Index: include/llvm/IR/IntrinsicsARM.td
===================================================================
--- include/llvm/IR/IntrinsicsARM.td
+++ include/llvm/IR/IntrinsicsARM.td
@@ -22,6 +22,13 @@
 // and return value are essentially chains, used to force ordering during ISel.
 def int_arm_space : Intrinsic<[llvm_i32_ty], [llvm_i32_ty, llvm_i32_ty], []>;
 
+// Intrinsics for the compiler to use to assert that the operand is either a
+// i8 or i16 that is already zero extended.
+def int_arm_codegen_zeroext_i8 :
+  Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem]>;
+def int_arm_codegen_zeroext_i16 :
+  Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem]>;
+
 // 16-bit multiplications
 def int_arm_smulbb : GCCBuiltin<"__builtin_arm_smulbb">,
     Intrinsic<[llvm_i32_ty], [llvm_i32_ty, llvm_i32_ty], [IntrNoMem]>;
Index: lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- lib/Target/ARM/ARMISelLowering.cpp
+++ lib/Target/ARM/ARMISelLowering.cpp
@@ -3376,6 +3376,12 @@
     }
     return Result;
   }
+  case Intrinsic::arm_codegen_zeroext_i8:
+    return DAG.getNode(ISD::AssertZext, dl, MVT::i32, Op->getOperand(1),
+                       DAG.getValueType(MVT::i8));
+  case Intrinsic::arm_codegen_zeroext_i16:
+    return DAG.getNode(ISD::AssertZext, dl, MVT::i32, Op->getOperand(1),
+                       DAG.getValueType(MVT::i16));
   case Intrinsic::arm_neon_vabs:
     return DAG.getNode(ISD::ABS, SDLoc(Op), Op.getValueType(),
                         Op.getOperand(1));
Index: test/CodeGen/ARM/codegen-zeroext-intrinsic.ll
===================================================================
--- /dev/null
+++ test/CodeGen/ARM/codegen-zeroext-intrinsic.ll
@@ -0,0 +1,45 @@
+; RUN: llc -mtriple=armv8 %s -o - | FileCheck %s
+; RUN: llc -mtriple=thumbv8m.main %s -o - | FileCheck %s
+
+; CHECK-LABEL: zero_i8
+; CHECK-NOT: uxt
+; CHECK: bx
+define zeroext i8 @zero_i8(i32 %arg) {
+entry:
+  %zeroext = call i32 @llvm.arm.codegen.zeroext.i8(i32 %arg)
+  %trunc = trunc i32 %zeroext to i8
+  ret i8 %trunc
+}
+
+; CHECK-LABEL: zero_i8_mismatch
+; CHECK-NOT: uxt
+; CHECK: bx
+define zeroext i16 @zero_i8_mismatch(i32 %arg) {
+entry:
+  %zeroext = call i32 @llvm.arm.codegen.zeroext.i8(i32 %arg)
+  %trunc = trunc i32 %zeroext to i16
+  ret i16 %trunc
+}
+
+; CHECK-LABEL: zero_i16
+; CHECK-NOT: uxt
+; CHECK: bx
+define zeroext i16 @zero_i16(i32 %arg) {
+entry:
+  %zeroext = call i32 @llvm.arm.codegen.zeroext.i16(i32 %arg)
+  %trunc = trunc i32 %zeroext to i16
+  ret i16 %trunc
+}
+
+; CHECK-LABEL: zero_i16_mismatch
+; CHECK: uxtb r0, r0
+; CHECK: bx
+define zeroext i8 @zero_i16_mismatch(i32 %arg) {
+entry:
+  %zeroext = call i32 @llvm.arm.codegen.zeroext.i16(i32 %arg)
+  %trunc = trunc i32 %zeroext to i8
+  ret i8 %trunc
+}
+
+declare i32 @llvm.arm.codegen.zeroext.i8(i32)
+declare i32 @llvm.arm.codegen.zeroext.i16(i32)