Hello.
Currently, whenever we find a first match predictor, we firstly find a predictor
which is defined first in the list of predictors and eventually we check that
the predictor is PRED_FLAG_FIRST_MATCH. Proper implementation is to consider
just
predictors with the flag set.
Patch reg&bootstraps on x86_64-linux-gnu and is pre-approved by Honza.
Installed as r237539.
Martin
>From c20cc4a5f3b7ae756ce286a1ef0045f50bc96d46 Mon Sep 17 00:00:00 2001
From: marxin <mli...@suse.cz>
Date: Thu, 16 Jun 2016 17:44:48 +0200
Subject: [PATCH] Fix finding of a first match predictor
gcc/ChangeLog:
2016-06-16 Martin Liska <mli...@suse.cz>
* predict.c (combine_predictions_for_insn): When we find a first
match predictor, we should consider just predictors with
PRED_FLAG_FIRST_MATCH. Print either first match (if any) or
DS theory predictor.
(combine_predictions_for_bb): Likewise.
---
gcc/predict.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/gcc/predict.c b/gcc/predict.c
index bafcc96..642bd62 100644
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -835,7 +835,8 @@ combine_predictions_for_insn (rtx_insn *insn, basic_block bb)
int probability = INTVAL (XEXP (XEXP (note, 0), 1));
found = true;
- if (best_predictor > predictor)
+ if (best_predictor > predictor
+ && predictor_info[predictor].flags & PRED_FLAG_FIRST_MATCH)
best_probability = probability, best_predictor = predictor;
d = (combined_probability * probability
@@ -855,7 +856,7 @@ combine_predictions_for_insn (rtx_insn *insn, basic_block bb)
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)
+ if (best_predictor != END_PREDICTORS)
first_match = true;
if (!found)
@@ -863,10 +864,12 @@ combine_predictions_for_insn (rtx_insn *insn, basic_block bb)
combined_probability, bb);
else
{
- dump_prediction (dump_file, PRED_DS_THEORY, combined_probability,
- bb, !first_match ? REASON_NONE : REASON_IGNORED);
- dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability,
- bb, first_match ? REASON_NONE : REASON_IGNORED);
+ if (!first_match)
+ dump_prediction (dump_file, PRED_DS_THEORY, combined_probability,
+ bb, !first_match ? REASON_NONE : REASON_IGNORED);
+ else
+ dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability,
+ bb, first_match ? REASON_NONE : REASON_IGNORED);
}
if (first_match)
@@ -1096,7 +1099,8 @@ combine_predictions_for_bb (basic_block bb, bool dry_run)
found = true;
/* First match heuristics would be widly confused if we predicted
both directions. */
- if (best_predictor > predictor)
+ if (best_predictor > predictor
+ && predictor_info[predictor].flags & PRED_FLAG_FIRST_MATCH)
{
struct edge_prediction *pred2;
int prob = probability;
@@ -1142,17 +1146,19 @@ combine_predictions_for_bb (basic_block bb, bool dry_run)
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)
+ if (best_predictor != END_PREDICTORS)
first_match = true;
if (!found)
dump_prediction (dump_file, PRED_NO_PREDICTION, combined_probability, bb);
else
{
- dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, bb,
- !first_match ? REASON_NONE : REASON_IGNORED);
- dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, bb,
- first_match ? REASON_NONE : REASON_IGNORED);
+ if (!first_match)
+ dump_prediction (dump_file, PRED_DS_THEORY, combined_probability, bb,
+ !first_match ? REASON_NONE : REASON_IGNORED);
+ else
+ dump_prediction (dump_file, PRED_FIRST_MATCH, best_probability, bb,
+ first_match ? REASON_NONE : REASON_IGNORED);
}
if (first_match)
--
2.8.3
