From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- gcc/predict.c | 2367 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 2367 insertions(+) create mode 100644 gcc/predict.c (limited to 'gcc/predict.c') diff --git a/gcc/predict.c b/gcc/predict.c new file mode 100644 index 000000000..18fda083d --- /dev/null +++ b/gcc/predict.c @@ -0,0 +1,2367 @@ +/* Branch prediction routines for the GNU compiler. + Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010 + 2011, 2012, 2013 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 +. */ + +/* 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 "tm.h" +#include "tree.h" +#include "rtl.h" +#include "tm_p.h" +#include "hard-reg-set.h" +#include "basic-block.h" +#include "insn-config.h" +#include "regs.h" +#include "flags.h" +#include "output.h" +#include "function.h" +#include "except.h" +#include "diagnostic-core.h" +#include "recog.h" +#include "expr.h" +#include "predict.h" +#include "coverage.h" +#include "sreal.h" +#include "params.h" +#include "target.h" +#include "cfgloop.h" +#include "tree-flow.h" +#include "ggc.h" +#include "tree-dump.h" +#include "tree-pass.h" +#include "timevar.h" +#include "tree-scalar-evolution.h" +#include "cfgloop.h" +#include "pointer-set.h" + +/* real constants: 0, 1, 1-1/REG_BR_PROB_BASE, REG_BR_PROB_BASE, + 1/REG_BR_PROB_BASE, 0.5, BB_FREQ_MAX. */ +static sreal real_zero, real_one, real_almost_one, real_br_prob_base, + real_inv_br_prob_base, real_one_half, real_bb_freq_max; + +/* Random guesstimation given names. + PROV_VERY_UNLIKELY should be small enough so basic block predicted + by it gets bellow HOT_BB_FREQUENCY_FRANCTION. */ +#define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 2000 - 1) +#define PROB_EVEN (REG_BR_PROB_BASE / 2) +#define PROB_VERY_LIKELY (REG_BR_PROB_BASE - PROB_VERY_UNLIKELY) +#define PROB_ALWAYS (REG_BR_PROB_BASE) + +static void combine_predictions_for_insn (rtx, basic_block); +static void dump_prediction (FILE *, enum br_predictor, int, basic_block, int); +static void predict_paths_leading_to (basic_block, enum br_predictor, enum prediction); +static void predict_paths_leading_to_edge (edge, enum br_predictor, enum prediction); +static bool can_predict_insn_p (const_rtx); + +/* 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 + +/* Return TRUE if frequency FREQ is considered to be hot. */ + +static inline bool +maybe_hot_frequency_p (int freq) +{ + struct cgraph_node *node = cgraph_node (current_function_decl); + if (!profile_info || !flag_branch_probabilities) + { + if (node->frequency == NODE_FREQUENCY_UNLIKELY_EXECUTED) + return false; + if (node->frequency == NODE_FREQUENCY_HOT) + return true; + } + if (profile_status == PROFILE_ABSENT) + return true; + if (node->frequency == NODE_FREQUENCY_EXECUTED_ONCE + && freq <= (ENTRY_BLOCK_PTR->frequency * 2 / 3)) + return false; + if (freq < ENTRY_BLOCK_PTR->frequency / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION)) + return false; + return true; +} + +/* Return TRUE if frequency FREQ is considered to be hot. */ + +static inline bool +maybe_hot_count_p (gcov_type count) +{ + if (profile_status != PROFILE_READ) + return true; + /* Code executed at most once is not hot. */ + if (profile_info->runs >= count) + return false; + return (count + > profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION)); +} + +/* Return true in case BB can be CPU intensive and should be optimized + for maximal performance. */ + +bool +maybe_hot_bb_p (const_basic_block bb) +{ + if (profile_status == PROFILE_READ) + return maybe_hot_count_p (bb->count); + return maybe_hot_frequency_p (bb->frequency); +} + +/* Return true if the call can be hot. */ + +bool +cgraph_maybe_hot_edge_p (struct cgraph_edge *edge) +{ + if (profile_info && flag_branch_probabilities + && (edge->count + <= profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION))) + return false; + if (edge->caller->frequency == NODE_FREQUENCY_UNLIKELY_EXECUTED + || edge->callee->frequency == NODE_FREQUENCY_UNLIKELY_EXECUTED) + return false; + if (edge->caller->frequency > NODE_FREQUENCY_UNLIKELY_EXECUTED + && edge->callee->frequency <= NODE_FREQUENCY_EXECUTED_ONCE) + return false; + if (optimize_size) + return false; + if (edge->caller->frequency == NODE_FREQUENCY_HOT) + return true; + if (edge->caller->frequency == NODE_FREQUENCY_EXECUTED_ONCE + && edge->frequency < CGRAPH_FREQ_BASE * 3 / 2) + return false; + if (flag_guess_branch_prob + && edge->frequency <= (CGRAPH_FREQ_BASE + / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION))) + return false; + return true; +} + +/* Return true in case BB can be CPU intensive and should be optimized + for maximal performance. */ + +bool +maybe_hot_edge_p (edge e) +{ + if (profile_status == PROFILE_READ) + return maybe_hot_count_p (e->count); + return maybe_hot_frequency_p (EDGE_FREQUENCY (e)); +} + +/* Return true in case BB is probably never executed. */ +bool +probably_never_executed_bb_p (const_basic_block bb) +{ + if (profile_info && flag_branch_probabilities) + return ((bb->count + profile_info->runs / 2) / profile_info->runs) == 0; + if ((!profile_info || !flag_branch_probabilities) + && cgraph_node (current_function_decl)->frequency == NODE_FREQUENCY_UNLIKELY_EXECUTED) + return true; + return false; +} + +/* Return true when current function should always be optimized for size. */ + +bool +optimize_function_for_size_p (struct function *fun) +{ + return (optimize_size + || (fun && fun->decl + && (cgraph_node (fun->decl)->frequency + == NODE_FREQUENCY_UNLIKELY_EXECUTED))); +} + +/* Return true when current function should always be optimized for speed. */ + +bool +optimize_function_for_speed_p (struct function *fun) +{ + return !optimize_function_for_size_p (fun); +} + +/* Return TRUE when BB should be optimized for size. */ + +bool +optimize_bb_for_size_p (const_basic_block bb) +{ + return optimize_function_for_size_p (cfun) || !maybe_hot_bb_p (bb); +} + +/* Return TRUE when BB should be optimized for speed. */ + +bool +optimize_bb_for_speed_p (const_basic_block bb) +{ + return !optimize_bb_for_size_p (bb); +} + +/* Return TRUE when BB should be optimized for size. */ + +bool +optimize_edge_for_size_p (edge e) +{ + return optimize_function_for_size_p (cfun) || !maybe_hot_edge_p (e); +} + +/* Return TRUE when BB should be optimized for speed. */ + +bool +optimize_edge_for_speed_p (edge e) +{ + return !optimize_edge_for_size_p (e); +} + +/* Return TRUE when BB should be optimized for size. */ + +bool +optimize_insn_for_size_p (void) +{ + return optimize_function_for_size_p (cfun) || !crtl->maybe_hot_insn_p; +} + +/* Return TRUE when BB should be optimized for speed. */ + +bool +optimize_insn_for_speed_p (void) +{ + return !optimize_insn_for_size_p (); +} + +/* Return TRUE when LOOP should be optimized for size. */ + +bool +optimize_loop_for_size_p (struct loop *loop) +{ + return optimize_bb_for_size_p (loop->header); +} + +/* Return TRUE when LOOP should be optimized for speed. */ + +bool +optimize_loop_for_speed_p (struct loop *loop) +{ + return optimize_bb_for_speed_p (loop->header); +} + +/* Return TRUE when LOOP nest should be optimized for speed. */ + +bool +optimize_loop_nest_for_speed_p (struct loop *loop) +{ + struct 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 when LOOP nest should be optimized for size. */ + +bool +optimize_loop_nest_for_size_p (struct loop *loop) +{ + return !optimize_loop_nest_for_speed_p (loop); +} + +/* Return true when edge E is likely to be well predictable by branch + predictor. */ + +bool +predictable_edge_p (edge e) +{ + if (profile_status == PROFILE_ABSENT) + return false; + if ((e->probability + <= PARAM_VALUE (PARAM_PREDICTABLE_BRANCH_OUTCOME) * REG_BR_PROB_BASE / 100) + || (REG_BR_PROB_BASE - e->probability + <= PARAM_VALUE (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 (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; +} + +/* This map contains for a basic block the list of predictions for the + outgoing edges. */ + +static struct pointer_map_t *bb_predictions; + +/* 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; +}; + +/* 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; + void **preds = pointer_map_contains (bb_predictions, bb); + + if (!preds) + return false; + + for (i = (struct edge_prediction *) *preds; i; i = i->ep_next) + if (i->ep_predictor == predictor) + return true; + return false; +} + +/* Return true when the probability of edge is reliable. + + The profile guessing code is good at predicting branch outcome (ie. + taken/not taken), that is predicted right slightly over 75% of time. + It is however notoriously poor on predicting the probability itself. + In general the profile appear a lot flatter (with probabilities closer + to 50%) than the reality so it is bad idea to use it to drive optimization + such as those disabling dynamic branch prediction for well predictable + branches. + + There are two exceptions - edges leading to noreturn edges and edges + predicted by number of iterations heuristics are predicted well. This macro + should be able to distinguish those, but at the moment it simply check for + noreturn heuristic that is only one giving probability over 99% or bellow + 1%. In future we might want to propagate reliability information across the + CFG if we find this information useful on multiple places. */ +static bool +probability_reliable_p (int prob) +{ + return (profile_status == PROFILE_READ + || (profile_status == PROFILE_GUESSED + && (prob <= HITRATE (1) || prob >= HITRATE (99)))); +} + +/* Same predicate as above, working on edges. */ +bool +edge_probability_reliable_p (const_edge e) +{ + return probability_reliable_p (e->probability); +} + +/* 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 probability_reliable_p (INTVAL (XEXP (note, 0))); +} + +static void +predict_insn (rtx 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, enum br_predictor predictor, + enum prediction taken) +{ + int probability = predictor_info[(int) predictor].hitrate; + + 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 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) +{ + gcc_assert (profile_status != PROFILE_GUESSED); + if ((e->src != ENTRY_BLOCK_PTR && EDGE_COUNT (e->src->succs) > 1) + && flag_guess_branch_prob && optimize) + { + struct edge_prediction *i = XNEW (struct edge_prediction); + void **preds = pointer_map_insert (bb_predictions, e->src); + + i->ep_next = (struct edge_prediction *) *preds; + *preds = i; + i->ep_probability = probability; + i->ep_predictor = predictor; + i->ep_edge = e; + } +} + +/* Remove all predictions on given basic block that are attached + to edge E. */ +void +remove_predictions_associated_with_edge (edge e) +{ + void **preds; + + if (!bb_predictions) + return; + + preds = pointer_map_contains (bb_predictions, e->src); + + if (preds) + { + struct edge_prediction **prediction = (struct edge_prediction **) preds; + struct edge_prediction *next; + + while (*prediction) + { + if ((*prediction)->ep_edge == e) + { + next = (*prediction)->ep_next; + free (*prediction); + *prediction = next; + } + else + prediction = &((*prediction)->ep_next); + } + } +} + +/* Clears the list of predictions stored for BB. */ + +static void +clear_bb_predictions (basic_block bb) +{ + void **preds = pointer_map_contains (bb_predictions, bb); + struct edge_prediction *pred, *next; + + if (!preds) + return; + + for (pred = (struct edge_prediction *) *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) +{ + 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) + XEXP (note, 0) = GEN_INT (REG_BR_PROB_BASE - INTVAL (XEXP (note, 0))); + 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, int used) +{ + edge e; + edge_iterator ei; + + if (!file) + return; + + FOR_EACH_EDGE (e, ei, bb->succs) + if (! (e->flags & EDGE_FALLTHRU)) + break; + + fprintf (file, " %s heuristics%s: %.1f%%", + predictor_info[predictor].name, + used ? "" : " (ignored)", probability * 100.0 / REG_BR_PROB_BASE); + + if (bb->count) + { + fprintf (file, " exec "); + fprintf (file, HOST_WIDEST_INT_PRINT_DEC, bb->count); + if (e) + { + fprintf (file, " hit "); + fprintf (file, HOST_WIDEST_INT_PRINT_DEC, e->count); + fprintf (file, " (%.1f%%)", e->count * 100.0 / bb->count); + } + } + + fprintf (file, "\n"); +} + +/* We can not predict the probabilities of outgoing edges of bb. Set them + evenly and hope for the best. */ +static void +set_even_probabilities (basic_block bb) +{ + int nedges = 0; + edge e; + edge_iterator ei; + + FOR_EACH_EDGE (e, ei, bb->succs) + if (!(e->flags & (EDGE_EH | EDGE_FAKE))) + nedges ++; + FOR_EACH_EDGE (e, ei, bb->succs) + if (!(e->flags & (EDGE_EH | EDGE_FAKE))) + e->probability = (REG_BR_PROB_BASE + nedges / 2) / nedges; + else + e->probability = 0; +} + +/* 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, 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) + 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 (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH) + first_match = true; + + if (!found) + dump_prediction (dump_file, PRED_NO_PREDICTION, + combined_probability, bb, true); + else + { + dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, + bb, !first_match); + dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, + bb, first_match); + } + + if (first_match) + combined_probability = best_probability; + dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true); + + 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); + *pnote = XEXP (*pnote, 1); + } + else + pnote = &XEXP (*pnote, 1); + } + + if (!prob_note) + { + add_reg_note (insn, REG_BR_PROB, GEN_INT (combined_probability)); + + /* Save the prediction into CFG in case we are seeing non-degenerated + conditional jump. */ + if (!single_succ_p (bb)) + { + BRANCH_EDGE (bb)->probability = combined_probability; + FALLTHRU_EDGE (bb)->probability + = REG_BR_PROB_BASE - combined_probability; + } + } + else if (!single_succ_p (bb)) + { + int prob = INTVAL (XEXP (prob_note, 0)); + + BRANCH_EDGE (bb)->probability = prob; + FALLTHRU_EDGE (bb)->probability = REG_BR_PROB_BASE - prob; + } + else + single_succ_edge (bb)->probability = REG_BR_PROB_BASE; +} + +/* Combine predictions into single probability and store them into CFG. + Remove now useless prediction entries. */ + +static void +combine_predictions_for_bb (basic_block bb) +{ + 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; + void **preds; + + FOR_EACH_EDGE (e, ei, bb->succs) + if (!(e->flags & (EDGE_EH | EDGE_FAKE))) + { + nedges ++; + if (first && !second) + second = e; + if (!first) + first = e; + } + + /* When there is no successor or only one choice, prediction is easy. + + We are lazy for now and predict only basic blocks with two outgoing + edges. It is possible to predict generic case too, but we have to + ignore first match heuristics and do more involved combining. Implement + this later. */ + if (nedges != 2) + { + if (!bb->count) + set_even_probabilities (bb); + clear_bb_predictions (bb); + if (dump_file) + fprintf (dump_file, "%i edges in bb %i predicted to even probabilities\n", + nedges, bb->index); + return; + } + + if (dump_file) + fprintf (dump_file, "Predictions for bb %i\n", bb->index); + + preds = pointer_map_contains (bb_predictions, bb); + if (preds) + { + /* We implement "first match" heuristics and use probability guessed + by predictor with smallest index. */ + for (pred = (struct edge_prediction *) *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) + { + 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 = pred->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 (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH) + first_match = true; + + if (!found) + dump_prediction (dump_file, PRED_NO_PREDICTION, combined_probability, bb, true); + else + { + dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, bb, + !first_match); + dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, bb, + first_match); + } + + if (first_match) + combined_probability = best_probability; + dump_prediction (dump_file, PRED_COMBINED, combined_probability, bb, true); + + 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; + + if (pred->ep_edge != EDGE_SUCC (bb, 0)) + probability = REG_BR_PROB_BASE - probability; + dump_prediction (dump_file, predictor, probability, bb, + !first_match || best_predictor == predictor); + } + } + clear_bb_predictions (bb); + + if (!bb->count) + { + first->probability = combined_probability; + second->probability = REG_BR_PROB_BASE - combined_probability; + } +} + +/* Predict edge probabilities by exploiting loop structure. */ + +static void +predict_loops (void) +{ + loop_iterator li; + struct loop *loop; + + /* Try to predict out blocks in a loop that are not part of a + natural loop. */ + FOR_EACH_LOOP (li, loop, 0) + { + basic_block bb, *bbs; + unsigned j, n_exits; + VEC (edge, heap) *exits; + struct tree_niter_desc niter_desc; + edge ex; + + exits = get_loop_exit_edges (loop); + n_exits = VEC_length (edge, exits); + + FOR_EACH_VEC_ELT (edge, exits, j, ex) + { + tree niter = NULL; + HOST_WIDE_INT nitercst; + int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS); + int probability; + enum br_predictor predictor; + + if (number_of_iterations_exit (loop, ex, &niter_desc, false)) + niter = niter_desc.niter; + if (!niter || TREE_CODE (niter_desc.niter) != INTEGER_CST) + niter = loop_niter_by_eval (loop, ex); + + if (TREE_CODE (niter) == INTEGER_CST) + { + if (host_integerp (niter, 1) + && max + && compare_tree_int (niter, max - 1) == -1) + nitercst = tree_low_cst (niter, 1) + 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) + { + nitercst = estimated_loop_iterations_int (loop, false); + if (nitercst < 0) + continue; + if (nitercst > max) + nitercst = max; + + predictor = PRED_LOOP_ITERATIONS_GUESSED; + } + else + continue; + + /* If the prediction for number of iterations is zero, do not + predict the exit edges. */ + if (nitercst == 0) + continue; + + probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst); + predict_edge (ex, predictor, probability); + } + VEC_free (edge, heap, exits); + + bbs = get_loop_body (loop); + + for (j = 0; j < loop->num_nodes; j++) + { + int header_found = 0; + 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)) + continue; + + /* Loop branch heuristics - predict an edge back to a + loop's head as taken. */ + if (bb == loop->latch) + { + e = find_edge (loop->latch, loop->header); + if (e) + { + header_found = 1; + predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN); + } + } + + /* Loop exit heuristics - predict an edge exiting the loop if the + conditional has no loop header successors as not taken. */ + if (!header_found + /* If we already used more reliable loop exit predictors, do not + bother with PRED_LOOP_EXIT. */ + && !predicted_by_p (bb, PRED_LOOP_ITERATIONS_GUESSED) + && !predicted_by_p (bb, PRED_LOOP_ITERATIONS)) + { + /* 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 [(int) 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)) + predict_edge (e, PRED_LOOP_EXIT, probability); + } + } + + /* 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 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); + +/* Helper function for expr_expected_value. */ + +static tree +expr_expected_value_1 (tree type, tree op0, enum tree_code code, tree op1, bitmap visited) +{ + gimple def; + + if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS) + { + if (TREE_CONSTANT (op0)) + return 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); + + /* 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; + + new_val = expr_expected_value (arg, visited); + 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); + } + + if (is_gimple_call (def)) + { + tree decl = gimple_call_fndecl (def); + if (!decl) + return NULL; + if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL + && DECL_FUNCTION_CODE (decl) == 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; + return gimple_call_arg (def, 1); + } + } + + return NULL; + } + + if (get_gimple_rhs_class (code) == GIMPLE_BINARY_RHS) + { + tree res; + op0 = expr_expected_value (op0, visited); + if (!op0) + return NULL; + op1 = expr_expected_value (op1, visited); + if (!op1) + return NULL; + res = fold_build2 (code, type, op0, op1); + if (TREE_CONSTANT (res)) + return res; + return NULL; + } + if (get_gimple_rhs_class (code) == GIMPLE_UNARY_RHS) + { + tree res; + op0 = expr_expected_value (op0, visited); + 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 tree_code code; + tree op0, op1; + + if (TREE_CONSTANT (expr)) + return expr; + + extract_ops_from_tree (expr, &code, &op0, &op1); + return expr_expected_value_1 (TREE_TYPE (expr), + op0, code, op1, visited); +} + + +/* Get rid of all builtin_expect calls and GIMPLE_PREDICT statements + we no longer need. */ +static unsigned int +strip_predict_hints (void) +{ + basic_block bb; + gimple ass_stmt; + tree var; + + FOR_EACH_BB (bb) + { + gimple_stmt_iterator bi; + for (bi = gsi_start_bb (bb); !gsi_end_p (bi);) + { + gimple stmt = gsi_stmt (bi); + + if (gimple_code (stmt) == GIMPLE_PREDICT) + { + gsi_remove (&bi, true); + continue; + } + else if (gimple_code (stmt) == GIMPLE_CALL) + { + tree fndecl = gimple_call_fndecl (stmt); + + if (fndecl + && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL + && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_EXPECT + && gimple_call_num_args (stmt) == 2) + { + var = gimple_call_lhs (stmt); + if (var) + { + ass_stmt + = gimple_build_assign (var, gimple_call_arg (stmt, 0)); + gsi_replace (&bi, ass_stmt, true); + } + else + { + gsi_remove (&bi, true); + continue; + } + } + } + gsi_next (&bi); + } + } + return 0; +} + +/* 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; + bitmap visited; + edge_iterator ei; + + if (!stmt || 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); + visited = BITMAP_ALLOC (NULL); + val = expr_expected_value_1 (boolean_type_node, op0, cmp, op1, visited); + BITMAP_FREE (visited); + if (val) + { + if (integer_zerop (val)) + predict_edge_def (then_edge, PRED_BUILTIN_EXPECT, NOT_TAKEN); + else + predict_edge_def (then_edge, PRED_BUILTIN_EXPECT, TAKEN); + return; + } + /* 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; + } +} + +/* 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 = TAKEN; + return PRED_CONST_RETURN; + } + } + return PRED_NO_PREDICTION; +} + +/* 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) +{ + gimple return_stmt = NULL; + tree return_val; + edge e; + gimple phi; + int phi_num_args, i; + enum br_predictor pred; + enum prediction direction; + edge_iterator ei; + + FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR->preds) + { + return_stmt = last_stmt (e->src); + if (return_stmt + && gimple_code (return_stmt) == GIMPLE_RETURN) + 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 = 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 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->preds) + if (!(e->flags & (EDGE_ABNORMAL | EDGE_FAKE | EDGE_EH))) + { + has_return_edges = true; + break; + } + + apply_return_prediction (); + + FOR_EACH_BB (bb) + { + 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_flags (stmt) & ECF_NORETURN) + && has_return_edges) + 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); + } + 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. */ + } + } + } +} + +#ifdef ENABLE_CHECKING + +/* Callback for pointer_map_traverse, asserts that the pointer map is + empty. */ + +static bool +assert_is_empty (const void *key ATTRIBUTE_UNUSED, void **value, + void *data ATTRIBUTE_UNUSED) +{ + gcc_assert (!*value); + return false; +} +#endif + +/* Predict branch probabilities and estimate profile for basic block BB. */ + +static void +tree_estimate_probability_bb (basic_block bb) +{ + edge e; + edge_iterator ei; + gimple last; + + FOR_EACH_EDGE (e, ei, bb->succs) + { + /* Predict early returns to be probable, as we've already taken + care for error returns and other cases are often used for + fast paths through function. + + Since we've already removed the return statements, we are + looking for CFG like: + + if (conditional) + { + .. + goto return_block + } + some other blocks + return_block: + return_stmt. */ + if (e->dest != bb->next_bb + && e->dest != EXIT_BLOCK_PTR + && single_succ_p (e->dest) + && single_succ_edge (e->dest)->dest == EXIT_BLOCK_PTR + && (last = last_stmt (e->dest)) != NULL + && gimple_code (last) == GIMPLE_RETURN) + { + edge e1; + edge_iterator ei1; + + if (single_succ_p (bb)) + { + FOR_EACH_EDGE (e1, ei1, bb->preds) + if (!predicted_by_p (e1->src, PRED_NULL_RETURN) + && !predicted_by_p (e1->src, PRED_CONST_RETURN) + && !predicted_by_p (e1->src, PRED_NEGATIVE_RETURN)) + predict_edge_def (e1, PRED_TREE_EARLY_RETURN, NOT_TAKEN); + } + else + if (!predicted_by_p (e->src, PRED_NULL_RETURN) + && !predicted_by_p (e->src, PRED_CONST_RETURN) + && !predicted_by_p (e->src, PRED_NEGATIVE_RETURN)) + predict_edge_def (e, PRED_TREE_EARLY_RETURN, NOT_TAKEN); + } + + /* Look for block we are guarding (ie we dominate it, + but it doesn't postdominate us). */ + if (e->dest != EXIT_BLOCK_PTR && e->dest != bb + && 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) + /* Constant and pure calls are hardly used to signalize + something exceptional. */ + && gimple_has_side_effects (stmt)) + { + predict_edge_def (e, PRED_CALL, NOT_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. */ + +void +tree_estimate_probability (void) +{ + basic_block bb; + + add_noreturn_fake_exit_edges (); + 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); + + bb_predictions = pointer_map_create (); + tree_bb_level_predictions (); + record_loop_exits (); + + if (number_of_loops () > 1) + predict_loops (); + + FOR_EACH_BB (bb) + tree_estimate_probability_bb (bb); + + FOR_EACH_BB (bb) + combine_predictions_for_bb (bb); + +#ifdef ENABLE_CHECKING + pointer_map_traverse (bb_predictions, assert_is_empty, NULL); +#endif + pointer_map_destroy (bb_predictions); + bb_predictions = NULL; + + estimate_bb_frequencies (); + free_dominance_info (CDI_POST_DOMINATORS); + remove_fake_exit_edges (); +} + +/* Predict branch probabilities and estimate profile of the tree CFG. + This is the driver function for PASS_PROFILE. */ + +static unsigned int +tree_estimate_probability_driver (void) +{ + unsigned nb_loops; + + loop_optimizer_init (0); + if (dump_file && (dump_flags & TDF_DETAILS)) + flow_loops_dump (dump_file, NULL, 0); + + mark_irreducible_loops (); + + nb_loops = number_of_loops (); + if (nb_loops > 1) + scev_initialize (); + + tree_estimate_probability (); + + if (nb_loops > 1) + scev_finalize (); + + loop_optimizer_finalize (); + if (dump_file && (dump_flags & TDF_DETAILS)) + gimple_dump_cfg (dump_file, dump_flags); + if (profile_status == PROFILE_ABSENT) + profile_status = PROFILE_GUESSED; + return 0; +} + +/* Predict edges to successors of CUR whose sources are not postdominated by + BB by PRED and recurse to all postdominators. */ + +static void +predict_paths_for_bb (basic_block cur, basic_block bb, + enum br_predictor pred, + enum prediction taken, + bitmap visited) +{ + edge e; + edge_iterator ei; + basic_block son; + + /* We are looking for all edges forming edge cut induced by + set of all blocks postdominated by BB. */ + FOR_EACH_EDGE (e, ei, cur->preds) + if (e->src->index >= NUM_FIXED_BLOCKS + && !dominated_by_p (CDI_POST_DOMINATORS, e->src, bb)) + { + edge e2; + edge_iterator ei2; + bool found = false; + + /* Ignore fake edges and eh, we predict them as not taken anyway. */ + if (e->flags & (EDGE_EH | EDGE_FAKE)) + continue; + gcc_assert (bb == cur || dominated_by_p (CDI_POST_DOMINATORS, cur, bb)); + + /* See if there is an edge from e->src that is not abnormal + and does not lead to BB. */ + FOR_EACH_EDGE (e2, ei2, e->src->succs) + if (e2 != e + && !(e2->flags & (EDGE_EH | EDGE_FAKE)) + && !dominated_by_p (CDI_POST_DOMINATORS, e2->dest, bb)) + { + found = true; + break; + } + + /* If there is non-abnormal path leaving e->src, predict edge + using predictor. Otherwise we need to look for paths + leading to e->src. + + The second may lead to infinite loop in the case we are predicitng + regions that are only reachable by abnormal edges. We simply + prevent visiting given BB twice. */ + if (found) + predict_edge_def (e, pred, taken); + else if (bitmap_set_bit (visited, e->src->index)) + predict_paths_for_bb (e->src, e->src, pred, taken, visited); + } + for (son = first_dom_son (CDI_POST_DOMINATORS, cur); + son; + son = next_dom_son (CDI_POST_DOMINATORS, son)) + predict_paths_for_bb (son, bb, pred, taken, visited); +} + +/* Sets branch probabilities according to PREDiction and + FLAGS. */ + +static void +predict_paths_leading_to (basic_block bb, enum br_predictor pred, + enum prediction taken) +{ + bitmap visited = BITMAP_ALLOC (NULL); + predict_paths_for_bb (bb, bb, pred, taken, visited); + BITMAP_FREE (visited); +} + +/* Like predict_paths_leading_to but take edge instead of basic block. */ + +static void +predict_paths_leading_to_edge (edge e, enum br_predictor pred, + enum prediction taken) +{ + bool has_nonloop_edge = false; + edge_iterator ei; + edge e2; + + basic_block bb = e->src; + FOR_EACH_EDGE (e2, ei, bb->succs) + if (e2->dest != e->src && e2->dest != e->dest + && !(e->flags & (EDGE_EH | EDGE_FAKE)) + && !dominated_by_p (CDI_POST_DOMINATORS, e->src, e2->dest)) + { + has_nonloop_edge = true; + break; + } + if (!has_nonloop_edge) + { + bitmap visited = BITMAP_ALLOC (NULL); + predict_paths_for_bb (bb, bb, pred, taken, visited); + BITMAP_FREE (visited); + } + else + predict_edge_def (e, pred, taken); +} + +/* This is used to carry information about basic blocks. It is + attached to the AUX field of the standard CFG block. */ + +typedef struct block_info_def +{ + /* Estimated frequency of execution of basic_block. */ + sreal frequency; + + /* To keep queue of basic blocks to process. */ + basic_block next; + + /* Number of predecessors we need to visit first. */ + int npredecessors; +} *block_info; + +/* Similar information for edges. */ +typedef struct edge_info_def +{ + /* In case edge is a loopback edge, the probability edge will be reached + in case header is. Estimated number of iterations of the loop can be + then computed as 1 / (1 - back_edge_prob). */ + sreal back_edge_prob; + /* True if the edge is a loopback edge in the natural loop. */ + unsigned int back_edge:1; +} *edge_info; + +#define BLOCK_INFO(B) ((block_info) (B)->aux) +#define EDGE_INFO(E) ((edge_info) (E)->aux) + +/* Helper function for estimate_bb_frequencies. + Propagate the frequencies in blocks marked in + TOVISIT, starting in HEAD. */ + +static void +propagate_freq (basic_block head, bitmap tovisit) +{ + basic_block bb; + basic_block last; + unsigned i; + edge e; + basic_block nextbb; + bitmap_iterator bi; + + /* For each basic block we need to visit count number of his predecessors + we need to visit first. */ + EXECUTE_IF_SET_IN_BITMAP (tovisit, 0, i, bi) + { + edge_iterator ei; + int count = 0; + + bb = BASIC_BLOCK (i); + + FOR_EACH_EDGE (e, ei, bb->preds) + { + bool visit = bitmap_bit_p (tovisit, e->src->index); + + if (visit && !(e->flags & EDGE_DFS_BACK)) + count++; + else if (visit && dump_file && !EDGE_INFO (e)->back_edge) + fprintf (dump_file, + "Irreducible region hit, ignoring edge to %i->%i\n", + e->src->index, bb->index); + } + BLOCK_INFO (bb)->npredecessors = count; + /* When function never returns, we will never process exit block. */ + if (!count && bb == EXIT_BLOCK_PTR) + bb->count = bb->frequency = 0; + } + + memcpy (&BLOCK_INFO (head)->frequency, &real_one, sizeof (real_one)); + last = head; + for (bb = head; bb; bb = nextbb) + { + edge_iterator ei; + sreal cyclic_probability, frequency; + + memcpy (&cyclic_probability, &real_zero, sizeof (real_zero)); + memcpy (&frequency, &real_zero, sizeof (real_zero)); + + nextbb = BLOCK_INFO (bb)->next; + BLOCK_INFO (bb)->next = NULL; + + /* Compute frequency of basic block. */ + if (bb != head) + { +#ifdef ENABLE_CHECKING + FOR_EACH_EDGE (e, ei, bb->preds) + gcc_assert (!bitmap_bit_p (tovisit, e->src->index) + || (e->flags & EDGE_DFS_BACK)); +#endif + + FOR_EACH_EDGE (e, ei, bb->preds) + if (EDGE_INFO (e)->back_edge) + { + sreal_add (&cyclic_probability, &cyclic_probability, + &EDGE_INFO (e)->back_edge_prob); + } + else if (!(e->flags & EDGE_DFS_BACK)) + { + sreal tmp; + + /* frequency += (e->probability + * BLOCK_INFO (e->src)->frequency / + REG_BR_PROB_BASE); */ + + sreal_init (&tmp, e->probability, 0); + sreal_mul (&tmp, &tmp, &BLOCK_INFO (e->src)->frequency); + sreal_mul (&tmp, &tmp, &real_inv_br_prob_base); + sreal_add (&frequency, &frequency, &tmp); + } + + if (sreal_compare (&cyclic_probability, &real_zero) == 0) + { + memcpy (&BLOCK_INFO (bb)->frequency, &frequency, + sizeof (frequency)); + } + else + { + if (sreal_compare (&cyclic_probability, &real_almost_one) > 0) + { + memcpy (&cyclic_probability, &real_almost_one, + sizeof (real_almost_one)); + } + + /* BLOCK_INFO (bb)->frequency = frequency + / (1 - cyclic_probability) */ + + sreal_sub (&cyclic_probability, &real_one, &cyclic_probability); + sreal_div (&BLOCK_INFO (bb)->frequency, + &frequency, &cyclic_probability); + } + } + + bitmap_clear_bit (tovisit, bb->index); + + e = find_edge (bb, head); + if (e) + { + sreal tmp; + + /* EDGE_INFO (e)->back_edge_prob + = ((e->probability * BLOCK_INFO (bb)->frequency) + / REG_BR_PROB_BASE); */ + + sreal_init (&tmp, e->probability, 0); + sreal_mul (&tmp, &tmp, &BLOCK_INFO (bb)->frequency); + sreal_mul (&EDGE_INFO (e)->back_edge_prob, + &tmp, &real_inv_br_prob_base); + } + + /* Propagate to successor blocks. */ + FOR_EACH_EDGE (e, ei, bb->succs) + if (!(e->flags & EDGE_DFS_BACK) + && BLOCK_INFO (e->dest)->npredecessors) + { + BLOCK_INFO (e->dest)->npredecessors--; + if (!BLOCK_INFO (e->dest)->npredecessors) + { + if (!nextbb) + nextbb = e->dest; + else + BLOCK_INFO (last)->next = e->dest; + + last = e->dest; + } + } + } +} + +/* Estimate probabilities of loopback edges in loops at same nest level. */ + +static void +estimate_loops_at_level (struct loop *first_loop) +{ + struct loop *loop; + + for (loop = first_loop; loop; loop = loop->next) + { + edge e; + basic_block *bbs; + unsigned i; + bitmap tovisit = BITMAP_ALLOC (NULL); + + estimate_loops_at_level (loop->inner); + + /* Find current loop back edge and mark it. */ + e = loop_latch_edge (loop); + EDGE_INFO (e)->back_edge = 1; + + bbs = get_loop_body (loop); + for (i = 0; i < loop->num_nodes; i++) + bitmap_set_bit (tovisit, bbs[i]->index); + free (bbs); + propagate_freq (loop->header, tovisit); + BITMAP_FREE (tovisit); + } +} + +/* Propagates frequencies through structure of loops. */ + +static void +estimate_loops (void) +{ + bitmap tovisit = BITMAP_ALLOC (NULL); + basic_block bb; + + /* Start by estimating the frequencies in the loops. */ + if (number_of_loops () > 1) + estimate_loops_at_level (current_loops->tree_root->inner); + + /* Now propagate the frequencies through all the blocks. */ + FOR_ALL_BB (bb) + { + bitmap_set_bit (tovisit, bb->index); + } + propagate_freq (ENTRY_BLOCK_PTR, tovisit); + BITMAP_FREE (tovisit); +} + +/* Convert counts measured by profile driven feedback to frequencies. + Return nonzero iff there was any nonzero execution count. */ + +int +counts_to_freqs (void) +{ + gcov_type count_max, true_count_max = 0; + basic_block bb; + + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) + true_count_max = MAX (bb->count, true_count_max); + + count_max = MAX (true_count_max, 1); + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) + bb->frequency = (bb->count * BB_FREQ_MAX + count_max / 2) / count_max; + + return true_count_max; +} + +/* Return true if function is likely to be expensive, so there is no point to + optimize performance of prologue, epilogue or do inlining at the expense + of code size growth. THRESHOLD is the limit of number of instructions + function can execute at average to be still considered not expensive. */ + +bool +expensive_function_p (int threshold) +{ + unsigned int sum = 0; + basic_block bb; + unsigned int limit; + + /* We can not compute accurately for large thresholds due to scaled + frequencies. */ + gcc_assert (threshold <= BB_FREQ_MAX); + + /* Frequencies are out of range. This either means that function contains + internal loop executing more than BB_FREQ_MAX times or profile feedback + is available and function has not been executed at all. */ + if (ENTRY_BLOCK_PTR->frequency == 0) + return true; + + /* Maximally BB_FREQ_MAX^2 so overflow won't happen. */ + limit = ENTRY_BLOCK_PTR->frequency * threshold; + FOR_EACH_BB (bb) + { + rtx insn; + + for (insn = BB_HEAD (bb); insn != NEXT_INSN (BB_END (bb)); + insn = NEXT_INSN (insn)) + if (active_insn_p (insn)) + { + sum += bb->frequency; + if (sum > limit) + return true; + } + } + + return false; +} + +/* Estimate basic blocks frequency by given branch probabilities. */ + +void +estimate_bb_frequencies (void) +{ + basic_block bb; + sreal freq_max; + + if (profile_status != PROFILE_READ || !counts_to_freqs ()) + { + static int real_values_initialized = 0; + + if (!real_values_initialized) + { + real_values_initialized = 1; + sreal_init (&real_zero, 0, 0); + sreal_init (&real_one, 1, 0); + sreal_init (&real_br_prob_base, REG_BR_PROB_BASE, 0); + sreal_init (&real_bb_freq_max, BB_FREQ_MAX, 0); + sreal_init (&real_one_half, 1, -1); + sreal_div (&real_inv_br_prob_base, &real_one, &real_br_prob_base); + sreal_sub (&real_almost_one, &real_one, &real_inv_br_prob_base); + } + + mark_dfs_back_edges (); + + single_succ_edge (ENTRY_BLOCK_PTR)->probability = REG_BR_PROB_BASE; + + /* Set up block info for each basic block. */ + alloc_aux_for_blocks (sizeof (struct block_info_def)); + alloc_aux_for_edges (sizeof (struct edge_info_def)); + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) + { + edge e; + edge_iterator ei; + + FOR_EACH_EDGE (e, ei, bb->succs) + { + sreal_init (&EDGE_INFO (e)->back_edge_prob, e->probability, 0); + sreal_mul (&EDGE_INFO (e)->back_edge_prob, + &EDGE_INFO (e)->back_edge_prob, + &real_inv_br_prob_base); + } + } + + /* First compute probabilities locally for each loop from innermost + to outermost to examine probabilities for back edges. */ + estimate_loops (); + + memcpy (&freq_max, &real_zero, sizeof (real_zero)); + FOR_EACH_BB (bb) + if (sreal_compare (&freq_max, &BLOCK_INFO (bb)->frequency) < 0) + memcpy (&freq_max, &BLOCK_INFO (bb)->frequency, sizeof (freq_max)); + + sreal_div (&freq_max, &real_bb_freq_max, &freq_max); + FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb) + { + sreal tmp; + + sreal_mul (&tmp, &BLOCK_INFO (bb)->frequency, &freq_max); + sreal_add (&tmp, &tmp, &real_one_half); + bb->frequency = sreal_to_int (&tmp); + } + + free_aux_for_blocks (); + free_aux_for_edges (); + } + compute_function_frequency (); +} + +/* Decide whether function is hot, cold or unlikely executed. */ +void +compute_function_frequency (void) +{ + basic_block bb; + struct cgraph_node *node = cgraph_node (current_function_decl); + if (DECL_STATIC_CONSTRUCTOR (current_function_decl) + || MAIN_NAME_P (DECL_NAME (current_function_decl))) + node->only_called_at_startup = true; + if (DECL_STATIC_DESTRUCTOR (current_function_decl)) + node->only_called_at_exit = true; + + if (!profile_info || !flag_branch_probabilities) + { + int flags = flags_from_decl_or_type (current_function_decl); + if (lookup_attribute ("cold", DECL_ATTRIBUTES (current_function_decl)) + != NULL) + node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED; + else if (lookup_attribute ("hot", DECL_ATTRIBUTES (current_function_decl)) + != NULL) + node->frequency = NODE_FREQUENCY_HOT; + else if (flags & ECF_NORETURN) + node->frequency = NODE_FREQUENCY_EXECUTED_ONCE; + else if (MAIN_NAME_P (DECL_NAME (current_function_decl))) + node->frequency = NODE_FREQUENCY_EXECUTED_ONCE; + else if (DECL_STATIC_CONSTRUCTOR (current_function_decl) + || DECL_STATIC_DESTRUCTOR (current_function_decl)) + node->frequency = NODE_FREQUENCY_EXECUTED_ONCE; + return; + } + node->frequency = NODE_FREQUENCY_UNLIKELY_EXECUTED; + FOR_EACH_BB (bb) + { + if (maybe_hot_bb_p (bb)) + { + node->frequency = NODE_FREQUENCY_HOT; + return; + } + if (!probably_never_executed_bb_p (bb)) + node->frequency = NODE_FREQUENCY_NORMAL; + } +} + +static bool +gate_estimate_probability (void) +{ + return flag_guess_branch_prob; +} + +/* Build PREDICT_EXPR. */ +tree +build_predict_expr (enum br_predictor predictor, enum prediction taken) +{ + tree t = build1 (PREDICT_EXPR, void_type_node, + build_int_cst (NULL, predictor)); + SET_PREDICT_EXPR_OUTCOME (t, taken); + return t; +} + +const char * +predictor_name (enum br_predictor predictor) +{ + return predictor_info[predictor].name; +} + +struct gimple_opt_pass pass_profile = +{ + { + GIMPLE_PASS, + "profile", /* name */ + gate_estimate_probability, /* gate */ + tree_estimate_probability_driver, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_BRANCH_PROB, /* tv_id */ + PROP_cfg, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */ + } +}; + +struct gimple_opt_pass pass_strip_predict_hints = +{ + { + GIMPLE_PASS, + "*strip_predict_hints", /* name */ + NULL, /* gate */ + strip_predict_hints, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_BRANCH_PROB, /* tv_id */ + PROP_cfg, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */ + } +}; + +/* Rebuild function frequencies. Passes are in general expected to + maintain profile by hand, however in some cases this is not possible: + for example when inlining several functions with loops freuqencies might run + out of scale and thus needs to be recomputed. */ + +void +rebuild_frequencies (void) +{ + timevar_push (TV_REBUILD_FREQUENCIES); + if (profile_status == PROFILE_GUESSED) + { + loop_optimizer_init (0); + add_noreturn_fake_exit_edges (); + mark_irreducible_loops (); + connect_infinite_loops_to_exit (); + estimate_bb_frequencies (); + remove_fake_exit_edges (); + loop_optimizer_finalize (); + } + else if (profile_status == PROFILE_READ) + counts_to_freqs (); + else + gcc_unreachable (); + timevar_pop (TV_REBUILD_FREQUENCIES); +} -- cgit v1.2.3