dead calls to llvm.stacksave can be deleted, even though they
have potential side-effects.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45392 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 187ebdc..4b648b3 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -17,6 +17,7 @@
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
@@ -173,8 +174,16 @@
bool llvm::isInstructionTriviallyDead(Instruction *I) {
if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
- if (!I->mayWriteToMemory()) return true;
+ if (!I->mayWriteToMemory())
+ return true;
+ // Special case intrinsics that "may write to memory" but can be deleted when
+ // dead.
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+ // Safe to delete llvm.stacksave if dead.
+ if (II->getIntrinsicID() == Intrinsic::stacksave)
+ return true;
+
return false;
}