/* Branch prediction routines for the GNU compiler.
- Copyright (C) 2000, 2001 Free Software Foundation, Inc.
+ Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
- This file is part of GNU CC.
+This file is part of GCC.
- GNU CC 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 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.
- GNU CC 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.
+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 GNU CC; see the file COPYING. If not, write to
- the Free Software Foundation, 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
+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, 59 Temple Place - Suite 330, Boston, MA
+02111-1307, USA. */
/* References:
[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.
-
-*/
+ Calder, Grunwald, Lindsay, Martin, Mozer, and Zorn; PLDI '95. */
#include "config.h"
#include "toplev.h"
#include "recog.h"
#include "expr.h"
-
+#include "predict.h"
/* Random guesstimation given names. */
#define PROB_NEVER (0)
#define PROB_VERY_LIKELY (REG_BR_PROB_BASE - PROB_VERY_UNLIKELY)
#define PROB_ALWAYS (REG_BR_PROB_BASE)
-static void predict_insn PARAMS ((rtx, int));
-static void predict_edge PARAMS ((edge, int));
+static void combine_predictions_for_insn PARAMS ((rtx, basic_block));
+static void dump_prediction PARAMS ((enum br_predictor, int,
+ basic_block, int));
+static void estimate_loops_at_level PARAMS ((struct loop *loop));
+static void propagate_freq PARAMS ((basic_block));
+static void estimate_bb_frequencies PARAMS ((struct loops *));
+static void counts_to_freqs PARAMS ((void));
-static void
-predict_insn (insn, probability)
- rtx insn;
- int probability;
+/* Information we hold about each branch predictor.
+ Filled using information from predict.def. */
+
+struct predictor_info
{
- rtx note = find_reg_note (insn, REG_BR_PROB, 0);
+ const char *const name; /* Name used in the debugging dumps. */
+ const int hitrate; /* Expected hitrate used by
+ predict_insn_def call. */
+ const int flags;
+};
- /* Implement "first match" heruistics. In case we already predicted
- insn somehow, keep it predicted that way. In future we would like
- to rather store all predictions and then combine them. */
- if (note)
- return;
+/* 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
+
+void
+predict_insn (insn, predictor, probability)
+ rtx insn;
+ int probability;
+ enum br_predictor predictor;
+{
if (!any_condjump_p (insn))
abort ();
+
REG_NOTES (insn)
- = gen_rtx_EXPR_LIST (REG_BR_PROB,
- GEN_INT (probability), 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 (insn, predictor, taken)
+ 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. */
-static void
-predict_edge (e, probability)
+
+void
+predict_edge (e, predictor, probability)
edge e;
int probability;
+ enum br_predictor predictor;
{
rtx last_insn;
last_insn = e->src->end;
if (e->flags & EDGE_FALLTHRU)
probability = REG_BR_PROB_BASE - probability;
- predict_insn (last_insn, probability);
+ predict_insn (last_insn, predictor, probability);
+}
+
+/* Predict edge E by given predictor if possible. */
+
+void
+predict_edge_def (e, predictor, taken)
+ 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 (insn)
+ 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 (predictor, probability, bb, used)
+ enum br_predictor predictor;
+ int probability;
+ basic_block bb;
+ int used;
+{
+ edge e = bb->succ;
+
+ if (!rtl_dump_file)
+ return;
+
+ while (e->flags & EDGE_FALLTHRU)
+ e = e->succ_next;
+
+ fprintf (rtl_dump_file, " %s heuristics%s: %.1f%%",
+ predictor_info[predictor].name,
+ used ? "" : " (ignored)", probability * 100.0 / REG_BR_PROB_BASE);
+
+ if (bb->count)
+ {
+ fprintf (rtl_dump_file, " exec ");
+ fprintf (rtl_dump_file, HOST_WIDEST_INT_PRINT_DEC, bb->count);
+ fprintf (rtl_dump_file, " hit ");
+ fprintf (rtl_dump_file, HOST_WIDEST_INT_PRINT_DEC, e->count);
+ fprintf (rtl_dump_file, " (%.1f%%)", e->count * 100.0 / bb->count);
+ }
+
+ fprintf (rtl_dump_file, "\n");
+}
+
+/* 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 (insn, bb)
+ rtx insn;
+ basic_block bb;
+{
+ rtx prob_note = find_reg_note (insn, REG_BR_PROB, 0);
+ rtx *pnote = ®_NOTES (insn);
+ 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 (rtl_dump_file)
+ fprintf (rtl_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. In the future we will use better
+ probability combination techniques. */
+ 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 (PRED_NO_PREDICTION, combined_probability, bb, true);
+ else
+ {
+ dump_prediction (PRED_DS_THEORY, combined_probability, bb, !first_match);
+ dump_prediction (PRED_FIRST_MATCH, best_probability, bb, first_match);
+ }
+
+ if (first_match)
+ combined_probability = best_probability;
+ dump_prediction (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 (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 (bb->succ->succ_next)
+ {
+ BRANCH_EDGE (bb)->probability = combined_probability;
+ FALLTHRU_EDGE (bb)->probability
+ = REG_BR_PROB_BASE - combined_probability;
+ }
+ }
}
/* Statically estimate the probability that a branch will be taken.
estimate_probability (loops_info)
struct loops *loops_info;
{
+ sbitmap *dominators, *post_dominators;
int i;
+ int found_noreturn = 0;
+
+ dominators = sbitmap_vector_alloc (n_basic_blocks, n_basic_blocks);
+ post_dominators = sbitmap_vector_alloc (n_basic_blocks, n_basic_blocks);
+ calculate_dominance_info (NULL, dominators, CDI_DOMINATORS);
+ calculate_dominance_info (NULL, post_dominators, CDI_POST_DOMINATORS);
/* Try to predict out blocks in a loop that are not part of a
natural loop. */
for (i = 0; i < loops_info->num; i++)
{
int j;
-
- for (j = loops_info->array[i].first->index;
- j <= loops_info->array[i].last->index;
- ++j)
- {
- if (TEST_BIT (loops_info->array[i].nodes, j))
- {
- int header_found = 0;
- edge e;
-
- /* Loop branch heruistics - predict as taken an edge back to
- a loop's head. */
+ int exits;
+ struct loop *loop = &loops_info->array[i];
+
+ flow_loop_scan (loops_info, loop, LOOP_EXIT_EDGES);
+ exits = loop->num_exits;
+
+ for (j = loop->first->index; j <= loop->last->index; ++j)
+ if (TEST_BIT (loop->nodes, j))
+ {
+ int header_found = 0;
+ edge e;
+
+ /* Loop branch heuristics - predict an edge back to a
+ loop's head as taken. */
+ for (e = BASIC_BLOCK(j)->succ; e; e = e->succ_next)
+ if (e->dest == loop->header
+ && e->src == loop->latch)
+ {
+ header_found = 1;
+ predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN);
+ }
+
+ /* Loop exit heuristics - predict an edge exiting the loop if the
+ conditinal has no loop header successors as not taken. */
+ if (!header_found)
for (e = BASIC_BLOCK(j)->succ; e; e = e->succ_next)
- if (e->dest == loops_info->array[i].header)
- {
- header_found = 1;
- predict_edge (e, PROB_VERY_LIKELY);
- }
- /* Loop exit heruistics - predict as not taken an edge exiting
- the loop if the conditinal has no loop header successors */
- if (!header_found)
- for (e = BASIC_BLOCK(j)->succ; e; e = e->succ_next)
- if (e->dest->index <= 0
- || !TEST_BIT (loops_info->array[i].nodes, e->dest->index))
- predict_edge (e, PROB_UNLIKELY);
- }
- }
+ if (e->dest->index < 0
+ || !TEST_BIT (loop->nodes, e->dest->index))
+ predict_edge
+ (e, PRED_LOOP_EXIT,
+ (REG_BR_PROB_BASE
+ - predictor_info [(int) PRED_LOOP_EXIT].hitrate)
+ / exits);
+ }
}
- /* Attempt to predict conditional jumps using a number of heuristics.
- For each conditional jump, we try each heuristic in a fixed order.
- If more than one heuristic applies to a particular branch, the first
- is used as the prediction for the branch. */
- for (i = 0; i < n_basic_blocks - 1; i++)
+ /* Attempt to predict conditional jumps using a number of heuristics. */
+ for (i = 0; i < n_basic_blocks; i++)
{
- rtx last_insn = BLOCK_END (i);
+ basic_block bb = BASIC_BLOCK (i);
+ rtx last_insn = bb->end;
rtx cond, earliest;
edge e;
- if (GET_CODE (last_insn) != JUMP_INSN
- || ! any_condjump_p (last_insn))
- continue;
+ /* If block has no successor, predict all possible paths to it as
+ improbable, as the block contains a call to a noreturn function and
+ thus can be executed only once. */
+ if (bb->succ == NULL && !found_noreturn)
+ {
+ int y;
+
+ /* ??? Postdominator claims each noreturn block to be postdominated
+ by each, so we need to run only once. This needs to be changed
+ once postdominace algorithm is updated to say something more
+ sane. */
+ found_noreturn = 1;
+ for (y = 0; y < n_basic_blocks; y++)
+ if (!TEST_BIT (post_dominators[y], i))
+ for (e = BASIC_BLOCK (y)->succ; e; e = e->succ_next)
+ if (e->dest->index >= 0
+ && TEST_BIT (post_dominators[e->dest->index], i))
+ predict_edge_def (e, PRED_NORETURN, NOT_TAKEN);
+ }
- if (find_reg_note (last_insn, REG_BR_PROB, 0))
+ if (GET_CODE (last_insn) != JUMP_INSN || ! any_condjump_p (last_insn))
continue;
- /* If one of the successor blocks has no successors, predict
- that side not taken. */
- /* ??? Ought to do the same for any subgraph with no exit. */
- for (e = BASIC_BLOCK (i)->succ; e; e = e->succ_next)
- if (e->dest->succ == NULL)
- predict_edge (e, PROB_NEVER);
+ for (e = bb->succ; e; e = e->succ_next)
+ {
+ /* Predict edges to blocks that return immediately to be
+ improbable. These are usually used to signal error states. */
+ if (e->dest == EXIT_BLOCK_PTR
+ || (e->dest->succ && !e->dest->succ->succ_next
+ && e->dest->succ->dest == EXIT_BLOCK_PTR))
+ predict_edge_def (e, PRED_ERROR_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
+ && TEST_BIT (dominators[e->dest->index], e->src->index)
+ && !TEST_BIT (post_dominators[e->src->index], e->dest->index))
+ {
+ rtx insn;
+
+ /* 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 (insn = e->dest->head; insn != NEXT_INSN (e->dest->end);
+ insn = NEXT_INSN (insn))
+ if (GET_CODE (insn) == CALL_INSN
+ /* Constant and pure calls are hardly used to signalize
+ something exceptional. */
+ && ! CONST_OR_PURE_CALL_P (insn))
+ {
+ predict_edge_def (e, PRED_CALL, NOT_TAKEN);
+ break;
+ }
+ }
+ }
cond = get_condition (last_insn, &earliest);
if (! cond)
/* Try "pointer heuristic."
A comparison ptr == 0 is predicted as false.
Similarly, a comparison ptr1 == ptr2 is predicted as false. */
- switch (GET_CODE (cond))
+ if (GET_RTX_CLASS (GET_CODE (cond)) == '<'
+ && ((REG_P (XEXP (cond, 0)) && REG_POINTER (XEXP (cond, 0)))
+ || (REG_P (XEXP (cond, 1)) && REG_POINTER (XEXP (cond, 1)))))
{
- case EQ:
- if (GET_CODE (XEXP (cond, 0)) == REG
- && REG_POINTER (XEXP (cond, 0))
- && (XEXP (cond, 1) == const0_rtx
- || (GET_CODE (XEXP (cond, 1)) == REG
- && REG_POINTER (XEXP (cond, 1)))))
-
- predict_insn (last_insn, PROB_UNLIKELY);
- break;
- case NE:
- if (GET_CODE (XEXP (cond, 0)) == REG
- && REG_POINTER (XEXP (cond, 0))
- && (XEXP (cond, 1) == const0_rtx
- || (GET_CODE (XEXP (cond, 1)) == REG
- && REG_POINTER (XEXP (cond, 1)))))
- predict_insn (last_insn, PROB_LIKELY);
- break;
-
- default:
- break;
+ 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 (last_insn,
- cond == const0_rtx ? PROB_NEVER : PROB_ALWAYS);
- break;
+ 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
+ inpredictable 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 usefull 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
+ inpredictable 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 usefull 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;
+ }
+ }
- case EQ:
- case UNEQ:
- predict_insn (last_insn, PROB_UNLIKELY);
- break;
- case NE:
- case LTGT:
- predict_insn (last_insn, PROB_LIKELY);
- break;
- case ORDERED:
- predict_insn (last_insn, PROB_LIKELY);
- break;
- case UNORDERED:
- predict_insn (last_insn, PROB_UNLIKELY);
- break;
- case LE:
- case LT:
- if (XEXP (cond, 1) == const0_rtx)
- predict_insn (last_insn, PROB_UNLIKELY);
- break;
- case GE:
- case GT:
- if (XEXP (cond, 1) == const0_rtx
- || (GET_CODE (XEXP (cond, 1)) == CONST_INT
- && INTVAL (XEXP (cond, 1)) == -1))
- predict_insn (last_insn, PROB_LIKELY);
- break;
+ /* Attach the combined probability to each conditional jump. */
+ for (i = 0; i < n_basic_blocks; i++)
+ if (GET_CODE (BLOCK_END (i)) == JUMP_INSN
+ && any_condjump_p (BLOCK_END (i)))
+ combine_predictions_for_insn (BLOCK_END (i), BASIC_BLOCK (i));
- default:
- break;
- }
- }
+ sbitmap_vector_free (post_dominators);
+ sbitmap_vector_free (dominators);
+
+ estimate_bb_frequencies (loops_info);
}
\f
-/* __builtin_expect dropped tokens into the insn stream describing
- expected values of registers. Generate branch probabilities
- based off these values. */
+/* __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 ()
{
ev = NOTE_EXPECTED_VALUE (insn);
ev_reg = XEXP (ev, 0);
+ delete_insn (insn);
}
continue;
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 (GET_CODE (insn) != JUMP_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;
-
- case JUMP_INSN:
- /* Look for simple conditional branches. If we havn't got an
- expected value yet, no point going further. */
- if (GET_CODE (insn) != JUMP_INSN || ev == NULL_RTX)
- continue;
- if (! condjump_p (insn) || simplejump_p (insn))
- continue;
- break;
}
/* Collect the branch condition, hopefully relative to EV_REG. */
(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
+ 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 (PATTERN (insn)), 0);
+ cond = XEXP (SET_SRC (pc_set (insn)), 0);
cond = canonicalize_condition (insn, cond, 0, NULL, ev_reg);
- if (! cond
- || XEXP (cond, 0) != ev_reg
+ if (! cond || XEXP (cond, 0) != ev_reg
|| GET_CODE (XEXP (cond, 1)) != CONST_INT)
continue;
- /* Substitute and simplify. Given that the expression we're
+ /* 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,
cond = simplify_rtx (cond);
/* Turn the condition into a scaled branch probability. */
- if (cond != const1_rtx && cond != const0_rtx)
+ if (cond != const_true_rtx && cond != const0_rtx)
abort ();
- predict_insn (insn,
- cond == const1_rtx ? PROB_VERY_LIKELY : PROB_VERY_UNLIKELY);
+ predict_insn_def (insn, PRED_BUILTIN_EXPECT,
+ cond == const_true_rtx ? TAKEN : NOT_TAKEN);
+ }
+}
+\f
+/* 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. */
+ volatile double frequency;
+
+ /* To keep queue of basic blocks to process. */
+ basic_block next;
+
+ /* True if block needs to be visited in prop_freqency. */
+ int tovisit:1;
+
+ /* 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 an 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).
+
+ Volatile is needed to avoid differences in the optimized and unoptimized
+ builds on machines where FP registers are wider than double. */
+ volatile double back_edge_prob;
+ /* True if the edge is an loopback edge in the natural loop. */
+ 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 loops headed by HEAD. */
+
+static void
+propagate_freq (head)
+ basic_block head;
+{
+ basic_block bb = head;
+ basic_block last = bb;
+ edge e;
+ basic_block nextbb;
+ int n;
+
+ /* For each basic block we need to visit count number of his predecessors
+ we need to visit first. */
+ for (n = 0; n < n_basic_blocks; n++)
+ {
+ basic_block bb = BASIC_BLOCK (n);
+ if (BLOCK_INFO (bb)->tovisit)
+ {
+ int count = 0;
+
+ for (e = bb->pred; e; e = e->pred_next)
+ if (BLOCK_INFO (e->src)->tovisit && !(e->flags & EDGE_DFS_BACK))
+ count++;
+ else if (BLOCK_INFO (e->src)->tovisit
+ && rtl_dump_file && !EDGE_INFO (e)->back_edge)
+ fprintf (rtl_dump_file,
+ "Irreducible region hit, ignoring edge to %i->%i\n",
+ e->src->index, bb->index);
+ BLOCK_INFO (bb)->npredecessors = count;
+ }
+ }
+
+ BLOCK_INFO (head)->frequency = 1;
+ for (; bb; bb = nextbb)
+ {
+ double cyclic_probability = 0, frequency = 0;
+
+ nextbb = BLOCK_INFO (bb)->next;
+ BLOCK_INFO (bb)->next = NULL;
+
+ /* Compute frequency of basic block. */
+ if (bb != head)
+ {
+#ifdef ENABLE_CHECKING
+ for (e = bb->pred; e; e = e->pred_next)
+ if (BLOCK_INFO (e->src)->tovisit && !(e->flags & EDGE_DFS_BACK))
+ abort ();
+#endif
+
+ for (e = bb->pred; e; e = e->pred_next)
+ if (EDGE_INFO (e)->back_edge)
+ cyclic_probability += EDGE_INFO (e)->back_edge_prob;
+ else if (!(e->flags & EDGE_DFS_BACK))
+ frequency += (e->probability
+ * BLOCK_INFO (e->src)->frequency /
+ REG_BR_PROB_BASE);
+
+ if (cyclic_probability > 1.0 - 1.0 / REG_BR_PROB_BASE)
+ cyclic_probability = 1.0 - 1.0 / REG_BR_PROB_BASE;
+
+ BLOCK_INFO (bb)->frequency = frequency / (1 - cyclic_probability);
+ }
+
+ BLOCK_INFO (bb)->tovisit = 0;
+
+ /* Compute back edge frequencies. */
+ for (e = bb->succ; e; e = e->succ_next)
+ if (e->dest == head)
+ EDGE_INFO (e)->back_edge_prob
+ = ((e->probability * BLOCK_INFO (bb)->frequency)
+ / REG_BR_PROB_BASE);
+
+ /* Propagate to successor blocks. */
+ for (e = bb->succ; e; e = e->succ_next)
+ 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 (first_loop)
+ struct loop *first_loop;
+{
+ struct loop *l, *loop = first_loop;
+
+ for (loop = first_loop; loop; loop = loop->next)
+ {
+ int n;
+ edge e;
+
+ estimate_loops_at_level (loop->inner);
+
+ /* Find current loop back edge and mark it. */
+ for (e = loop->latch->succ; e->dest != loop->header; e = e->succ_next)
+ ;
+
+ EDGE_INFO (e)->back_edge = 1;
+
+ /* In case the loop header is shared, ensure that it is the last
+ one sharing the same header, so we avoid redundant work. */
+ if (loop->shared)
+ {
+ for (l = loop->next; l; l = l->next)
+ if (l->header == loop->header)
+ break;
+
+ if (l)
+ continue;
+ }
+
+ /* Now merge all nodes of all loops with given header as not visited. */
+ for (l = loop->shared ? first_loop : loop; l != loop->next; l = l->next)
+ if (loop->header == l->header)
+ EXECUTE_IF_SET_IN_SBITMAP (l->nodes, 0, n,
+ BLOCK_INFO (BASIC_BLOCK (n))->tovisit = 1
+ );
+
+ propagate_freq (loop->header);
+ }
+}
+
+/* Convert counts measured by profile driven feedback to frequencies. */
+
+static void
+counts_to_freqs ()
+{
+ HOST_WIDEST_INT count_max = 1;
+ int i;
+
+ for (i = 0; i < n_basic_blocks; i++)
+ count_max = MAX (BASIC_BLOCK (i)->count, count_max);
+
+ for (i = -2; i < n_basic_blocks; i++)
+ {
+ basic_block bb;
+
+ if (i == -2)
+ bb = ENTRY_BLOCK_PTR;
+ else if (i == -1)
+ bb = EXIT_BLOCK_PTR;
+ else
+ bb = BASIC_BLOCK (i);
+
+ bb->frequency = (bb->count * BB_FREQ_MAX + count_max / 2) / 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 isntructions
+ function can execute at average to be still considered not expensive. */
+
+bool
+expensive_function_p (threshold)
+ int threshold;
+{
+ unsigned int sum = 0;
+ int i;
+ unsigned int limit;
+
+ /* We can not compute accurately for large thresholds due to scaled
+ frequencies. */
+ if (threshold > BB_FREQ_MAX)
+ abort ();
+
+ /* 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 (i = 0; i < n_basic_blocks; i++)
+ {
+ basic_block bb = BASIC_BLOCK (i);
+ rtx insn;
+
+ for (insn = bb->head; insn != NEXT_INSN (bb->end);
+ 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 (loops)
+ struct loops *loops;
+{
+ int i;
+ double freq_max = 0;
+
+ mark_dfs_back_edges ();
+ if (flag_branch_probabilities)
+ {
+ counts_to_freqs ();
+ return;
+ }
+
+ /* Fill in the probability values in flowgraph based on the REG_BR_PROB
+ notes. */
+ for (i = 0; i < n_basic_blocks; i++)
+ {
+ rtx last_insn = BLOCK_END (i);
+ int probability;
+ edge fallthru, branch;
+
+ if (GET_CODE (last_insn) != JUMP_INSN || !any_condjump_p (last_insn)
+ /* Avoid handling of conditional jumps jumping to fallthru edge. */
+ || BASIC_BLOCK (i)->succ->succ_next == NULL)
+ {
+ /* We can predict only conditional jumps at the moment.
+ Expect each edge to be equally probable.
+ ?? In the future we want to make abnormal edges improbable. */
+ int nedges = 0;
+ edge e;
+
+ for (e = BASIC_BLOCK (i)->succ; e; e = e->succ_next)
+ {
+ nedges++;
+ if (e->probability != 0)
+ break;
+ }
+ if (!e)
+ for (e = BASIC_BLOCK (i)->succ; e; e = e->succ_next)
+ e->probability = (REG_BR_PROB_BASE + nedges / 2) / nedges;
+ }
+ else
+ {
+ probability = INTVAL (XEXP (find_reg_note (last_insn,
+ REG_BR_PROB, 0), 0));
+ fallthru = BASIC_BLOCK (i)->succ;
+ if (!fallthru->flags & EDGE_FALLTHRU)
+ fallthru = fallthru->succ_next;
+ branch = BASIC_BLOCK (i)->succ;
+ if (branch->flags & EDGE_FALLTHRU)
+ branch = branch->succ_next;
+
+ branch->probability = probability;
+ fallthru->probability = REG_BR_PROB_BASE - probability;
+ }
+ }
+
+ ENTRY_BLOCK_PTR->succ->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 (i = -2; i < n_basic_blocks; i++)
+ {
+ edge e;
+ basic_block bb;
+
+ if (i == -2)
+ bb = ENTRY_BLOCK_PTR;
+ else if (i == -1)
+ bb = EXIT_BLOCK_PTR;
+ else
+ bb = BASIC_BLOCK (i);
+
+ BLOCK_INFO (bb)->tovisit = 0;
+ for (e = bb->succ; e; e = e->succ_next)
+ EDGE_INFO (e)->back_edge_prob = ((double) e->probability
+ / REG_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);
+
+ /* Now fake loop around whole function to finalize probabilities. */
+ for (i = 0; i < n_basic_blocks; i++)
+ BLOCK_INFO (BASIC_BLOCK (i))->tovisit = 1;
+
+ BLOCK_INFO (ENTRY_BLOCK_PTR)->tovisit = 1;
+ BLOCK_INFO (EXIT_BLOCK_PTR)->tovisit = 1;
+ propagate_freq (ENTRY_BLOCK_PTR);
+
+ for (i = 0; i < n_basic_blocks; i++)
+ if (BLOCK_INFO (BASIC_BLOCK (i))->frequency > freq_max)
+ freq_max = BLOCK_INFO (BASIC_BLOCK (i))->frequency;
+
+ for (i = -2; i < n_basic_blocks; i++)
+ {
+ basic_block bb;
+
+ if (i == -2)
+ bb = ENTRY_BLOCK_PTR;
+ else if (i == -1)
+ bb = EXIT_BLOCK_PTR;
+ else
+ bb = BASIC_BLOCK (i);
+ bb->frequency
+ = BLOCK_INFO (bb)->frequency * BB_FREQ_MAX / freq_max + 0.5;
+ }
+
+ free_aux_for_blocks ();
+ free_aux_for_edges ();
+}
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