate_bb_frequencies (false); |
| free_dominance_info (CDI_POST_DOMINATORS); |
| remove_fake_exit_edges (); |
| } |
| |
| /* Set edge->probability for each successor edge of BB. */ |
| void |
| tree_guess_outgoing_edge_probabilities (basic_block bb) |
| { |
| bb_predictions = new hash_map<const_basic_block, edge_prediction *>; |
| tree_estimate_probability_bb (bb, true); |
| combine_predictions_for_bb (bb, false); |
| if (flag_checking) |
| bb_predictions-> |