[Reassociate] Removing instructions mutates the IR.

Fixes PR 30784. Discussed with Justin, who pointed out that
in the new PassManager infrastructure we can have more fine-grained
control on which analyses we want to preserve, but this is the
best we can do with the current infrastructure.

llvm-svn: 285380

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 1ec7fcea109..ac0d7b8f1dd 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -2198,8 +2198,10 @@ PreservedAnalyses ReassociatePass::run(Function &F, FunctionAnalysisManager &) {
     // trivially dead instructions have been removed.
     while (!ToRedo.empty()) {
       Instruction *I = ToRedo.pop_back_val();
-      if (isInstructionTriviallyDead(I))
+      if (isInstructionTriviallyDead(I)) {
         RecursivelyEraseDeadInsts(I, ToRedo);
+        MadeChange = true;
+      }
     }
 
     // Now that we have removed dead instructions, we can reoptimize the