[WebAssembly] Add bulk memory target feature

Summary: Also clean up some preexisting target feature code.

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, jfb

Differential Revision: https://reviews.llvm.org/D57495

llvm-svn: 352793
diff --git a/llvm/lib/Target/WebAssembly/WebAssembly.td b/llvm/lib/Target/WebAssembly/WebAssembly.td
index bb0cae9..230c120 100644
--- a/llvm/lib/Target/WebAssembly/WebAssembly.td
+++ b/llvm/lib/Target/WebAssembly/WebAssembly.td
@@ -47,6 +47,10 @@
       SubtargetFeature<"exception-handling", "HasExceptionHandling", "true",
                        "Enable Wasm exception handling">;
 
+def FeatureBulkMemory :
+      SubtargetFeature<"bulk-memory", "HasBulkMemory", "true",
+                       "Enable bulk memory operations">;
+
 //===----------------------------------------------------------------------===//
 // Architectures.
 //===----------------------------------------------------------------------===//