// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/signature.h"
#include "src/bit-vector.h"
#include "src/flags.h"
#include "src/handles.h"
#include "src/zone-containers.h"
#include "src/wasm/ast-decoder.h"
#include "src/wasm/decoder.h"
#include "src/wasm/wasm-module.h"
#include "src/wasm/wasm-opcodes.h"
#include "src/ostreams.h"
#include "src/compiler/wasm-compiler.h"
namespace v8 {
namespace internal {
namespace wasm {
#if DEBUG
#define TRACE(...) \
do { \
if (FLAG_trace_wasm_decoder) PrintF(__VA_ARGS__); \
} while (false)
#else
#define TRACE(...)
#endif
// The root of a decoded tree.
struct Tree {
LocalType type; // tree type.
uint32_t count; // number of children.
const byte* pc; // start of the syntax tree.
TFNode* node; // node in the TurboFan graph.
Tree* children[1]; // pointers to children.
WasmOpcode opcode() const { return static_cast<WasmOpcode>(*pc); }
};
// An SsaEnv environment carries the current local variable renaming
// as well as the current effect and control dependency in the TF graph.
// It maintains a control state that tracks whether the environment
// is reachable, has reached a control end, or has been merged.
struct SsaEnv {
enum State { kControlEnd, kUnreachable, kReached, kMerged };
State state;
TFNode* control;
TFNode* effect;
TFNode** locals;
bool go() { return state >= kReached; }
void Kill(State new_state = kControlEnd) {
state = new_state;
locals = nullptr;
control = nullptr;
effect = nullptr;
}
void SetNotMerged() {
if (state == kMerged) state = kReached;
}
};
// An entry on the value stack.
struct Value {
const byte* pc;
TFNode* node;
LocalType type;
};
// An entry on the control stack (i.e. if, block, loop).
struct Control {
const byte* pc;
int stack_depth; // stack height at the beginning of the construct.
SsaEnv* end_env; // end environment for the construct.
SsaEnv* false_env; // false environment (only for if).
TFNode* node; // result node for the construct.
LocalType type; // result type for the construct.
bool is_loop; // true if this is the inner label of a loop.
bool is_if() { return *pc == kExprIf; }
bool is_block() { return *pc == kExprBlock; }
};
// Macros that build nodes only if there is a graph and the current SSA
// environment is reachable from start. This avoids problems with malformed
// TF graphs when decoding inputs that have unreachable code.
#define BUILD(func, ...) (build() ? builder_->func(__VA_ARGS__) : nullptr)
#define BUILD0(func) (build() ? builder_->func() : nullptr)
// Generic Wasm bytecode decoder with utilities for decoding operands,
// lengths, etc.
class WasmDecoder : public Decoder {
public:
WasmDecoder(ModuleEnv* module, FunctionSig* sig, const byte* start,
const byte* end)
: Decoder(start, end),
module_(module),
sig_(sig),
total_locals_(0),
local_types_(nullptr) {}
ModuleEnv* module_;
FunctionSig* sig_;
size_t total_locals_;
ZoneVector<LocalType>* local_types_;
byte ByteOperand(const byte* pc, const char* msg = "missing 1-byte operand") {
if ((pc + sizeof(byte)) >= limit_) {
error(pc, msg);
return 0;
}
return pc[1];
}
uint32_t Uint32Operand(const byte* pc) {
if ((pc + sizeof(uint32_t)) >= limit_) {
error(pc, "missing 4-byte operand");
return 0;
}
return read_u32(pc + 1);
}
uint64_t Uint64Operand(const byte* pc) {
if ((pc + sizeof(uint64_t)) >= limit_) {
error(pc, "missing 8-byte operand");
return 0;
}
return read_u64(pc + 1);
}
inline bool Validate(const byte* pc, LocalIndexOperand& operand) {
if (operand.index < total_locals_) {
if (local_types_) {
operand.type = local_types_->at(operand.index);
} else {
operand.type = kAstStmt;
}
return true;
}
error(pc, pc + 1, "invalid local index");
return false;
}
inline bool Validate(const byte* pc, GlobalIndexOperand& operand) {
ModuleEnv* m = module_;
if (m && m->module && operand.index < m->module->globals.size()) {
operand.machine_type = m->module->globals[operand.index].type;
operand.type = WasmOpcodes::LocalTypeFor(operand.machine_type);
return true;
}
error(pc, pc + 1, "invalid global index");
return false;
}
inline bool Validate(const byte* pc, CallFunctionOperand& operand) {
ModuleEnv* m = module_;
if (m && m->module && operand.index < m->module->functions.size()) {
operand.sig = m->module->functions[operand.index].sig;
uint32_t expected = static_cast<uint32_t>(operand.sig->parameter_count());
if (operand.arity != expected) {
error(pc, pc + 1,
"arity mismatch in direct function call (expected %u, got %u)",
expected, operand.arity);
return false;
}
return true;
}
error(pc, pc + 1, "invalid function index");
return false;
}
inline bool Validate(const byte* pc, CallIndirectOperand& operand) {
ModuleEnv* m = module_;
if (m && m->module && operand.index < m->module->signatures.size()) {
operand.sig = m->module->signatures[operand.index];
uint32_t expected = static_cast<uint32_t>(operand.sig->parameter_count());
if (operand.arity != expected) {
error(pc, pc + 1,
"arity mismatch in indirect function call (expected %u, got %u)",
expected, operand.arity);
return false;
}
return true;
}
error(pc, pc + 1, "invalid signature index");
return false;
}
inline bool Validate(const byte* pc, CallImportOperand& operand) {
ModuleEnv* m = module_;
if (m && m->module && operand.index < m->module->import_table.size()) {
operand.sig = m->module->import_table[operand.index].sig;
uint32_t expected = static_cast<uint32_t>(operand.sig->parameter_count());
if (operand.arity != expected) {
error(pc, pc + 1, "arity mismatch in import call (expected %u, got %u)",
expected, operand.arity);
return false;
}
return true;
}
error(pc, pc + 1, "invalid signature index");
return false;
}
inline bool Validate(const byte* pc, BreakDepthOperand& operand,
ZoneVector<Control>& control) {
if (operand.arity > 1) {
error(pc, pc + 1, "invalid arity for br or br_if");
return false;
}
if (operand.depth < control.size()) {
operand.target = &control[control.size() - operand.depth - 1];
return true;
}
error(pc, pc + 1, "invalid break depth");
return false;
}
bool Validate(const byte* pc, BranchTableOperand& operand,
size_t block_depth) {
if (operand.arity > 1) {
error(pc, pc + 1, "invalid arity for break");
return false;
}
// Verify table.
for (uint32_t i = 0; i < operand.table_count + 1; i++) {
uint32_t target = operand.read_entry(this, i);
if (target >= block_depth) {
error(operand.table + i * 2, "improper branch in br_table");
return false;
}
}
return true;
}
int OpcodeArity(const byte* pc) {
#define DECLARE_ARITY(name, ...) \
static const LocalType kTypes_##name[] = {__VA_ARGS__}; \
static const int kArity_##name = \
static_cast<int>(arraysize(kTypes_##name) - 1);
FOREACH_SIGNATURE(DECLARE_ARITY);
#undef DECLARE_ARITY
switch (static_cast<WasmOpcode>(*pc)) {
case kExprI8Const:
case kExprI32Const:
case kExprI64Const:
case kExprF64Const:
case kExprF32Const:
case kExprGetLocal:
case kExprLoadGlobal:
case kExprNop:
case kExprUnreachable:
case kExprEnd:
case kExprBlock:
case kExprLoop:
return 0;
case kExprStoreGlobal:
case kExprSetLocal:
case kExprElse:
return 1;
case kExprBr: {
BreakDepthOperand operand(this, pc);
return operand.arity;
}
case kExprBrIf: {
BreakDepthOperand operand(this, pc);
return 1 + operand.arity;
}
case kExprBrTable: {
BranchTableOperand operand(this, pc);
return 1 + operand.arity;
}
case kExprIf:
return 1;
case kExprSelect:
return 3;
case kExprCallFunction: {
CallFunctionOperand operand(this, pc);
return operand.arity;
}
case kExprCallIndirect: {
CallIndirectOperand operand(this, pc);
return 1 + operand.arity;
}
case kExprCallImport: {
CallImportOperand operand(this, pc);
return operand.arity;
}
case kExprReturn: {
ReturnArityOperand operand(this, pc);
return operand.arity;
}
#define DECLARE_OPCODE_CASE(name, opcode, sig) \
case kExpr##name: \
return kArity_##sig;
FOREACH_LOAD_MEM_OPCODE(DECLARE_OPCODE_CASE)
FOREACH_STORE_MEM_OPCODE(DECLARE_OPCODE_CASE)
FOREACH_MISC_MEM_OPCODE(DECLARE_OPCODE_CASE)
FOREACH_SIMPLE_OPCODE(DECLARE_OPCODE_CASE)
FOREACH_ASMJS_COMPAT_OPCODE(DECLARE_OPCODE_CASE)
#undef DECLARE_OPCODE_CASE
default:
UNREACHABLE();
return 0;
}
}
int OpcodeLength(const byte* pc) {
switch (static_cast<WasmOpcode>(*pc)) {
#define DECLARE_OPCODE_CASE(name, opcode, sig) case kExpr##name:
FOREACH_LOAD_MEM_OPCODE(DECLARE_OPCODE_CASE)
FOREACH_STORE_MEM_OPCODE(DECLARE_OPCODE_CASE)
#undef DECLARE_OPCODE_CASE
{
MemoryAccessOperand operand(this, pc);
return 1 + operand.length;
}
case kExprBr:
case kExprBrIf: {
BreakDepthOperand operand(this, pc);
return 1 + operand.length;
}
case kExprStoreGlobal:
case kExprLoadGlobal: {
GlobalIndexOperand operand(this, pc);
return 1 + operand.length;
}
case kExprCallFunction: {
CallFunctionOperand operand(this, pc);
return 1 + operand.length;
}
case kExprCallIndirect: {
CallIndirectOperand operand(this, pc);
return 1 + operand.length;
}
case kExprCallImport: {
CallImportOperand operand(this, pc);
return 1 + operand.length;
}
case kExprSetLocal:
case kExprGetLocal: {
LocalIndexOperand operand(this, pc);
return 1 + operand.length;
}
case kExprBrTable: {
BranchTableOperand operand(this, pc);
return 1 + operand.length;
}
case kExprI32Const: {
ImmI32Operand operand(this, pc);
return 1 + operand.length;
}
case kExprI64Const: {
ImmI64Operand operand(this, pc);
return 1 + operand.length;
}
case kExprI8Const:
return 2;
case kExprF32Const:
return 5;
case kExprF64Const:
return 9;
case kExprReturn: {
ReturnArityOperand operand(this, pc);
return 1 + operand.length;
}
default:
return 1;
}
}
};
// A shift-reduce-parser strategy for decoding Wasm code that uses an explicit
// shift-reduce strategy with multiple internal stacks.
class SR_WasmDecoder : public WasmDecoder {
public:
SR_WasmDecoder(Zone* zone, TFBuilder* builder, FunctionBody& body)
: WasmDecoder(body.module, body.sig, body.start, body.end),
zone_(zone),
builder_(builder),
base_(body.base),
local_type_vec_(zone),
stack_(zone),
control_(zone) {
local_types_ = &local_type_vec_;
}
bool Decode() {
base::ElapsedTimer decode_timer;
if (FLAG_trace_wasm_decode_time) {
decode_timer.Start();
}
stack_.clear();
control_.clear();
if (end_ < pc_) {
error(pc_, "function body end < start");
return false;
}
DecodeLocalDecls();
InitSsaEnv();
DecodeFunctionBody();
if (failed()) return TraceFailed();
if (!control_.empty()) {
error(pc_, control_.back().pc, "unterminated control structure");
return TraceFailed();
}
if (ssa_env_->go()) {
TRACE(" @%-6d #xx:%-20s|", startrel(pc_), "ImplicitReturn");
DoReturn();
if (failed()) return TraceFailed();
TRACE("\n");
}
if (FLAG_trace_wasm_decode_time) {
double ms = decode_timer.Elapsed().InMillisecondsF();
PrintF("wasm-decode ok (%0.3f ms)\n\n", ms);
} else {
TRACE("wasm-decode ok\n\n");
}
return true;
}
bool TraceFailed() {
TRACE("wasm-error module+%-6d func+%d: %s\n\n", baserel(error_pc_),
startrel(error_pc_), error_msg_.get());
return false;
}
bool DecodeLocalDecls(AstLocalDecls& decls) {
DecodeLocalDecls();
if (failed()) return false;
decls.decls_encoded_size = pc_offset();
decls.local_types.reserve(local_type_vec_.size());
for (size_t pos = 0; pos < local_type_vec_.size();) {
uint32_t count = 0;
LocalType type = local_type_vec_[pos];
while (pos < local_type_vec_.size() && local_type_vec_[pos] == type) {
pos++;
count++;
}
decls.local_types.push_back(std::pair<LocalType, uint32_t>(type, count));
}
decls.total_local_count = static_cast<uint32_t>(local_type_vec_.size());
return true;
}
BitVector* AnalyzeLoopAssignmentForTesting(const byte* pc,
size_t num_locals) {
total_locals_ = num_locals;
local_type_vec_.reserve(num_locals);
if (num_locals > local_type_vec_.size()) {
local_type_vec_.insert(local_type_vec_.end(),
num_locals - local_type_vec_.size(), kAstI32);
}
return AnalyzeLoopAssignment(pc);
}
private:
static const size_t kErrorMsgSize = 128;
Zone* zone_;
TFBuilder* builder_;
const byte* base_;
SsaEnv* ssa_env_;
ZoneVector<LocalType> local_type_vec_; // types of local variables.
ZoneVector<Value> stack_; // stack of values.
ZoneVector<Control> control_; // stack of blocks, loops, and ifs.
inline bool build() { return builder_ && ssa_env_->go(); }
void InitSsaEnv() {
TFNode* start = nullptr;
SsaEnv* ssa_env = reinterpret_cast<SsaEnv*>(zone_->New(sizeof(SsaEnv)));
size_t size = sizeof(TFNode*) * EnvironmentCount();
ssa_env->state = SsaEnv::kReached;
ssa_env->locals =
size > 0 ? reinterpret_cast<TFNode**>(zone_->New(size)) : nullptr;
if (builder_) {
start = builder_->Start(static_cast<int>(sig_->parameter_count() + 1));
// Initialize local variables.
uint32_t index = 0;
while (index < sig_->parameter_count()) {
ssa_env->locals[index] = builder_->Param(index, local_type_vec_[index]);
index++;
}
while (index < local_type_vec_.size()) {
LocalType type = local_type_vec_[index];
TFNode* node = DefaultValue(type);
while (index < local_type_vec_.size() &&
local_type_vec_[index] == type) {
// Do a whole run of like-typed locals at a time.
ssa_env->locals[index++] = node;
}
}
builder_->set_module(module_);
}
ssa_env->control = start;
ssa_env->effect = start;
SetEnv("initial", ssa_env);
}
TFNode* DefaultValue(LocalType type) {
switch (type) {
case kAstI32:
return builder_->Int32Constant(0);
case kAstI64:
return builder_->Int64Constant(0);
case kAstF32:
return builder_->Float32Constant(0);
case kAstF64:
return builder_->Float64Constant(0);
default:
UNREACHABLE();
return nullptr;
}
}
char* indentation() {
static const int kMaxIndent = 64;
static char bytes[kMaxIndent + 1];
for (int i = 0; i < kMaxIndent; i++) bytes[i] = ' ';
bytes[kMaxIndent] = 0;
if (stack_.size() < kMaxIndent / 2) {
bytes[stack_.size() * 2] = 0;
}
return bytes;
}
// Decodes the locals declarations, if any, populating {local_type_vec_}.
void DecodeLocalDecls() {
DCHECK_EQ(0, local_type_vec_.size());
// Initialize {local_type_vec} from signature.
if (sig_) {
local_type_vec_.reserve(sig_->parameter_count());
for (size_t i = 0; i < sig_->parameter_count(); i++) {
local_type_vec_.push_back(sig_->GetParam(i));
}
}
// Decode local declarations, if any.
int length;
uint32_t entries = consume_u32v(&length, "local decls count");
while (entries-- > 0 && pc_ < limit_) {
uint32_t count = consume_u32v(&length, "local count");
byte code = consume_u8("local type");
LocalType type;
switch (code) {
case kLocalI32:
type = kAstI32;
break;
case kLocalI64:
type = kAstI64;
break;
case kLocalF32:
type = kAstF32;
break;
case kLocalF64:
type = kAstF64;
break;
default:
error(pc_ - 1, "invalid local type");
return;
}
local_type_vec_.insert(local_type_vec_.end(), count, type);
}
total_locals_ = local_type_vec_.size();
}
// Decodes the body of a function.
void DecodeFunctionBody() {
TRACE("wasm-decode %p...%p (module+%d, %d bytes) %s\n",
reinterpret_cast<const void*>(start_),
reinterpret_cast<const void*>(limit_), baserel(pc_),
static_cast<int>(limit_ - start_), builder_ ? "graph building" : "");
if (pc_ >= limit_) return; // Nothing to do.
while (true) { // decoding loop.
int len = 1;
WasmOpcode opcode = static_cast<WasmOpcode>(*pc_);
TRACE(" @%-6d #%02x:%-20s|", startrel(pc_), opcode,
WasmOpcodes::ShortOpcodeName(opcode));
FunctionSig* sig = WasmOpcodes::Signature(opcode);
if (sig) {
// Fast case of a simple operator.
TFNode* node;
switch (sig->parameter_count()) {
case 1: {
Value val = Pop(0, sig->GetParam(0));
node = BUILD(Unop, opcode, val.node, position());
break;
}
case 2: {
Value rval = Pop(1, sig->GetParam(1));
Value lval = Pop(0, sig->GetParam(0));
node = BUILD(Binop, opcode, lval.node, rval.node, position());
break;
}
default:
UNREACHABLE();
node = nullptr;
break;
}
Push(GetReturnType(sig), node);
} else {
// Complex bytecode.
switch (opcode) {
case kExprNop:
Push(kAstStmt, nullptr);
break;
case kExprBlock: {
// The break environment is the outer environment.
SsaEnv* break_env = ssa_env_;
PushBlock(break_env);
SetEnv("block:start", Steal(break_env));
break;
}
case kExprLoop: {
// The break environment is the outer environment.
SsaEnv* break_env = ssa_env_;
PushBlock(break_env);
SsaEnv* cont_env = Steal(break_env);
// The continue environment is the inner environment.
PrepareForLoop(pc_, cont_env);
SetEnv("loop:start", Split(cont_env));
ssa_env_->SetNotMerged();
PushLoop(cont_env);
break;
}
case kExprIf: {
// Condition on top of stack. Split environments for branches.
Value cond = Pop(0, kAstI32);
TFNode* if_true = nullptr;
TFNode* if_false = nullptr;
BUILD(Branch, cond.node, &if_true, &if_false);
SsaEnv* end_env = ssa_env_;
SsaEnv* false_env = Split(ssa_env_);
false_env->control = if_false;
SsaEnv* true_env = Steal(ssa_env_);
true_env->control = if_true;
PushIf(end_env, false_env);
SetEnv("if:true", true_env);
break;
}
case kExprElse: {
if (control_.empty()) {
error(pc_, "else does not match any if");
break;
}
Control* c = &control_.back();
if (!c->is_if()) {
error(pc_, c->pc, "else does not match an if");
break;
}
if (c->false_env == nullptr) {
error(pc_, c->pc, "else already present for if");
break;
}
Value val = PopUpTo(c->stack_depth);
MergeInto(c->end_env, &c->node, &c->type, val);
// Switch to environment for false branch.
SetEnv("if_else:false", c->false_env);
c->false_env = nullptr; // record that an else is already seen
break;
}
case kExprEnd: {
if (control_.empty()) {
error(pc_, "end does not match any if or block");
break;
}
const char* name = "block:end";
Control* c = &control_.back();
if (c->is_loop) {
// Loops always push control in pairs.
control_.pop_back();
c = &control_.back();
name = "loop:end";
}
Value val = PopUpTo(c->stack_depth);
if (c->is_if()) {
if (c->false_env != nullptr) {
// End the true branch of a one-armed if.
Goto(c->false_env, c->end_env);
val = {val.pc, nullptr, kAstStmt};
name = "if:merge";
} else {
// End the false branch of a two-armed if.
name = "if_else:merge";
}
}
if (ssa_env_->go()) {
MergeInto(c->end_env, &c->node, &c->type, val);
}
SetEnv(name, c->end_env);
stack_.resize(c->stack_depth);
Push(c->type, c->node);
control_.pop_back();
break;
}
case kExprSelect: {
Value cond = Pop(2, kAstI32);
Value fval = Pop();
Value tval = Pop();
if (tval.type == kAstStmt || tval.type != fval.type) {
if (tval.type != kAstEnd && fval.type != kAstEnd) {
error(pc_, "type mismatch in select");
break;
}
}
if (build()) {
DCHECK(tval.type != kAstEnd);
DCHECK(fval.type != kAstEnd);
DCHECK(cond.type != kAstEnd);
TFNode* controls[2];
builder_->Branch(cond.node, &controls[0], &controls[1]);
TFNode* merge = builder_->Merge(2, controls);
TFNode* vals[2] = {tval.node, fval.node};
TFNode* phi = builder_->Phi(tval.type, 2, vals, merge);
Push(tval.type, phi);
ssa_env_->control = merge;
} else {
Push(tval.type, nullptr);
}
break;
}
case kExprBr: {
BreakDepthOperand operand(this, pc_);
Value val = {pc_, nullptr, kAstStmt};
if (operand.arity) val = Pop();
if (Validate(pc_, operand, control_)) {
BreakTo(operand.target, val);
}
len = 1 + operand.length;
Push(kAstEnd, nullptr);
break;
}
case kExprBrIf: {
BreakDepthOperand operand(this, pc_);
Value cond = Pop(operand.arity, kAstI32);
Value val = {pc_, nullptr, kAstStmt};
if (operand.arity == 1) val = Pop();
if (Validate(pc_, operand, control_)) {
SsaEnv* fenv = ssa_env_;
SsaEnv* tenv = Split(fenv);
fenv->SetNotMerged();
BUILD(Branch, cond.node, &tenv->control, &fenv->control);
ssa_env_ = tenv;
BreakTo(operand.target, val);
ssa_env_ = fenv;
}
len = 1 + operand.length;
Push(kAstStmt, nullptr);
break;
}
case kExprBrTable: {
BranchTableOperand operand(this, pc_);
if (Validate(pc_, operand, control_.size())) {
Value key = Pop(operand.arity, kAstI32);
Value val = {pc_, nullptr, kAstStmt};
if (operand.arity == 1) val = Pop();
if (failed()) break;
SsaEnv* break_env = ssa_env_;
if (operand.table_count > 0) {
// Build branches to the various blocks based on the table.
TFNode* sw = BUILD(Switch, operand.table_count + 1, key.node);
SsaEnv* copy = Steal(break_env);
ssa_env_ = copy;
for (uint32_t i = 0; i < operand.table_count + 1; i++) {
uint16_t target = operand.read_entry(this, i);
ssa_env_ = Split(copy);
ssa_env_->control = (i == operand.table_count)
? BUILD(IfDefault, sw)
: BUILD(IfValue, i, sw);
int depth = target;
Control* c = &control_[control_.size() - depth - 1];
MergeInto(c->end_env, &c->node, &c->type, val);
}
} else {
// Only a default target. Do the equivalent of br.
uint16_t target = operand.read_entry(this, 0);
int depth = target;
Control* c = &control_[control_.size() - depth - 1];
MergeInto(c->end_env, &c->node, &c->type, val);
}
// br_table ends the control flow like br.
ssa_env_ = break_env;
Push(kAstStmt, nullptr);
}
len = 1 + operand.length;
break;
}
case kExprReturn: {
ReturnArityOperand operand(this, pc_);
if (operand.arity != sig_->return_count()) {
error(pc_, pc_ + 1, "arity mismatch in return");
}
DoReturn();
len = 1 + operand.length;
break;
}
case kExprUnreachable: {
Push(kAstEnd, BUILD(Unreachable, position()));
ssa_env_->Kill(SsaEnv::kControlEnd);
break;
}
case kExprI8Const: {
ImmI8Operand operand(this, pc_);
Push(kAstI32, BUILD(Int32Constant, operand.value));
len = 1 + operand.length;
break;
}
case kExprI32Const: {
ImmI32Operand operand(this, pc_);
Push(kAstI32, BUILD(Int32Constant, operand.value));
len = 1 + operand.length;
break;
}
case kExprI64Const: {
ImmI64Operand operand(this, pc_);
Push(kAstI64, BUILD(Int64Constant, operand.value));
len = 1 + operand.length;
break;
}
case kExprF32Const: {
ImmF32Operand operand(this, pc_);
Push(kAstF32, BUILD(Float32Constant, operand.value));
len = 1 + operand.length;
break;
}
case kExprF64Const: {
ImmF64Operand operand(this, pc_);
Push(kAstF64, BUILD(Float64Constant, operand.value));
len = 1 + operand.length;
break;
}
case kExprGetLocal: {
LocalIndexOperand operand(this, pc_);
if (Validate(pc_, operand)) {
if (build()) {
Push(operand.type, ssa_env_->locals[operand.index]);
} else {
Push(operand.type, nullptr);
}
}
len = 1 + operand.length;
break;
}
case kExprSetLocal: {
LocalIndexOperand operand(this, pc_);
if (Validate(pc_, operand)) {
Value val = Pop(0, local_type_vec_[operand.index]);
if (ssa_env_->locals) ssa_env_->locals[operand.index] = val.node;
Push(val.type, val.node);
}
len = 1 + operand.length;
break;
}
case kExprLoadGlobal: {
GlobalIndexOperand operand(this, pc_);
if (Validate(pc_, operand)) {
Push(operand.type, BUILD(LoadGlobal, operand.index));
}
len = 1 + operand.length;
break;
}
case kExprStoreGlobal: {
GlobalIndexOperand operand(this, pc_);
if (Validate(pc_, operand)) {
Value val = Pop(0, operand.type);
BUILD(StoreGlobal, operand.index, val.node);
Push(val.type, val.node);
}
len = 1 + operand.length;
break;
}
case kExprI32LoadMem8S:
len = DecodeLoadMem(kAstI32, MachineType::Int8());
break;
case kExprI32LoadMem8U:
len = DecodeLoadMem(kAstI32, MachineType::Uint8());
break;
case kExprI32LoadMem16S:
len = DecodeLoadMem(kAstI32, MachineType::Int16());
break;
case kExprI32LoadMem16U:
len = DecodeLoadMem(kAstI32, MachineType::Uint16());
break;
case kExprI32LoadMem:
len = DecodeLoadMem(kAstI32, MachineType::Int32());
break;
case kExprI64LoadMem8S:
len = DecodeLoadMem(kAstI64, MachineType::Int8());
break;
case kExprI64LoadMem8U:
len = DecodeLoadMem(kAstI64, MachineType::Uint8());
break;
case kExprI64LoadMem16S:
len = DecodeLoadMem(kAstI64, MachineType::Int16());
break;
case kExprI64LoadMem16U:
len = DecodeLoadMem(kAstI64, MachineType::Uint16());
break;
case kExprI64LoadMem32S:
len = DecodeLoadMem(kAstI64, MachineType::Int32());
break;
case kExprI64LoadMem32U:
len = DecodeLoadMem(kAstI64, MachineType::Uint32());
break;
case kExprI64LoadMem:
len = DecodeLoadMem(kAstI64, MachineType::Int64());
break;
case kExprF32LoadMem:
len = DecodeLoadMem(kAstF32, MachineType::Float32());
break;
case kExprF64LoadMem:
len = DecodeLoadMem(kAstF64, MachineType::Float64());
break;
case kExprI32StoreMem8:
len = DecodeStoreMem(kAstI32, MachineType::Int8());
break;
case kExprI32StoreMem16:
len = DecodeStoreMem(kAstI32, MachineType::Int16());
break;
case kExprI32StoreMem:
len = DecodeStoreMem(kAstI32, MachineType::Int32());
break;
case kExprI64StoreMem8:
len = DecodeStoreMem(kAstI64, MachineType::Int8());
break;
case kExprI64StoreMem16:
len = DecodeStoreMem(kAstI64, MachineType::Int16());
break;
case kExprI64StoreMem32:
len = DecodeStoreMem(kAstI64, MachineType::Int32());
break;
case kExprI64StoreMem:
len = DecodeStoreMem(kAstI64, MachineType::Int64());
break;
case kExprF32StoreMem:
len = DecodeStoreMem(kAstF32, MachineType::Float32());
break;
case kExprF64StoreMem:
len = DecodeStoreMem(kAstF64, MachineType::Float64());
break;
case kExprMemorySize:
Push(kAstI32, BUILD(MemSize, 0));
break;
case kExprGrowMemory: {
Value val = Pop(0, kAstI32);
USE(val); // TODO(titzer): build node for grow memory
Push(kAstI32, BUILD(Int32Constant, 0));
break;
}
case kExprCallFunction: {
CallFunctionOperand operand(this, pc_);
if (Validate(pc_, operand)) {
TFNode** buffer = PopArgs(operand.sig);
TFNode* call =
BUILD(CallDirect, operand.index, buffer, position());
Push(GetReturnType(operand.sig), call);
}
len = 1 + operand.length;
break;
}
case kExprCallIndirect: {
CallIndirectOperand operand(this, pc_);
if (Validate(pc_, operand)) {
TFNode** buffer = PopArgs(operand.sig);
Value index = Pop(0, kAstI32);
if (buffer) buffer[0] = index.node;
TFNode* call =
BUILD(CallIndirect, operand.index, buffer, position());
Push(GetReturnType(operand.sig), call);
}
len = 1 + operand.length;
break;
}
case kExprCallImport: {
CallImportOperand operand(this, pc_);
if (Validate(pc_, operand)) {
TFNode** buffer = PopArgs(operand.sig);
TFNode* call =
BUILD(CallImport, operand.index, buffer, position());
Push(GetReturnType(operand.sig), call);
}
len = 1 + operand.length;
break;
}
default:
error("Invalid opcode");
return;
}
} // end complex bytecode
#if DEBUG
if (FLAG_trace_wasm_decoder) {
for (size_t i = 0; i < stack_.size(); i++) {
Value& val = stack_[i];
WasmOpcode opcode = static_cast<WasmOpcode>(*val.pc);
PrintF(" %c@%d:%s", WasmOpcodes::ShortNameOf(val.type),
static_cast<int>(val.pc - start_),
WasmOpcodes::ShortOpcodeName(opcode));
switch (opcode) {
case kExprI32Const: {
ImmI32Operand operand(this, val.pc);
PrintF("[%d]", operand.value);
break;
}
case kExprGetLocal: {
LocalIndexOperand operand(this, val.pc);
PrintF("[%u]", operand.index);
break;
}
case kExprSetLocal: {
LocalIndexOperand operand(this, val.pc);
PrintF("[%u]", operand.index);
break;
}
default:
break;
}
}
PrintF("\n");
}
#endif
pc_ += len;
if (pc_ >= limit_) {
// End of code reached or exceeded.
if (pc_ > limit_ && ok()) error("Beyond end of code");
return;
}
} // end decode loop
} // end DecodeFunctionBody()
TFNode** PopArgs(FunctionSig* sig) {
if (build()) {
int count = static_cast<int>(sig->parameter_count());
TFNode** buffer = builder_->Buffer(count + 1);
buffer[0] = nullptr; // reserved for code object or function index.
for (int i = count - 1; i >= 0; i--) {
buffer[i + 1] = Pop(i, sig->GetParam(i)).node;
}
return buffer;
} else {
int count = static_cast<int>(sig->parameter_count());
for (int i = count - 1; i >= 0; i--) {
Pop(i, sig->GetParam(i));
}
return nullptr;
}
}
LocalType GetReturnType(FunctionSig* sig) {
return sig->return_count() == 0 ? kAstStmt : sig->GetReturn();
}
void PushBlock(SsaEnv* end_env) {
int stack_depth = static_cast<int>(stack_.size());
control_.push_back(
{pc_, stack_depth, end_env, nullptr, nullptr, kAstEnd, false});
}
void PushLoop(SsaEnv* end_env) {
int stack_depth = static_cast<int>(stack_.size());
control_.push_back(
{pc_, stack_depth, end_env, nullptr, nullptr, kAstEnd, true});
}
void PushIf(SsaEnv* end_env, SsaEnv* false_env) {
int stack_depth = static_cast<int>(stack_.size());
control_.push_back(
{pc_, stack_depth, end_env, false_env, nullptr, kAstStmt, false});
}
int DecodeLoadMem(LocalType type, MachineType mem_type) {
MemoryAccessOperand operand(this, pc_);
Value index = Pop(0, kAstI32);
TFNode* node =
BUILD(LoadMem, type, mem_type, index.node, operand.offset, position());
Push(type, node);
return 1 + operand.length;
}
int DecodeStoreMem(LocalType type, MachineType mem_type) {
MemoryAccessOperand operand(this, pc_);
Value val = Pop(1, type);
Value index = Pop(0, kAstI32);
BUILD(StoreMem, mem_type, index.node, operand.offset, val.node, position());
Push(type, val.node);
return 1 + operand.length;
}
void DoReturn() {
int count = static_cast<int>(sig_->return_count());
TFNode** buffer = nullptr;
if (build()) buffer = builder_->Buffer(count);
// Pop return values off the stack in reverse order.
for (int i = count - 1; i >= 0; i--) {
Value val = Pop(i, sig_->GetReturn(i));
if (buffer) buffer[i] = val.node;
}
Push(kAstEnd, BUILD(Return, count, buffer));
ssa_env_->Kill(SsaEnv::kControlEnd);
}
void Push(LocalType type, TFNode* node) {
stack_.push_back({pc_, node, type});
}
const char* SafeOpcodeNameAt(const byte* pc) {
if (pc >= end_) return "<end>";
return WasmOpcodes::ShortOpcodeName(static_cast<WasmOpcode>(*pc));
}
Value Pop(int index, LocalType expected) {
Value val = Pop();
if (val.type != expected) {
if (val.type != kAstEnd) {
error(pc_, val.pc, "%s[%d] expected type %s, found %s of type %s",
SafeOpcodeNameAt(pc_), index, WasmOpcodes::TypeName(expected),
SafeOpcodeNameAt(val.pc), WasmOpcodes::TypeName(val.type));
}
}
return val;
}
Value Pop() {
size_t limit = control_.empty() ? 0 : control_.back().stack_depth;
if (stack_.size() <= limit) {
Value val = {pc_, nullptr, kAstStmt};
error(pc_, pc_, "%s found empty stack", SafeOpcodeNameAt(pc_));
return val;
}
Value val = stack_.back();
stack_.pop_back();
return val;
}
Value PopUpTo(int stack_depth) {
if (stack_depth == stack_.size()) {
Value val = {pc_, nullptr, kAstStmt};
return val;
} else {
DCHECK_LE(stack_depth, static_cast<int>(stack_.size()));
Value val = Pop();
stack_.resize(stack_depth);
return val;
}
}
int baserel(const byte* ptr) {
return base_ ? static_cast<int>(ptr - base_) : 0;
}
int startrel(const byte* ptr) { return static_cast<int>(ptr - start_); }
void BreakTo(Control* block, Value& val) {
if (block->is_loop) {
// This is the inner loop block, which does not have a value.
Goto(ssa_env_, block->end_env);
} else {
// Merge the value into the production for the block.
MergeInto(block->end_env, &block->node, &block->type, val);
}
}
void MergeInto(SsaEnv* target, TFNode** node, LocalType* type, Value& val) {
if (!ssa_env_->go()) return;
DCHECK_NE(kAstEnd, val.type);
bool first = target->state == SsaEnv::kUnreachable;
Goto(ssa_env_, target);
if (first) {
// first merge to this environment; set the type and the node.
*type = val.type;
*node = val.node;
} else if (val.type == *type && val.type != kAstStmt) {
// merge with the existing value for this block.
*node = CreateOrMergeIntoPhi(*type, target->control, *node, val.node);
} else {
// types don't match, or block is already a stmt.
*type = kAstStmt;
*node = nullptr;
}
}
void SetEnv(const char* reason, SsaEnv* env) {
#if DEBUG
if (FLAG_trace_wasm_decoder) {
char state = 'X';
if (env) {
switch (env->state) {
case SsaEnv::kReached:
state = 'R';
break;
case SsaEnv::kUnreachable:
state = 'U';
break;
case SsaEnv::kMerged:
state = 'M';
break;
case SsaEnv::kControlEnd:
state = 'E';
break;
}
}
PrintF(" env = %p, state = %c, reason = %s", static_cast<void*>(env),
state, reason);
if (env && env->control) {
PrintF(", control = ");
compiler::WasmGraphBuilder::PrintDebugName(env->control);
}
PrintF("\n");
}
#endif
ssa_env_ = env;
if (builder_) {
builder_->set_control_ptr(&env->control);
builder_->set_effect_ptr(&env->effect);
}
}
void Goto(SsaEnv* from, SsaEnv* to) {
DCHECK_NOT_NULL(to);
if (!from->go()) return;
switch (to->state) {
case SsaEnv::kUnreachable: { // Overwrite destination.
to->state = SsaEnv::kReached;
to->locals = from->locals;
to->control = from->control;
to->effect = from->effect;
break;
}
case SsaEnv::kReached: { // Create a new merge.
to->state = SsaEnv::kMerged;
if (!builder_) break;
// Merge control.
TFNode* controls[] = {to->control, from->control};
TFNode* merge = builder_->Merge(2, controls);
to->control = merge;
// Merge effects.
if (from->effect != to->effect) {
TFNode* effects[] = {to->effect, from->effect, merge};
to->effect = builder_->EffectPhi(2, effects, merge);
}
// Merge SSA values.
for (int i = EnvironmentCount() - 1; i >= 0; i--) {
TFNode* a = to->locals[i];
TFNode* b = from->locals[i];
if (a != b) {
TFNode* vals[] = {a, b};
to->locals[i] = builder_->Phi(local_type_vec_[i], 2, vals, merge);
}
}
break;
}
case SsaEnv::kMerged: {
if (!builder_) break;
TFNode* merge = to->control;
// Extend the existing merge.
builder_->AppendToMerge(merge, from->control);
// Merge effects.
if (builder_->IsPhiWithMerge(to->effect, merge)) {
builder_->AppendToPhi(to->effect, from->effect);
} else if (to->effect != from->effect) {
uint32_t count = builder_->InputCount(merge);
TFNode** effects = builder_->Buffer(count);
for (uint32_t j = 0; j < count - 1; j++) {
effects[j] = to->effect;
}
effects[count - 1] = from->effect;
to->effect = builder_->EffectPhi(count, effects, merge);
}
// Merge locals.
for (int i = EnvironmentCount() - 1; i >= 0; i--) {
TFNode* tnode = to->locals[i];
TFNode* fnode = from->locals[i];
if (builder_->IsPhiWithMerge(tnode, merge)) {
builder_->AppendToPhi(tnode, fnode);
} else if (tnode != fnode) {
uint32_t count = builder_->InputCount(merge);
TFNode** vals = builder_->Buffer(count);
for (uint32_t j = 0; j < count - 1; j++) {
vals[j] = tnode;
}
vals[count - 1] = fnode;
to->locals[i] =
builder_->Phi(local_type_vec_[i], count, vals, merge);
}
}
break;
}
default:
UNREACHABLE();
}
return from->Kill();
}
TFNode* CreateOrMergeIntoPhi(LocalType type, TFNode* merge, TFNode* tnode,
TFNode* fnode) {
if (builder_->IsPhiWithMerge(tnode, merge)) {
builder_->AppendToPhi(tnode, fnode);
} else if (tnode != fnode) {
uint32_t count = builder_->InputCount(merge);
TFNode** vals = builder_->Buffer(count);
for (uint32_t j = 0; j < count - 1; j++) vals[j] = tnode;
vals[count - 1] = fnode;
return builder_->Phi(type, count, vals, merge);
}
return tnode;
}
void PrepareForLoop(const byte* pc, SsaEnv* env) {
if (!env->go()) return;
env->state = SsaEnv::kMerged;
if (!builder_) return;
env->control = builder_->Loop(env->control);
env->effect = builder_->EffectPhi(1, &env->effect, env->control);
builder_->Terminate(env->effect, env->control);
if (FLAG_wasm_loop_assignment_analysis) {
BitVector* assigned = AnalyzeLoopAssignment(pc);
if (assigned != nullptr) {
// Only introduce phis for variables assigned in this loop.
for (int i = EnvironmentCount() - 1; i >= 0; i--) {
if (!assigned->Contains(i)) continue;
env->locals[i] = builder_->Phi(local_type_vec_[i], 1, &env->locals[i],
env->control);
}
return;
}
}
// Conservatively introduce phis for all local variables.
for (int i = EnvironmentCount() - 1; i >= 0; i--) {
env->locals[i] =
builder_->Phi(local_type_vec_[i], 1, &env->locals[i], env->control);
}
}
// Create a complete copy of the {from}.
SsaEnv* Split(SsaEnv* from) {
DCHECK_NOT_NULL(from);
SsaEnv* result = reinterpret_cast<SsaEnv*>(zone_->New(sizeof(SsaEnv)));
size_t size = sizeof(TFNode*) * EnvironmentCount();
result->control = from->control;
result->effect = from->effect;
if (from->go()) {
result->state = SsaEnv::kReached;
result->locals =
size > 0 ? reinterpret_cast<TFNode**>(zone_->New(size)) : nullptr;
memcpy(result->locals, from->locals, size);
} else {
result->state = SsaEnv::kUnreachable;
result->locals = nullptr;
}
return result;
}
// Create a copy of {from} that steals its state and leaves {from}
// unreachable.
SsaEnv* Steal(SsaEnv* from) {
DCHECK_NOT_NULL(from);
if (!from->go()) return UnreachableEnv();
SsaEnv* result = reinterpret_cast<SsaEnv*>(zone_->New(sizeof(SsaEnv)));
result->state = SsaEnv::kReached;
result->locals = from->locals;
result->control = from->control;
result->effect = from->effect;
from->Kill(SsaEnv::kUnreachable);
return result;
}
// Create an unreachable environment.
SsaEnv* UnreachableEnv() {
SsaEnv* result = reinterpret_cast<SsaEnv*>(zone_->New(sizeof(SsaEnv)));
result->state = SsaEnv::kUnreachable;
result->control = nullptr;
result->effect = nullptr;
result->locals = nullptr;
return result;
}
int EnvironmentCount() {
if (builder_) return static_cast<int>(local_type_vec_.size());
return 0; // if we aren't building a graph, don't bother with SSA renaming.
}
virtual void onFirstError() {
limit_ = start_; // Terminate decoding loop.
builder_ = nullptr; // Don't build any more nodes.
TRACE(" !%s\n", error_msg_.get());
}
BitVector* AnalyzeLoopAssignment(const byte* pc) {
if (pc >= limit_) return nullptr;
if (*pc != kExprLoop) return nullptr;
BitVector* assigned =
new (zone_) BitVector(static_cast<int>(local_type_vec_.size()), zone_);
int depth = 0;
// Iteratively process all AST nodes nested inside the loop.
while (pc < limit_) {
WasmOpcode opcode = static_cast<WasmOpcode>(*pc);
int length = 1;
switch (opcode) {
case kExprLoop:
case kExprIf:
case kExprBlock:
depth++;
DCHECK_EQ(1, OpcodeLength(pc));
break;
case kExprSetLocal: {
LocalIndexOperand operand(this, pc);
if (assigned->length() > 0 &&
static_cast<int>(operand.index) < assigned->length()) {
// Unverified code might have an out-of-bounds index.
assigned->Add(operand.index);
}
length = 1 + operand.length;
break;
}
case kExprEnd:
depth--;
break;
default:
length = OpcodeLength(pc);
break;
}
if (depth <= 0) break;
pc += length;
}
return assigned;
}
inline wasm::WasmCodePosition position() {
int offset = static_cast<int>(pc_ - start_);
DCHECK_EQ(pc_ - start_, offset); // overflows cannot happen
return offset;
}
};
bool DecodeLocalDecls(AstLocalDecls& decls, const byte* start,
const byte* end) {
base::AccountingAllocator allocator;
Zone tmp(&allocator);
FunctionBody body = {nullptr, nullptr, nullptr, start, end};
SR_WasmDecoder decoder(&tmp, nullptr, body);
return decoder.DecodeLocalDecls(decls);
}
TreeResult VerifyWasmCode(base::AccountingAllocator* allocator,
FunctionBody& body) {
Zone zone(allocator);
SR_WasmDecoder decoder(&zone, nullptr, body);
decoder.Decode();
return decoder.toResult<Tree*>(nullptr);
}
TreeResult BuildTFGraph(base::AccountingAllocator* allocator,
TFBuilder* builder, FunctionBody& body) {
Zone zone(allocator);
SR_WasmDecoder decoder(&zone, builder, body);
decoder.Decode();
return decoder.toResult<Tree*>(nullptr);
}
std::ostream& operator<<(std::ostream& os, const Tree& tree) {
if (tree.pc == nullptr) {
os << "null";
return os;
}
PrintF("%s", WasmOpcodes::OpcodeName(tree.opcode()));
if (tree.count > 0) os << "(";
for (uint32_t i = 0; i < tree.count; i++) {
if (i > 0) os << ", ";
os << *tree.children[i];
}
if (tree.count > 0) os << ")";
return os;
}
int OpcodeLength(const byte* pc, const byte* end) {
WasmDecoder decoder(nullptr, nullptr, pc, end);
return decoder.OpcodeLength(pc);
}
int OpcodeArity(const byte* pc, const byte* end) {
WasmDecoder decoder(nullptr, nullptr, pc, end);
return decoder.OpcodeArity(pc);
}
void PrintAstForDebugging(const byte* start, const byte* end) {
FunctionBody body = {nullptr, nullptr, start, start, end};
base::AccountingAllocator allocator;
PrintAst(&allocator, body);
}
void PrintAst(base::AccountingAllocator* allocator, FunctionBody& body) {
Zone zone(allocator);
SR_WasmDecoder decoder(&zone, nullptr, body);
OFStream os(stdout);
// Print the function signature.
if (body.sig) {
os << "// signature: " << *body.sig << std::endl;
}
// Print the local declarations.
AstLocalDecls decls(&zone);
decoder.DecodeLocalDecls(decls);
const byte* pc = decoder.pc();
if (body.start != decoder.pc()) {
os << "// locals: ";
for (auto p : decls.local_types) {
LocalType type = p.first;
uint32_t count = p.second;
os << " " << count << " " << WasmOpcodes::TypeName(type);
}
os << std::endl;
for (const byte* locals = body.start; locals < pc; locals++) {
printf(" 0x%02x,", *locals);
}
os << std::endl;
}
os << "// body: \n";
int control_depth = 0;
while (pc < body.end) {
size_t length = decoder.OpcodeLength(pc);
WasmOpcode opcode = static_cast<WasmOpcode>(*pc);
if (opcode == kExprElse) control_depth--;
for (int i = 0; i < control_depth && i < 32; i++) printf(" ");
printf("k%s,", WasmOpcodes::OpcodeName(opcode));
for (size_t i = 1; i < length; i++) {
printf(" 0x%02x,", pc[i]);
}
switch (opcode) {
case kExprIf:
case kExprElse:
case kExprLoop:
case kExprBlock:
os << " // @" << static_cast<int>(pc - body.start);
control_depth++;
break;
case kExprEnd:
os << " // @" << static_cast<int>(pc - body.start);
control_depth--;
break;
case kExprBr: {
BreakDepthOperand operand(&decoder, pc);
os << " // arity=" << operand.arity << " depth=" << operand.depth;
break;
}
case kExprBrIf: {
BreakDepthOperand operand(&decoder, pc);
os << " // arity=" << operand.arity << " depth" << operand.depth;
break;
}
case kExprBrTable: {
BranchTableOperand operand(&decoder, pc);
os << " // arity=" << operand.arity
<< " entries=" << operand.table_count;
break;
}
case kExprCallIndirect: {
CallIndirectOperand operand(&decoder, pc);
if (decoder.Validate(pc, operand)) {
os << " // sig #" << operand.index << ": " << *operand.sig;
} else {
os << " // arity=" << operand.arity << " sig #" << operand.index;
}
break;
}
case kExprCallImport: {
CallImportOperand operand(&decoder, pc);
if (decoder.Validate(pc, operand)) {
os << " // import #" << operand.index << ": " << *operand.sig;
} else {
os << " // arity=" << operand.arity << " import #" << operand.index;
}
break;
}
case kExprCallFunction: {
CallFunctionOperand operand(&decoder, pc);
if (decoder.Validate(pc, operand)) {
os << " // function #" << operand.index << ": " << *operand.sig;
} else {
os << " // arity=" << operand.arity << " function #" << operand.index;
}
break;
}
case kExprReturn: {
ReturnArityOperand operand(&decoder, pc);
os << " // arity=" << operand.arity;
break;
}
default:
break;
}
pc += length;
os << std::endl;
}
}
BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
const byte* start, const byte* end) {
FunctionBody body = {nullptr, nullptr, nullptr, start, end};
SR_WasmDecoder decoder(zone, nullptr, body);
return decoder.AnalyzeLoopAssignmentForTesting(start, num_locals);
}
} // namespace wasm
} // namespace internal
} // namespace v8