Update exception handling support to current proposal (#1596)

This PR updates the support of exception handling to the latest proposal (that is compatible with future 2-phase exception handling) described in https://github.com/WebAssembly/exception-handling/pull/137 and https://github.com/WebAssembly/exception-handling/pull/143.

* Adds back tagged `catch $e`, `catch_all`, and `rethrow N` from a previous version of wabt, but with updates to match the current spec (e.g., `catch_all` shares an opcode with `else`, `rethrow`'s depth indexes only catch blocks, etc).
* Adds `unwind` and `delegate` instructions.
* Removes `exnref` and `br_on_exn`.
* Updates relevant tests.

There are some details that could still change (e.g., maybe how `delegate`'s depth is validated), but I'd be happy to submit further PRs if the spec details change.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/interp/istream.cc b/src/interp/istream.cc
index e4693c11..6c531a88 100644
--- a/src/interp/istream.cc
+++ b/src/interp/istream.cc
@@ -692,8 +692,8 @@ Instr Istream::Read(Offset* offset) const {
       break;
 
     case Opcode::Block:
-    case Opcode::BrOnExn:
     case Opcode::Catch:
+    case Opcode::Delegate:
     case Opcode::Else:
     case Opcode::End:
     case Opcode::If:
@@ -703,6 +703,7 @@ Instr Istream::Read(Offset* offset) const {
     case Opcode::Rethrow:
     case Opcode::Throw:
     case Opcode::Try:
+    case Opcode::Unwind:
     case Opcode::ReturnCall:
       // Not used.
       break;