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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
*
*
* 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_; }
// Updates the type of the LitVal. 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; }
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_;
}
// 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.
//
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.
//
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