[WebAssembly] Add missing feature methods

Author: aheejin

llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td

@@ -78,6 +78,10 @@ def HasMultiMemory :
     Predicate<"Subtarget->hasMultiMemory()">,
     AssemblerPredicate<(all_of FeatureMultiMemory), "multimemory">;
 
+def HasMutableGlobals:
+    Predicate<"Subtarget->hasMutableGlobals()">,
+    AssemblerPredicate<(all_of FeatureMutableGlobals), "mutable-globals">;
+
 //===----------------------------------------------------------------------===//
 // WebAssembly-specific DAG Node Types.
 //===----------------------------------------------------------------------===//

llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h

@@ -105,6 +105,7 @@ class WebAssemblySubtarget final : public WebAssemblyGenSubtargetInfo {
   bool hasTailCall() const { return HasTailCall; }
   bool hasReferenceTypes() const { return HasReferenceTypes; }
   bool hasMultiMemory() const { return HasMultiMemory; }
+  bool hasExtendedConst() const { return HasExtendedConst; }
 
   /// Parses features string setting specified subtarget options. Definition of
   /// function is auto generated by tblgen.