diff --git a/lib/Target/WebAssembly/WebAssembly.td b/lib/Target/WebAssembly/WebAssembly.td
index 243a71f..ec9dbff 100644
--- a/lib/Target/WebAssembly/WebAssembly.td
+++ b/lib/Target/WebAssembly/WebAssembly.td
@@ -25,13 +25,6 @@
 
 def FeatureSIMD128 : SubtargetFeature<"simd128", "HasSIMD128", "true",
                                       "Enable 128-bit SIMD">;
-
-def FeatureSIMD128Unimplemented :
-      SubtargetFeature<"simd128-unimplemented",
-                       "HasSIMD128Unimplemented", "true",
-                       "Enable 128-bit SIMD not yet implemented in engines",
-                       [FeatureSIMD128]>;
-
 def FeatureAtomics : SubtargetFeature<"atomics", "HasAtomics", "true",
                                       "Enable Atomics">;
 def FeatureNontrappingFPToInt :
diff --git a/lib/Target/WebAssembly/WebAssemblyFastISel.cpp b/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
index f687c4d..a452a00 100644
--- a/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
@@ -44,6 +44,8 @@
 
 #define DEBUG_TYPE "wasm-fastisel"
 
+extern cl::opt<bool> EnableUnimplementedWasmSIMDInstrs;
+
 namespace {
 
 class WebAssemblyFastISel final : public FastISel {
@@ -143,7 +145,7 @@
       break;
     case MVT::v2i64:
     case MVT::v2f64:
-      if (Subtarget->hasSIMD128Unimplemented())
+      if (Subtarget->hasSIMD128() && EnableUnimplementedWasmSIMDInstrs)
         return VT;
       break;
     default:
diff --git a/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp b/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp
index 0a7464c..29678f3 100644
--- a/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp
@@ -25,6 +25,8 @@
 
 #define DEBUG_TYPE "wasm-isel"
 
+extern cl::opt<bool> EnableUnimplementedWasmSIMDInstrs;
+
 //===--------------------------------------------------------------------===//
 /// WebAssembly-specific code to select WebAssembly machine instructions for
 /// SelectionDAG operations.
diff --git a/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index 1f33888..d267358 100644
--- a/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -37,6 +37,12 @@
 
 #define DEBUG_TYPE "wasm-lower"
 
+// Emit proposed instructions that may not have been implemented in engines
+cl::opt<bool> EnableUnimplementedWasmSIMDInstrs(
+    "wasm-enable-unimplemented-simd",
+    cl::desc("Emit potentially-unimplemented WebAssembly SIMD instructions"),
+    cl::init(false));
+
 WebAssemblyTargetLowering::WebAssemblyTargetLowering(
     const TargetMachine &TM, const WebAssemblySubtarget &STI)
     : TargetLowering(TM), Subtarget(&STI) {
@@ -64,7 +70,7 @@
     addRegisterClass(MVT::v8i16, &WebAssembly::V128RegClass);
     addRegisterClass(MVT::v4i32, &WebAssembly::V128RegClass);
     addRegisterClass(MVT::v4f32, &WebAssembly::V128RegClass);
-    if (Subtarget->hasSIMD128Unimplemented()) {
+    if (EnableUnimplementedWasmSIMDInstrs) {
       addRegisterClass(MVT::v2i64, &WebAssembly::V128RegClass);
       addRegisterClass(MVT::v2f64, &WebAssembly::V128RegClass);
     }
@@ -129,7 +135,7 @@
       for (auto T : {MVT::v16i8, MVT::v8i16, MVT::v4i32}) {
         setOperationAction(Op, T, Expand);
       }
-      if (Subtarget->hasSIMD128Unimplemented()) {
+      if (EnableUnimplementedWasmSIMDInstrs) {
         setOperationAction(Op, MVT::v2i64, Expand);
       }
     }
@@ -143,7 +149,7 @@
     for (auto T : {MVT::v16i8, MVT::v8i16, MVT::v4i32, MVT::v4f32}) {
       setOperationAction(ISD::VECTOR_SHUFFLE, T, Custom);
     }
-    if (Subtarget->hasSIMD128Unimplemented()) {
+    if (EnableUnimplementedWasmSIMDInstrs) {
       setOperationAction(ISD::VECTOR_SHUFFLE, MVT::v2i64, Custom);
       setOperationAction(ISD::VECTOR_SHUFFLE, MVT::v2f64, Custom);
     }
@@ -154,7 +160,7 @@
     for (auto T : {MVT::v16i8, MVT::v8i16, MVT::v4i32})
       for (auto Op : {ISD::SHL, ISD::SRA, ISD::SRL})
         setOperationAction(Op, T, Custom);
-    if (Subtarget->hasSIMD128Unimplemented())
+    if (EnableUnimplementedWasmSIMDInstrs)
       for (auto Op : {ISD::SHL, ISD::SRA, ISD::SRL})
         setOperationAction(Op, MVT::v2i64, Custom);
   }
@@ -164,7 +170,7 @@
     for (auto Op : {ISD::VSELECT, ISD::SELECT_CC, ISD::SELECT}) {
       for (auto T : {MVT::v16i8, MVT::v8i16, MVT::v4i32, MVT::v4f32})
         setOperationAction(Op, T, Expand);
-      if (Subtarget->hasSIMD128Unimplemented())
+      if (EnableUnimplementedWasmSIMDInstrs)
         for (auto T : {MVT::v2i64, MVT::v2f64})
           setOperationAction(Op, T, Expand);
     }
@@ -173,10 +179,8 @@
   // sign-extend from.
   setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);
   if (!Subtarget->hasSignExt()) {
-    // Sign extends are legal only when extending a vector extract
-    auto Action = Subtarget->hasSIMD128() ? Custom : Expand;
     for (auto T : {MVT::i8, MVT::i16, MVT::i32})
-      setOperationAction(ISD::SIGN_EXTEND_INREG, T, Action);
+      setOperationAction(ISD::SIGN_EXTEND_INREG, T, Expand);
   }
   for (auto T : MVT::integer_vector_valuetypes())
     setOperationAction(ISD::SIGN_EXTEND_INREG, T, Expand);
@@ -221,7 +225,7 @@
   }
 
   // Expand additional SIMD ops that V8 hasn't implemented yet
-  if (Subtarget->hasSIMD128() && !Subtarget->hasSIMD128Unimplemented()) {
+  if (Subtarget->hasSIMD128() && !EnableUnimplementedWasmSIMDInstrs) {
     setOperationAction(ISD::FSQRT, MVT::v4f32, Expand);
     setOperationAction(ISD::FDIV, MVT::v4f32, Expand);
   }
@@ -232,7 +236,7 @@
       setOperationAction(ISD::EXTRACT_VECTOR_ELT, T, Custom);
       setOperationAction(ISD::INSERT_VECTOR_ELT, T, Custom);
     }
-    if (Subtarget->hasSIMD128Unimplemented()) {
+    if (EnableUnimplementedWasmSIMDInstrs) {
       for (auto T : {MVT::v2i64, MVT::v2f64}) {
         setOperationAction(ISD::EXTRACT_VECTOR_ELT, T, Custom);
         setOperationAction(ISD::INSERT_VECTOR_ELT, T, Custom);
@@ -896,8 +900,6 @@
     return LowerAccessVectorElement(Op, DAG);
   case ISD::INTRINSIC_VOID:
     return LowerINTRINSIC_VOID(Op, DAG);
-  case ISD::SIGN_EXTEND_INREG:
-    return LowerSIGN_EXTEND_INREG(Op, DAG);
   case ISD::VECTOR_SHUFFLE:
     return LowerVECTOR_SHUFFLE(Op, DAG);
   case ISD::SHL:
@@ -1100,22 +1102,6 @@
 }
 
 SDValue
-WebAssemblyTargetLowering::LowerSIGN_EXTEND_INREG(SDValue Op,
-                                                  SelectionDAG &DAG) const {
-  // If sign extension operations are disabled, allow sext_inreg only if operand
-  // is a vector extract. SIMD does not depend on sign extension operations, but
-  // allowing sext_inreg in this context lets us have simple patterns to select
-  // extract_lane_s instructions. Expanding sext_inreg everywhere would be
-  // simpler in this file, but would necessitate large and brittle patterns to
-  // undo the expansion and select extract_lane_s instructions.
-  assert(!Subtarget->hasSignExt() && Subtarget->hasSIMD128());
-  if (Op.getOperand(0).getOpcode() == ISD::EXTRACT_VECTOR_ELT)
-    return Op;
-  // Otherwise expand
-  return SDValue();
-}
-
-SDValue
 WebAssemblyTargetLowering::LowerVECTOR_SHUFFLE(SDValue Op,
                                                SelectionDAG &DAG) const {
   SDLoc DL(Op);
diff --git a/lib/Target/WebAssembly/WebAssemblyISelLowering.h b/lib/Target/WebAssembly/WebAssemblyISelLowering.h
index 59f4230..8007681 100644
--- a/lib/Target/WebAssembly/WebAssemblyISelLowering.h
+++ b/lib/Target/WebAssembly/WebAssemblyISelLowering.h
@@ -99,7 +99,6 @@
   SDValue LowerCopyToReg(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerINTRINSIC_VOID(SDValue Op, SelectionDAG &DAG) const;
-  SDValue LowerSIGN_EXTEND_INREG(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerAccessVectorElement(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerShift(SDValue Op, SelectionDAG &DAG) const;
diff --git a/lib/Target/WebAssembly/WebAssemblyInstrInfo.td b/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
index 14e2de0..d172537 100644
--- a/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
+++ b/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
@@ -20,9 +20,7 @@
 def HasAddr64 : Predicate<"Subtarget->hasAddr64()">;
 def HasSIMD128 : Predicate<"Subtarget->hasSIMD128()">,
                            AssemblerPredicate<"FeatureSIMD128", "simd128">;
-def HasUnimplementedSIMD :
-    Predicate<"Subtarget->hasSIMD128Unimplemented()">,
-    AssemblerPredicate<"FeatureSIMD128Unimplemented", "simd128-unimplemented">;
+def HasUnimplementedSIMD : Predicate<"EnableUnimplementedWasmSIMDInstrs">;
 def HasAtomics : Predicate<"Subtarget->hasAtomics()">,
                            AssemblerPredicate<"FeatureAtomics", "atomics">;
 def HasNontrappingFPToInt :
diff --git a/lib/Target/WebAssembly/WebAssemblySubtarget.h b/lib/Target/WebAssembly/WebAssemblySubtarget.h
index bd2e995..b170dbf 100644
--- a/lib/Target/WebAssembly/WebAssemblySubtarget.h
+++ b/lib/Target/WebAssembly/WebAssemblySubtarget.h
@@ -30,7 +30,6 @@
 
 class WebAssemblySubtarget final : public WebAssemblyGenSubtargetInfo {
   bool HasSIMD128;
-  bool HasSIMD128Unimplemented;
   bool HasAtomics;
   bool HasNontrappingFPToInt;
   bool HasSignExt;
@@ -79,7 +78,6 @@
   // Predicates used by WebAssemblyInstrInfo.td.
   bool hasAddr64() const { return TargetTriple.isArch64Bit(); }
   bool hasSIMD128() const { return HasSIMD128; }
-  bool hasSIMD128Unimplemented() const { return HasSIMD128Unimplemented; }
   bool hasAtomics() const { return HasAtomics; }
   bool hasNontrappingFPToInt() const { return HasNontrappingFPToInt; }
   bool hasSignExt() const { return HasSignExt; }
diff --git a/test/CodeGen/WebAssembly/simd-arith.ll b/test/CodeGen/WebAssembly/simd-arith.ll
index c87a418..91480a4 100644
--- a/test/CodeGen/WebAssembly/simd-arith.ll
+++ b/test/CodeGen/WebAssembly/simd-arith.ll
@@ -1,13 +1,13 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented | FileCheck %s --check-prefixes CHECK,SIMD128,SIMD128-SLOW
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented -fast-isel | FileCheck %s --check-prefixes CHECK,SIMD128,SIMD128-FAST
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128,SIMD128-SLOW
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128 -fast-isel | FileCheck %s --check-prefixes CHECK,SIMD128,SIMD128-FAST
 ; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128-VM
 ; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128 -fast-isel | FileCheck %s --check-prefixes CHECK,SIMD128-VM
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers | FileCheck %s --check-prefixes CHECK,NO-SIMD128
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -fast-isel | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=-simd128 | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=-simd128 -fast-isel | FileCheck %s --check-prefixes CHECK,NO-SIMD128
 
 ; check that a non-test run (including explicit locals pass) at least finishes
-; RUN: llc < %s -O0 -mattr=+simd128-unimplemented
-; RUN: llc < %s -O2 -mattr=+simd128-unimplemented
+; RUN: llc < %s -O0 -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext
+; RUN: llc < %s -O2 -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext
 
 ; Test that basic SIMD128 arithmetic operations assemble as expected.
 
@@ -122,14 +122,22 @@
 ; NO-SIMD128-NOT: i8x16
 ; SIMD128-NEXT: .functype shr_s_vec_v16i8 (v128, v128) -> (v128){{$}}
 ; SIMD128-NEXT: i8x16.extract_lane_s $push[[L0:[0-9]+]]=, $0, 0{{$}}
-; SIMD128-NEXT: i8x16.extract_lane_u $push[[L1:[0-9]+]]=, $1, 0{{$}}
-; SIMD128-NEXT: i32.shr_s $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]{{$}}
-; SIMD128-NEXT: i8x16.splat $push[[L3:[0-9]+]]=, $pop[[L2]]{{$}}
+; SIMD128-NEXT: i32.const $push[[L1:[0-9]+]]=, 24{{$}}
+; SIMD128-NEXT: i32.shl $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]{{$}}
+; SIMD128-NEXT: i32.const $push[[L3:[0-9]+]]=, 24{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L4:[0-9]+]]=, $pop[[L2]], $pop[[L3]]{{$}}
+; SIMD128-NEXT: i8x16.extract_lane_u $push[[L5:[0-9]+]]=, $1, 0{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L6:[0-9]+]]=, $pop[[L4]], $pop[[L5]]{{$}}
+; SIMD128-NEXT: i8x16.splat $push[[L7:[0-9]+]]=, $pop[[L6]]{{$}}
 ; Skip 14 lanes
-; SIMD128:      i8x16.extract_lane_s $push[[L0:[0-9]+]]=, $0, 15{{$}}
-; SIMD128-NEXT: i8x16.extract_lane_u $push[[L1:[0-9]+]]=, $1, 15{{$}}
-; SIMD128-NEXT: i32.shr_s $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]{{$}}
-; SIMD128-NEXT: i8x16.replace_lane $push[[R:[0-9]+]]=, $pop{{[0-9]+}}, 15, $pop[[L2]]{{$}}
+; SIMD128:      i8x16.extract_lane_s $push[[L7:[0-9]+]]=, $0, 15{{$}}
+; SIMD128-NEXT: i32.const $push[[L8:[0-9]+]]=, 24{{$}}
+; SIMD128-NEXT: i32.shl $push[[L9:[0-9]+]]=, $pop[[L7]], $pop[[L8]]{{$}}
+; SIMD128-NEXT: i32.const $push[[L10:[0-9]+]]=, 24{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L11:[0-9]+]]=, $pop[[L9]], $pop[[L10]]{{$}}
+; SIMD128-NEXT: i8x16.extract_lane_u $push[[L12:[0-9]+]]=, $1, 15{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L13:[0-9]+]]=, $pop[[L11]], $pop[[L12]]{{$}}
+; SIMD128-NEXT: i8x16.replace_lane $push[[R:[0-9]+]]=, $pop[[L14:[0-9]+]], 15, $pop[[L13]]{{$}}
 ; SIMD128-NEXT: return $pop[[R]]{{$}}
 define <16 x i8> @shr_s_vec_v16i8(<16 x i8> %v, <16 x i8> %x) {
   %a = ashr <16 x i8> %v, %x
@@ -335,14 +343,22 @@
 ; NO-SIMD128-NOT: i16x8
 ; SIMD128-NEXT: .functype shr_s_vec_v8i16 (v128, v128) -> (v128){{$}}
 ; SIMD128-NEXT: i16x8.extract_lane_s $push[[L0:[0-9]+]]=, $0, 0{{$}}
-; SIMD128-NEXT: i16x8.extract_lane_u $push[[L1:[0-9]+]]=, $1, 0{{$}}
-; SIMD128-NEXT: i32.shr_s $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]{{$}}
-; SIMD128-NEXT: i16x8.splat $push[[L3:[0-9]+]]=, $pop[[L2]]{{$}}
+; SIMD128-NEXT: i32.const $push[[L1:[0-9]+]]=, 16{{$}}
+; SIMD128-NEXT: i32.shl $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]{{$}}
+; SIMD128-NEXT: i32.const $push[[L3:[0-9]+]]=, 16{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L4:[0-9]+]]=, $pop[[L2]], $pop[[L3]]{{$}}
+; SIMD128-NEXT: i16x8.extract_lane_u $push[[L5:[0-9]+]]=, $1, 0{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L6:[0-9]+]]=, $pop[[L4]], $pop[[L5]]{{$}}
+; SIMD128-NEXT: i16x8.splat $push[[L7:[0-9]+]]=, $pop[[L6]]{{$}}
 ; Skip 6 lanes
-; SIMD128:      i16x8.extract_lane_s $push[[L0:[0-9]+]]=, $0, 7{{$}}
-; SIMD128-NEXT: i16x8.extract_lane_u $push[[L1:[0-9]+]]=, $1, 7{{$}}
-; SIMD128-NEXT: i32.shr_s $push[[L2:[0-9]+]]=, $pop[[L0]], $pop[[L1]]{{$}}
-; SIMD128-NEXT: i16x8.replace_lane $push[[R:[0-9]+]]=, $pop{{[0-9]+}}, 7, $pop[[L2]]{{$}}
+; SIMD128:      i16x8.extract_lane_s $push[[L7:[0-9]+]]=, $0, 7{{$}}
+; SIMD128-NEXT: i32.const $push[[L8:[0-9]+]]=, 16{{$}}
+; SIMD128-NEXT: i32.shl $push[[L9:[0-9]+]]=, $pop[[L7]], $pop[[L8]]{{$}}
+; SIMD128-NEXT: i32.const $push[[L10:[0-9]+]]=, 16{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L11:[0-9]+]]=, $pop[[L9]], $pop[[L10]]{{$}}
+; SIMD128-NEXT: i16x8.extract_lane_u $push[[L12:[0-9]+]]=, $1, 7{{$}}
+; SIMD128-NEXT: i32.shr_s $push[[L13:[0-9]+]]=, $pop[[L11]], $pop[[L12]]{{$}}
+; SIMD128-NEXT: i16x8.replace_lane $push[[R:[0-9]+]]=, $pop[[L14:[0-9]+]], 7, $pop[[L13]]{{$}}
 ; SIMD128-NEXT: return $pop[[R]]{{$}}
 define <8 x i16> @shr_s_vec_v8i16(<8 x i16> %v, <8 x i16> %x) {
   %a = ashr <8 x i16> %v, %x
diff --git a/test/CodeGen/WebAssembly/simd-bitcasts.ll b/test/CodeGen/WebAssembly/simd-bitcasts.ll
index 0f04cae..f143720 100644
--- a/test/CodeGen/WebAssembly/simd-bitcasts.ll
+++ b/test/CodeGen/WebAssembly/simd-bitcasts.ll
@@ -1,6 +1,6 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128-unimplemented | FileCheck %s --check-prefixes CHECK,SIMD128
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128-VM
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128-VM
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=-simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,NO-SIMD128
 
 ; Test that bitcasts between vector types are lowered to zero instructions
 
diff --git a/test/CodeGen/WebAssembly/simd-comparisons.ll b/test/CodeGen/WebAssembly/simd-comparisons.ll
index 2791345..b2e7cb5 100644
--- a/test/CodeGen/WebAssembly/simd-comparisons.ll
+++ b/test/CodeGen/WebAssembly/simd-comparisons.ll
@@ -1,6 +1,6 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128-unimplemented | FileCheck %s --check-prefixes CHECK,SIMD128
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128-VM
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128-VM
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=-simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,NO-SIMD128
 
 ; Test SIMD comparison operators
 
diff --git a/test/CodeGen/WebAssembly/simd-conversions.ll b/test/CodeGen/WebAssembly/simd-conversions.ll
index 4f3c863..582f05c 100644
--- a/test/CodeGen/WebAssembly/simd-conversions.ll
+++ b/test/CodeGen/WebAssembly/simd-conversions.ll
@@ -1,6 +1,6 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+simd128-unimplemented | FileCheck %s --check-prefixes CHECK,SIMD128
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128-VM
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128-VM
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=-simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,NO-SIMD128
 
 ; Test that vector float-to-int and int-to-float instructions lower correctly
 
diff --git a/test/CodeGen/WebAssembly/simd-ext-load-trunc-store.ll b/test/CodeGen/WebAssembly/simd-ext-load-trunc-store.ll
index 0885a72..004f8cd 100644
--- a/test/CodeGen/WebAssembly/simd-ext-load-trunc-store.ll
+++ b/test/CodeGen/WebAssembly/simd-ext-load-trunc-store.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128 | FileCheck %s
 
 ; Check that store in memory with smaller lanes are loaded and stored
 ; as expected. This is a regression test for part of bug 39275.
diff --git a/test/CodeGen/WebAssembly/simd-intrinsics.ll b/test/CodeGen/WebAssembly/simd-intrinsics.ll
index f6f7f66..ec44f48 100644
--- a/test/CodeGen/WebAssembly/simd-intrinsics.ll
+++ b/test/CodeGen/WebAssembly/simd-intrinsics.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented | FileCheck %s --check-prefixes CHECK,SIMD128
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented -fast-isel | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128 -fast-isel | FileCheck %s --check-prefixes CHECK,SIMD128
 
 ; Test that SIMD128 intrinsics lower as expected. These intrinsics are
 ; only expected to lower successfully if the simd128 attribute is
diff --git a/test/CodeGen/WebAssembly/simd-load-store-alignment.ll b/test/CodeGen/WebAssembly/simd-load-store-alignment.ll
index 83d32cb..904e1a5 100644
--- a/test/CodeGen/WebAssembly/simd-load-store-alignment.ll
+++ b/test/CodeGen/WebAssembly/simd-load-store-alignment.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128 | FileCheck %s
 
 ; Test loads and stores with custom alignment values.
 
diff --git a/test/CodeGen/WebAssembly/simd-offset.ll b/test/CodeGen/WebAssembly/simd-offset.ll
index a441fce..43f87eb 100644
--- a/test/CodeGen/WebAssembly/simd-offset.ll
+++ b/test/CodeGen/WebAssembly/simd-offset.ll
@@ -1,6 +1,6 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128-unimplemented | FileCheck %s --check-prefixes CHECK,SIMD128
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128-VM
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128-VM
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-keep-registers -wasm-disable-explicit-locals -mattr=-simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,NO-SIMD128
 
 ; Test SIMD loads and stores
 
diff --git a/test/CodeGen/WebAssembly/simd-select.ll b/test/CodeGen/WebAssembly/simd-select.ll
index d38989e..4832d41 100644
--- a/test/CodeGen/WebAssembly/simd-select.ll
+++ b/test/CodeGen/WebAssembly/simd-select.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s
 
 ; Test that vector selects of various varieties lower correctly to bitselects.
 
diff --git a/test/CodeGen/WebAssembly/simd-sext-inreg.ll b/test/CodeGen/WebAssembly/simd-sext-inreg.ll
index 702c19f..4637d69 100644
--- a/test/CodeGen/WebAssembly/simd-sext-inreg.ll
+++ b/test/CodeGen/WebAssembly/simd-sext-inreg.ll
@@ -1,6 +1,6 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+simd128-unimplemented | FileCheck %s --check-prefixes CHECK,SIMD128
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+simd128 | FileCheck %s --check-prefixes CHECK,SIMD128-VM
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128-VM
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -wasm-keep-registers -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=-simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,NO-SIMD128
 
 ; Test that vector sign extensions lower to shifts
 
diff --git a/test/CodeGen/WebAssembly/simd.ll b/test/CodeGen/WebAssembly/simd.ll
index 748b648..1590064 100644
--- a/test/CodeGen/WebAssembly/simd.ll
+++ b/test/CodeGen/WebAssembly/simd.ll
@@ -1,6 +1,6 @@
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128-unimplemented,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -wasm-enable-unimplemented-simd -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128
 ; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,SIMD128-VM
-; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers | FileCheck %s --check-prefixes CHECK,NO-SIMD128
+; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=-simd128,+sign-ext | FileCheck %s --check-prefixes CHECK,NO-SIMD128
 
 ; Test that basic SIMD128 vector manipulation operations assemble as expected.
 
diff --git a/test/MC/WebAssembly/basic-assembly.s b/test/MC/WebAssembly/basic-assembly.s
index 50bf727..ad247f5 100644
--- a/test/MC/WebAssembly/basic-assembly.s
+++ b/test/MC/WebAssembly/basic-assembly.s
@@ -1,6 +1,6 @@
-# RUN: llvm-mc -triple=wasm32-unknown-unknown -mattr=+simd128-unimplemented,+nontrapping-fptoint,+exception-handling < %s | FileCheck %s
+# RUN: llvm-mc -triple=wasm32-unknown-unknown -mattr=+simd128,+nontrapping-fptoint,+exception-handling < %s | FileCheck %s
 # this one is just here to see if it converts to .o without errors, but doesn't check any output:
-# RUN: llvm-mc -triple=wasm32-unknown-unknown -filetype=obj -mattr=+simd128-unimplemented,+nontrapping-fptoint,+exception-handling < %s
+# RUN: llvm-mc -triple=wasm32-unknown-unknown -filetype=obj -mattr=+simd128,+nontrapping-fptoint,+exception-handling < %s
 
     .text
     .section .text.main,"",@
diff --git a/test/MC/WebAssembly/simd-encodings.s b/test/MC/WebAssembly/simd-encodings.s
index d6b1fa0..cbc81b8 100644
--- a/test/MC/WebAssembly/simd-encodings.s
+++ b/test/MC/WebAssembly/simd-encodings.s
@@ -1,4 +1,4 @@
-# RUN: llvm-mc -show-encoding -triple=wasm32-unkown-unknown -mattr=+simd128-unimplemented < %s | FileCheck %s
+# RUN: llvm-mc -show-encoding -triple=wasm32-unkown-unknown -mattr=+sign-ext,+simd128 < %s | FileCheck %s
 
 main:
     .functype main () -> ()
diff --git a/test/MC/WebAssembly/types.ll b/test/MC/WebAssembly/types.ll
index e91cef6..b801242 100644
--- a/test/MC/WebAssembly/types.ll
+++ b/test/MC/WebAssembly/types.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mattr=+simd128-unimplemented -filetype=obj %s -o - | obj2yaml | FileCheck %s
+; RUN: llc -wasm-enable-unimplemented-simd -mattr=+sign-ext,+simd128 -filetype=obj %s -o - | obj2yaml | FileCheck %s
 
 target triple = "wasm32-unknown-unknown"