Add br_on_exn instruction (#1016)

It takes two u32 immediates: the branch depth and an exception index. The
stack signature is `[expect_ref] -> [except_ref]`, so the `except_ref`
can be tested easily against multiple exception types.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/binary-reader-ir.cc b/src/binary-reader-ir.cc
index 4a5ce416..a60de398 100644
--- a/src/binary-reader-ir.cc
+++ b/src/binary-reader-ir.cc
@@ -137,6 +137,7 @@ class BinaryReaderIR : public BinaryReaderNop {
   Result OnBlockExpr(Type sig_type) override;
   Result OnBrExpr(Index depth) override;
   Result OnBrIfExpr(Index depth) override;
+  Result OnBrOnExnExpr(Index depth, Index event_index) override;
   Result OnBrTableExpr(Index num_targets,
                        Index* target_depths,
                        Index default_target_depth) override;
@@ -649,6 +650,13 @@ Result BinaryReaderIR::OnBrIfExpr(Index depth) {
   return AppendExpr(MakeUnique<BrIfExpr>(Var(depth)));
 }
 
+Result BinaryReaderIR::OnBrOnExnExpr(Index depth, Index event_index) {
+  auto expr = MakeUnique<BrOnExnExpr>();
+  expr->label_var = Var(depth);
+  expr->event_var = Var(event_index);
+  return AppendExpr(std::move(expr));
+}
+
 Result BinaryReaderIR::OnBrTableExpr(Index num_targets,
                                      Index* target_depths,
                                      Index default_target_depth) {