Represent ref.as_{func,data,i31} with RefCast (#5413)

These operations are deprecated and directly representable as casts, so remove
their opcodes in the internal IR and parse them as casts instead. For now, add
logic to the printing and binary writing of RefCast to continue emitting the
legacy instructions to minimize test changes. The few test changes necessary are
because it is no longer valid to perform a ref.as_func on values outside the
func type hierarchy now that ref.as_func is subject to the ref.cast validation
rules.

RefAsExternInternalize, RefAsExternExternalize, and RefAsNonNull are left
unmodified. A future PR may remove RefAsNonNull as well, since it is also
expressible with casts.

16 files changed, 91 insertions, 145 deletions

diff --git a/src/binaryen-c.cpp b/src/binaryen-c.cpp
index 416c8d45b..e37270f61 100644
--- a/src/binaryen-c.cpp
+++ b/src/binaryen-c.cpp
@@ -1009,9 +1009,6 @@ BinaryenOp BinaryenPromoteLowVecF32x4ToVecF64x2(void) {
 }
 BinaryenOp BinaryenSwizzleVecI8x16(void) { return SwizzleVecI8x16; }
 BinaryenOp BinaryenRefAsNonNull(void) { return RefAsNonNull; }
-BinaryenOp BinaryenRefAsFunc(void) { return RefAsFunc; }
-BinaryenOp BinaryenRefAsData(void) { return RefAsData; }
-BinaryenOp BinaryenRefAsI31(void) { return RefAsI31; }
 BinaryenOp BinaryenRefAsExternInternalize(void) { return ExternInternalize; }
 BinaryenOp BinaryenRefAsExternExternalize(void) { return ExternExternalize; }
 BinaryenOp BinaryenBrOnNull(void) { return BrOnNull; }
diff --git a/src/binaryen-c.h b/src/binaryen-c.h
index 2c861a141..b9f78e2a7 100644
--- a/src/binaryen-c.h
+++ b/src/binaryen-c.h
@@ -671,9 +671,6 @@ BINARYEN_API BinaryenOp BinaryenDemoteZeroVecF64x2ToVecF32x4(void);
 BINARYEN_API BinaryenOp BinaryenPromoteLowVecF32x4ToVecF64x2(void);
 BINARYEN_API BinaryenOp BinaryenSwizzleVecI8x16(void);
 BINARYEN_API BinaryenOp BinaryenRefAsNonNull(void);
-BINARYEN_API BinaryenOp BinaryenRefAsFunc(void);
-BINARYEN_API BinaryenOp BinaryenRefAsData(void);
-BINARYEN_API BinaryenOp BinaryenRefAsI31(void);
 BINARYEN_API BinaryenOp BinaryenRefAsExternInternalize(void);
 BINARYEN_API BinaryenOp BinaryenRefAsExternExternalize(void);
 BINARYEN_API BinaryenOp BinaryenBrOnNull(void);
diff --git a/src/gen-s-parser.inc b/src/gen-s-parser.inc
index 70644827c..dbf3b71bf 100644
--- a/src/gen-s-parser.inc
+++ b/src/gen-s-parser.inc
@@ -3000,13 +3000,13 @@ switch (buf[0]) {
           case 'a': {
             switch (buf[7]) {
               case 'd':
-                if (op == "ref.as_data"sv) { return makeRefAs(s, RefAsData); }
+                if (op == "ref.as_data"sv) { return makeRefCast(s, Type(HeapType::data, NonNullable)); }
                 goto parse_error;
               case 'f':
-                if (op == "ref.as_func"sv) { return makeRefAs(s, RefAsFunc); }
+                if (op == "ref.as_func"sv) { return makeRefCast(s, Type(HeapType::func, NonNullable)); }
                 goto parse_error;
               case 'i':
-                if (op == "ref.as_i31"sv) { return makeRefAs(s, RefAsI31); }
+                if (op == "ref.as_i31"sv) { return makeRefCast(s, Type(HeapType::i31, NonNullable)); }
                 goto parse_error;
               case 'n':
                 if (op == "ref.as_non_null"sv) { return makeRefAs(s, RefAsNonNull); }
@@ -8599,21 +8599,21 @@ switch (buf[0]) {
             switch (buf[7]) {
               case 'd':
                 if (op == "ref.as_data"sv) {
-                  auto ret = makeRefAs(ctx, pos, RefAsData);
+                  auto ret = makeRefCast(ctx, pos, Type(HeapType::data, NonNullable));
                   CHECK_ERR(ret);
                   return *ret;
                 }
                 goto parse_error;
               case 'f':
                 if (op == "ref.as_func"sv) {
-                  auto ret = makeRefAs(ctx, pos, RefAsFunc);
+                  auto ret = makeRefCast(ctx, pos, Type(HeapType::func, NonNullable));
                   CHECK_ERR(ret);
                   return *ret;
                 }
                 goto parse_error;
               case 'i':
                 if (op == "ref.as_i31"sv) {
-                  auto ret = makeRefAs(ctx, pos, RefAsI31);
+                  auto ret = makeRefCast(ctx, pos, Type(HeapType::i31, NonNullable));
                   CHECK_ERR(ret);
                   return *ret;
                 }
diff --git a/src/ir/gc-type-utils.h b/src/ir/gc-type-utils.h
index c8f2b26af..318b1b3a3 100644
--- a/src/ir/gc-type-utils.h
+++ b/src/ir/gc-type-utils.h
@@ -119,28 +119,6 @@ inline EvaluationResult evaluateKindCheck(Expression* curr) {
         WASM_UNREACHABLE("unhandled BrOn");
     }
     child = br->ref;
-  } else if (auto* as = curr->dynCast<RefAs>()) {
-    switch (as->op) {
-      // We don't check nullability here.
-      case RefAsNonNull:
-        return Unknown;
-      case RefAsFunc:
-        expected = Func;
-        break;
-      case RefAsData:
-        expected = Data;
-        break;
-      case RefAsI31:
-        expected = I31;
-        break;
-      case ExternInternalize:
-      case ExternExternalize:
-        // These instructions can never be removed.
-        return Unknown;
-      default:
-        WASM_UNREACHABLE("unhandled RefAs");
-    }
-    child = as->value;
   } else {
     WASM_UNREACHABLE("invalid input to evaluateKindCheck");
   }
diff --git a/src/js/binaryen.js-post.js b/src/js/binaryen.js-post.js
index 2a08c5e5a..da121e23a 100644
--- a/src/js/binaryen.js-post.js
+++ b/src/js/binaryen.js-post.js
@@ -550,9 +550,6 @@ function initializeConstants() {
     'PromoteLowVecF32x4ToVecF64x2',
     'SwizzleVecI8x16',
     'RefAsNonNull',
-    'RefAsFunc',
-    'RefAsData',
-    'RefAsI31',
     'RefAsExternInternalize',
     'RefAsExternExternalize',
     'BrOnNull',
@@ -2345,15 +2342,6 @@ function wrapModule(module, self = {}) {
     'as_non_null'(value) {
       return Module['_BinaryenRefAs'](module, Module['RefAsNonNull'], value);
     },
-    'as_func'(value) {
-      return Module['_BinaryenRefAs'](module, Module['RefAsFunc'], value);
-    },
-    'as_data'(value) {
-      return Module['_BinaryenRefAs'](module, Module['RefAsData'], value);
-    },
-    'as_i31'(value) {
-      return Module['_BinaryenRefAs'](module, Module['RefAsI31'], value);
-    },
     'func'(func, type) {
       return preserveStack(() => Module['_BinaryenRefFunc'](module, strToStack(func), type));
     },
diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 884afcdd4..e8c6dc1fe 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -2118,35 +2118,13 @@ struct OptimizeInstructions
 
     if (curr->op == ExternExternalize || curr->op == ExternInternalize) {
       // We can't optimize these. Even removing a non-null cast is not valid as
-      // they allow nulls to filter through, unlike other RefAs*
+      // they allow nulls to filter through, unlike other RefAs*.
       return;
     }
 
+    assert(curr->op == RefAsNonNull);
     skipNonNullCast(curr->value);
-
-    // Check if the type is the kind we are checking for.
-    auto result = GCTypeUtils::evaluateKindCheck(curr);
-
-    if (result == GCTypeUtils::Success) {
-      // We know the kind is correct, so all that is left is a check for
-      // non-nullability, which we do lower down.
-      curr->op = RefAsNonNull;
-    } else if (result == GCTypeUtils::Failure) {
-      // This is the wrong kind, so it will trap. The binaryen optimizer does
-      // not differentiate traps, so we can perform a replacement here. We
-      // replace 2 bytes of ref.as_* with one byte of unreachable and one of a
-      // drop, which is no worse, and the value and the drop can be optimized
-      // out later if the value has no side effects.
-      Builder builder(*getModule());
-      // Make sure to emit a block with the same type as us; leave updating
-      // types for other passes.
-      replaceCurrent(builder.makeBlock(
-        {builder.makeDrop(curr->value), builder.makeUnreachable()},
-        curr->type));
-      return;
-    }
-
-    if (curr->op == RefAsNonNull && !curr->value->type.isNullable()) {
+    if (!curr->value->type.isNullable()) {
       replaceCurrent(curr->value);
       return;
     }
diff --git a/src/passes/Print.cpp b/src/passes/Print.cpp
index 12c185e69..e0d9a46a3 100644
--- a/src/passes/Print.cpp
+++ b/src/passes/Print.cpp
@@ -2122,6 +2122,23 @@ struct PrintExpressionContents
     if (curr->safety == RefCast::Unsafe) {
       printMedium(o, "ref.cast_nop ");
     } else {
+      // TODO: These instructions are deprecated. Remove them.
+      if (auto type = curr->type.getHeapType();
+          type.isBasic() && curr->type.isNonNullable()) {
+        switch (type.getBasic()) {
+          case HeapType::func:
+            printMedium(o, "ref.as_func");
+            return;
+          case HeapType::data:
+            printMedium(o, "ref.as_data");
+            return;
+          case HeapType::i31:
+            printMedium(o, "ref.as_i31");
+            return;
+          default:
+            break;
+        }
+      }
       if (curr->type.isNullable()) {
         printMedium(o, "ref.cast null ");
       } else {
@@ -2329,15 +2346,6 @@ struct PrintExpressionContents
       case RefAsNonNull:
         printMedium(o, "ref.as_non_null");
         break;
-      case RefAsFunc:
-        printMedium(o, "ref.as_func");
-        break;
-      case RefAsData:
-        printMedium(o, "ref.as_data");
-        break;
-      case RefAsI31:
-        printMedium(o, "ref.as_i31");
-        break;
       case ExternInternalize:
         printMedium(o, "extern.internalize");
         break;
diff --git a/src/wasm-binary.h b/src/wasm-binary.h
index 1a3e5c82b..b2e1ef0c6 100644
--- a/src/wasm-binary.h
+++ b/src/wasm-binary.h
@@ -1748,6 +1748,7 @@ public:
   void visitThrow(Throw* curr);
   void visitRethrow(Rethrow* curr);
   void visitCallRef(CallRef* curr);
+  void visitRefAsCast(RefCast* curr, uint32_t code);
   void visitRefAs(RefAs* curr, uint8_t code);
 
   [[noreturn]] void throwError(std::string text);
diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index 104f06585..43b001f35 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -1787,29 +1787,12 @@ public:
     switch (curr->op) {
       case RefAsNonNull:
         // We've already checked for a null.
-        break;
-      case RefAsFunc:
-        if (!value.type.isFunction()) {
-          trap("not a func");
-        }
-        break;
-      case RefAsData:
-        if (!value.isData()) {
-          trap("not a data");
-        }
-        break;
-      case RefAsI31:
-        if (value.type.getHeapType() != HeapType::i31) {
-          trap("not an i31");
-        }
-        break;
+        return value;
       case ExternInternalize:
       case ExternExternalize:
         WASM_UNREACHABLE("unimplemented extern conversion");
-      default:
-        WASM_UNREACHABLE("unimplemented ref.as_*");
     }
-    return value;
+    WASM_UNREACHABLE("unimplemented ref.as_*");
   }
   Flow visitStringNew(StringNew* curr) { WASM_UNREACHABLE("unimp"); }
   Flow visitStringConst(StringConst* curr) { WASM_UNREACHABLE("unimp"); }
diff --git a/src/wasm-s-parser.h b/src/wasm-s-parser.h
index 6ae3e57be..013730c52 100644
--- a/src/wasm-s-parser.h
+++ b/src/wasm-s-parser.h
@@ -285,7 +285,8 @@ private:
   Expression* makeI31Get(Element& s, bool signed_);
   Expression* makeRefTest(Element& s,
                           std::optional<Type> castType = std::nullopt);
-  Expression* makeRefCast(Element& s);
+  Expression* makeRefCast(Element& s,
+                          std::optional<Type> castType = std::nullopt);
   Expression* makeRefCastNop(Element& s);
   Expression* makeBrOnNull(Element& s, bool onFail = false);
   Expression*
@@ -302,6 +303,7 @@ private:
   Expression* makeArrayLen(Element& s);
   Expression* makeArrayCopy(Element& s);
   Expression* makeRefAs(Element& s, RefAsOp op);
+  Expression* makeRefAsNonNull(Element& s);
   Expression* makeStringNew(Element& s, StringNewOp op);
   Expression* makeStringConst(Element& s);
   Expression* makeStringMeasure(Element& s, StringMeasureOp op);
diff --git a/src/wasm.h b/src/wasm.h
index 7b75ec3b8..f7683e6bb 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -559,9 +559,6 @@ enum SIMDTernaryOp {
 
 enum RefAsOp {
   RefAsNonNull,
-  RefAsFunc,
-  RefAsData,
-  RefAsI31,
   ExternInternalize,
   ExternExternalize,
 };
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index b1f4b8907..767e0c2ab 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -4032,8 +4032,12 @@ BinaryConsts::ASTNodes WasmBinaryBuilder::readExpression(Expression*& curr) {
       }
       if (opcode == BinaryConsts::RefAsFunc ||
           opcode == BinaryConsts::RefAsData ||
-          opcode == BinaryConsts::RefAsI31 ||
-          opcode == BinaryConsts::ExternInternalize ||
+          opcode == BinaryConsts::RefAsI31) {
+        visitRefAsCast((curr = allocator.alloc<RefCast>())->cast<RefCast>(),
+                       opcode);
+        break;
+      }
+      if (opcode == BinaryConsts::ExternInternalize ||
           opcode == BinaryConsts::ExternExternalize) {
         visitRefAs((curr = allocator.alloc<RefAs>())->cast<RefAs>(), opcode);
         break;
@@ -6910,6 +6914,26 @@ bool WasmBinaryBuilder::maybeVisitRefTest(Expression*& out, uint32_t code) {
   return false;
 }
 
+void WasmBinaryBuilder::visitRefAsCast(RefCast* curr, uint32_t code) {
+  // TODO: These instructions are deprecated. Remove them.
+  switch (code) {
+    case BinaryConsts::RefAsFunc:
+      curr->type = Type(HeapType::func, NonNullable);
+      break;
+    case BinaryConsts::RefAsData:
+      curr->type = Type(HeapType::data, NonNullable);
+      break;
+    case BinaryConsts::RefAsI31:
+      curr->type = Type(HeapType::i31, NonNullable);
+      break;
+    default:
+      WASM_UNREACHABLE("unexpected ref.as*");
+  }
+  curr->ref = popNonVoidExpression();
+  curr->safety = RefCast::Safe;
+  curr->finalize();
+}
+
 bool WasmBinaryBuilder::maybeVisitRefCast(Expression*& out, uint32_t code) {
   if (code == BinaryConsts::RefCastStatic || code == BinaryConsts::RefCast ||
       code == BinaryConsts::RefCastNull || code == BinaryConsts::RefCastNop) {
@@ -7439,15 +7463,6 @@ void WasmBinaryBuilder::visitRefAs(RefAs* curr, uint8_t code) {
     case BinaryConsts::RefAsNonNull:
       curr->op = RefAsNonNull;
       break;
-    case BinaryConsts::RefAsFunc:
-      curr->op = RefAsFunc;
-      break;
-    case BinaryConsts::RefAsData:
-      curr->op = RefAsData;
-      break;
-    case BinaryConsts::RefAsI31:
-      curr->op = RefAsI31;
-      break;
     case BinaryConsts::ExternInternalize:
       curr->op = ExternInternalize;
       break;
diff --git a/src/wasm/wasm-s-parser.cpp b/src/wasm/wasm-s-parser.cpp
index 4f725d48b..03dba223b 100644
--- a/src/wasm/wasm-s-parser.cpp
+++ b/src/wasm/wasm-s-parser.cpp
@@ -2790,27 +2790,27 @@ Expression* SExpressionWasmBuilder::makeRefTest(Element& s,
   return Builder(wasm).makeRefTest(ref, *castType);
 }
 
-Expression* SExpressionWasmBuilder::makeRefCast(Element& s) {
+Expression* SExpressionWasmBuilder::makeRefCast(Element& s,
+                                                std::optional<Type> castType) {
   int i = 1;
-  Nullability nullability;
   bool legacy = false;
-  if (s[0]->str().str == "ref.cast_static") {
-    legacy = true;
-  } else {
-    nullability = NonNullable;
-    if (s[i]->str().str == "null") {
+  if (!castType) {
+    Nullability nullability = NonNullable;
+    if (s[0]->str().str == "ref.cast_static") {
+      legacy = true;
+    } else if (s[i]->str().str == "null") {
       nullability = Nullable;
       ++i;
     }
+    auto type = parseHeapType(*s[i++]);
+    castType = Type(type, nullability);
   }
-  auto heapType = parseHeapType(*s[i++]);
   auto* ref = parseExpression(*s[i++]);
   if (legacy) {
     // Legacy polymorphic behavior.
-    nullability = ref->type.getNullability();
+    castType = Type(castType->getHeapType(), ref->type.getNullability());
   }
-  auto type = Type(heapType, nullability);
-  return Builder(wasm).makeRefCast(ref, type, RefCast::Safe);
+  return Builder(wasm).makeRefCast(ref, *castType, RefCast::Safe);
 }
 
 Expression* SExpressionWasmBuilder::makeRefCastNop(Element& s) {
diff --git a/src/wasm/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index 82c7c511f..c4e1a863c 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -2041,6 +2041,23 @@ void BinaryInstWriter::visitRefCast(RefCast* curr) {
     o << U32LEB(BinaryConsts::RefCastNop);
     parent.writeIndexedHeapType(curr->type.getHeapType());
   } else {
+    // TODO: These instructions are deprecated. Remove them.
+    if (auto type = curr->type.getHeapType();
+        type.isBasic() && curr->type.isNonNullable()) {
+      switch (type.getBasic()) {
+        case HeapType::func:
+          o << U32LEB(BinaryConsts::RefAsFunc);
+          return;
+        case HeapType::data:
+          o << U32LEB(BinaryConsts::RefAsData);
+          return;
+        case HeapType::i31:
+          o << U32LEB(BinaryConsts::RefAsI31);
+          return;
+        default:
+          break;
+      }
+    }
     if (curr->type.isNullable()) {
       o << U32LEB(BinaryConsts::RefCastNull);
     } else {
@@ -2244,15 +2261,6 @@ void BinaryInstWriter::visitRefAs(RefAs* curr) {
     case RefAsNonNull:
       o << int8_t(BinaryConsts::RefAsNonNull);
       break;
-    case RefAsFunc:
-      o << int8_t(BinaryConsts::GCPrefix) << U32LEB(BinaryConsts::RefAsFunc);
-      break;
-    case RefAsData:
-      o << int8_t(BinaryConsts::GCPrefix) << U32LEB(BinaryConsts::RefAsData);
-      break;
-    case RefAsI31:
-      o << int8_t(BinaryConsts::GCPrefix) << U32LEB(BinaryConsts::RefAsI31);
-      break;
     case ExternInternalize:
       o << int8_t(BinaryConsts::GCPrefix)
         << U32LEB(BinaryConsts::ExternInternalize);
diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index c121ba89a..4a72f6ea6 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -1115,15 +1115,6 @@ void RefAs::finalize() {
     case RefAsNonNull:
       type = Type(value->type.getHeapType(), NonNullable);
       break;
-    case RefAsFunc:
-      type = Type(HeapType::func, NonNullable);
-      break;
-    case RefAsData:
-      type = Type(HeapType::data, NonNullable);
-      break;
-    case RefAsI31:
-      type = Type(HeapType::i31, NonNullable);
-      break;
     case ExternInternalize:
       type = Type(HeapType::any, value->type.getNullability());
       break;
diff --git a/src/wasm/wat-parser.cpp b/src/wasm/wat-parser.cpp
index 08eec41c6..c2d06ae90 100644
--- a/src/wasm/wat-parser.cpp
+++ b/src/wasm/wat-parser.cpp
@@ -2346,7 +2346,9 @@ Result<typename Ctx::InstrT> makeI31Get(Ctx&, Index, bool signed_);
 template<typename Ctx>
 Result<typename Ctx::InstrT>
 makeRefTest(Ctx&, Index, std::optional<Type> castType = std::nullopt);
-template<typename Ctx> Result<typename Ctx::InstrT> makeRefCast(Ctx&, Index);
+template<typename Ctx>
+Result<typename Ctx::InstrT>
+makeRefCast(Ctx&, Index, std::optional<Type> castType = std::nullopt);
 template<typename Ctx> Result<typename Ctx::InstrT> makeRefCastNop(Ctx&, Index);
 template<typename Ctx>
 Result<typename Ctx::InstrT> makeBrOnNull(Ctx&, Index, bool onFail = false);
@@ -3444,7 +3446,8 @@ makeRefTest(Ctx& ctx, Index pos, std::optional<Type> castType) {
 }
 
 template<typename Ctx>
-Result<typename Ctx::InstrT> makeRefCast(Ctx& ctx, Index pos) {
+Result<typename Ctx::InstrT>
+makeRefCast(Ctx& ctx, Index pos, std::optional<Type> castType) {
   return ctx.in.err("unimplemented instruction");
 }