[DeadStoreElimination] Check function modref behavior before considering memory clobbered

Differential Revision: https://reviews.llvm.org/D29996

llvm-svn: 296625

2 files changed, 13 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index c3c0295bee5..53590175be8 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -551,7 +551,7 @@ static bool memoryIsNotModifiedBetween(Instruction *FirstI,
       Instruction *I = &*BI;
       if (I->mayWriteToMemory() && I != SecondI) {
         auto Res = AA->getModRefInfo(I, MemLoc);
-        if (Res != MRI_NoModRef)
+        if (Res & MRI_Mod)
           return false;
       }
     }
diff --git a/llvm/test/Transforms/DeadStoreElimination/operand-bundles.ll b/llvm/test/Transforms/DeadStoreElimination/operand-bundles.ll
index d71b9673ed1..784b2e8e55f 100644
--- a/llvm/test/Transforms/DeadStoreElimination/operand-bundles.ll
+++ b/llvm/test/Transforms/DeadStoreElimination/operand-bundles.ll
@@ -41,3 +41,15 @@ define void @test3() {
   store i64 0, i64* %s
   ret void
 }
+
+declare noalias i8* @calloc(i64, i64)
+
+define void @test4() {
+; CHECK-LABEL: @test4
+  %local_obj = call i8* @calloc(i64 1, i64 4)
+  call void @foo() ["deopt" (i8* %local_obj)]
+  store i8 0, i8* %local_obj, align 4
+  ; CHECK-NOT: store i8 0, i8* %local_obj, align 4
+  call void @bar(i8* nocapture %local_obj)
+  ret void
+}