From patchwork Mon Oct 22 15:26:25 2012
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Subject: Minor record_upper_bound tweek
Date: Mon, 22 Oct 2012 05:26:25 -0000
From: Jan Hubicka <hubicka@ucw.cz>
X-Patchwork-Id: 193179
Message-Id: <20121022152625.GA18262@kam.mff.cuni.cz>
To: gcc-patches@gcc.gnu.org, rguenther@suse.de

Hi,
with profile feedback we may misupdate the profile and start to believe that loops
iterate more times than they do.  This patch makes at least nb_iterations_estimate
no greater than nb_iterations_upper_bound.  This makes the unrolling/peeling/unswitching
heuristics to behave more consistently.
Bootstrapped/regtested x86_64-linux, OK?

Honza

	* tree-sssa-loop-niter.c (record_niter_bound): Be sure that realistic
	estimate is not bigger than upper bound.


Index: tree-ssa-loop-niter.c
===================================================================
--- tree-ssa-loop-niter.c	(revision 192632)
+++ tree-ssa-loop-niter.c	(working copy)
@@ -2506,13 +2506,20 @@ record_niter_bound (struct loop *loop, d
     {
       loop->any_upper_bound = true;
       loop->nb_iterations_upper_bound = i_bound;
+      if (loop->any_estimate
+	  && i_bound.ult (loop->nb_iterations_estimate))
+        loop->nb_iterations_estimate = i_bound;
     }
   if (realistic
       && (!loop->any_estimate
 	  || i_bound.ult (loop->nb_iterations_estimate)))
     {
       loop->any_estimate = true;
-      loop->nb_iterations_estimate = i_bound;
+      if (loop->nb_iterations_upper_bound.ult (i_bound)
+	   && loop->any_upper_bound)
+        loop->nb_iterations_estimate = loop->nb_iterations_upper_bound;
+      else
+        loop->nb_iterations_estimate = i_bound;
     }
 
   /* If an upper bound is smaller than the realistic estimate of the