Patchwork One 4.6 backport

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Submitter Marek Polacek
Date April 4, 2013, 10:29 a.m.
Message ID <20130404102948.GB24873@redhat.com>
Download mbox | patch
Permalink /patch/233708/
State New
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Comments

Marek Polacek - April 4, 2013, 10:29 a.m.
I'm about to backport one patch (a fix for PR48189) to 4.6 branch.
Bootstrapped/regtested on x86_64-linux, acked by Jakub on IRC.
Will commit soon.

ChangeLog:
2013-04-04  Marek Polacek  <polacek@redhat.com>

	Backported from mainline
	2013-01-09  Steven Bosscher  <steven@gcc.gnu.org>
		    Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/48189
	* predict.c (predict_loops): If max is 0, don't call compare_tree_int.
	If nitercst is 0, don't predict the exit edge.

testsuite/ChangeLog:
2013-04-04  Marek Polacek  <polacek@redhat.com>

	Backported from mainline
	2013-01-09  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/48189
	* gcc.dg/pr48189.c: New test.


	Marek

Patch

--- gcc/predict.c.mp	2013-04-04 11:59:59.816219085 +0200
+++ gcc/predict.c	2013-04-04 12:00:13.418263854 +0200
@@ -1,6 +1,6 @@ 
 /* Branch prediction routines for the GNU compiler.
    Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010
-   Free Software Foundation, Inc.
+   2011, 2012, 2013 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -966,7 +966,8 @@  predict_loops (void)
 	  if (TREE_CODE (niter) == INTEGER_CST)
 	    {
 	      if (host_integerp (niter, 1)
-		  && compare_tree_int (niter, max-1) == -1)
+		  && max
+		  && compare_tree_int (niter, max - 1) == -1)
 		nitercst = tree_low_cst (niter, 1) + 1;
 	      else
 		nitercst = max;
@@ -988,6 +989,11 @@  predict_loops (void)
 	  else
 	    continue;
 
+	  /* If the prediction for number of iterations is zero, do not
+	     predict the exit edges.  */
+	  if (nitercst == 0)
+	    continue;
+
 	  probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst);
 	  predict_edge (ex, predictor, probability);
 	}
--- gcc/testsuite/gcc.dg/pr48189.c.mp	2013-04-04 11:59:45.581173690 +0200
+++ gcc/testsuite/gcc.dg/pr48189.c	2013-04-04 11:59:36.446144550 +0200
@@ -0,0 +1,13 @@ 
+/* PR tree-optimization/48189 */
+/* { dg-do compile } */
+/* { dg-options "-O --param max-predicted-iterations=0" } */
+
+struct S { int s[8]; };
+  
+void
+foo (int *x, struct S *y)
+{
+  int i;
+  for (i = 0; y[i].s[i]; i++)
+    *x++ = y[i].s[i];
+}