[wasm-gc] Implement ref.eq

Changes:
- Implement subtyping for eqref.
- (Driveby) Declare more functions as constexpr in ValueType.
- Make minor changes needed to handle ref.eq.
- Write an elementary test.

Bug: v8:7748
Change-Id: I11d54227798ce56de70f3a6f83305b2f80b2f57f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2193715
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67752}

src/compiler/wasm-compiler.cc

@@ -660,6 +660,8 @@ Node* WasmGraphBuilder::Binop(wasm::WasmOpcode opcode, Node* left, Node* right,
       break;
     case wasm::kExprF64Mod:
       return BuildF64Mod(left, right);
+    case wasm::kExprRefEq:
+      return gasm_->TaggedEqual(left, right);
     case wasm::kExprI32AsmjsDivS:
       return BuildI32AsmjsDivS(left, right);
     case wasm::kExprI32AsmjsDivU:

src/wasm/function-body-decoder-impl.h

@@ -41,22 +41,18 @@ struct WasmException;
     return true;                  \
   }())
 
-#define RET_ON_PROTOTYPE_OPCODE(feat)                                          \
+#define CHECK_PROTOTYPE_OPCODE_GEN(feat, opt_break)                            \
   DCHECK(!this->module_ || this->module_->origin == kWasmOrigin);              \
   if (!this->enabled_.has_##feat()) {                                          \
     this->error("Invalid opcode (enable with --experimental-wasm-" #feat ")"); \
+    opt_break                                                                  \
   } else {                                                                     \
     this->detected_->Add(kFeature_##feat);                                     \
   }
 
-#define CHECK_PROTOTYPE_OPCODE(feat)                                           \
-  DCHECK(!this->module_ || this->module_->origin == kWasmOrigin);              \
-  if (!this->enabled_.has_##feat()) {                                          \
-    this->error("Invalid opcode (enable with --experimental-wasm-" #feat ")"); \
-    break;                                                                     \
-  } else {                                                                     \
-    this->detected_->Add(kFeature_##feat);                                     \
-  }
+#define CHECK_PROTOTYPE_OPCODE(feat) CHECK_PROTOTYPE_OPCODE_GEN(feat, break;)
+
+#define RET_ON_PROTOTYPE_OPCODE(feat) CHECK_PROTOTYPE_OPCODE_GEN(feat, )
 
 #define OPCODE_ERROR(opcode, message)                                 \
   (this->errorf(this->pc_, "%s: %s", WasmOpcodes::OpcodeName(opcode), \
@@ -3524,10 +3520,11 @@ class WasmFullDecoder : public WasmDecoder<validate> {
   }
 
   void BuildSimplePrototypeOperator(WasmOpcode opcode) {
-    if (WasmOpcodes::IsAnyRefOpcode(opcode)) {
+    if (opcode == kExprRefIsNull) {
       RET_ON_PROTOTYPE_OPCODE(anyref);
+    } else if (opcode == kExprRefEq) {
+      RET_ON_PROTOTYPE_OPCODE(gc);
     }
-    // TODO(7748): Add RefEq support here.
     const FunctionSig* sig = WasmOpcodes::Signature(opcode);
     BuildSimpleOperator(opcode, sig);
   }
@@ -3598,6 +3595,8 @@ class EmptyInterface {
 #undef TRACE_INST_FORMAT
 #undef VALIDATE
 #undef CHECK_PROTOTYPE_OPCODE
+#undef RET_ON_PROTOTYPE_OPCODE
+#undef CHECK_PROTOTYPE_OPCODE_GEN
 #undef OPCODE_ERROR
 
 }  // namespace wasm

src/wasm/value-type.h

@@ -25,8 +25,10 @@ class Simd128;
 // For every two types connected by a line, the top type is a
 // (direct) subtype of the bottom type.
 //
-//                           AnyRef
-//                         /    |   \
+//                            AnyRef
+//                           /      \
+//                          /      EqRef
+//                         /       /   \
 //                  FuncRef  ExnRef  OptRef(S)
 //                         \    |   /        \
 // I32  I64  F32  F64        NullRef        Ref(S)
@@ -38,7 +40,7 @@ class Simd128;
 // - "ref" types per https://github.com/WebAssembly/function-references
 // - "optref"/"eqref" per https://github.com/WebAssembly/gc
 //
-// TODO(7748): Extend this with eqref, struct and function subtyping.
+// TODO(7748): Extend this with struct and function subtyping.
 //             Keep up to date with funcref vs. anyref subtyping.
 #define FOREACH_VALUE_TYPE(V)                                                \
   V(Stmt, -1, Void, None, 'v', "<stmt>")                                     \
@@ -71,11 +73,15 @@ class ValueType {
   constexpr ValueType() : bit_field_(KindField::encode(kStmt)) {}
   explicit constexpr ValueType(Kind kind)
       : bit_field_(KindField::encode(kind)) {
+#if V8_HAS_CXX14_CONSTEXPR
     DCHECK(!has_immediate());
+#endif
   }
   constexpr ValueType(Kind kind, uint32_t ref_index)
       : bit_field_(KindField::encode(kind) | RefIndexField::encode(ref_index)) {
+#if V8_HAS_CXX14_CONSTEXPR
     DCHECK(has_immediate());
+#endif
   }
 
   constexpr Kind kind() const { return KindField::decode(bit_field_); }
@@ -110,27 +116,25 @@ class ValueType {
     return bit_field_ != other.bit_field_;
   }
 
-  // TODO(7748): Extend this with eqref, struct and function subtyping.
+  // TODO(7748): Extend this with struct and function subtyping.
   //             Keep up to date with funcref vs. anyref subtyping.
-  bool IsSubTypeOf(ValueType other) const {
-    return (*this == other) ||
-           (kind() == kNullRef &&
-            (other.kind() == kAnyRef || other.kind() == kFuncRef ||
-             other.kind() == kExnRef || other.kind() == kOptRef)) ||
-           (other.kind() == kAnyRef &&
-            (kind() == kFuncRef || kind() == kExnRef || kind() == kOptRef ||
-             kind() == kRef)) ||
+  constexpr bool IsSubTypeOf(ValueType other) const {
+    return (*this == other) || (other.kind() == kAnyRef && IsReferenceType()) ||
+           (kind() == kNullRef && other.kind() != kRef &&
+            other.IsReferenceType()) ||
+           (other.kind() == kEqRef &&
+            (kind() == kExnRef || kind() == kOptRef || kind() == kRef)) ||
            (kind() == kRef && other.kind() == kOptRef &&
             ref_index() == other.ref_index());
   }
 
-  bool IsReferenceType() const {
+  constexpr bool IsReferenceType() const {
     return kind() == kAnyRef || kind() == kFuncRef || kind() == kNullRef ||
            kind() == kExnRef || kind() == kRef || kind() == kOptRef ||
            kind() == kEqRef;
   }
 
-  // TODO(7748): Extend this with eqref, struct and function subtyping.
+  // TODO(7748): Extend this with struct and function subtyping.
   //             Keep up to date with funcref vs. anyref subtyping.
   static ValueType CommonSubType(ValueType a, ValueType b) {
     if (a == b) return a;
@@ -143,12 +147,14 @@ class ValueType {
     // {a} and {b} are not each other's subtype.
     // If one of them is not nullable, their greatest subtype is bottom,
     // otherwise null.
-    return (a.kind() == kRef || b.kind() == kRef) ? ValueType(kBottom)
-                                                  : ValueType(kNullRef);
+    if (a.kind() == kRef || b.kind() == kRef) return ValueType(kBottom);
+    return ValueType(kNullRef);
   }
 
-  ValueTypeCode value_type_code() const {
+  constexpr ValueTypeCode value_type_code() const {
+#if V8_HAS_CXX14_CONSTEXPR
     DCHECK_NE(kBottom, kind());
+#endif
 
     constexpr ValueTypeCode kValueTypeCode[] = {
 #define TYPE_CODE(kind, log2Size, code, ...) kLocal##code,
@@ -159,8 +165,10 @@ class ValueType {
     return kValueTypeCode[kind()];
   }
 
-  MachineType machine_type() const {
+  constexpr MachineType machine_type() const {
+#if V8_HAS_CXX14_CONSTEXPR
     DCHECK_NE(kBottom, kind());
+#endif
 
     constexpr MachineType kMachineType[] = {
 #define MACH_TYPE(kind, log2Size, code, machineType, ...) \
@@ -172,7 +180,7 @@ class ValueType {
     return kMachineType[kind()];
   }
 
-  MachineRepresentation machine_representation() {
+  constexpr MachineRepresentation machine_representation() const {
     return machine_type().representation();
   }
 

test/cctest/wasm/test-gc.cc

@@ -129,6 +129,35 @@ WASM_EXEC_TEST(BasicStruct) {
       kExprEnd};
   m->EmitCode(m_code, sizeof(m_code));
 
+  // Test ref.eq
+  WasmFunctionBuilder* n = builder->AddFunction(sigs.i_v());
+  uint32_t n_local_index = n->AddLocal(kOptRefType);
+  n->builder()->AddExport(CStrVector("n"), n);
+  byte n_code[] = {
+      WASM_SET_LOCAL(n_local_index,
+                     WASM_STRUCT_NEW(type_index, WASM_I32V(55), WASM_I32V(66))),
+      WASM_I32_ADD(
+          WASM_I32_SHL(
+              WASM_REF_EQ(  // true
+                  WASM_GET_LOCAL(n_local_index), WASM_GET_LOCAL(n_local_index)),
+              WASM_I32V(0)),
+          WASM_I32_ADD(
+              WASM_I32_SHL(WASM_REF_EQ(  // false
+                               WASM_GET_LOCAL(n_local_index),
+                               WASM_STRUCT_NEW(type_index, WASM_I32V(55),
+                                               WASM_I32V(66))),
+                           WASM_I32V(1)),
+              WASM_I32_ADD(
+                  WASM_I32_SHL(  // false
+                      WASM_REF_EQ(WASM_GET_LOCAL(n_local_index), WASM_REF_NULL),
+                      WASM_I32V(2)),
+                  WASM_I32_SHL(WASM_REF_EQ(  // true
+                                   WASM_REF_NULL, WASM_REF_NULL),
+                               WASM_I32V(3))))),
+      kExprEnd};
+  n->EmitCode(n_code, sizeof(n_code));
+  // Result: 0b1001
+
   ZoneBuffer buffer(&zone);
   builder->WriteTo(&buffer);
 
@@ -168,6 +197,9 @@ WASM_EXEC_TEST(BasicStruct) {
 
   CHECK_EQ(52, testing::CallWasmFunctionForTesting(isolate, instance, &thrower,
                                                    "m", 0, nullptr));
+
+  CHECK_EQ(0b1001, testing::CallWasmFunctionForTesting(
+                       isolate, instance, &thrower, "n", 0, nullptr));
 }
 
 WASM_EXEC_TEST(BasicArray) {

test/common/wasm/wasm-macro-gen.h

@@ -436,6 +436,7 @@ inline WasmOpcode LoadStoreOpcodeOf(MachineType type, bool store) {
 #define WASM_REF_FUNC(val) kExprRefFunc, val
 #define WASM_REF_IS_NULL(val) val, kExprRefIsNull
 #define WASM_REF_AS_NON_NULL(val) val, kExprRefAsNonNull
+#define WASM_REF_EQ(lhs, rhs) lhs, rhs, kExprRefEq
 
 #define WASM_ARRAY_NEW(index, default_value, length) \
   default_value, length, WASM_GC_OP(kExprArrayNew), static_cast<byte>(index)