fix PR6642, GVN forwarding from memset to load of the base of the memset.
llvm-svn: 99488
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index fcb802a..642d59d 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1004,18 +1004,18 @@
// If the load and store are to the exact same address, they should have been
// a must alias. AA must have gotten confused.
- // FIXME: Study to see if/when this happens.
- if (LoadOffset == StoreOffset) {
+ // FIXME: Study to see if/when this happens. One case is forwarding a memset
+ // to a load from the base of the memset.
#if 0
+ if (LoadOffset == StoreOffset) {
dbgs() << "STORE/LOAD DEP WITH COMMON POINTER MISSED:\n"
<< "Base = " << *StoreBase << "\n"
<< "Store Ptr = " << *WritePtr << "\n"
<< "Store Offs = " << StoreOffset << "\n"
<< "Load Ptr = " << *LoadPtr << "\n";
abort();
-#endif
- return -1;
}
+#endif
// If the load and store don't overlap at all, the store doesn't provide
// anything to the load. In this case, they really don't alias at all, AA
@@ -1031,11 +1031,11 @@
bool isAAFailure = false;
- if (StoreOffset < LoadOffset) {
+ if (StoreOffset < LoadOffset)
isAAFailure = StoreOffset+int64_t(StoreSize) <= LoadOffset;
- } else {
+ else
isAAFailure = LoadOffset+int64_t(LoadSize) <= StoreOffset;
- }
+
if (isAAFailure) {
#if 0
dbgs() << "STORE LOAD DEP WITH COMMON BASE:\n"