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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ *
+ * Copyright 2021 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef wasm_val_h
+#define wasm_val_h
+
+#include "js/Class.h" // JSClassOps, ClassSpec
+#include "vm/JSObject.h"
+#include "vm/NativeObject.h" // NativeObject
+#include "wasm/WasmAnyRef.h"
+#include "wasm/WasmSerialize.h"
+#include "wasm/WasmTypeDef.h"
+
+namespace js {
+namespace wasm {
+
+// A V128 value.
+
+struct V128 {
+ uint8_t bytes[16] = {}; // Little-endian
+
+ WASM_CHECK_CACHEABLE_POD(bytes);
+
+ V128() = default;
+
+ explicit V128(uint8_t splatValue) {
+ memset(bytes, int(splatValue), sizeof(bytes));
+ }
+
+ template <typename T>
+ void extractLane(unsigned lane, T* result) const {
+ MOZ_ASSERT(lane < 16 / sizeof(T));
+ memcpy(result, bytes + sizeof(T) * lane, sizeof(T));
+ }
+
+ template <typename T>
+ void insertLane(unsigned lane, T value) {
+ MOZ_ASSERT(lane < 16 / sizeof(T));
+ memcpy(bytes + sizeof(T) * lane, &value, sizeof(T));
+ }
+
+ bool operator==(const V128& rhs) const {
+ for (size_t i = 0; i < sizeof(bytes); i++) {
+ if (bytes[i] != rhs.bytes[i]) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ bool operator!=(const V128& rhs) const { return !(*this == rhs); }
+};
+
+WASM_DECLARE_CACHEABLE_POD(V128);
+
+static_assert(sizeof(V128) == 16, "Invariant");
+
+// A FuncRef is a JSFunction* and is hence also an AnyRef, and the remarks above
+// about AnyRef apply also to FuncRef. When 'funcref' is used as a value type
+// in wasm code, the value that is held is "the canonical function value", which
+// is a function for which IsWasmExportedFunction() is true, and which has the
+// correct identity wrt reference equality of functions. Notably, if a function
+// is imported then its ref.func value compares === in JS to the function that
+// was passed as an import when the instance was created.
+//
+// These rules ensure that casts from funcref to anyref are non-converting
+// (generate no code), and that no wrapping or unwrapping needs to happen when a
+// funcref or anyref flows across the JS/wasm boundary, and that functions have
+// the necessary identity when observed from JS, and in the future, from wasm.
+//
+// Functions stored in tables, whether wasm tables or internal tables, can be
+// stored in a form that optimizes for eg call speed, however.
+//
+// Reading a funcref from a funcref table, writing a funcref to a funcref table,
+// and generating the value for a ref.func instruction are therefore nontrivial
+// operations that require mapping between the canonical JSFunction and the
+// optimized table representation. Once we get an instruction to call a
+// ref.func directly it too will require such a mapping.
+
+// In many cases, a FuncRef is exactly the same as AnyRef and we can use AnyRef
+// functionality on funcref values. The FuncRef class exists mostly to add more
+// checks and to make it clear, when we need to, that we're manipulating funcref
+// values. FuncRef does not currently subclass AnyRef because there's been no
+// need to, but it probably could.
+
+class FuncRef {
+ // mutable so that tracing may access a JSFunction* from a `const FuncRef`
+ mutable JSFunction* value_;
+
+ explicit FuncRef() : value_((JSFunction*)-1) {}
+ explicit FuncRef(JSFunction* p) : value_(p) {
+ MOZ_ASSERT(((uintptr_t)p & 0x03) == 0);
+ }
+
+ public:
+ // Given a void* that comes from compiled wasm code, turn it into FuncRef.
+ static FuncRef fromCompiledCode(void* p) { return FuncRef((JSFunction*)p); }
+
+ // Given a JSFunction* that comes from JS, turn it into FuncRef.
+ static FuncRef fromJSFunction(JSFunction* p) { return FuncRef(p); }
+
+ // Given an AnyRef that represents a possibly-null funcref, turn it into a
+ // FuncRef.
+ static FuncRef fromAnyRefUnchecked(AnyRef p);
+
+ static FuncRef null() { return FuncRef(nullptr); }
+
+ AnyRef toAnyRef() { return AnyRef::fromJSObjectOrNull((JSObject*)value_); }
+
+ void* forCompiledCode() const { return value_; }
+
+ JSFunction* asJSFunction() { return value_; }
+
+ bool isNull() const { return value_ == nullptr; }
+
+ void trace(JSTracer* trc) const;
+};
+
+using RootedFuncRef = Rooted<FuncRef>;
+using HandleFuncRef = Handle<FuncRef>;
+using MutableHandleFuncRef = MutableHandle<FuncRef>;
+
+// Given any FuncRef, unbox it as a JS Value -- always a JSFunction*.
+
+Value UnboxFuncRef(FuncRef val);
+
+// The LitVal class represents a single WebAssembly value of a given value
+// type, mostly for the purpose of numeric literals and initializers. A LitVal
+// does not directly map to a JS value since there is not (currently) a precise
+// representation of i64 values. A LitVal may contain non-canonical NaNs since,
+// within WebAssembly, floats are not canonicalized. Canonicalization must
+// happen at the JS boundary.
+
+class LitVal {
+ public:
+ union Cell {
+ uint32_t i32_;
+ uint64_t i64_;
+ float f32_;
+ double f64_;
+ wasm::V128 v128_;
+ // Mutable so that it can be traced
+ mutable wasm::AnyRef ref_;
+
+ Cell() : v128_() {}
+ ~Cell() = default;
+
+ WASM_CHECK_CACHEABLE_POD(i32_, i64_, f32_, f64_, v128_);
+ WASM_ALLOW_NON_CACHEABLE_POD_FIELD(
+ ref_,
+ "The pointer value in ref_ is guaranteed to always be null in a "
+ "LitVal.");
+ };
+
+ protected:
+ ValType type_;
+ Cell cell_;
+
+ public:
+ LitVal() = default;
+
+ explicit LitVal(ValType type) : type_(type) {
+ switch (type.kind()) {
+ case ValType::Kind::I32: {
+ cell_.i32_ = 0;
+ break;
+ }
+ case ValType::Kind::I64: {
+ cell_.i64_ = 0;
+ break;
+ }
+ case ValType::Kind::F32: {
+ cell_.f32_ = 0;
+ break;
+ }
+ case ValType::Kind::F64: {
+ cell_.f64_ = 0;
+ break;
+ }
+ case ValType::Kind::V128: {
+ new (&cell_.v128_) V128();
+ break;
+ }
+ case ValType::Kind::Ref: {
+ cell_.ref_ = nullptr;
+ break;
+ }
+ }
+ }
+
+ explicit LitVal(uint32_t i32) : type_(ValType::I32) { cell_.i32_ = i32; }
+ explicit LitVal(uint64_t i64) : type_(ValType::I64) { cell_.i64_ = i64; }
+
+ explicit LitVal(float f32) : type_(ValType::F32) { cell_.f32_ = f32; }
+ explicit LitVal(double f64) : type_(ValType::F64) { cell_.f64_ = f64; }
+
+ explicit LitVal(V128 v128) : type_(ValType::V128) { cell_.v128_ = v128; }
+
+ explicit LitVal(ValType type, AnyRef any) : type_(type) {
+ MOZ_ASSERT(type.isRefRepr());
+ MOZ_ASSERT(any.isNull(),
+ "use Val for non-nullptr ref types to get tracing");
+ cell_.ref_ = any;
+ }
+
+ ValType type() const { return type_; }
+ static constexpr size_t sizeofLargestValue() { return sizeof(cell_); }
+
+ Cell& cell() { return cell_; }
+ const Cell& cell() const { return cell_; }
+
+ uint32_t i32() const {
+ MOZ_ASSERT(type_ == ValType::I32);
+ return cell_.i32_;
+ }
+ uint64_t i64() const {
+ MOZ_ASSERT(type_ == ValType::I64);
+ return cell_.i64_;
+ }
+ const float& f32() const {
+ MOZ_ASSERT(type_ == ValType::F32);
+ return cell_.f32_;
+ }
+ const double& f64() const {
+ MOZ_ASSERT(type_ == ValType::F64);
+ return cell_.f64_;
+ }
+ AnyRef ref() const {
+ MOZ_ASSERT(type_.isRefRepr());
+ return cell_.ref_;
+ }
+ const V128& v128() const {
+ MOZ_ASSERT(type_ == ValType::V128);
+ return cell_.v128_;
+ }
+
+ WASM_DECLARE_FRIEND_SERIALIZE(LitVal);
+};
+
+WASM_DECLARE_CACHEABLE_POD(LitVal::Cell);
+
+// A Val is a LitVal that can contain (non-null) pointers to GC things. All Vals
+// must be used with the rooting APIs as they may contain JS objects.
+
+class MOZ_NON_PARAM Val : public LitVal {
+ public:
+ Val() = default;
+ explicit Val(ValType type) : LitVal(type) {}
+ explicit Val(const LitVal& val);
+ explicit Val(uint32_t i32) : LitVal(i32) {}
+ explicit Val(uint64_t i64) : LitVal(i64) {}
+ explicit Val(float f32) : LitVal(f32) {}
+ explicit Val(double f64) : LitVal(f64) {}
+ explicit Val(V128 v128) : LitVal(v128) {}
+ explicit Val(ValType type, AnyRef val) : LitVal(type, AnyRef::null()) {
+ MOZ_ASSERT(type.isRefRepr());
+ cell_.ref_ = val;
+ }
+ explicit Val(ValType type, FuncRef val) : LitVal(type, AnyRef::null()) {
+ MOZ_ASSERT(type.refType().isFuncHierarchy());
+ cell_.ref_ = val.toAnyRef();
+ }
+
+ Val(const Val&) = default;
+ Val& operator=(const Val&) = default;
+
+ bool operator==(const Val& rhs) const {
+ if (type_ != rhs.type_) {
+ return false;
+ }
+ switch (type_.kind()) {
+ case ValType::I32:
+ return cell_.i32_ == rhs.cell_.i32_;
+ case ValType::I64:
+ return cell_.i64_ == rhs.cell_.i64_;
+ case ValType::F32:
+ return cell_.f32_ == rhs.cell_.f32_;
+ case ValType::F64:
+ return cell_.f64_ == rhs.cell_.f64_;
+ case ValType::V128:
+ return cell_.v128_ == rhs.cell_.v128_;
+ case ValType::Ref:
+ return cell_.ref_ == rhs.cell_.ref_;
+ }
+ MOZ_ASSERT_UNREACHABLE();
+ return false;
+ }
+ bool operator!=(const Val& rhs) const { return !(*this == rhs); }
+
+ bool isInvalid() const { return !type_.isValid(); }
+ bool isAnyRef() const { return type_.isValid() && type_.isRefRepr(); }
+ AnyRef& toAnyRef() const {
+ MOZ_ASSERT(isAnyRef());
+ return cell_.ref_;
+ }
+
+ // Updates the type of the Val. Does not check that the type is valid for the
+ // actual value, so make sure the type is definitely correct via validation or
+ // something.
+ void unsafeSetType(ValType type) { type_ = type; }
+
+ // Initialize from `loc` which is a rooted location and needs no barriers.
+ void initFromRootedLocation(ValType type, const void* loc);
+ void initFromHeapLocation(ValType type, const void* loc);
+
+ // Write to `loc` which is a rooted location and needs no barriers.
+ void writeToRootedLocation(void* loc, bool mustWrite64) const;
+
+ // Read from `loc` which is in the heap.
+ void readFromHeapLocation(const void* loc);
+ // Write to `loc` which is in the heap and must be barriered.
+ void writeToHeapLocation(void* loc) const;
+
+ // See the comment for `ToWebAssemblyValue` below.
+ static bool fromJSValue(JSContext* cx, ValType targetType, HandleValue val,
+ MutableHandle<Val> rval);
+ // See the comment for `ToJSValue` below.
+ bool toJSValue(JSContext* cx, MutableHandleValue rval) const;
+
+ void trace(JSTracer* trc) const;
+};
+
+using GCPtrVal = GCPtr<Val>;
+using RootedVal = Rooted<Val>;
+using HandleVal = Handle<Val>;
+using MutableHandleVal = MutableHandle<Val>;
+
+using ValVector = GCVector<Val, 0, SystemAllocPolicy>;
+using RootedValVector = Rooted<ValVector>;
+using HandleValVector = Handle<ValVector>;
+using MutableHandleValVector = MutableHandle<ValVector>;
+
+template <int N>
+using ValVectorN = GCVector<Val, N, SystemAllocPolicy>;
+template <int N>
+using RootedValVectorN = Rooted<ValVectorN<N>>;
+
+// Check a value against the given reference type. If the targetType
+// is RefType::Extern then the test always passes, but the value may be boxed.
+// If the test passes then the value is stored either in fnval (for
+// RefType::Func) or in refval (for other types); this split is not strictly
+// necessary but is convenient for the users of this function.
+//
+// This can return false if the type check fails, or if a boxing into AnyRef
+// throws an OOM.
+[[nodiscard]] extern bool CheckRefType(JSContext* cx, RefType targetType,
+ HandleValue v,
+ MutableHandleFunction fnval,
+ MutableHandleAnyRef refval);
+
+// The same as above for when the target type is 'funcref'.
+[[nodiscard]] extern bool CheckFuncRefValue(JSContext* cx, HandleValue v,
+ MutableHandleFunction fun);
+
+// The same as above for when the target type is 'anyref'.
+[[nodiscard]] extern bool CheckAnyRefValue(JSContext* cx, HandleValue v,
+ MutableHandleAnyRef vp);
+
+// The same as above for when the target type is 'nullexternref'.
+[[nodiscard]] extern bool CheckNullExternRefValue(JSContext* cx, HandleValue v,
+ MutableHandleAnyRef vp);
+
+// The same as above for when the target type is 'nullfuncref'.
+[[nodiscard]] extern bool CheckNullFuncRefValue(JSContext* cx, HandleValue v,
+ MutableHandleFunction fun);
+
+// The same as above for when the target type is 'nullref'.
+[[nodiscard]] extern bool CheckNullRefValue(JSContext* cx, HandleValue v,
+ MutableHandleAnyRef vp);
+
+// The same as above for when the target type is 'eqref'.
+[[nodiscard]] extern bool CheckEqRefValue(JSContext* cx, HandleValue v,
+ MutableHandleAnyRef vp);
+
+// The same as above for when the target type is 'i31ref'.
+[[nodiscard]] extern bool CheckI31RefValue(JSContext* cx, HandleValue v,
+ MutableHandleAnyRef vp);
+
+// The same as above for when the target type is 'structref'.
+[[nodiscard]] extern bool CheckStructRefValue(JSContext* cx, HandleValue v,
+ MutableHandleAnyRef vp);
+
+// The same as above for when the target type is 'arrayref'.
+[[nodiscard]] extern bool CheckArrayRefValue(JSContext* cx, HandleValue v,
+ MutableHandleAnyRef vp);
+
+// The same as above for when the target type is '(ref T)'.
+[[nodiscard]] extern bool CheckTypeRefValue(JSContext* cx,
+ const TypeDef* typeDef,
+ HandleValue v,
+ MutableHandleAnyRef vp);
+class NoDebug;
+class DebugCodegenVal;
+
+// The level of coercion to apply in `ToWebAssemblyValue` and `ToJSValue`.
+enum class CoercionLevel {
+ // The default coercions given by the JS-API specification.
+ Spec,
+ // Allow for the coercions given by `Spec` but also use WebAssembly.Global
+ // as a container for lossless conversions. This is only available through
+ // the wasmLosslessInvoke testing function and is used in tests.
+ Lossless,
+};
+
+// Coercion function from a JS value to a WebAssembly value [1].
+//
+// This function may fail for any of the following reasons:
+// * The input value has an incorrect type for the targetType
+// * The targetType is not exposable
+// * An OOM ocurred
+// An error will be set upon failure.
+//
+// [1] https://webassembly.github.io/spec/js-api/index.html#towebassemblyvalue
+template <typename Debug = NoDebug>
+extern bool ToWebAssemblyValue(JSContext* cx, HandleValue val, ValType type,
+ void* loc, bool mustWrite64,
+ CoercionLevel level = CoercionLevel::Spec);
+
+// Coercion function from a WebAssembly value to a JS value [1].
+//
+// This function will only fail if an OOM ocurred. If the type of WebAssembly
+// value being coerced is not exposable to JS, then it will be coerced to
+// 'undefined'. Callers are responsible for guarding against this if this is
+// not desirable.
+//
+// [1] https://webassembly.github.io/spec/js-api/index.html#tojsvalue
+template <typename Debug = NoDebug>
+extern bool ToJSValue(JSContext* cx, const void* src, StorageType type,
+ MutableHandleValue dst,
+ CoercionLevel level = CoercionLevel::Spec);
+template <typename Debug = NoDebug>
+extern bool ToJSValueMayGC(StorageType type);
+template <typename Debug = NoDebug>
+extern bool ToJSValue(JSContext* cx, const void* src, ValType type,
+ MutableHandleValue dst,
+ CoercionLevel level = CoercionLevel::Spec);
+template <typename Debug = NoDebug>
+extern bool ToJSValueMayGC(ValType type);
+} // namespace wasm
+
+template <>
+struct InternalBarrierMethods<wasm::AnyRef> {
+ static bool isMarkable(const wasm::AnyRef v) { return v.isGCThing(); }
+
+ static void preBarrier(const wasm::AnyRef v) {
+ if (v.isGCThing()) {
+ gc::PreWriteBarrierImpl(v.toGCThing());
+ }
+ }
+
+ static MOZ_ALWAYS_INLINE void postBarrier(wasm::AnyRef* vp,
+ const wasm::AnyRef prev,
+ const wasm::AnyRef next) {
+ // If the target needs an entry, add it.
+ gc::StoreBuffer* sb;
+ if (next.isGCThing() && (sb = next.toGCThing()->storeBuffer())) {
+ // If we know that the prev has already inserted an entry, we can
+ // skip doing the lookup to add the new entry. Note that we cannot
+ // safely assert the presence of the entry because it may have been
+ // added via a different store buffer.
+ if (prev.isGCThing() && prev.toGCThing()->storeBuffer()) {
+ return;
+ }
+ sb->putWasmAnyRef(vp);
+ return;
+ }
+ // Remove the prev entry if the new value does not need it.
+ if (prev.isGCThing() && (sb = prev.toGCThing()->storeBuffer())) {
+ sb->unputWasmAnyRef(vp);
+ }
+ }
+
+ static void readBarrier(const wasm::AnyRef v) {
+ if (v.isGCThing()) {
+ gc::ReadBarrierImpl(v.toGCThing());
+ }
+ }
+
+#ifdef DEBUG
+ static void assertThingIsNotGray(const wasm::AnyRef v) {
+ if (v.isGCThing()) {
+ JS::AssertCellIsNotGray(v.toGCThing());
+ }
+ }
+#endif
+};
+
+template <>
+struct InternalBarrierMethods<wasm::Val> {
+ static bool isMarkable(const wasm::Val& v) { return v.isAnyRef(); }
+
+ static void preBarrier(const wasm::Val& v) {
+ if (v.isAnyRef()) {
+ InternalBarrierMethods<wasm::AnyRef>::preBarrier(v.toAnyRef());
+ }
+ }
+
+ static MOZ_ALWAYS_INLINE void postBarrier(wasm::Val* vp,
+ const wasm::Val& prev,
+ const wasm::Val& next) {
+ // A wasm::Val can transition from being uninitialized to holding an anyref
+ // but cannot change kind after that.
+ MOZ_ASSERT_IF(next.isAnyRef(), prev.isAnyRef() || prev.isInvalid());
+ MOZ_ASSERT_IF(prev.isAnyRef(), next.isAnyRef());
+
+ if (next.isAnyRef()) {
+ InternalBarrierMethods<wasm::AnyRef>::postBarrier(
+ &vp->toAnyRef(),
+ prev.isAnyRef() ? prev.toAnyRef() : wasm::AnyRef::null(),
+ next.toAnyRef());
+ return;
+ }
+ }
+
+ static void readBarrier(const wasm::Val& v) {
+ if (v.isAnyRef()) {
+ InternalBarrierMethods<wasm::AnyRef>::readBarrier(v.toAnyRef());
+ }
+ }
+
+#ifdef DEBUG
+ static void assertThingIsNotGray(const wasm::Val& v) {
+ if (v.isAnyRef()) {
+ InternalBarrierMethods<wasm::AnyRef>::assertThingIsNotGray(v.toAnyRef());
+ }
+ }
+#endif
+};
+
+} // namespace js
+
+template <>
+struct JS::SafelyInitialized<js::wasm::AnyRef> {
+ static js::wasm::AnyRef create() { return js::wasm::AnyRef::null(); }
+};
+
+#endif // wasm_val_h
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