Realize the gep P, <zeros> must aliases P.
This is a partial fix for PR 86
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10399 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 3024917..b5a72f0 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -175,12 +175,22 @@
// If there is at least one non-zero constant index, we know they cannot
// alias.
bool ConstantFound = false;
+ bool AllZerosFound = true;
for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
- if (const Constant *C = dyn_cast<Constant>(GEP->getOperand(i)))
+ if (const Constant *C = dyn_cast<Constant>(GEP->getOperand(i))) {
if (!C->isNullValue()) {
ConstantFound = true;
break;
+ }
+ } else {
+ AllZerosFound = false;
}
+
+ // If we have getelementptr <ptr>, 0, 0, 0, 0, ... and V2 must aliases
+ // the ptr, the end result is a must alias also.
+ if (AllZerosFound)
+ return MustAlias;
+
if (ConstantFound) {
if (V2Size <= 1 && V1Size <= 1) // Just pointer check?
return NoAlias;