Revert "[WebAssembly] Add unimplemented-simd128 subtarget feature"

This reverts L350778.

llvm-svn: 350789
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
index 2f9e719..d172537 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td
+++ b/llvm/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->hasUnimplementedSIMD128()">,
-    AssemblerPredicate<"FeatureUnimplementedSIMD128", "unimplemented-simd128">;
+def HasUnimplementedSIMD : Predicate<"EnableUnimplementedWasmSIMDInstrs">;
 def HasAtomics : Predicate<"Subtarget->hasAtomics()">,
                            AssemblerPredicate<"FeatureAtomics", "atomics">;
 def HasNontrappingFPToInt :