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// Copyright 2017 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 <memory>
#include <string>
#include "src/asmjs/asm-scanner.h"
#include "src/asmjs/asm-types.h"
#include "src/base/enum-set.h"
#include "src/utils/vector.h"
#include "src/wasm/wasm-module-builder.h"
#include "src/zone/zone-containers.h"
namespace v8 {
namespace internal {
class Utf16CharacterStream;
namespace wasm {
// A custom parser + validator + wasm converter for asm.js:
// This parser intentionally avoids the portion of JavaScript parsing
// that are not required to determine if code is valid asm.js code.
// * It is mostly one pass.
// * It bails out on unexpected input.
// * It assumes strict ordering insofar as permitted by asm.js validation rules.
// * It relies on a custom scanner that provides de-duped identifiers in two
// scopes (local + module wide).
class AsmJsParser {
// clang-format off
enum StandardMember {
#define V(_unused1, name, _unused2, _unused3) kMath##name,
#undef V
#define V(name, _unused1) kMath##name,
#undef V
#define V(name, _unused1, _unused2, _unused3) k##name,
#undef V
// clang-format on
using StdlibSet = base::EnumSet<StandardMember, uint64_t>;
explicit AsmJsParser(Zone* zone, uintptr_t stack_limit,
Utf16CharacterStream* stream);
bool Run();
const char* failure_message() const { return failure_message_; }
int failure_location() const { return failure_location_; }
WasmModuleBuilder* module_builder() { return module_builder_; }
const StdlibSet* stdlib_uses() const { return &stdlib_uses_; }
// clang-format off
enum class VarKind {
#define V(_unused0, Name, _unused1, _unused2) kMath##Name,
#undef V
#define V(Name, _unused1) kMath##Name,
#undef V
// clang-format on
// A single import in asm.js can require multiple imports in wasm, if the
// function is used with different signatures. {cache} keeps the wasm
// imports for the single asm.js import of name {function_name}.
struct FunctionImportInfo {
Vector<const char> function_name;
ZoneUnorderedMap<FunctionSig, uint32_t> cache;
// Constructor.
FunctionImportInfo(Vector<const char> name, Zone* zone)
: function_name(name), cache(zone) {}
struct VarInfo {
AsmType* type = AsmType::None();
WasmFunctionBuilder* function_builder = nullptr;
FunctionImportInfo* import = nullptr;
uint32_t mask = 0;
uint32_t index = 0;
VarKind kind = VarKind::kUnused;
bool mutable_variable = true;
bool function_defined = false;
struct GlobalImport {
Vector<const char> import_name;
ValueType value_type;
VarInfo* var_info;
// Distinguish different kinds of blocks participating in {block_stack}. Each
// entry on that stack represents one block in the wasm code, and determines
// which block 'break' and 'continue' target in the current context:
// - kRegular: The target of a 'break' (with & without identifier).
// Pushed by an IterationStatement and a SwitchStatement.
// - kLoop : The target of a 'continue' (with & without identifier).
// Pushed by an IterationStatement.
// - kNamed : The target of a 'break' with a specific identifier.
// Pushed by a BlockStatement.
// - kOther : Only used for internal blocks, can never be targeted.
enum class BlockKind { kRegular, kLoop, kNamed, kOther };
// One entry in the {block_stack}, see {BlockKind} above for details. Blocks
// without a label have {kTokenNone} set as their label.
struct BlockInfo {
BlockKind kind;
AsmJsScanner::token_t label;
// Helper class to make {TempVariable} safe for nesting.
class TemporaryVariableScope;
template <typename T>
class CachedVectors {
explicit CachedVectors(Zone* zone) : reusable_vectors_(zone) {}
Zone* zone() const { return reusable_vectors_.get_allocator().zone(); }
inline void fill(ZoneVector<T>* vec) {
if (reusable_vectors_.empty()) return;
inline void reuse(ZoneVector<T>* vec) {
ZoneVector<ZoneVector<T>> reusable_vectors_;
template <typename T>
class CachedVector final : public ZoneVector<T> {
explicit CachedVector(CachedVectors<T>* cache)
: ZoneVector<T>(cache->zone()), cache_(cache) {
~CachedVector() { cache_->reuse(this); }
CachedVectors<T>* cache_;
Zone* zone_;
AsmJsScanner scanner_;
WasmModuleBuilder* module_builder_;
WasmFunctionBuilder* current_function_builder_;
AsmType* return_type_;
uintptr_t stack_limit_;
StdlibSet stdlib_uses_;
ZoneVector<VarInfo> global_var_info_;
ZoneVector<VarInfo> local_var_info_;
CachedVectors<ValueType> cached_valuetype_vectors_{zone_};
CachedVectors<AsmType*> cached_asm_type_p_vectors_{zone_};
CachedVectors<AsmJsScanner::token_t> cached_token_t_vectors_{zone_};
CachedVectors<int32_t> cached_int_vectors_{zone_};
int function_temp_locals_offset_;
int function_temp_locals_used_;
int function_temp_locals_depth_;
// Error Handling related
bool failed_;
const char* failure_message_;
int failure_location_;
// Module Related.
AsmJsScanner::token_t stdlib_name_;
AsmJsScanner::token_t foreign_name_;
AsmJsScanner::token_t heap_name_;
static const AsmJsScanner::token_t kTokenNone = 0;
// Track if parsing a heap assignment.
bool inside_heap_assignment_;
AsmType* heap_access_type_;
ZoneVector<BlockInfo> block_stack_;
// Types used for stdlib function and their set up.
AsmType* stdlib_dq2d_;
AsmType* stdlib_dqdq2d_;
AsmType* stdlib_i2s_;
AsmType* stdlib_ii2s_;
AsmType* stdlib_minmax_;
AsmType* stdlib_abs_;
AsmType* stdlib_ceil_like_;
AsmType* stdlib_fround_;
// When making calls, the return type is needed to lookup signatures.
// For `+callsite(..)` or `fround(callsite(..))` use this value to pass
// along the coercion.
AsmType* call_coercion_;
// The source position associated with the above {call_coercion}.
size_t call_coercion_position_;
// When making calls, the coercion can also appear in the source stream
// syntactically "behind" the call site. For `callsite(..)|0` use this
// value to flag that such a coercion must happen.
AsmType* call_coercion_deferred_;
// The source position at which requesting a deferred coercion via the
// aforementioned {call_coercion_deferred} is allowed.
size_t call_coercion_deferred_position_;
// The code position of the last heap access shift by an immediate value.
// For `heap[expr >> value:NumericLiteral]` this indicates from where to
// delete code when the expression is used as part of a valid heap access.
// Will be set to {kNoHeapAccessShift} if heap access shift wasn't matched.
size_t heap_access_shift_position_;
uint32_t heap_access_shift_value_;
static const size_t kNoHeapAccessShift = -1;
// Used to track the last label we've seen so it can be matched to later
// statements it's attached to.
AsmJsScanner::token_t pending_label_;
// Global imports. The list of imported variables that are copied during
// module instantiation into a corresponding global variable.
ZoneLinkedList<GlobalImport> global_imports_;
Zone* zone() { return zone_; }
inline bool Peek(AsmJsScanner::token_t token) {
return scanner_.Token() == token;
inline bool Check(AsmJsScanner::token_t token) {
if (scanner_.Token() == token) {
return true;
} else {
return false;
inline bool CheckForZero() {
if (scanner_.IsUnsigned() && scanner_.AsUnsigned() == 0) {
return true;
} else {
return false;
inline bool CheckForDouble(double* value) {
if (scanner_.IsDouble()) {
*value = scanner_.AsDouble();
return true;
} else {
return false;
inline bool CheckForUnsigned(uint32_t* value) {
if (scanner_.IsUnsigned()) {
*value = scanner_.AsUnsigned();
return true;
} else {
return false;
inline bool CheckForUnsignedBelow(uint32_t limit, uint32_t* value) {
if (scanner_.IsUnsigned() && scanner_.AsUnsigned() < limit) {
*value = scanner_.AsUnsigned();
return true;
} else {
return false;
inline AsmJsScanner::token_t Consume() {
AsmJsScanner::token_t ret = scanner_.Token();
return ret;
void SkipSemicolon();
VarInfo* GetVarInfo(AsmJsScanner::token_t token);
uint32_t VarIndex(VarInfo* info);
void DeclareGlobal(VarInfo* info, bool mutable_variable, AsmType* type,
ValueType vtype,
const WasmInitExpr& init = WasmInitExpr());
void DeclareStdlibFunc(VarInfo* info, VarKind kind, AsmType* type);
void AddGlobalImport(Vector<const char> name, AsmType* type, ValueType vtype,
bool mutable_variable, VarInfo* info);
// Allocates a temporary local variable. The given {index} is absolute within
// the function body, consider using {TemporaryVariableScope} when nesting.
uint32_t TempVariable(int index);
// Preserves a copy of the scanner's current identifier string in the zone.
Vector<const char> CopyCurrentIdentifierString();
// Use to set up block stack layers (including synthetic ones for if-else).
// Begin/Loop/End below are implemented with these plus code generation.
void BareBegin(BlockKind kind, AsmJsScanner::token_t label = 0);
void BareEnd();
int FindContinueLabelDepth(AsmJsScanner::token_t label);
int FindBreakLabelDepth(AsmJsScanner::token_t label);
// Use to set up actual wasm blocks/loops.
void Begin(AsmJsScanner::token_t label = 0);
void Loop(AsmJsScanner::token_t label = 0);
void End();
void InitializeStdlibTypes();
FunctionSig* ConvertSignature(AsmType* return_type,
const ZoneVector<AsmType*>& params);
void ValidateModule(); // 6.1 ValidateModule
void ValidateModuleParameters(); // 6.1 ValidateModule - parameters
void ValidateModuleVars(); // 6.1 ValidateModule - variables
void ValidateModuleVar(bool mutable_variable);
void ValidateModuleVarImport(VarInfo* info, bool mutable_variable);
void ValidateModuleVarStdlib(VarInfo* info);
void ValidateModuleVarNewStdlib(VarInfo* info);
void ValidateModuleVarFromGlobal(VarInfo* info, bool mutable_variable);
void ValidateExport(); // 6.2 ValidateExport
void ValidateFunctionTable(); // 6.3 ValidateFunctionTable
void ValidateFunction(); // 6.4 ValidateFunction
void ValidateFunctionParams(ZoneVector<AsmType*>* params);
void ValidateFunctionLocals(size_t param_count,
ZoneVector<ValueType>* locals);
void ValidateStatement(); // 6.5 ValidateStatement
void Block(); // 6.5.1 Block
void ExpressionStatement(); // 6.5.2 ExpressionStatement
void EmptyStatement(); // 6.5.3 EmptyStatement
void IfStatement(); // 6.5.4 IfStatement
void ReturnStatement(); // 6.5.5 ReturnStatement
bool IterationStatement(); // 6.5.6 IterationStatement
void WhileStatement(); // 6.5.6 IterationStatement - while
void DoStatement(); // 6.5.6 IterationStatement - do
void ForStatement(); // 6.5.6 IterationStatement - for
void BreakStatement(); // 6.5.7 BreakStatement
void ContinueStatement(); // 6.5.8 ContinueStatement
void LabelledStatement(); // 6.5.9 LabelledStatement
void SwitchStatement(); // 6.5.10 SwitchStatement
void ValidateCase(); // 6.6. ValidateCase
void ValidateDefault(); // 6.7 ValidateDefault
AsmType* ValidateExpression(); // 6.8 ValidateExpression
AsmType* Expression(AsmType* expect); // 6.8.1 Expression
AsmType* NumericLiteral(); // 6.8.2 NumericLiteral
AsmType* Identifier(); // 6.8.3 Identifier
AsmType* CallExpression(); // 6.8.4 CallExpression
AsmType* MemberExpression(); // 6.8.5 MemberExpression
AsmType* AssignmentExpression(); // 6.8.6 AssignmentExpression
AsmType* UnaryExpression(); // 6.8.7 UnaryExpression
AsmType* MultiplicativeExpression(); // 6.8.8 MultiplicativeExpression
AsmType* AdditiveExpression(); // 6.8.9 AdditiveExpression
AsmType* ShiftExpression(); // 6.8.10 ShiftExpression
AsmType* RelationalExpression(); // 6.8.11 RelationalExpression
AsmType* EqualityExpression(); // 6.8.12 EqualityExpression
AsmType* BitwiseANDExpression(); // 6.8.13 BitwiseANDExpression
AsmType* BitwiseXORExpression(); // 6.8.14 BitwiseXORExpression
AsmType* BitwiseORExpression(); // 6.8.15 BitwiseORExpression
AsmType* ConditionalExpression(); // 6.8.16 ConditionalExpression
AsmType* ParenthesizedExpression(); // 6.8.17 ParenthesiedExpression
AsmType* ValidateCall(); // 6.9 ValidateCall
bool PeekCall(); // 6.9 ValidateCall - helper
void ValidateHeapAccess(); // 6.10 ValidateHeapAccess
void ValidateFloatCoercion(); // 6.11 ValidateFloatCoercion
// Used as part of {ForStatement}. Scans forward to the next `)` in order to
// skip over the third expression in a for-statement. This is one piece that
// makes this parser not be a pure single-pass.
void ScanToClosingParenthesis();
// Used as part of {SwitchStatement}. Collects all case labels in the current
// switch-statement, then resets the scanner position. This is one piece that
// makes this parser not be a pure single-pass.
void GatherCases(ZoneVector<int32_t>* cases);
} // namespace wasm
} // namespace internal
} // namespace v8
#endif // V8_ASMJS_ASM_PARSER_H_