[Wasm GC] Add array support to TypeMerging (#5329)

2 files changed, 55 insertions, 15 deletions

diff --git a/src/passes/TypeMerging.cpp b/src/passes/TypeMerging.cpp
index 94a198adf..0fc766f4e 100644
--- a/src/passes/TypeMerging.cpp
+++ b/src/passes/TypeMerging.cpp
@@ -149,22 +149,21 @@ struct TypeMerging : public Pass {
         continue;
       }
 
-      // TODO: arrays
-      if (!type.isStruct()) {
-        continue;
-      }
-
-      auto& fields = type.getStruct().fields;
-      auto& superFields = super->getStruct().fields;
-      if (fields != superFields) {
-        // This adds a field, or refines one, so it differs from the super, and
-        // we cannot merge it with the super.
-        continue;
+      if (type.isStruct()) {
+        auto& fields = type.getStruct().fields;
+        auto& superFields = super->getStruct().fields;
+        if (fields == superFields) {
+          // We can merge! This is identical structurally to the super, and also
+          // not distinguishable nominally.
+          merges[type] = *super;
+        }
+      } else if (type.isArray()) {
+        auto element = type.getArray().element;
+        auto superElement = super->getArray().element;
+        if (element == superElement) {
+          merges[type] = *super;
+        }
       }
-
-      // We can merge! This is identical structurally to the super, and also not
-      // distinguishable nominally.
-      merges[type] = *super;
     }
 
     if (merges.empty()) {
diff --git a/test/lit/passes/type-merging.wast b/test/lit/passes/type-merging.wast
index 4df8d7e88..f28cf0e1d 100644
--- a/test/lit/passes/type-merging.wast
+++ b/test/lit/passes/type-merging.wast
@@ -235,3 +235,44 @@
     )
   )
 )
+
+;; Arrays
+(module
+  ;; CHECK:      (type $none_=>_none (func))
+
+  ;; CHECK:      (type $intarray (array (mut i32)))
+  (type $intarray (array (mut i32)))
+  (type $sub-intarray (array_subtype (mut i32) $intarray))
+
+  ;; CHECK:      (type $refarray (array anyref))
+  (type $refarray (array (ref null any)))
+  (type $sub-refarray    (array_subtype (ref null any) $refarray))
+  ;; CHECK:      (type $sub-refarray-nn (array_subtype (ref any) $refarray))
+  (type $sub-refarray-nn (array_subtype (ref      any) $refarray))
+
+  ;; CHECK:      (func $foo (type $none_=>_none)
+  ;; CHECK-NEXT:  (local $a (ref null $intarray))
+  ;; CHECK-NEXT:  (local $b (ref null $intarray))
+  ;; CHECK-NEXT:  (nop)
+  ;; CHECK-NEXT: )
+  (func $foo
+    ;; $A will remain the same.
+    (local $a (ref null $intarray))
+    ;; $B can be merged into $A.
+    (local $b (ref null $sub-intarray))
+  )
+
+  ;; CHECK:      (func $bar (type $none_=>_none)
+  ;; CHECK-NEXT:  (local $a (ref null $refarray))
+  ;; CHECK-NEXT:  (local $b (ref null $refarray))
+  ;; CHECK-NEXT:  (local $c (ref null $sub-refarray-nn))
+  ;; CHECK-NEXT:  (nop)
+  ;; CHECK-NEXT: )
+  (func $bar
+    (local $a (ref null $refarray))
+    ;; $B can be merged into $A.
+    (local $b (ref null $sub-refarray))
+    ;; $C cannot be merged as the element type is more refined.
+    (local $c (ref null $sub-refarray-nn))
+  )
+)