Don't remove side effecting instructions due to ConstantFoldInstruction

Just because we can constant fold the result of an instruction does not
imply that we can delete the instruction.  It may have side effects.

This fixes PR28655.

llvm-svn: 276389

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index b9e717cf763..d1769fc3ebb 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -758,7 +758,8 @@ bool JumpThreadingPass::ProcessBlock(BasicBlock *BB) {
         ConstantFoldInstruction(I, BB->getModule()->getDataLayout(), TLI);
     if (SimpleVal) {
       I->replaceAllUsesWith(SimpleVal);
-      I->eraseFromParent();
+      if (isInstructionTriviallyDead(I, TLI))
+        I->eraseFromParent();
       Condition = SimpleVal;
     }
   }