Support subtyping in tail calls

src/wasm/wasm-validator.cpp

@@ -460,9 +460,9 @@ struct FunctionValidator : public WalkerPass<PostWalker<FunctionValidator>> {
                     Type(Type::unreachable),
                     curr,
                     "return_call* should have unreachable type");
-      shouldBeEqual(
-        getFunction()->getResults(),
+      shouldBeSubType(
         sig.results,
+        getFunction()->getResults(),
         curr,
         "return_call* callee return type must match caller return type");
     } else {
@@ -798,9 +798,11 @@ void FunctionValidator::visitCallIndirect(CallIndirect* curr) {
   if (curr->target->type != Type::unreachable) {
     auto* table = getModule()->getTableOrNull(curr->table);
     shouldBeTrue(!!table, curr, "call-indirect table must exist");
-    shouldBeTrue(table->type.isFunction(),
-                 curr,
-                 "call-indirect table must be of function type.");
+    if (table) {
+      shouldBeTrue(table->type.isFunction(),
+                   curr,
+                   "call-indirect table must be of function type.");
+    }
   }
 
   validateCallParamsAndResult(curr, curr->sig);

test/lit/tail-call.wast

@@ -0,0 +1,78 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+
+;; Check that tail calls are parsed, validated, and printed correctly
+
+;; RUN: foreach %s %t wasm-opt -all -S -o - | filecheck %s
+;; TODO: --nominal as well
+
+(module
+
+  ;; CHECK:      (type $void (func))
+  (type $void (func))
+
+  ;; CHECK:      (table $t 1 1 funcref)
+  (table $t 1 1 funcref)
+
+  ;; CHECK:      (elem $e (i32.const 0) $foo)
+  (elem $e (i32.const 0) $foo)
+
+  ;; CHECK:      (func $foo
+  ;; CHECK-NEXT:  (return_call $bar)
+  ;; CHECK-NEXT: )
+  (func $foo
+    (return_call $bar)
+  )
+
+  ;; CHECK:      (func $bar
+  ;; CHECK-NEXT:  (return_call_indirect $t (type $void)
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $bar
+    (return_call_indirect (type $void) (i32.const 0))
+  )
+)
+
+;; Check GC types and subtyping
+(module
+  ;; CHECK:      (type $return-B (func (result (ref $B))))
+  (type $return-B (func (result (ref $B))))
+
+  ;; CHECK:      (type $return-A (func (result (ref null $A))))
+  (type $return-A (func (result (ref null $A))))
+
+  ;; CHECK:      (type $A (struct (field i32)))
+  (type $A (struct i32))
+
+  ;; CHECK:      (type $B (struct (field i32) (field i32)))
+  (type $B (struct i32 i32) (supertype $A))
+
+  ;; CHECK:      (table $t 1 1 funcref)
+  (table $t 1 1 funcref)
+
+  ;; CHECK:      (elem $e (i32.const 0) $callee)
+  (elem $e (i32.const 0) $callee)
+
+  ;; CHECK:      (func $caller (result (ref null $A))
+  ;; CHECK-NEXT:  (return_call $callee)
+  ;; CHECK-NEXT: )
+  (func $caller (type $return-A)
+    (return_call $callee)
+  )
+
+  ;; CHECK:      (func $caller-indirect (result (ref $B))
+  ;; CHECK-NEXT:  (return_call_indirect $t (type $return-B)
+  ;; CHECK-NEXT:   (i32.const 0)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $caller-indirect (type $return-B)
+    (return_call_indirect $t (type $return-B) (i32.const 0))
+  )
+
+  ;; CHECK:      (func $callee (result (ref $B))
+  ;; CHECK-NEXT:  (unreachable)
+  ;; CHECK-NEXT: )
+  (func $callee (type $return-B)
+    (unreachable)
+  )
+)