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Update TCO with fine-tuned heuristic #1278

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Nov 22, 2023
Merged

Update TCO with fine-tuned heuristic #1278

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16deb90
Update TCO to handle tail recursion with non-identical argument counts
clover2123 Nov 9, 2023
7147c8c
Simplify TCO check code
clover2123 Nov 21, 2023
b2d077d
Add fine-tuned TCO condition check in parsing phase
clover2123 Nov 21, 2023
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2 changes: 2 additions & 0 deletions src/interpreter/ByteCode.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2020,6 +2020,7 @@ class CallReturn : public ByteCode {
, m_argumentCount(argumentCount)
{
}

ByteCodeRegisterIndex m_calleeIndex;
ByteCodeRegisterIndex m_argumentsStartIndex;
uint16_t m_argumentCount;
Expand All @@ -2045,6 +2046,7 @@ class TailRecursion : public ByteCode {
, m_argumentCount(argumentCount)
{
}

ByteCodeRegisterIndex m_calleeIndex;
ByteCodeRegisterIndex m_argumentsStartIndex;
uint16_t m_argumentCount;
Expand Down
104 changes: 56 additions & 48 deletions src/interpreter/ByteCodeInterpreter.cpp
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Expand Up @@ -1540,32 +1540,36 @@ Value Interpreter::interpret(ExecutionState* state, ByteCodeBlock* byteCodeBlock
TailRecursion* code = (TailRecursion*)programCounter;
const Value& callee = registerFile[code->m_calleeIndex];

if (UNLIKELY((callee != Value(state->resolveCallee())) || (state->m_argc != code->m_argumentCount))) {
if (UNLIKELY(callee != Value(state->lexicalEnvironment()->record()->asDeclarativeEnvironmentRecord()->asFunctionEnvironmentRecord()->functionObject()))) {
// goto slow path
return InterpreterSlowPath::tailRecursionSlowCase(*state, code, callee, registerFile);
}

// fast tail recursion
ASSERT(callee.isPointerValue() && callee.asPointerValue()->isScriptFunctionObject());
ASSERT(callee.asPointerValue()->asScriptFunctionObject()->codeBlock() == byteCodeBlock->codeBlock());
ASSERT(state->m_argc == code->m_argumentCount);

if (code->m_argumentCount) {
if (UNLIKELY(!state->initTCO())) {
// At the start of tail call, we need to allocate a buffer for arguments
// because recursive tail call reuses this buffer
if (UNLIKELY(!state->initTCO())) {
Value* newArgs = ALLOCA(sizeof(Value) * code->m_argumentCount, Value);
state->setTCOArguments(newArgs);
}
state->m_argc = code->m_argumentCount;
Value* newArgs = code->m_argumentCount ? ALLOCA(sizeof(Value) * code->m_argumentCount, Value) : nullptr;
state->setTCOArguments(newArgs);
}

// its safe to overwrite arguments because old arguments are no longer necessary
for (size_t i = 0; i < state->m_argc; i++) {
state->m_argv[i] = registerFile[code->m_argumentsStartIndex + i];
}
// fast tail recursion
ASSERT(callee.isPointerValue() && callee.asPointerValue()->isScriptFunctionObject());
ASSERT(callee.asPointerValue()->asScriptFunctionObject()->codeBlock() == byteCodeBlock->codeBlock());
ASSERT(state->initTCO() && (state->m_argc == code->m_argumentCount));
#ifndef NDEBUG
// check this value
if (state->inStrictMode()) {
ASSERT(registerFile[byteCodeBlock->m_requiredOperandRegisterNumber].isUndefined());
} else {
ASSERT(registerFile[byteCodeBlock->m_requiredOperandRegisterNumber] == Value(state->context()->globalObjectProxy()));
}
#endif

// set this value
registerFile[byteCodeBlock->m_requiredOperandRegisterNumber] = state->inStrictMode() ? Value() : state->context()->globalObjectProxy();
// its safe to overwrite arguments because old arguments are no longer necessary
for (size_t i = 0; i < state->m_argc; i++) {
state->m_argv[i] = registerFile[code->m_argumentsStartIndex + i];
}

// set programCounter
programCounter = reinterpret_cast<size_t>(byteCodeBlock->m_code.data());
Expand All @@ -1582,31 +1586,30 @@ Value Interpreter::interpret(ExecutionState* state, ByteCodeBlock* byteCodeBlock
const Value& callee = registerFile[code->m_calleeIndex];
const Value& receiver = registerFile[code->m_receiverIndex];

if (UNLIKELY((callee != Value(state->resolveCallee())) || (state->m_argc != code->m_argumentCount))) {
if (UNLIKELY(callee != Value(state->lexicalEnvironment()->record()->asDeclarativeEnvironmentRecord()->asFunctionEnvironmentRecord()->functionObject()))) {
// goto slow path
return InterpreterSlowPath::tailRecursionWithReceiverSlowCase(*state, code, callee, receiver, registerFile);
}

if (UNLIKELY(!state->initTCO())) {
// At the start of tail call, we need to allocate a buffer for arguments
// because recursive tail call reuses this buffer
state->m_argc = code->m_argumentCount;
Value* newArgs = code->m_argumentCount ? ALLOCA(sizeof(Value) * code->m_argumentCount, Value) : nullptr;
state->setTCOArguments(newArgs);
}

// fast tail recursion with receiver
ASSERT(callee.isPointerValue() && callee.asPointerValue()->isScriptFunctionObject());
ASSERT(callee.asPointerValue()->asScriptFunctionObject()->codeBlock() == byteCodeBlock->codeBlock());
ASSERT(state->m_argc == code->m_argumentCount);

if (code->m_argumentCount) {
// At the start of tail call, we need to allocate a buffer for arguments
// because recursive tail call reuses this buffer
if (UNLIKELY(!state->initTCO())) {
Value* newArgs = ALLOCA(sizeof(Value) * code->m_argumentCount, Value);
state->setTCOArguments(newArgs);
}
ASSERT(state->initTCO() && (state->m_argc == code->m_argumentCount));

// its safe to overwrite arguments because old arguments are no longer necessary
for (size_t i = 0; i < state->m_argc; i++) {
state->m_argv[i] = registerFile[code->m_argumentsStartIndex + i];
}
// its safe to overwrite arguments because old arguments are no longer necessary
for (size_t i = 0; i < state->m_argc; i++) {
state->m_argv[i] = registerFile[code->m_argumentsStartIndex + i];
}

// set this value (receiver) // FIXME
// set this value (receiver)
if (state->inStrictMode()) {
registerFile[byteCodeBlock->m_requiredOperandRegisterNumber] = receiver;
} else {
Expand All @@ -1631,7 +1634,8 @@ Value Interpreter::interpret(ExecutionState* state, ByteCodeBlock* byteCodeBlock
TailRecursionInTry* code = (TailRecursionInTry*)programCounter;
const Value& callee = registerFile[code->m_calleeIndex];

if (UNLIKELY((callee != Value(state->resolveCallee())) || (state->m_argc != code->m_argumentCount))) {
if (UNLIKELY(callee != Value(state->resolveCallee()))) {
// should call resolveCallee because try-catch-finally block is executed in a sub-interpreter
// goto slow path
code->changeOpcode(Opcode::CallOpcode);
if (UNLIKELY(!callee.isPointerValue())) {
Expand All @@ -1647,7 +1651,6 @@ Value Interpreter::interpret(ExecutionState* state, ByteCodeBlock* byteCodeBlock

ASSERT(callee.isPointerValue() && callee.asPointerValue()->isScriptFunctionObject());
ASSERT(callee.asPointerValue()->asScriptFunctionObject()->codeBlock() == byteCodeBlock->codeBlock());
ASSERT(state->m_argc == code->m_argumentCount);
ASSERT(state->rareData()->controlFlowRecordVector() && state->rareData()->controlFlowRecordVector()->size());

// postpone recursion call
Expand Down Expand Up @@ -3222,26 +3225,31 @@ NEVER_INLINE Value InterpreterSlowPath::tryOperation(ExecutionState*& state, siz
ASSERT(!inPauserScope && !inPauserResumeProcess);
ASSERT(code->m_hasCatch || code->m_hasFinalizer);
ASSERT(record->m_value == state->resolveCallee());
#ifndef NDEBUG
// check this value
if (state->inStrictMode()) {
ASSERT(registerFile[byteCodeBlock->m_requiredOperandRegisterNumber].isUndefined());
} else {
ASSERT(registerFile[byteCodeBlock->m_requiredOperandRegisterNumber] == Value(state->context()->globalObjectProxy()));
}
#endif

Value callee = record->m_value;
size_t argCount = record->m_count;
size_t argStartIndex = record->m_outerLimitCount;
if (argCount) {
// At the start of tail call, we need to allocate a buffer for arguments
// because recursive tail call reuses this buffer
if (UNLIKELY(!state->initTCO())) {
Value* newArgs = (Value*)GC_MALLOC(sizeof(Value) * argCount);
state->setTCOArguments(newArgs);
}

// its safe to overwrite arguments because old arguments are no longer necessary
for (size_t i = 0; i < state->m_argc; i++) {
state->m_argv[i] = registerFile[argStartIndex + i];
}
// At the start of tail call, we need to allocate a buffer for arguments
// because recursive tail call reuses this buffer
if (UNLIKELY(!state->initTCO())) {
state->m_argc = argCount;
Value* newArgs = argCount ? (Value*)GC_MALLOC(sizeof(Value) * argCount) : nullptr;
state->setTCOArguments(newArgs);
}

// set this value
registerFile[byteCodeBlock->m_requiredOperandRegisterNumber] = state->inStrictMode() ? Value() : state->context()->globalObjectProxy();
// its safe to overwrite arguments because old arguments are no longer necessary
ASSERT(state->m_argc == argCount);
for (size_t i = 0; i < state->m_argc; i++) {
state->m_argv[i] = registerFile[argStartIndex + i];
}

// set programCounter
programCounter = reinterpret_cast<size_t>(byteCodeBlock->m_code.data());
Expand Down
16 changes: 15 additions & 1 deletion src/parser/CodeBlock.h
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Original file line number Diff line number Diff line change
Expand Up @@ -616,10 +616,24 @@ class InterpretedCodeBlock : public CodeBlock {
}

// for TCO
bool isTailRecursionTarget() const
bool isTailRecursionTarget(size_t argc, const AtomicString& calleeName) const
{
// global scope cannot create a return statement, neither tail recursion
ASSERT(!isGlobalScope());

// check argc
if (m_parameterCount != argc) {
return false;
}

#ifndef ESCARGOT_ENABLE_TEST
// check callee name
// this check is disabled in test build to pass test262 tco-related test cases
if (m_functionName.string()->length() && m_functionName != calleeName) {
return false;
}
#endif

return (!m_canAllocateVariablesOnStack || m_isArrowFunctionExpression || m_isClassConstructor || m_isDerivedClassConstructor || m_isClassMethod || m_isClassStaticMethod || m_isGenerator || m_isAsync || m_usesArgumentsObject) != true;
}

Expand Down
6 changes: 4 additions & 2 deletions src/parser/ast/CallExpressionNode.h
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Expand Up @@ -417,7 +417,8 @@ class CallExpressionNode : public ExpressionNode {
if (dstRegister == context->m_returnRegister) {
// Try tail recursion optimization (TCO)
isTailCall = true;
bool isTailRecursion = context->m_codeBlock->isTailRecursionTarget();
const AtomicString& calleeName = m_callee->asMemberExpression()->property()->isIdentifier() ? m_callee->asMemberExpression()->property()->asIdentifier()->name() : AtomicString();
bool isTailRecursion = context->m_codeBlock->isTailRecursionTarget(m_arguments.size(), calleeName);
if (UNLIKELY(context->tryCatchWithBlockStatementCount())) {
codeBlock->pushCode(CallWithReceiver(ByteCodeLOC(m_loc.index), receiverIndex, calleeIndex, argumentsStartIndex, dstRegister, m_arguments.size()), context, this->m_loc.index);
} else {
Expand All @@ -434,7 +435,8 @@ class CallExpressionNode : public ExpressionNode {
if (dstRegister == context->m_returnRegister) {
// Try tail recursion optimization (TCO)
isTailCall = true;
bool isTailRecursion = context->m_codeBlock->isTailRecursionTarget();
const AtomicString& calleeName = m_callee->isIdentifier() ? m_callee->asIdentifier()->name() : AtomicString();
bool isTailRecursion = context->m_codeBlock->isTailRecursionTarget(m_arguments.size(), calleeName);
if (UNLIKELY(context->tryCatchWithBlockStatementCount())) {
if (isTailRecursion) {
codeBlock->pushCode(TailRecursionInTry(ByteCodeLOC(m_loc.index), calleeIndex, argumentsStartIndex, dstRegister, m_arguments.size()), context, this->m_loc.index);
Expand Down
2 changes: 1 addition & 1 deletion src/runtime/ExecutionState.h
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Expand Up @@ -258,8 +258,8 @@ class ExecutionState : public gc {
// allocate a new argument buffer
// because tail call reuses this buffer which can modify caller's register file
ASSERT(!m_initTCO && !!argv);
m_initTCO = true;
m_argv = argv;
m_initTCO = true; // initialize of TCO done
}
#endif

Expand Down