Source code
Revision control
Copy as Markdown
Other Tools
/* -*- 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_expr_type_h
#define wasm_expr_type_h
#include <stdint.h>
#include "wasm/WasmTypeDef.h"
#include "wasm/WasmValType.h"
namespace js {
namespace wasm {
template <typename PointerType>
class TaggedValue {
public:
enum Kind {
ImmediateKind1 = 0,
ImmediateKind2 = 1,
PointerKind1 = 2,
PointerKind2 = 3
};
using PackedRepr = uint64_t;
static_assert(std::is_same<PackedTypeCode::PackedRepr, uint64_t>(),
"can use pointer tagging with PackedTypeCode");
private:
PackedRepr bits_;
static constexpr PackedRepr PayloadShift = 2;
static constexpr PackedRepr KindMask = 0x3;
static constexpr PackedRepr PointerKindBit = 0x2;
constexpr static bool IsPointerKind(Kind kind) {
return PackedRepr(kind) & PointerKindBit;
}
constexpr static bool IsImmediateKind(Kind kind) {
return !IsPointerKind(kind);
}
static_assert(IsImmediateKind(ImmediateKind1), "immediate kind 1");
static_assert(IsImmediateKind(ImmediateKind2), "immediate kind 2");
static_assert(IsPointerKind(PointerKind1), "pointer kind 1");
static_assert(IsPointerKind(PointerKind2), "pointer kind 2");
static PackedRepr PackImmediate(Kind kind, PackedRepr imm) {
MOZ_ASSERT(IsImmediateKind(kind));
MOZ_ASSERT((PackedRepr(kind) & KindMask) == kind);
MOZ_ASSERT((imm & (PackedRepr(KindMask)
<< ((sizeof(PackedRepr) * 8) - PayloadShift))) == 0);
return PackedRepr(kind) | (PackedRepr(imm) << PayloadShift);
}
static PackedRepr PackPointer(Kind kind, PointerType* ptr) {
PackedRepr ptrBits = reinterpret_cast<PackedRepr>(ptr);
MOZ_ASSERT(IsPointerKind(kind));
MOZ_ASSERT((PackedRepr(kind) & KindMask) == kind);
MOZ_ASSERT((ptrBits & KindMask) == 0);
return PackedRepr(kind) | ptrBits;
}
public:
TaggedValue(Kind kind, PackedRepr imm) : bits_(PackImmediate(kind, imm)) {}
TaggedValue(Kind kind, PointerType* ptr) : bits_(PackPointer(kind, ptr)) {}
PackedRepr bits() const { return bits_; }
Kind kind() const { return Kind(bits() & KindMask); }
PackedRepr immediate() const {
MOZ_ASSERT(IsImmediateKind(kind()));
return mozilla::AssertedCast<PackedRepr>(bits() >> PayloadShift);
}
PointerType* pointer() const {
MOZ_ASSERT(IsPointerKind(kind()));
return reinterpret_cast<PointerType*>(bits() & ~KindMask);
}
};
// ResultType represents the WebAssembly spec's `resulttype`. Semantically, a
// result type is just a vec(valtype). For effiency, though, the ResultType
// value is packed into a word, with separate encodings for these 3 cases:
// []
// [valtype]
// pointer to ValTypeVector
//
// Additionally there is an encoding indicating uninitialized ResultType
// values.
//
// Generally in the latter case the ValTypeVector is the args() or results() of
// a FuncType in the compilation unit, so as long as the lifetime of the
// ResultType value is less than the OpIter, we can just borrow the pointer
// without ownership or copying.
class ResultType {
using Tagged = TaggedValue<const ValTypeVector>;
Tagged tagged_;
enum Kind {
EmptyKind = Tagged::ImmediateKind1,
SingleKind = Tagged::ImmediateKind2,
VectorKind = Tagged::PointerKind1,
InvalidKind = Tagged::PointerKind2,
};
ResultType(Kind kind, Tagged::PackedRepr imm)
: tagged_(Tagged::Kind(kind), imm) {}
explicit ResultType(const ValTypeVector* ptr)
: tagged_(Tagged::Kind(VectorKind), ptr) {}
Kind kind() const { return Kind(tagged_.kind()); }
ValType singleValType() const {
MOZ_ASSERT(kind() == SingleKind);
return ValType(PackedTypeCode::fromBits(tagged_.immediate()));
}
const ValTypeVector& values() const {
MOZ_ASSERT(kind() == VectorKind);
return *tagged_.pointer();
}
public:
ResultType() : tagged_(Tagged::Kind(InvalidKind), nullptr) {}
static ResultType Empty() {
return ResultType(EmptyKind, Tagged::PackedRepr(0));
}
static ResultType Single(ValType vt) {
return ResultType(SingleKind, vt.bitsUnsafe());
}
static ResultType Vector(const ValTypeVector& vals) {
switch (vals.length()) {
case 0:
return Empty();
case 1:
return Single(vals[0]);
default:
return ResultType(&vals);
}
}
[[nodiscard]] bool cloneToVector(ValTypeVector* out) {
MOZ_ASSERT(out->empty());
switch (kind()) {
case EmptyKind:
return true;
case SingleKind:
return out->append(singleValType());
case VectorKind:
return out->appendAll(values());
default:
MOZ_CRASH("bad resulttype");
}
}
bool valid() const { return kind() != InvalidKind; }
bool empty() const { return kind() == EmptyKind; }
size_t length() const {
switch (kind()) {
case EmptyKind:
return 0;
case SingleKind:
return 1;
case VectorKind:
return values().length();
default:
MOZ_CRASH("bad resulttype");
}
}
// Polyfill the Span API, which is polyfilling the std library
size_t size() const { return length(); }
ValType operator[](size_t i) const {
switch (kind()) {
case SingleKind:
MOZ_ASSERT(i == 0);
return singleValType();
case VectorKind:
return values()[i];
default:
MOZ_CRASH("bad resulttype");
}
}
bool operator==(ResultType rhs) const {
switch (kind()) {
case EmptyKind:
case SingleKind:
case InvalidKind:
return tagged_.bits() == rhs.tagged_.bits();
case VectorKind: {
if (rhs.kind() != VectorKind) {
return false;
}
return EqualContainers(values(), rhs.values());
}
default:
MOZ_CRASH("bad resulttype");
}
}
bool operator!=(ResultType rhs) const { return !(*this == rhs); }
};
// BlockType represents the WebAssembly spec's `blocktype`. Semantically, a
// block type is just a (vec(valtype) -> vec(valtype)) with four special
// encodings which are represented explicitly in BlockType:
// [] -> []
// [] -> [valtype]
// [params] -> [results] via pointer to FuncType
// [] -> [results] via pointer to FuncType (ignoring [params])
class BlockType {
using Tagged = TaggedValue<const FuncType>;
Tagged tagged_;
enum Kind {
VoidToVoidKind = Tagged::ImmediateKind1,
VoidToSingleKind = Tagged::ImmediateKind2,
FuncKind = Tagged::PointerKind1,
FuncResultsKind = Tagged::PointerKind2
};
BlockType(Kind kind, Tagged::PackedRepr imm)
: tagged_(Tagged::Kind(kind), imm) {}
BlockType(Kind kind, const FuncType& type)
: tagged_(Tagged::Kind(kind), &type) {}
Kind kind() const { return Kind(tagged_.kind()); }
ValType singleValType() const {
MOZ_ASSERT(kind() == VoidToSingleKind);
return ValType(PackedTypeCode::fromBits(tagged_.immediate()));
}
const FuncType& funcType() const { return *tagged_.pointer(); }
public:
BlockType()
: tagged_(Tagged::Kind(VoidToVoidKind),
PackedTypeCode::invalid().bits()) {}
static BlockType VoidToVoid() {
return BlockType(VoidToVoidKind, Tagged::PackedRepr(0));
}
static BlockType VoidToSingle(ValType vt) {
return BlockType(VoidToSingleKind, vt.bitsUnsafe());
}
static BlockType Func(const FuncType& type) {
if (type.args().length() == 0) {
return FuncResults(type);
}
return BlockType(FuncKind, type);
}
static BlockType FuncResults(const FuncType& type) {
switch (type.results().length()) {
case 0:
return VoidToVoid();
case 1:
return VoidToSingle(type.results()[0]);
default:
return BlockType(FuncResultsKind, type);
}
}
ResultType params() const {
switch (kind()) {
case VoidToVoidKind:
case VoidToSingleKind:
case FuncResultsKind:
return ResultType::Empty();
case FuncKind:
return ResultType::Vector(funcType().args());
default:
MOZ_CRASH("unexpected kind");
}
}
ResultType results() const {
switch (kind()) {
case VoidToVoidKind:
return ResultType::Empty();
case VoidToSingleKind:
return ResultType::Single(singleValType());
case FuncKind:
case FuncResultsKind:
return ResultType::Vector(funcType().results());
default:
MOZ_CRASH("unexpected kind");
}
}
bool operator==(BlockType rhs) const {
if (kind() != rhs.kind()) {
return false;
}
switch (kind()) {
case VoidToVoidKind:
case VoidToSingleKind:
return tagged_.bits() == rhs.tagged_.bits();
case FuncKind:
return FuncType::strictlyEquals(funcType(), rhs.funcType());
case FuncResultsKind:
return EqualContainers(funcType().results(), rhs.funcType().results());
default:
MOZ_CRASH("unexpected kind");
}
}
bool operator!=(BlockType rhs) const { return !(*this == rhs); }
};
} // namespace wasm
} // namespace js
#endif // wasm_expr_type_h