[WebAssembly] Add exception handling option and feature

Summary:
Add a llc command line option and WebAssembly architecture feature for
exception handling.

Reviewers: dschuff

Subscribers: jfb, sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D43683

llvm-svn: 326004
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp b/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp
index 78602a3..6addaa3 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.cpp
@@ -42,8 +42,8 @@
                                            const TargetMachine &TM)
     : WebAssemblyGenSubtargetInfo(TT, CPU, FS), HasSIMD128(false),
       HasAtomics(false), HasNontrappingFPToInt(false), HasSignExt(false),
-      CPUString(CPU), TargetTriple(TT), FrameLowering(),
-      InstrInfo(initializeSubtargetDependencies(FS)), TSInfo(),
+      HasExceptionHandling(false), CPUString(CPU), TargetTriple(TT),
+      FrameLowering(), InstrInfo(initializeSubtargetDependencies(FS)), TSInfo(),
       TLInfo(TM, *this) {}
 
 bool WebAssemblySubtarget::enableMachineScheduler() const {