[WebAssembly] Add unimplemented-simd128 subtarget feature

Summary:
This is a third attempt, but this time we have vetted it on Windows
first. The previous errors were due to an uninitialized class member.

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, sunfish, jfb, llvm-commits

Differential Revision: https://reviews.llvm.org/D56560

llvm-svn: 350901
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
index a452a00..527908d 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyFastISel.cpp
@@ -44,8 +44,6 @@
 
 #define DEBUG_TYPE "wasm-fastisel"
 
-extern cl::opt<bool> EnableUnimplementedWasmSIMDInstrs;
-
 namespace {
 
 class WebAssemblyFastISel final : public FastISel {
@@ -145,7 +143,7 @@
       break;
     case MVT::v2i64:
     case MVT::v2f64:
-      if (Subtarget->hasSIMD128() && EnableUnimplementedWasmSIMDInstrs)
+      if (Subtarget->hasUnimplementedSIMD128())
         return VT;
       break;
     default: