diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1456,7 +1456,7 @@
   // If we have seen an instruction with side effects, it's unsafe to reorder an
   // instruction which reads memory or itself has side effects.
   if ((Flags & SkipSideEffect) &&
-      (I->mayReadFromMemory() || I->mayHaveSideEffects()))
+      (I->mayReadFromMemory() || I->mayHaveSideEffects() || isa<AllocaInst>(I)))
     return false;
 
   // Reordering across an instruction which does not necessarily transfer
@@ -1484,6 +1484,37 @@
 
 static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValueMayBeModified = false);
 
+/// Helper function for HoistThenElseCodeToIf. Return true if identical
+/// instructions \p I1 and \p I2 can and should be hoisted.
+static bool shouldHoistCommonInstructions(Instruction *I1, Instruction *I2,
+                                          const TargetTransformInfo &TTI) {
+  // If we're going to hoist a call, make sure that the two instructions
+  // we're commoning/hoisting are both marked with musttail, or neither of
+  // them is marked as such. Otherwise, we might end up in a situation where
+  // we hoist from a block where the terminator is a `ret` to a block where
+  // the terminator is a `br`, and `musttail` calls expect to be followed by
+  // a return.
+  auto *C1 = dyn_cast<CallInst>(I1);
+  auto *C2 = dyn_cast<CallInst>(I2);
+  if (C1 && C2)
+    if (C1->isMustTailCall() != C2->isMustTailCall())
+      return false;
+
+  if (!TTI.isProfitableToHoist(I1) || !TTI.isProfitableToHoist(I2))
+    return false;
+
+  // If any of the two call sites has nomerge or convergent attribute, stop
+  // hoisting.
+  if (const auto *CB1 = dyn_cast<CallBase>(I1))
+    if (CB1->cannotMerge() || CB1->isConvergent())
+      return false;
+  if (const auto *CB2 = dyn_cast<CallBase>(I2))
+    if (CB2->cannotMerge() || CB2->isConvergent())
+      return false;
+
+  return true;
+}
+
 /// Given a conditional branch that goes to BB1 and BB2, hoist any common code
 /// in the two blocks up into the branch block. The caller of this function
 /// guarantees that BI's block dominates BB1 and BB2. If EqTermsOnly is given,
@@ -1564,38 +1595,13 @@
       goto HoistTerminator;
     }
 
-    if (I1->isIdenticalToWhenDefined(I2)) {
-      // Even if the instructions are identical, it may not be safe to hoist
-      // them if we have skipped over instructions with side effects or their
-      // operands weren't hoisted.
-      if (!isSafeToHoistInstr(I1, SkipFlagsBB1) ||
-          !isSafeToHoistInstr(I2, SkipFlagsBB2))
-        return Changed;
-
-      // If we're going to hoist a call, make sure that the two instructions
-      // we're commoning/hoisting are both marked with musttail, or neither of
-      // them is marked as such. Otherwise, we might end up in a situation where
-      // we hoist from a block where the terminator is a `ret` to a block where
-      // the terminator is a `br`, and `musttail` calls expect to be followed by
-      // a return.
-      auto *C1 = dyn_cast<CallInst>(I1);
-      auto *C2 = dyn_cast<CallInst>(I2);
-      if (C1 && C2)
-        if (C1->isMustTailCall() != C2->isMustTailCall())
-          return Changed;
-
-      if (!TTI.isProfitableToHoist(I1) || !TTI.isProfitableToHoist(I2))
-        return Changed;
-
-      // If any of the two call sites has nomerge or convergent attribute, stop
-      // hoisting.
-      if (const auto *CB1 = dyn_cast<CallBase>(I1))
-        if (CB1->cannotMerge() || CB1->isConvergent())
-          return Changed;
-      if (const auto *CB2 = dyn_cast<CallBase>(I2))
-        if (CB2->cannotMerge() || CB2->isConvergent())
-          return Changed;
-
+    if (I1->isIdenticalToWhenDefined(I2) &&
+        // Even if the instructions are identical, it may not be safe to hoist
+        // them if we have skipped over instructions with side effects or their
+        // operands weren't hoisted.
+        isSafeToHoistInstr(I1, SkipFlagsBB1) &&
+        isSafeToHoistInstr(I2, SkipFlagsBB2) &&
+        shouldHoistCommonInstructions(I1, I2, TTI)) {
       if (isa<DbgInfoIntrinsic>(I1) || isa<DbgInfoIntrinsic>(I2)) {
         assert(isa<DbgInfoIntrinsic>(I1) && isa<DbgInfoIntrinsic>(I2));
         // The debug location is an integral part of a debug info intrinsic
diff --git a/llvm/test/Transforms/SimplifyCFG/convergent.ll b/llvm/test/Transforms/SimplifyCFG/convergent.ll
--- a/llvm/test/Transforms/SimplifyCFG/convergent.ll
+++ b/llvm/test/Transforms/SimplifyCFG/convergent.ll
@@ -82,6 +82,8 @@
 ; SINK-NEXT:    [[TMP0:%.*]] = tail call i32 @tid()
 ; SINK-NEXT:    [[REM:%.*]] = and i32 [[TMP0]], 1
 ; SINK-NEXT:    [[CMP_NOT:%.*]] = icmp eq i32 [[REM]], 0
+; SINK-NEXT:    [[IDXPROM4:%.*]] = zext i32 [[TMP0]] to i64
+; SINK-NEXT:    [[ARRAYIDX5:%.*]] = getelementptr inbounds i32, ptr [[Y_COERCE:%.*]], i64 [[IDXPROM4]]
 ; SINK-NEXT:    br i1 [[CMP_NOT]], label [[IF_ELSE:%.*]], label [[IF_THEN:%.*]]
 ; SINK:       if.then:
 ; SINK-NEXT:    [[TMP1:%.*]] = tail call i32 @mbcnt(i32 -1, i32 0)
@@ -101,8 +103,6 @@
 ; SINK-NEXT:    br label [[IF_END]]
 ; SINK:       if.end:
 ; SINK-NEXT:    [[DOTSINK:%.*]] = phi i32 [ [[TMP6]], [[IF_ELSE]] ], [ [[TMP3]], [[IF_THEN]] ]
-; SINK-NEXT:    [[IDXPROM4:%.*]] = zext i32 [[TMP0]] to i64
-; SINK-NEXT:    [[ARRAYIDX5:%.*]] = getelementptr inbounds i32, ptr [[Y_COERCE:%.*]], i64 [[IDXPROM4]]
 ; SINK-NEXT:    store i32 [[DOTSINK]], ptr [[ARRAYIDX5]], align 4
 ; SINK-NEXT:    ret void
 ;