Improve mod/ref information based on the pointsToConstantMemory method.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11021 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index c881ec2..373524b 100644
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -44,8 +44,15 @@
AliasAnalysis::ModRefResult
AliasAnalysis::getModRefInfo(StoreInst *S, Value *P, unsigned Size) {
- return alias(S->getOperand(1), TD->getTypeSize(S->getOperand(0)->getType()),
- P, Size) ? Mod : NoModRef;
+ // If the stored address cannot alias the pointer in question, then the
+ // pointer cannot be modified by the store.
+ if (!alias(S->getOperand(1), TD->getTypeSize(S->getOperand(0)->getType()),
+ P, Size))
+ return NoModRef;
+
+ // If the pointer is a pointer to constant memory, then it could not have been
+ // modified by this store.
+ return pointsToConstantMemory(P) ? NoModRef : Mod;
}