2 files changed, 11 insertions, 5 deletions
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index 5ab6953bdbd..88c8ed42e6c 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -2885,7 +2885,13 @@ void AssemblyWriter::printInstruction(const Instruction &I) {
     if (AI->isUsedWithInAlloca())
       Out << "inalloca ";
     TypePrinter.print(AI->getAllocatedType(), Out);
-    if (!AI->getArraySize() || AI->isArrayAllocation()) {
+
+    // Explicitly write the array size if the code is broken, if it's an array
+    // allocation, or if the type is not canonical for scalar allocations.  The
+    // latter case prevents the type from mutating when round-tripping through
+    // assembly.
+    if (!AI->getArraySize() || AI->isArrayAllocation() ||
+        !AI->getArraySize()->getType()->isIntegerTy(32)) {
       Out << ", ";
       writeOperand(AI->getArraySize(), true);
     }
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index b19d2396585..a44a8deda1a 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -165,6 +165,10 @@ isOnlyCopiedFromConstantGlobal(AllocaInst *AI,
 }
 
 static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
+  // Check for array size of 1 (scalar allocation).
+  if (!AI.isArrayAllocation())
+    return nullptr;
+
   // Ensure that the alloca array size argument has type intptr_t, so that
   // any casting is exposed early.
   Type *IntPtrTy = IC.getDataLayout().getIntPtrType(AI.getType());
@@ -174,10 +178,6 @@ static Instruction *simplifyAllocaArraySize(InstCombiner &IC, AllocaInst &AI) {
     return &AI;
   }
 
-  // Check C != 1
-  if (!AI.isArrayAllocation())
-    return nullptr;
-
   // Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1
   if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) {
     Type *NewTy = ArrayType::get(AI.getAllocatedType(), C->getZExtValue());