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Fix first match heuristics

Message ID f5346742-0cba-9972-51cc-0baf030be544@suse.cz
State New
Headers show

Commit Message

Martin Liška June 2, 2016, 11:18 a.m. UTC 
Hi.

Following patch fixes a typo in first match heuristics that blocks
selection of best first match heuristics.

It's questionable whether to add a spacial test-case for that? I'm bit
concerned that it can be a bit fragile.

Bootstrapped and regtested on x86_64-linux.

Ready for trunk?
Thanks,
Martin

Comments

Jan Hubicka June 2, 2016, 12:19 p.m. UTC | #1 
> Hi.
> 
> Following patch fixes a typo in first match heuristics that blocks
> selection of best first match heuristics.
> 
> It's questionable whether to add a spacial test-case for that? I'm bit
> concerned that it can be a bit fragile.

Lets add it now to have better coverage. If it will keep breaking, we can 
always remove it later.
> 
> Bootstrapped and regtested on x86_64-linux.
> 
> Ready for trunk?
OK.

Honza
diff mbox

Patch

From 4106928c3eea80c732d32d73d653525c698515d6 Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Thu, 2 Jun 2016 11:51:57 +0200
Subject: [PATCH] Fix first match heuristics

gcc/ChangeLog:

2016-06-02  Martin Liska  <mliska@suse.cz>

	* predict.c (combine_predictions_for_bb): Fix first match in
	cases where a first predictor contains more than one occurence
	in list of predictors.  Take the best value in such case.

gcc/testsuite/ChangeLog:

2016-06-02  Martin Liska  <mliska@suse.cz>

	* gcc.dg/predict-9.c: New test.
---
 gcc/predict.c                    |  2 +-
 gcc/testsuite/gcc.dg/predict-9.c | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/predict-9.c

diff --git a/gcc/predict.c b/gcc/predict.c
index e9dda20..429f44e 100644
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -939,7 +939,7 @@  combine_predictions_for_bb (basic_block bb, bool dry_run)
 		   pred2; pred2 = pred2->ep_next)
 	       if (pred2 != pred && pred2->ep_predictor == pred->ep_predictor)
 	         {
-	           int probability2 = pred->ep_probability;
+		   int probability2 = pred2->ep_probability;
 
 		   if (pred2->ep_edge != first)
 		     probability2 = REG_BR_PROB_BASE - probability2;
diff --git a/gcc/testsuite/gcc.dg/predict-9.c b/gcc/testsuite/gcc.dg/predict-9.c
new file mode 100644
index 0000000..59be16e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/predict-9.c
@@ -0,0 +1,23 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-profile_estimate" } */
+
+extern int global;
+extern int global2;
+extern int global3;
+
+void foo (int base)
+{
+  int i;
+  while (global < 10)
+  {
+    if(global || global2 || global3)
+      return;
+
+    for (i = base; i < 10; i++)
+      if (i > 123)
+	return;
+  }
+}
+
+/* { dg-final { scan-tree-dump-times "first match heuristics: 2.0%" 4 "profile_estimate"} } */
+/* { dg-final { scan-tree-dump-times "first match heuristics: 4.5%" 0 "profile_estimate"} } */
-- 
2.8.3