From: Dan Gohman <gohman@apple.com>
Date: Mon, 27 Aug 2007 16:32:11 +0000 (+0000)
Subject: Make DAGCombiner's global alias analysis query more precise in the case
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e9c8fa095e503933840fa1ea41b4583817db5680;p=oota-llvm.git

Make DAGCombiner's global alias analysis query more precise in the case
where both pointers have non-zero offsets.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41491 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index fda0589a6de..0514bc181be 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4606,8 +4606,9 @@ bool DAGCombiner::isAlias(SDOperand Ptr1, int64_t Size1,
 
   if (CombinerGlobalAA) {
     // Use alias analysis information.
-    int Overlap1 = Size1 + SrcValueOffset1;
-    int Overlap2 = Size2 + SrcValueOffset2;
+    int64_t MinOffset = std::min(SrcValueOffset1, SrcValueOffset2);
+    int64_t Overlap1 = Size1 + SrcValueOffset1 - MinOffset;
+    int64_t Overlap2 = Size2 + SrcValueOffset2 - MinOffset;
     AliasAnalysis::AliasResult AAResult = 
                              AA.alias(SrcValue1, Overlap1, SrcValue2, Overlap2);
     if (AAResult == AliasAnalysis::NoAlias)