Add support for reference types proposal (#2451)

This adds support for the reference type proposal. This includes support
for all reference types (`anyref`, `funcref`(=`anyfunc`), and `nullref`)
and four new instructions: `ref.null`, `ref.is_null`, `ref.func`, and
new typed `select`. This also adds subtype relationship support between
reference types.

This does not include table instructions yet. This also does not include
wasm2js support.

Fixes #2444 and fixes #2447.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 6de1d3d00..edd6ba2b6 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -751,12 +751,12 @@ struct OptimizeInstructions
           // condition, do that
           auto needCondition =
             EffectAnalyzer(getPassOptions(), iff->condition).hasSideEffects();
-          auto typeIsIdentical = iff->ifTrue->type == iff->type;
-          if (typeIsIdentical && !needCondition) {
+          auto isSubType = Type::isSubType(iff->ifTrue->type, iff->type);
+          if (isSubType && !needCondition) {
             return iff->ifTrue;
           } else {
             Builder builder(*getModule());
-            if (typeIsIdentical) {
+            if (isSubType) {
               return builder.makeSequence(builder.makeDrop(iff->condition),
                                           iff->ifTrue);
             } else {