aboutsummaryrefslogtreecommitdiffstats
path: root/gcc-4.2.1-5666.3/gcc/predict.c
diff options
context:
space:
mode:
Diffstat (limited to 'gcc-4.2.1-5666.3/gcc/predict.c')
-rw-r--r--gcc-4.2.1-5666.3/gcc/predict.c1925
1 files changed, 0 insertions, 1925 deletions
diff --git a/gcc-4.2.1-5666.3/gcc/predict.c b/gcc-4.2.1-5666.3/gcc/predict.c
deleted file mode 100644
index 572f6c26c..000000000
--- a/gcc-4.2.1-5666.3/gcc/predict.c
+++ /dev/null
@@ -1,1925 +0,0 @@
-/* Branch prediction routines for the GNU compiler.
- Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005
- 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 2, 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 COPYING. If not, write to the Free
-Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
-02110-1301, USA. */
-
-/* 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 "toplev.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"
-
-/* 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. */
-#define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 100 - 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 estimate_loops_at_level (struct loop *, bitmap);
-static void propagate_freq (struct loop *, bitmap);
-static void estimate_bb_frequencies (struct loops *);
-static void predict_paths_leading_to (basic_block, int *, enum br_predictor, enum prediction);
-static bool last_basic_block_p (basic_block);
-static void compute_function_frequency (void);
-static void choose_function_section (void);
-static bool can_predict_insn_p (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 in case BB can be CPU intensive and should be optimized
- for maximal performance. */
-
-bool
-maybe_hot_bb_p (basic_block bb)
-{
- if (profile_info && flag_branch_probabilities
- && (bb->count
- < profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION)))
- return false;
- if (bb->frequency < BB_FREQ_MAX / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION))
- return false;
- return true;
-}
-
-/* Return true in case BB is cold and should be optimized for size. */
-
-bool
-probably_cold_bb_p (basic_block bb)
-{
- if (profile_info && flag_branch_probabilities
- && (bb->count
- < profile_info->sum_max / PARAM_VALUE (HOT_BB_COUNT_FRACTION)))
- return true;
- if (bb->frequency < BB_FREQ_MAX / PARAM_VALUE (HOT_BB_FREQUENCY_FRACTION))
- return true;
- return false;
-}
-
-/* Return true in case BB is probably never executed. */
-bool
-probably_never_executed_bb_p (basic_block bb)
-{
- if (profile_info && flag_branch_probabilities)
- /* APPLE LOCAL hot/cold partitioning */
- return (bb->count == 0);
- return false;
-}
-
-/* Return true if the one of outgoing edges is already predicted by
- PREDICTOR. */
-
-bool
-rtl_predicted_by_p (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;
-}
-
-/* Return true if the one of outgoing edges is already predicted by
- PREDICTOR. */
-
-bool
-tree_predicted_by_p (basic_block bb, enum br_predictor predictor)
-{
- struct edge_prediction *i;
- for (i = bb->predictions; 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 (edge e)
-{
- return probability_reliable_p (e->probability);
-}
-
-/* Same predicate as edge_probability_reliable_p, working on notes. */
-bool
-br_prob_note_reliable_p (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;
-
- REG_NOTES (insn)
- = gen_rtx_EXPR_LIST (REG_BR_PRED,
- gen_rtx_CONCAT (VOIDmode,
- GEN_INT ((int) predictor),
- GEN_INT ((int) probability)),
- REG_NOTES (insn));
-}
-
-/* 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
-tree_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 = ggc_alloc (sizeof (struct edge_prediction));
-
- i->ep_next = e->src->predictions;
- e->src->predictions = 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)
-{
- if (e->src->predictions)
- {
- struct edge_prediction **prediction = &e->src->predictions;
- while (*prediction)
- {
- if ((*prediction)->ep_edge == e)
- *prediction = (*prediction)->ep_next;
- else
- prediction = &((*prediction)->ep_next);
- }
- }
-}
-
-/* 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 (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;
- int 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 = &REG_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)
- {
- int 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)
- {
- int 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)
- {
- REG_NOTES (insn)
- = gen_rtx_EXPR_LIST (REG_BR_PROB,
- GEN_INT (combined_probability), REG_NOTES (insn));
-
- /* 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;
- int 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;
-
- 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);
- bb->predictions = NULL;
- 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);
-
- /* We implement "first match" heuristics and use probability guessed
- by predictor with smallest index. */
- for (pred = bb->predictions; pred; pred = pred->ep_next)
- {
- int predictor = pred->ep_predictor;
- int probability = pred->ep_probability;
-
- if (pred->ep_edge != first)
- probability = REG_BR_PROB_BASE - probability;
-
- 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);
-
- for (pred = bb->predictions; pred; pred = pred->ep_next)
- {
- int 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);
- }
- bb->predictions = NULL;
-
- if (!bb->count)
- {
- first->probability = combined_probability;
- second->probability = REG_BR_PROB_BASE - combined_probability;
- }
-}
-
-/* Predict edge probabilities by exploiting loop structure.
- When RTLSIMPLELOOPS is set, attempt to count number of iterations by analyzing
- RTL otherwise use tree based approach. */
-static void
-predict_loops (struct loops *loops_info, bool rtlsimpleloops)
-{
- unsigned i;
-
- if (!rtlsimpleloops)
- scev_initialize (loops_info);
-
- /* Try to predict out blocks in a loop that are not part of a
- natural loop. */
- for (i = 1; i < loops_info->num; i++)
- {
- basic_block bb, *bbs;
- unsigned j;
- unsigned n_exits;
- struct loop *loop = loops_info->parray[i];
- struct niter_desc desc;
- unsigned HOST_WIDE_INT niter;
- edge *exits;
-
- exits = get_loop_exit_edges (loop, &n_exits);
-
- if (rtlsimpleloops)
- {
- iv_analysis_loop_init (loop);
- find_simple_exit (loop, &desc);
-
- if (desc.simple_p && desc.const_iter)
- {
- int prob;
- niter = desc.niter + 1;
- if (niter == 0) /* We might overflow here. */
- niter = desc.niter;
- if (niter
- > (unsigned int) PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS))
- niter = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
-
- prob = (REG_BR_PROB_BASE
- - (REG_BR_PROB_BASE + niter /2) / niter);
- /* Branch prediction algorithm gives 0 frequency for everything
- after the end of loop for loop having 0 probability to finish. */
- if (prob == REG_BR_PROB_BASE)
- prob = REG_BR_PROB_BASE - 1;
- predict_edge (desc.in_edge, PRED_LOOP_ITERATIONS,
- prob);
- }
- }
- else
- {
- struct tree_niter_desc niter_desc;
-
- for (j = 0; j < n_exits; j++)
- {
- tree niter = NULL;
-
- if (number_of_iterations_exit (loop, exits[j], &niter_desc, false))
- niter = niter_desc.niter;
- if (!niter || TREE_CODE (niter_desc.niter) != INTEGER_CST)
- niter = loop_niter_by_eval (loop, exits[j]);
-
- if (TREE_CODE (niter) == INTEGER_CST)
- {
- int probability;
- int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
- if (host_integerp (niter, 1)
- && tree_int_cst_lt (niter,
- build_int_cstu (NULL_TREE, max - 1)))
- {
- HOST_WIDE_INT nitercst = tree_low_cst (niter, 1) + 1;
- probability = ((REG_BR_PROB_BASE + nitercst / 2)
- / nitercst);
- }
- else
- probability = ((REG_BR_PROB_BASE + max / 2) / max);
-
- predict_edge (exits[j], PRED_LOOP_ITERATIONS, probability);
- }
- }
-
- }
- free (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 ((rtlsimpleloops && !can_predict_insn_p (BB_END (bb)))
- || 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)
- {
- /* 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);
- }
-
- if (!rtlsimpleloops)
- {
- scev_finalize ();
- current_loops = NULL;
- }
-}
-
-/* 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);
-}
-
-/* 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)
-{
- if (TREE_CONSTANT (expr))
- return expr;
- else if (TREE_CODE (expr) == SSA_NAME)
- {
- tree def = SSA_NAME_DEF_STMT (expr);
-
- /* If we were already here, break the infinite cycle. */
- if (bitmap_bit_p (visited, SSA_NAME_VERSION (expr)))
- return NULL;
- bitmap_set_bit (visited, SSA_NAME_VERSION (expr));
-
- if (TREE_CODE (def) == PHI_NODE)
- {
- /* All the arguments of the PHI node must have the same constant
- length. */
- int i;
- tree val = NULL, new_val;
-
- for (i = 0; i < PHI_NUM_ARGS (def); 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 (TREE_CODE (def) != MODIFY_EXPR || TREE_OPERAND (def, 0) != expr)
- return NULL;
- return expr_expected_value (TREE_OPERAND (def, 1), visited);
- }
- else if (TREE_CODE (expr) == CALL_EXPR)
- {
- tree decl = get_callee_fndecl (expr);
- if (!decl)
- return NULL;
- if (DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL
- && DECL_FUNCTION_CODE (decl) == BUILT_IN_EXPECT)
- {
- tree arglist = TREE_OPERAND (expr, 1);
- tree val;
-
- if (arglist == NULL_TREE
- || TREE_CHAIN (arglist) == NULL_TREE)
- return NULL;
- val = TREE_VALUE (TREE_CHAIN (TREE_OPERAND (expr, 1)));
- if (TREE_CONSTANT (val))
- return val;
- return TREE_VALUE (TREE_CHAIN (TREE_OPERAND (expr, 1)));
- }
- }
- if (BINARY_CLASS_P (expr) || COMPARISON_CLASS_P (expr))
- {
- tree op0, op1, res;
- op0 = expr_expected_value (TREE_OPERAND (expr, 0), visited);
- if (!op0)
- return NULL;
- op1 = expr_expected_value (TREE_OPERAND (expr, 1), visited);
- if (!op1)
- return NULL;
- res = fold_build2 (TREE_CODE (expr), TREE_TYPE (expr), op0, op1);
- if (TREE_CONSTANT (res))
- return res;
- return NULL;
- }
- if (UNARY_CLASS_P (expr))
- {
- tree op0, res;
- op0 = expr_expected_value (TREE_OPERAND (expr, 0), visited);
- if (!op0)
- return NULL;
- res = fold_build1 (TREE_CODE (expr), TREE_TYPE (expr), op0);
- if (TREE_CONSTANT (res))
- return res;
- return NULL;
- }
- return NULL;
-}
-
-/* Get rid of all builtin_expect calls we no longer need. */
-static void
-strip_builtin_expect (void)
-{
- basic_block bb;
- FOR_EACH_BB (bb)
- {
- block_stmt_iterator bi;
- for (bi = bsi_start (bb); !bsi_end_p (bi); bsi_next (&bi))
- {
- tree stmt = bsi_stmt (bi);
- tree fndecl;
- tree arglist;
-
- if (TREE_CODE (stmt) == MODIFY_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR
- && (fndecl = get_callee_fndecl (TREE_OPERAND (stmt, 1)))
- && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
- && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_EXPECT
- && (arglist = TREE_OPERAND (TREE_OPERAND (stmt, 1), 1))
- && TREE_CHAIN (arglist))
- {
- TREE_OPERAND (stmt, 1) = TREE_VALUE (arglist);
- update_stmt (stmt);
- }
- }
- }
-}
-
-/* Predict using opcode of the last statement in basic block. */
-static void
-tree_predict_by_opcode (basic_block bb)
-{
- tree stmt = last_stmt (bb);
- edge then_edge;
- tree cond;
- tree op0;
- tree type;
- tree val;
- bitmap visited;
- edge_iterator ei;
-
- if (!stmt || TREE_CODE (stmt) != COND_EXPR)
- return;
- FOR_EACH_EDGE (then_edge, ei, bb->succs)
- if (then_edge->flags & EDGE_TRUE_VALUE)
- break;
- cond = TREE_OPERAND (stmt, 0);
- if (!COMPARISON_CLASS_P (cond))
- return;
- op0 = TREE_OPERAND (cond, 0);
- type = TREE_TYPE (op0);
- visited = BITMAP_ALLOC (NULL);
- val = expr_expected_value (cond, 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 (TREE_CODE (cond) == EQ_EXPR)
- predict_edge_def (then_edge, PRED_TREE_POINTER, NOT_TAKEN);
- else if (TREE_CODE (cond) == 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 (TREE_CODE (cond))
- {
- 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 (TREE_OPERAND (cond, 1)))
- ;
- 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 (TREE_OPERAND (cond, 1)))
- ;
- 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 (TREE_OPERAND (cond, 1))
- || integer_onep (TREE_OPERAND (cond, 1))
- || integer_all_onesp (TREE_OPERAND (cond, 1))
- || real_zerop (TREE_OPERAND (cond, 1))
- || real_onep (TREE_OPERAND (cond, 1))
- || real_minus_onep (TREE_OPERAND (cond, 1)))
- predict_edge_def (then_edge, PRED_TREE_OPCODE_POSITIVE, NOT_TAKEN);
- break;
-
- case GE_EXPR:
- case GT_EXPR:
- if (integer_zerop (TREE_OPERAND (cond, 1))
- || integer_onep (TREE_OPERAND (cond, 1))
- || integer_all_onesp (TREE_OPERAND (cond, 1))
- || real_zerop (TREE_OPERAND (cond, 1))
- || real_onep (TREE_OPERAND (cond, 1))
- || real_minus_onep (TREE_OPERAND (cond, 1)))
- 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_NEGATIVE_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 (int *heads)
-{
- tree return_stmt = NULL;
- tree return_val;
- edge e;
- tree 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 (TREE_CODE (return_stmt) == RETURN_EXPR)
- break;
- }
- if (!e)
- return;
- return_val = TREE_OPERAND (return_stmt, 0);
- if (!return_val)
- return;
- if (TREE_CODE (return_val) == MODIFY_EXPR)
- return_val = TREE_OPERAND (return_val, 1);
- if (TREE_CODE (return_val) != SSA_NAME
- || !SSA_NAME_DEF_STMT (return_val)
- || TREE_CODE (SSA_NAME_DEF_STMT (return_val)) != PHI_NODE)
- return;
- for (phi = SSA_NAME_DEF_STMT (return_val); phi; phi = PHI_CHAIN (phi))
- if (PHI_RESULT (phi) == return_val)
- break;
- if (!phi)
- return;
- phi_num_args = 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 (PHI_ARG_EDGE (phi, i)->src, heads, 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;
- int *heads;
-
- heads = XNEWVEC (int, last_basic_block);
- memset (heads, ENTRY_BLOCK, sizeof (int) * last_basic_block);
- heads[ENTRY_BLOCK_PTR->next_bb->index] = last_basic_block;
-
- apply_return_prediction (heads);
-
- FOR_EACH_BB (bb)
- {
- block_stmt_iterator bsi = bsi_last (bb);
-
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
- {
- tree stmt = bsi_stmt (bsi);
- switch (TREE_CODE (stmt))
- {
- case MODIFY_EXPR:
- if (TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR)
- {
- stmt = TREE_OPERAND (stmt, 1);
- goto call_expr;
- }
- break;
- case CALL_EXPR:
-call_expr:;
- if (call_expr_flags (stmt) & ECF_NORETURN)
- predict_paths_leading_to (bb, heads, PRED_NORETURN,
- NOT_TAKEN);
- break;
- default:
- break;
- }
- }
- }
-
- free (heads);
-}
-
-/* Predict branch probabilities and estimate profile of the tree CFG. */
-static unsigned int
-tree_estimate_probability (void)
-{
- basic_block bb;
- struct loops loops_info;
-
- flow_loops_find (&loops_info);
- if (dump_file && (dump_flags & TDF_DETAILS))
- flow_loops_dump (&loops_info, dump_file, NULL, 0);
-
- add_noreturn_fake_exit_edges ();
- connect_infinite_loops_to_exit ();
- calculate_dominance_info (CDI_DOMINATORS);
- calculate_dominance_info (CDI_POST_DOMINATORS);
-
- tree_bb_level_predictions ();
-
- mark_irreducible_loops (&loops_info);
- predict_loops (&loops_info, false);
-
- FOR_EACH_BB (bb)
- {
- edge e;
- edge_iterator ei;
-
- 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. */
- if (e->dest == EXIT_BLOCK_PTR
- && TREE_CODE (last_stmt (bb)) == RETURN_EXPR
- && !single_pred_p (bb))
- {
- edge e1;
- edge_iterator ei1;
-
- 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)
- && !last_basic_block_p (e1->src))
- predict_edge_def (e1, 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))
- {
- block_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 = bsi_start (e->dest); !bsi_end_p (bi);
- bsi_next (&bi))
- {
- tree stmt = bsi_stmt (bi);
- if ((TREE_CODE (stmt) == CALL_EXPR
- || (TREE_CODE (stmt) == MODIFY_EXPR
- && TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR))
- /* Constant and pure calls are hardly used to signalize
- something exceptional. */
- && TREE_SIDE_EFFECTS (stmt))
- {
- predict_edge_def (e, PRED_CALL, NOT_TAKEN);
- break;
- }
- }
- }
- }
- tree_predict_by_opcode (bb);
- }
- FOR_EACH_BB (bb)
- combine_predictions_for_bb (bb);
-
- strip_builtin_expect ();
- estimate_bb_frequencies (&loops_info);
- free_dominance_info (CDI_POST_DOMINATORS);
- remove_fake_exit_edges ();
- flow_loops_free (&loops_info);
- if (dump_file && (dump_flags & TDF_DETAILS))
- dump_tree_cfg (dump_file, dump_flags);
- if (profile_status == PROFILE_ABSENT)
- profile_status = PROFILE_GUESSED;
- return 0;
-}
-
-/* __builtin_expect dropped tokens into the insn stream describing expected
- values of registers. Generate branch probabilities based off these
- values. */
-
-void
-expected_value_to_br_prob (void)
-{
- rtx insn, cond, ev = NULL_RTX, ev_reg = NULL_RTX;
-
- for (insn = get_insns (); insn ; insn = NEXT_INSN (insn))
- {
- switch (GET_CODE (insn))
- {
- case NOTE:
- /* Look for expected value notes. */
- if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_EXPECTED_VALUE)
- {
- ev = NOTE_EXPECTED_VALUE (insn);
- ev_reg = XEXP (ev, 0);
- delete_insn (insn);
- }
- continue;
-
- case CODE_LABEL:
- /* Never propagate across labels. */
- ev = NULL_RTX;
- continue;
-
- case JUMP_INSN:
- /* Look for simple conditional branches. If we haven't got an
- expected value yet, no point going further. */
- if (!JUMP_P (insn) || ev == NULL_RTX
- || ! any_condjump_p (insn))
- continue;
- break;
-
- default:
- /* Look for insns that clobber the EV register. */
- if (ev && reg_set_p (ev_reg, insn))
- ev = NULL_RTX;
- continue;
- }
-
- /* Collect the branch condition, hopefully relative to EV_REG. */
- /* ??? At present we'll miss things like
- (expected_value (eq r70 0))
- (set r71 -1)
- (set r80 (lt r70 r71))
- (set pc (if_then_else (ne r80 0) ...))
- as canonicalize_condition will render this to us as
- (lt r70, r71)
- Could use cselib to try and reduce this further. */
- cond = XEXP (SET_SRC (pc_set (insn)), 0);
- cond = canonicalize_condition (insn, cond, 0, NULL, ev_reg,
- false, false);
- if (! cond || XEXP (cond, 0) != ev_reg
- || GET_CODE (XEXP (cond, 1)) != CONST_INT)
- continue;
-
- /* Substitute and simplify. Given that the expression we're
- building involves two constants, we should wind up with either
- true or false. */
- cond = gen_rtx_fmt_ee (GET_CODE (cond), VOIDmode,
- XEXP (ev, 1), XEXP (cond, 1));
- cond = simplify_rtx (cond);
-
- /* Turn the condition into a scaled branch probability. */
- gcc_assert (cond == const_true_rtx || cond == const0_rtx);
- predict_insn_def (insn, PRED_BUILTIN_EXPECT,
- cond == const_true_rtx ? TAKEN : NOT_TAKEN);
- }
-}
-
-/* Check whether this is the last basic block of function. Commonly
- there is one extra common cleanup block. */
-static bool
-last_basic_block_p (basic_block bb)
-{
- if (bb == EXIT_BLOCK_PTR)
- return false;
-
- return (bb->next_bb == EXIT_BLOCK_PTR
- || (bb->next_bb->next_bb == EXIT_BLOCK_PTR
- && single_succ_p (bb)
- && single_succ (bb)->next_bb == EXIT_BLOCK_PTR));
-}
-
-/* Sets branch probabilities according to PREDiction and
- FLAGS. HEADS[bb->index] should be index of basic block in that we
- need to alter branch predictions (i.e. the first of our dominators
- such that we do not post-dominate it) (but we fill this information
- on demand, so -1 may be there in case this was not needed yet). */
-
-static void
-predict_paths_leading_to (basic_block bb, int *heads, enum br_predictor pred,
- enum prediction taken)
-{
- edge e;
- edge_iterator ei;
- int y;
-
- if (heads[bb->index] == ENTRY_BLOCK)
- {
- /* This is first time we need this field in heads array; so
- find first dominator that we do not post-dominate (we are
- using already known members of heads array). */
- basic_block ai = bb;
- basic_block next_ai = get_immediate_dominator (CDI_DOMINATORS, bb);
- int head;
-
- while (heads[next_ai->index] == ENTRY_BLOCK)
- {
- if (!dominated_by_p (CDI_POST_DOMINATORS, next_ai, bb))
- break;
- heads[next_ai->index] = ai->index;
- ai = next_ai;
- next_ai = get_immediate_dominator (CDI_DOMINATORS, next_ai);
- }
- if (!dominated_by_p (CDI_POST_DOMINATORS, next_ai, bb))
- head = next_ai->index;
- else
- head = heads[next_ai->index];
- while (next_ai != bb)
- {
- next_ai = ai;
- ai = BASIC_BLOCK (heads[ai->index]);
- heads[next_ai->index] = head;
- }
- }
- y = heads[bb->index];
-
- /* Now find the edge that leads to our branch and aply the prediction. */
-
- if (y == last_basic_block)
- return;
- FOR_EACH_EDGE (e, ei, BASIC_BLOCK (y)->succs)
- if (e->dest->index >= NUM_FIXED_BLOCKS
- && dominated_by_p (CDI_POST_DOMINATORS, e->dest, bb))
- 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 for LOOP. */
-
-static void
-propagate_freq (struct loop *loop, bitmap tovisit)
-{
- basic_block head = loop->header;
- 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;
-
- /* The outermost "loop" includes the exit block, which we can not
- look up via BASIC_BLOCK. Detect this and use EXIT_BLOCK_PTR
- directly. Do the same for the entry block. */
- 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;
- }
-
- 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, bitmap tovisit)
-{
- struct loop *loop;
-
- for (loop = first_loop; loop; loop = loop->next)
- {
- edge e;
- basic_block *bbs;
- unsigned i;
-
- estimate_loops_at_level (loop->inner, tovisit);
-
- /* Do not do this for dummy function loop. */
- if (EDGE_COUNT (loop->latch->succs) > 0)
- {
- /* 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, 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_EACH_BB (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. */
-
-static void
-estimate_bb_frequencies (struct loops *loops)
-{
- basic_block bb;
- sreal freq_max;
-
- if (!flag_branch_probabilities || !counts_to_freqs ())
- {
- static int real_values_initialized = 0;
- bitmap tovisit;
-
- 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. */
- tovisit = BITMAP_ALLOC (NULL);
- 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_at_level (loops->tree_root, tovisit);
-
- 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 ();
- BITMAP_FREE (tovisit);
- }
- compute_function_frequency ();
- if (flag_reorder_functions)
- choose_function_section ();
-}
-
-/* Decide whether function is hot, cold or unlikely executed. */
-static void
-compute_function_frequency (void)
-{
- basic_block bb;
-
- if (!profile_info || !flag_branch_probabilities)
- return;
- cfun->function_frequency = FUNCTION_FREQUENCY_UNLIKELY_EXECUTED;
- FOR_EACH_BB (bb)
- {
- if (maybe_hot_bb_p (bb))
- {
- cfun->function_frequency = FUNCTION_FREQUENCY_HOT;
- return;
- }
- if (!probably_never_executed_bb_p (bb))
- cfun->function_frequency = FUNCTION_FREQUENCY_NORMAL;
- }
-}
-
-/* Choose appropriate section for the function. */
-static void
-choose_function_section (void)
-{
- if (DECL_SECTION_NAME (current_function_decl)
- || !targetm.have_named_sections
- /* Theoretically we can split the gnu.linkonce text section too,
- but this requires more work as the frequency needs to match
- for all generated objects so we need to merge the frequency
- of all instances. For now just never set frequency for these. */
- || DECL_ONE_ONLY (current_function_decl))
- return;
-
- /* If we are doing the partitioning optimization, let the optimization
- choose the correct section into which to put things. */
-
- if (flag_reorder_blocks_and_partition)
- return;
-
- if (cfun->function_frequency == FUNCTION_FREQUENCY_HOT)
- DECL_SECTION_NAME (current_function_decl) =
- build_string (strlen (HOT_TEXT_SECTION_NAME), HOT_TEXT_SECTION_NAME);
- if (cfun->function_frequency == FUNCTION_FREQUENCY_UNLIKELY_EXECUTED)
- DECL_SECTION_NAME (current_function_decl) =
- build_string (strlen (UNLIKELY_EXECUTED_TEXT_SECTION_NAME),
- UNLIKELY_EXECUTED_TEXT_SECTION_NAME);
-}
-
-static bool
-gate_estimate_probability (void)
-{
- return flag_guess_branch_prob;
-}
-
-struct tree_opt_pass pass_profile =
-{
- "profile", /* name */
- gate_estimate_probability, /* gate */
- tree_estimate_probability, /* 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 */
- 0 /* letter */
-};