[GC] Add br_on_func/data/i31 (#3525)

This expands the existing BrOnCast into BrOn that can also handle the
func/data/i31 variants. This is not as elegant as RefIs / RefAs in that BrOnCast
has an extra rtt field, but I think it is still the best option. We already have optional
fields on Break (the value and condition), so making rtt optional is not odd. And
it allows us to share all the behavior of br_on_* which aside from the cast or the
check itself, is identical - returning the value if the branch is not taken, etc.

1 files changed, 18 insertions, 4 deletions

diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index 1e4ff6e3e..a62435412 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -931,15 +931,29 @@ void RefCast::finalize() {
 
 Type RefCast::getCastType() { return doGetCastType(this); }
 
-void BrOnCast::finalize() {
-  if (ref->type == Type::unreachable || rtt->type == Type::unreachable) {
+void BrOn::finalize() {
+  if (ref->type == Type::unreachable ||
+      (rtt && rtt->type == Type::unreachable)) {
     type = Type::unreachable;
   } else {
     type = ref->type;
   }
 }
 
-Type BrOnCast::getCastType() { return Type(rtt->type.getHeapType(), Nullable); }
+Type BrOn::getCastType() {
+  switch (op) {
+    case BrOnCast:
+      return Type(rtt->type.getHeapType(), Nullable);
+    case BrOnFunc:
+      return Type::funcref;
+    case BrOnData:
+      return Type::dataref;
+    case BrOnI31:
+      return Type::i31ref;
+    default:
+      WASM_UNREACHABLE("invalid br_on_*");
+  }
+}
 
 void RttCanon::finalize() {
   // Nothing to do - the type must have been set already during construction.
@@ -1032,7 +1046,7 @@ void RefAs::finalize() {
       type = Type::i31ref;
       break;
     default:
-      WASM_UNREACHABLE("unimplemented ref.is_*");
+      WASM_UNREACHABLE("invalid ref.as_*");
   }
 }