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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 2015 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_stubs_h
#define wasm_stubs_h
#include "wasm/WasmFrameIter.h" // js::wasm::ExitReason
#include "wasm/WasmGenerator.h"
#include "wasm/WasmOpIter.h"
namespace js {
namespace wasm {
using jit::FloatRegister;
using jit::Register;
using jit::Register64;
// ValType and location for a single result: either in a register or on the
// stack.
class ABIResult {
ValType type_;
enum class Location { Gpr, Gpr64, Fpr, Stack } loc_;
union {
Register gpr_;
Register64 gpr64_;
FloatRegister fpr_;
uint32_t stackOffset_;
};
void validate() {
#ifdef DEBUG
if (onStack()) {
return;
}
MOZ_ASSERT(inRegister());
switch (type_.kind()) {
case ValType::I32:
MOZ_ASSERT(loc_ == Location::Gpr);
break;
case ValType::I64:
MOZ_ASSERT(loc_ == Location::Gpr64);
break;
case ValType::F32:
case ValType::F64:
MOZ_ASSERT(loc_ == Location::Fpr);
break;
case ValType::Ref:
MOZ_ASSERT(loc_ == Location::Gpr);
break;
case ValType::V128:
MOZ_ASSERT(loc_ == Location::Fpr);
break;
}
#endif
}
friend class ABIResultIter;
ABIResult() {}
public:
// Sizes of items in the stack area.
//
// The size values come from the implementations of Push() in
// MacroAssembler-x86-shared.cpp and MacroAssembler-arm-shared.cpp, and from
// VFPRegister::size() in Architecture-arm.h.
//
// On ARM unlike on x86 we push a single for float.
static constexpr size_t StackSizeOfPtr = sizeof(intptr_t);
static constexpr size_t StackSizeOfInt32 = StackSizeOfPtr;
static constexpr size_t StackSizeOfInt64 = sizeof(int64_t);
#if defined(JS_CODEGEN_ARM)
static constexpr size_t StackSizeOfFloat = sizeof(float);
#else
static constexpr size_t StackSizeOfFloat = sizeof(double);
#endif
static constexpr size_t StackSizeOfDouble = sizeof(double);
#ifdef ENABLE_WASM_SIMD
static constexpr size_t StackSizeOfV128 = sizeof(V128);
#endif
ABIResult(ValType type, Register gpr)
: type_(type), loc_(Location::Gpr), gpr_(gpr) {
validate();
}
ABIResult(ValType type, Register64 gpr64)
: type_(type), loc_(Location::Gpr64), gpr64_(gpr64) {
validate();
}
ABIResult(ValType type, FloatRegister fpr)
: type_(type), loc_(Location::Fpr), fpr_(fpr) {
validate();
}
ABIResult(ValType type, uint32_t stackOffset)
: type_(type), loc_(Location::Stack), stackOffset_(stackOffset) {
validate();
}
ValType type() const { return type_; }
bool onStack() const { return loc_ == Location::Stack; }
bool inRegister() const { return !onStack(); }
Register gpr() const {
MOZ_ASSERT(loc_ == Location::Gpr);
return gpr_;
}
Register64 gpr64() const {
MOZ_ASSERT(loc_ == Location::Gpr64);
return gpr64_;
}
FloatRegister fpr() const {
MOZ_ASSERT(loc_ == Location::Fpr);
return fpr_;
}
// Offset from SP.
uint32_t stackOffset() const {
MOZ_ASSERT(loc_ == Location::Stack);
return stackOffset_;
}
uint32_t size() const;
};
// Just as WebAssembly functions can take multiple arguments, they can also
// return multiple results. As with a call, a limited number of results will be
// located in registers, and the rest will be stored in a stack area. The
// |ABIResultIter| computes result locations, given a |ResultType|.
//
// Recall that a |ResultType| represents a sequence of value types t1..tN,
// indexed from 1 to N. In principle it doesn't matter how we decide which
// results get to be in registers and which go to the stack. To better
// harmonize with WebAssembly's abstract stack machine, whose properties are
// taken advantage of by the baseline compiler, our strategy is to start
// allocating result locations in "reverse" order: from result N down to 1.
//
// If a result with index I is in a register, then all results with index J > I
// are also in registers. If a result I is on the stack, then all results with
// index K < I are also on the stack, farther away from the stack pointer than
// result I.
//
// Currently only a single result is ever stored in a register, though this may
// change in the future on register-rich platforms.
//
// NB: The baseline compiler also uses thie ABI for locations of block
// parameters and return values, within individual WebAssembly functions.
class ABIResultIter {
ResultType type_;
uint32_t count_;
uint32_t index_;
uint32_t nextStackOffset_;
enum { Next, Prev } direction_;
ABIResult cur_;
void settleRegister(ValType type);
void settleNext();
void settlePrev();
public:
explicit ABIResultIter(const ResultType& type)
: type_(type), count_(type.length()) {
reset();
}
void reset() {
index_ = nextStackOffset_ = 0;
direction_ = Next;
if (!done()) {
settleNext();
}
}
bool done() const { return index_ == count_; }
uint32_t index() const { return index_; }
uint32_t count() const { return count_; }
uint32_t remaining() const { return count_ - index_; }
void switchToNext() {
MOZ_ASSERT(direction_ == Prev);
if (!done() && cur().onStack()) {
nextStackOffset_ += cur().size();
}
index_ = count_ - index_;
direction_ = Next;
if (!done()) {
settleNext();
}
}
void switchToPrev() {
MOZ_ASSERT(direction_ == Next);
if (!done() && cur().onStack()) {
nextStackOffset_ -= cur().size();
}
index_ = count_ - index_;
direction_ = Prev;
if (!done()) settlePrev();
}
void next() {
MOZ_ASSERT(direction_ == Next);
MOZ_ASSERT(!done());
index_++;
if (!done()) {
settleNext();
}
}
void prev() {
MOZ_ASSERT(direction_ == Prev);
MOZ_ASSERT(!done());
index_++;
if (!done()) {
settlePrev();
}
}
const ABIResult& cur() const {
MOZ_ASSERT(!done());
return cur_;
}
uint32_t stackBytesConsumedSoFar() const { return nextStackOffset_; }
static inline bool HasStackResults(const ResultType& type) {
return type.length() > MaxRegisterResults;
}
static uint32_t MeasureStackBytes(const ResultType& type) {
if (!HasStackResults(type)) {
return 0;
}
ABIResultIter iter(type);
while (!iter.done()) {
iter.next();
}
return iter.stackBytesConsumedSoFar();
}
};
extern bool GenerateBuiltinThunk(jit::MacroAssembler& masm,
jit::ABIFunctionType abiType,
ExitReason exitReason, void* funcPtr,
CallableOffsets* offsets);
extern bool GenerateImportFunctions(const ModuleEnvironment& env,
const FuncImportVector& imports,
CompiledCode* code);
extern bool GenerateStubs(const ModuleEnvironment& env,
const FuncImportVector& imports,
const FuncExportVector& exports, CompiledCode* code);
extern bool GenerateEntryStubs(jit::MacroAssembler& masm,
size_t funcExportIndex, const FuncExport& fe,
const FuncType& funcType,
const Maybe<jit::ImmPtr>& callee, bool isAsmJS,
CodeRangeVector* codeRanges);
extern void GenerateTrapExitRegisterOffsets(jit::RegisterOffsets* offsets,
size_t* numWords);
extern bool GenerateProvisionalLazyJitEntryStub(jit::MacroAssembler& masm,
Offsets* offsets);
// A value that is written into the trap exit frame, which is useful for
// cross-checking during garbage collection.
static constexpr uintptr_t TrapExitDummyValue = 1337;
// And its offset, in words, down from the highest-addressed word of the trap
// exit frame. The value is written into the frame using WasmPush. In the
// case where WasmPush allocates more than one word, the value will therefore
// be written at the lowest-addressed word.
#ifdef JS_CODEGEN_ARM64
static constexpr size_t TrapExitDummyValueOffsetFromTop = 1;
#else
static constexpr size_t TrapExitDummyValueOffsetFromTop = 0;
#endif
// An argument that will end up on the stack according to the system ABI, to be
// passed to GenerateDirectCallFromJit. Since the direct JIT call creates its
// own frame, it is its responsibility to put stack arguments to their expected
// locations; so the caller of GenerateDirectCallFromJit can put them anywhere.
class JitCallStackArg {
public:
enum class Tag {
Imm32,
GPR,
FPU,
Address,
Undefined,
};
private:
Tag tag_;
union U {
int32_t imm32_;
jit::Register gpr_;
jit::FloatRegister fpu_;
jit::Address addr_;
U() {}
} arg;
public:
JitCallStackArg() : tag_(Tag::Undefined) {}
explicit JitCallStackArg(int32_t imm32) : tag_(Tag::Imm32) {
arg.imm32_ = imm32;
}
explicit JitCallStackArg(jit::Register gpr) : tag_(Tag::GPR) {
arg.gpr_ = gpr;
}
explicit JitCallStackArg(jit::FloatRegister fpu) : tag_(Tag::FPU) {
new (&arg) jit::FloatRegister(fpu);
}
explicit JitCallStackArg(const jit::Address& addr) : tag_(Tag::Address) {
new (&arg) jit::Address(addr);
}
Tag tag() const { return tag_; }
int32_t imm32() const {
MOZ_ASSERT(tag_ == Tag::Imm32);
return arg.imm32_;
}
jit::Register gpr() const {
MOZ_ASSERT(tag_ == Tag::GPR);
return arg.gpr_;
}
jit::FloatRegister fpu() const {
MOZ_ASSERT(tag_ == Tag::FPU);
return arg.fpu_;
}
const jit::Address& addr() const {
MOZ_ASSERT(tag_ == Tag::Address);
return arg.addr_;
}
};
using JitCallStackArgVector = Vector<JitCallStackArg, 4, SystemAllocPolicy>;
// Generates an inline wasm call (during jit compilation) to a specific wasm
// function (as specifed by the given FuncExport).
// This call doesn't go through a wasm entry, but rather creates its own
// inlined exit frame.
// Assumes:
// - all the registers have been preserved by the caller,
// - all arguments passed in registers have been set up at the expected
// locations,
// - all arguments passed on stack slot are alive as defined by a corresponding
// JitCallStackArg.
extern void GenerateDirectCallFromJit(jit::MacroAssembler& masm,
const FuncExport& fe,
const Instance& inst,
const JitCallStackArgVector& stackArgs,
jit::Register scratch,
uint32_t* callOffset);
} // namespace wasm
} // namespace js
#endif // wasm_stubs_h