[EH][GC] Send a non-nullable exnref from TryTable (#7013)

When EH+GC are enabled then wasm has non-nullable types, and the
sent exnref should be non-nullable. In BinaryenIR we use the non-
nullable type all the time, which we also do for function references
and other things; we lower it if GC is not enabled to a nullable type
for the binary format (see `WasmBinaryWriter::writeType`, to which
comments were added in this PR). That is, this PR makes us handle
exnref the same as those other types.

A new test verifies that behavior. Various existing tests are updated
because ReFinalize will now use the more refined type, so this is
an optimization. It is also a bugfix as in #6987 we started to emit
the refined form in the fuzzer, and this PR makes us handle it
properly in validation and ReFinalization.

1 files changed, 27 insertions, 0 deletions

diff --git a/test/lit/basic/exception-handling-no-gc.wast b/test/lit/basic/exception-handling-no-gc.wast
new file mode 100644
index 000000000..4ab0708c4
--- /dev/null
+++ b/test/lit/basic/exception-handling-no-gc.wast
@@ -0,0 +1,27 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+
+;; Test that we do not emit an invalid (ref exn) when exceptions are enabled
+;; but not GC. GC is required for us to be non-nullable.
+
+;; RUN: wasm-opt %s --enable-reference-types --enable-exception-handling --disable-gc --roundtrip -S -o - | filecheck %s
+
+(module
+ ;; CHECK:      (func $test (result exnref)
+ ;; CHECK-NEXT:  (block $label$1 (result exnref)
+ ;; CHECK-NEXT:   (try_table (catch_all_ref $label$1)
+ ;; CHECK-NEXT:    (unreachable)
+ ;; CHECK-NEXT:   )
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $test (result exnref)
+  ;; It is valid to write (ref exn) in Binaryen IR, and internally that is how
+  ;; we represent things, but when we emit the binary we emit a nullable type,
+  ;; so after the roundtrip we are less refined.
+  (block $label (result (ref exn))
+   (try_table (catch_all_ref $label)
+    (unreachable)
+   )
+  )
+ )
+)
+