[InstCombine] Don't widen metadata on store-to-load forwarding

The original check for load CSE or store-to-load forwarding is wrong
when the forwarded stored value happened to be a load.

Ref https://github.com/JuliaLang/julia/issues/16894

Differential Revision: http://reviews.llvm.org/D21271

Patch by Yichao Yu!

llvm-svn: 272868

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index 6a5d5a62e1b..d312983ed51 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -819,10 +819,12 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
   // separated by a few arithmetic operations.
   BasicBlock::iterator BBI(LI);
   AAMDNodes AATags;
+  bool IsLoadCSE = false;
   if (Value *AvailableVal =
       FindAvailableLoadedValue(&LI, LI.getParent(), BBI,
-                               DefMaxInstsToScan, AA, &AATags)) {
-    if (LoadInst *NLI = dyn_cast<LoadInst>(AvailableVal)) {
+                               DefMaxInstsToScan, AA, &AATags, &IsLoadCSE)) {
+    if (IsLoadCSE) {
+      LoadInst *NLI = cast<LoadInst>(AvailableVal);
       unsigned KnownIDs[] = {
           LLVMContext::MD_tbaa,            LLVMContext::MD_alias_scope,
           LLVMContext::MD_noalias,         LLVMContext::MD_range,