Correctly report modified status for DSE

[serge-sans-paille]

Summary

Related to https://reviews.llvm.org/D80916

[fhahn]

LGTM, thanks.

llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp

for (unsigned I = 0; I < State.MemDefs.size(); I++) {
 
     // Check if we're storing a value that we just loaded.
     if (auto *Load = dyn_cast<LoadInst>(SI->getOperand(0))) {
       if (storeIsNoop(MSSA, Load, KillingDef)) {
         State.deleteDeadInstruction(SI);
         LLVM_DEBUG(dbgs() << "DSE: Remove Dead Store:\n  DEAD: " << *SI
                           << '\n');
         NumNoopStores++;
+        MadeChange = true;
         continue;
       }
     }
 
     auto MaybeSILoc = State.getLocForWriteEx(SI);
     if (!MaybeSILoc) {
       LLVM_DEBUG(dbgs() << "Failed to find analyzable write location for "
                         << *SI << "\n");
const TargetLibraryInfo &TLI =
         getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
 
     bool Changed = false;
     if (EnableMemorySSA) {
       MemorySSA &MSSA = getAnalysis<MemorySSAWrapperPass>().getMSSA();
       PostDominatorTree &PDT =
           getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
 
-      eliminateDeadStoresMemorySSA(F, AA, MSSA, DT, PDT, TLI);
+      Changed = eliminateDeadStoresMemorySSA(F, AA, MSSA, DT, PDT, TLI);
     } else {
       MemoryDependenceResults &MD =
           getAnalysis<MemoryDependenceWrapperPass>().getMemDep();
 
       Changed = eliminateDeadStores(F, &AA, &MD, &DT, &TLI);
     }
 
 #ifdef LLVM_ENABLE_STATS