From 55e4dcad36c4060bfba354ebffff4b041789f0ba Mon Sep 17 00:00:00 2001
From: Jim Laskey <jlaskey@mac.com>
Date: Wed, 18 Oct 2006 19:08:31 +0000
Subject: [PATCH] Add option for controlling inclusion of global AA.

llvm-svn: 31040
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 3c260d310ca1..a4d3c54e1c3b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -51,6 +51,10 @@ namespace {
     CombinerAA("combiner-alias-analysis", cl::Hidden,
                cl::desc("Turn on alias analysis during testing"));
 
+  static cl::opt<bool>
+    CombinerGlobalAA("combiner-global-alias-analysis", cl::Hidden,
+               cl::desc("Include global information in alias analysis"));
+
 //------------------------------ DAGCombiner ---------------------------------//
 
   class VISIBILITY_HIDDEN DAGCombiner {
@@ -4036,13 +4040,15 @@ bool DAGCombiner::isAlias(SDOperand Ptr1, int64_t Size1,
   // If we know both bases then they can't alias.
   if (KnownBase1 && KnownBase2) return false;
 
-  // Use alias analysis information.
-  int Overlap1 = Size1 + SrcValueOffset1 + Offset1;
-  int Overlap2 = Size2 + SrcValueOffset2 + Offset2;
-  AliasAnalysis::AliasResult AAResult = 
+  if (CombinerGlobalAA) {
+    // Use alias analysis information.
+    int Overlap1 = Size1 + SrcValueOffset1 + Offset1;
+    int Overlap2 = Size2 + SrcValueOffset2 + Offset2;
+    AliasAnalysis::AliasResult AAResult = 
                              AA.alias(SrcValue1, Overlap1, SrcValue2, Overlap2);
-  if (AAResult == AliasAnalysis::NoAlias)
-    return false;
+    if (AAResult == AliasAnalysis::NoAlias)
+      return false;
+  }
 
   // Otherwise we have to assume they alias.
   return true;