[WebAssembly] Add except_ref as a first-class type

Summary: Add except_ref as a first-class type, according to the [[https://github.com/WebAssembly/exception-handling/blob/master/proposals/Level-1.md | Level 1 exception handling proposal ]].

Reviewers: dschuff

Subscribers: jfb, sbc100, llvm-commits

Differential Revision: https://reviews.llvm.org/D43706

llvm-svn: 326985
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
index e27a740..364aac3 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
@@ -159,18 +159,19 @@
 
 /// This is used to indicate block signatures.
 enum class ExprType : unsigned {
-  Void    = 0x40,
-  I32     = 0x7F,
-  I64     = 0x7E,
-  F32     = 0x7D,
-  F64     = 0x7C,
-  I8x16   = 0x7B,
-  I16x8   = 0x7A,
-  I32x4   = 0x79,
-  F32x4   = 0x78,
-  B8x16   = 0x77,
-  B16x8   = 0x76,
-  B32x4   = 0x75
+  Void      = 0x40,
+  I32       = 0x7F,
+  I64       = 0x7E,
+  F32       = 0x7D,
+  F64       = 0x7C,
+  I8x16     = 0x7B,
+  I16x8     = 0x7A,
+  I32x4     = 0x79,
+  F32x4     = 0x78,
+  B8x16     = 0x77,
+  B16x8     = 0x76,
+  B32x4     = 0x75,
+  ExceptRef = 0x68
 };
 
 /// Instruction opcodes emitted via means other than CodeGen.