/* Branch prediction routines for the GNU compiler.
- Copyright (C) 2000 Free Software Foundation, Inc.
+ Copyright (C) 2000, 2001 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
+ 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. */
+ 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:
Wu and Larus; MICRO-27.
[3] "Corpus-based Static Branch Prediction"
Calder, Grunwald, Lindsay, Martin, Mozer, and Zorn; PLDI '95.
+
*/
#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 "hard-reg-set.h"
#include "flags.h"
#include "output.h"
#include "function.h"
#include "except.h"
#include "toplev.h"
#include "recog.h"
-#include "insn-flags.h"
#include "expr.h"
+#include "predict.h"
+
+/* Random guesstimation given names. */
+#define PROB_NEVER (0)
+#define PROB_VERY_UNLIKELY (REG_BR_PROB_BASE / 10 - 1)
+#define PROB_UNLIKELY (REG_BR_PROB_BASE * 4 / 10 - 1)
+#define PROB_EVEN (REG_BR_PROB_BASE / 2)
+#define PROB_LIKELY (REG_BR_PROB_BASE - PROB_UNLIKELY)
+#define PROB_VERY_LIKELY (REG_BR_PROB_BASE - PROB_VERY_UNLIKELY)
+#define PROB_ALWAYS (REG_BR_PROB_BASE)
+
+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));
+
+/* 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
+
+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_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. */
+void
+predict_edge (e, predictor, probability)
+ edge e;
+ int probability;
+ enum br_predictor predictor;
+{
+ rtx last_insn;
+ last_insn = e->src->end;
+
+ /* 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 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 = REG_NOTES (insn);
+
+ while (note)
+ {
+ 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)));
+ note = XEXP (note, 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,
+ (HOST_WIDEST_INT) bb->count);
+ fprintf (rtl_dump_file, " hit ");
+ fprintf (rtl_dump_file, HOST_WIDEST_INT_PRINT_DEC,
+ (HOST_WIDEST_INT) 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 = REG_NOTES (insn);
+ 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. */
+ while (note)
+ {
+ 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));
+ /* An FP math to avoid overflows of 32bit integers. */
+ combined_probability = (((double)combined_probability) * probability
+ * REG_BR_PROB_BASE / d + 0.5);
+ }
+ note = XEXP (note, 1);
+ }
+
+ /* Decide 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.
??? In the next revision there will be a number of other predictors added
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. */
j <= loops_info->array[i].last->index;
++j)
{
- edge e;
-
- if (! TEST_BIT (loops_info->array[i].nodes, j))
- for (e = BASIC_BLOCK(j)->pred; e; e = e->pred_next)
- if (TEST_BIT (loops_info->array[i].nodes, e->src->index))
- {
- rtx last_insn = BLOCK_END (e->src->index);
- rtx cond, earliest;
-
- if (GET_CODE (last_insn) != JUMP_INSN
- || ! condjump_p (last_insn) || simplejump_p (last_insn))
- continue;
- cond = get_condition (last_insn, &earliest);
- if (! cond)
- continue;
- if (! find_reg_note (last_insn, REG_BR_PROB, 0))
- REG_NOTES (last_insn)
- = gen_rtx_EXPR_LIST (REG_BR_PROB,
- GEN_INT (REG_BR_PROB_BASE),
- REG_NOTES (last_insn));
- }
+ if (TEST_BIT (loops_info->array[i].nodes, j))
+ {
+ int header_found = 0;
+ edge e;
+
+ /* Loop branch heuristics - predict as taken an edge back to
+ a loop's head. */
+ for (e = BASIC_BLOCK(j)->succ; e; e = e->succ_next)
+ if (e->dest == loops_info->array[i].header
+ && e->src == loops_info->array[i].latch)
+ {
+ header_found = 1;
+ predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN);
+ }
+ /* Loop exit heuristics - 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_def (e, PRED_LOOP_EXIT, NOT_TAKEN);
+ }
}
}
- /* 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;
- int prob;
edge e;
+ /* 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 (GET_CODE (last_insn) != JUMP_INSN
- || ! condjump_p (last_insn) || simplejump_p (last_insn))
+ || ! any_condjump_p (last_insn))
continue;
- if (find_reg_note (last_insn, REG_BR_PROB, 0))
- continue;
+ 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)
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)
- {
- if (e->flags & EDGE_FALLTHRU)
- prob = REG_BR_PROB_BASE;
- else
- prob = 0;
- goto emitnote;
- }
-
/* Try "pointer heuristic."
A comparison ptr == 0 is predicted as false.
Similarly, a comparison ptr1 == ptr2 is predicted as false. */
{
case EQ:
if (GET_CODE (XEXP (cond, 0)) == REG
- && REGNO_POINTER_FLAG (REGNO (XEXP (cond, 0)))
+ && REG_POINTER (XEXP (cond, 0))
&& (XEXP (cond, 1) == const0_rtx
|| (GET_CODE (XEXP (cond, 1)) == REG
- && REGNO_POINTER_FLAG (REGNO (XEXP (cond, 1))))))
- {
- prob = REG_BR_PROB_BASE / 10;
- goto emitnote;
- }
+ && REG_POINTER (XEXP (cond, 1)))))
+
+ predict_insn_def (last_insn, PRED_POINTER, NOT_TAKEN);
break;
case NE:
if (GET_CODE (XEXP (cond, 0)) == REG
- && REGNO_POINTER_FLAG (REGNO (XEXP (cond, 0)))
+ && REG_POINTER (XEXP (cond, 0))
&& (XEXP (cond, 1) == const0_rtx
|| (GET_CODE (XEXP (cond, 1)) == REG
- && REGNO_POINTER_FLAG (REGNO (XEXP (cond, 1))))))
- {
- prob = REG_BR_PROB_BASE - (REG_BR_PROB_BASE / 10);
- goto emitnote;
- }
+ && REG_POINTER (XEXP (cond, 1)))))
+ predict_insn_def (last_insn, PRED_POINTER, TAKEN);
break;
default:
{
case CONST_INT:
/* Unconditional branch. */
- prob = (cond == const0_rtx ? 0 : REG_BR_PROB_BASE);
- goto emitnote;
+ predict_insn_def (last_insn, PRED_UNCONDITIONAL,
+ cond == const0_rtx ? NOT_TAKEN : TAKEN);
+ break;
case EQ:
- prob = REG_BR_PROB_BASE / 10;
- goto emitnote;
+ case UNEQ:
+ predict_insn_def (last_insn, PRED_OPCODE, NOT_TAKEN);
+ break;
case NE:
- prob = REG_BR_PROB_BASE - (REG_BR_PROB_BASE / 10);
- goto emitnote;
+ case LTGT:
+ predict_insn_def (last_insn, PRED_OPCODE, TAKEN);
+ break;
+ case ORDERED:
+ predict_insn_def (last_insn, PRED_OPCODE, TAKEN);
+ break;
+ case UNORDERED:
+ predict_insn_def (last_insn, PRED_OPCODE, NOT_TAKEN);
+ break;
case LE:
case LT:
- if (XEXP (cond, 1) == const0_rtx)
- {
- prob = REG_BR_PROB_BASE / 10;
- goto emitnote;
- }
+ if (XEXP (cond, 1) == const0_rtx
+ || (GET_CODE (XEXP (cond, 1)) == CONST_INT
+ && INTVAL (XEXP (cond, 1)) == -1))
+ predict_insn_def (last_insn, PRED_OPCODE, NOT_TAKEN);
break;
case GE:
case GT:
if (XEXP (cond, 1) == const0_rtx
|| (GET_CODE (XEXP (cond, 1)) == CONST_INT
&& INTVAL (XEXP (cond, 1)) == -1))
- {
- prob = REG_BR_PROB_BASE - (REG_BR_PROB_BASE / 10);
- goto emitnote;
- }
+ predict_insn_def (last_insn, PRED_OPCODE, TAKEN);
break;
default:
break;
}
+ }
- /* If we havn't chosen something by now, predict 50-50. */
- prob = REG_BR_PROB_BASE / 2;
+ /* Attach the combined probability to each conditional jump. */
+ for (i = 0; i < n_basic_blocks; i++)
+ {
+ rtx last_insn = BLOCK_END (i);
- emitnote:
- REG_NOTES (last_insn)
- = gen_rtx_EXPR_LIST (REG_BR_PROB, GEN_INT (prob),
- REG_NOTES (last_insn));
+ if (GET_CODE (last_insn) != JUMP_INSN
+ || ! any_condjump_p (last_insn))
+ continue;
+ combine_predictions_for_insn (last_insn, BASIC_BLOCK (i));
}
+ 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
+ expected values of registers. Generate branch probabilities
based off these values. */
void
{
ev = NOTE_EXPECTED_VALUE (insn);
ev_reg = XEXP (ev, 0);
+ delete_insn (insn);
}
continue;
continue;
case JUMP_INSN:
- /* Look for simple conditional branches. If we havn't got an
+ /* 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)
continue;
- if (! condjump_p (insn) || simplejump_p (insn))
+ if (! any_condjump_p (insn))
continue;
break;
}
(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
|| 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 = GEN_INT (REG_BR_PROB_BASE);
- else if (cond != const0_rtx)
+ if (cond != const_true_rtx && cond != const0_rtx)
abort ();
- REG_NOTES (insn) = alloc_EXPR_LIST (REG_BR_PROB, cond, REG_NOTES (insn));
+ 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)
+ {
+ volatile 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++)
+ if (BASIC_BLOCK (i)->count > count_max)
+ count_max = BASIC_BLOCK (i)->count;
+
+ 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 optimizer 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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