From 7446416058ee318db515443ba79e15c23d0f61f1 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Wed, 30 Jun 2010 06:58:35 +0000
Subject: [PATCH] When computing a new ConservativeResult, intersect it with
 the old one instead of replacing it, to be more precise.

llvm-svn: 107256
---
 lib/Analysis/ScalarEvolution.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index b5acd6bfd6e..240126eef8c 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2958,7 +2958,8 @@ ScalarEvolution::getUnsignedRange(const SCEV *S) {
       if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
         if (!C->getValue()->isZero())
           ConservativeResult =
-            ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0));
+            ConservativeResult.intersectWith(
+              ConstantRange(C->getValue()->getValue(), APInt(BitWidth, 0)));
 
     // TODO: non-affine addrec
     if (AddRec->isAffine()) {