[WebAssembly] Use Windows EH instructions for Wasm EH

Summary:
Because wasm control flow needs to be structured, using WinEH
instructions to support wasm EH brings several benefits. This patch
makes wasm EH uses Windows EH instructions, with some changes:
1. Because wasm uses a single catch block to catch all C++ exceptions,
   this merges all catch clauses into a single catchpad, within which we
   test the EH selector as in Itanium EH.
2. Generates a call to `__clang_call_terminate` in case a cleanup
   throws. Wasm does not have a runtime to handle this.
3. In case there is no catch-all clause, inserts a call to
   `__cxa_rethrow` at the end of a catchpad in order to unwind to an
   enclosing EH scope.

Reviewers: majnemer, dschuff

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

Differential Revision: https://reviews.llvm.org/D44931

llvm-svn: 333703

1 files changed, 2 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 56b07e5f853..3ee66b007b4 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -877,7 +877,8 @@ public:
 
   llvm::BasicBlock *getEHResumeBlock(bool isCleanup);
   llvm::BasicBlock *getEHDispatchBlock(EHScopeStack::stable_iterator scope);
-  llvm::BasicBlock *getMSVCDispatchBlock(EHScopeStack::stable_iterator scope);
+  llvm::BasicBlock *
+  getFuncletEHDispatchBlock(EHScopeStack::stable_iterator scope);
 
   /// An object to manage conditionally-evaluated expressions.
   class ConditionalEvaluation {