4 files changed, 41 insertions, 15 deletions
diff --git a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
index 0e93b0a37b0..9d0ef42e039 100644
--- a/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
+++ b/llvm/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -582,11 +582,18 @@ bool EarlyCSE::processNode(DomTreeNode *Node) {
     // its simpler value.
     if (Value *V = SimplifyInstruction(Inst, DL, &TLI, &DT, &AC)) {
       DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << "  to: " << *V << '\n');
-      Inst->replaceAllUsesWith(V);
-      Inst->eraseFromParent();
-      Changed = true;
-      ++NumSimplify;
-      continue;
+      if (!Inst->use_empty()) {
+        Inst->replaceAllUsesWith(V);
+        Changed = true;
+      }
+      if (isInstructionTriviallyDead(Inst, &TLI)) {
+        Inst->eraseFromParent();
+        Changed = true;
+      }
+      if (Changed) {
+        ++NumSimplify;
+        continue;
+      }
     }
 
     // If this is a simple instruction that we can value number, process it.
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index 944e06d4391..a963b2f50ed 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -2056,12 +2056,21 @@ bool GVN::processInstruction(Instruction *I) {
   // "%z = and i32 %x, %y" becomes "%z = and i32 %x, %x" which we now simplify.
   const DataLayout &DL = I->getModule()->getDataLayout();
   if (Value *V = SimplifyInstruction(I, DL, TLI, DT, AC)) {
-    I->replaceAllUsesWith(V);
-    if (MD && V->getType()->getScalarType()->isPointerTy())
-      MD->invalidateCachedPointerInfo(V);
-    markInstructionForDeletion(I);
-    ++NumGVNSimpl;
-    return true;
+    bool Changed = false;
+    if (!I->use_empty()) {
+      I->replaceAllUsesWith(V);
+      Changed = true;
+    }
+    if (isInstructionTriviallyDead(I, TLI)) {
+      markInstructionForDeletion(I);
+      Changed = true;
+    }
+    if (Changed) {
+      if (MD && V->getType()->getScalarType()->isPointerTy())
+        MD->invalidateCachedPointerInfo(V);
+      ++NumGVNSimpl;
+      return true;
+    }
   }
 
   if (IntrinsicInst *IntrinsicI = dyn_cast<IntrinsicInst>(I))
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index 1d8d2a5e469..e7957f9599a 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1746,13 +1746,18 @@ bool JumpThreadingPass::DuplicateCondBranchOnPHIIntoPred(
     // phi translation.
     if (Value *IV =
             SimplifyInstruction(New, BB->getModule()->getDataLayout())) {
-      delete New;
       ValueMapping[&*BI] = IV;
+      if (!New->mayHaveSideEffects()) {
+        delete New;
+        New = nullptr;
+      }
     } else {
+      ValueMapping[&*BI] = New;
+    }
+    if (New) {
       // Otherwise, insert the new instruction into the block.
       New->setName(BI->getName());
       PredBB->getInstList().insert(OldPredBranch->getIterator(), New);
-      ValueMapping[&*BI] = New;
     }
   }
 
diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index c6709d5334a..46db8f1210b 100644
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -312,13 +312,18 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
     if (V && LI->replacementPreservesLCSSAForm(C, V)) {
       // If so, then delete the temporary instruction and stick the folded value
       // in the map.
-      delete C;
       ValueMap[Inst] = V;
+      if (!C->mayHaveSideEffects()) {
+        delete C;
+        C = nullptr;
+      }
     } else {
+      ValueMap[Inst] = C;
+    }
+    if (C) {
       // Otherwise, stick the new instruction into the new block!
       C->setName(Inst->getName());
       C->insertBefore(LoopEntryBranch);
-      ValueMap[Inst] = C;
     }
   }