diff --git a/lib/IR/AsmWriter.cpp b/lib/IR/AsmWriter.cpp
index 5ab6953bdbd..88c8ed42e6c 100644
--- a/lib/IR/AsmWriter.cpp
+++ b/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/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index b19d2396585..a44a8deda1a 100644
--- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/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());
diff --git a/test/Assembler/alloca-size-one.ll b/test/Assembler/alloca-size-one.ll
new file mode 100644
index 00000000000..fc5ee34254a
--- /dev/null
+++ b/test/Assembler/alloca-size-one.ll
@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
+; RUN: verify-uselistorder %s
+
+define void @foo() {
+entry:
+; CHECK: %alloc32 = alloca i1, align 8
+; CHECK: %alloc64 = alloca i1, i64 1, align 8
+  %alloc32 = alloca i1, i32 1, align 8
+  %alloc64 = alloca i1, i64 1, align 8
+  unreachable
+}
diff --git a/test/Transforms/InstCombine/alloca.ll b/test/Transforms/InstCombine/alloca.ll
index 105029fb699..db26218f3b8 100644
--- a/test/Transforms/InstCombine/alloca.ll
+++ b/test/Transforms/InstCombine/alloca.ll
@@ -1,6 +1,6 @@
-; RUN: opt < %s -instcombine -S -default-data-layout="E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s
-; RUN: opt < %s -instcombine -S -default-data-layout="E-p:32:32:32-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=P32
-; RUN: opt < %s -instcombine -S | FileCheck %s -check-prefix=NODL
+; RUN: opt < %s -instcombine -S -default-data-layout="E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=CHECK -check-prefix=ALL
+; RUN: opt < %s -instcombine -S -default-data-layout="E-p:32:32:32-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" | FileCheck %s -check-prefix=P32 -check-prefix=ALL
+; RUN: opt < %s -instcombine -S | FileCheck %s -check-prefix=NODL -check-prefix=ALL
 
 
 declare void @use(...)
@@ -150,3 +150,16 @@ entry:
   call void @llvm.stackrestore(i8* %inalloca.save)
   ret void
 }
+
+define void @test10() {
+entry:
+; ALL-LABEL: @test10(
+; ALL: %v32 = alloca i1, align 8
+; ALL: %v64 = alloca i1, i64 1, align 8
+; ALL: %v33 = alloca i1, i33 1, align 8
+  %v32 = alloca i1, align 8
+  %v64 = alloca i1, i64 1, align 8
+  %v33 = alloca i1, i33 1, align 8
+  call void (...)* @use(i1* %v32, i1* %v64, i1* %v33)
+  ret void
+}