[WebAssembly] Add skeleton MC support for the Wasm container format

This just adds the basic skeleton for supporting a new object file format.
All of the actual encoding will be implemented in followup patches.

Differential Revision: https://reviews.llvm.org/D26722

llvm-svn: 295803
diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 2493e71..f27957c 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5484,7 +5484,8 @@
   enum {
     COFF = (1 << MCObjectFileInfo::IsCOFF),
     ELF = (1 << MCObjectFileInfo::IsELF),
-    MACHO = (1 << MCObjectFileInfo::IsMachO)
+    MACHO = (1 << MCObjectFileInfo::IsMachO),
+    WASM = (1 << MCObjectFileInfo::IsWasm),
   };
   static const struct PrefixEntry {
     const char *Spelling;
@@ -5518,6 +5519,9 @@
   case MCObjectFileInfo::IsCOFF:
     CurrentFormat = COFF;
     break;
+  case MCObjectFileInfo::IsWasm:
+    CurrentFormat = WASM;
+    break;
   }
 
   if (~Prefix->SupportedFormats & CurrentFormat) {