bytecodegenerator.cpp

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    ASSERT(!m_scopeContextStack.last().isFinallyBlock);

    emitOpcode(op_pop_scope);

    m_scopeContextStack.removeLast();
    m_dynamicScopeDepth--;
}

void BytecodeGenerator::emitDebugHook(DebugHookID debugHookID, int firstLine, int lastLine)
{
    if (!m_shouldEmitDebugHooks)
        return;
    emitOpcode(op_debug);
    instructions().append(debugHookID);
    instructions().append(firstLine);
    instructions().append(lastLine);
}

void BytecodeGenerator::pushFinallyContext(Label* target, RegisterID* retAddrDst)
{
    ControlFlowContext scope;
    scope.isFinallyBlock = true;
    FinallyContext context = { target, retAddrDst };
    scope.finallyContext = context;
    m_scopeContextStack.append(scope);
    m_finallyDepth++;
}

void BytecodeGenerator::popFinallyContext()
{
    ASSERT(m_scopeContextStack.size());
    ASSERT(m_scopeContextStack.last().isFinallyBlock);
    ASSERT(m_finallyDepth > 0);
    m_scopeContextStack.removeLast();
    m_finallyDepth--;
}

LabelScope* BytecodeGenerator::breakTarget(const Identifier& name)
{
    // Reclaim free label scopes.
    while (m_labelScopes.size() && !m_labelScopes.last().refCount())
        m_labelScopes.removeLast();

    if (!m_labelScopes.size())
        return 0;

    // We special-case the following, which is a syntax error in Firefox:
    // label:
    //     break;
    if (name.isEmpty()) {
        for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
            LabelScope* scope = &m_labelScopes[i];
            if (scope->type() != LabelScope::NamedLabel) {
                ASSERT(scope->breakTarget());
                return scope;
            }
        }
        return 0;
    }

    for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
        LabelScope* scope = &m_labelScopes[i];
        if (scope->name() && *scope->name() == name) {
            ASSERT(scope->breakTarget());
            return scope;
        }
    }
    return 0;
}

LabelScope* BytecodeGenerator::continueTarget(const Identifier& name)
{
    // Reclaim free label scopes.
    while (m_labelScopes.size() && !m_labelScopes.last().refCount())
        m_labelScopes.removeLast();

    if (!m_labelScopes.size())
        return 0;

    if (name.isEmpty()) {
        for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
            LabelScope* scope = &m_labelScopes[i];
            if (scope->type() == LabelScope::Loop) {
                ASSERT(scope->continueTarget());
                return scope;
            }
        }
        return 0;
    }

    // Continue to the loop nested nearest to the label scope that matches
    // 'name'.
    LabelScope* result = 0;
    for (int i = m_labelScopes.size() - 1; i >= 0; --i) {
        LabelScope* scope = &m_labelScopes[i];
        if (scope->type() == LabelScope::Loop) {
            ASSERT(scope->continueTarget());
            result = scope;
        }
        if (scope->name() && *scope->name() == name)
            return result; // may be 0
    }
    return 0;
}

PassRefPtr<Label> BytecodeGenerator::emitComplexJumpScopes(Label* target, ControlFlowContext* topScope, ControlFlowContext* bottomScope)
{
    while (topScope > bottomScope) {
        // First we count the number of dynamic scopes we need to remove to get
        // to a finally block.
        int nNormalScopes = 0;
        while (topScope > bottomScope) {
            if (topScope->isFinallyBlock)
                break;
            ++nNormalScopes;
            --topScope;
        }

        if (nNormalScopes) {
            // We need to remove a number of dynamic scopes to get to the next
            // finally block
            emitOpcode(op_jmp_scopes);
            instructions().append(nNormalScopes);

            // If topScope == bottomScope then there isn't actually a finally block
            // left to emit, so make the jmp_scopes jump directly to the target label
            if (topScope == bottomScope) {
                instructions().append(target->offsetFrom(instructions().size()));
                return target;
            }

            // Otherwise we just use jmp_scopes to pop a group of scopes and go
            // to the next instruction
            RefPtr<Label> nextInsn = newLabel();
            instructions().append(nextInsn->offsetFrom(instructions().size()));
            emitLabel(nextInsn.get());
        }

        // To get here there must be at least one finally block present
        do {
            ASSERT(topScope->isFinallyBlock);
            emitJumpSubroutine(topScope->finallyContext.retAddrDst, topScope->finallyContext.finallyAddr);
            --topScope;
            if (!topScope->isFinallyBlock)
                break;
        } while (topScope > bottomScope);
    }
    return emitJump(target);
}

PassRefPtr<Label> BytecodeGenerator::emitJumpScopes(Label* target, int targetScopeDepth)
{
    ASSERT(scopeDepth() - targetScopeDepth >= 0);
    ASSERT(target->isForward());

    size_t scopeDelta = scopeDepth() - targetScopeDepth;
    ASSERT(scopeDelta <= m_scopeContextStack.size());
    if (!scopeDelta)
        return emitJump(target);

    if (m_finallyDepth)
        return emitComplexJumpScopes(target, &m_scopeContextStack.last(), &m_scopeContextStack.last() - scopeDelta);

    emitOpcode(op_jmp_scopes);
    instructions().append(scopeDelta);
    instructions().append(target->offsetFrom(instructions().size()));
    return target;
}

RegisterID* BytecodeGenerator::emitNextPropertyName(RegisterID* dst, RegisterID* iter, Label* target)
{
    emitOpcode(op_next_pname);
    instructions().append(dst->index());
    instructions().append(iter->index());
    instructions().append(target->offsetFrom(instructions().size()));
    return dst;
}

RegisterID* BytecodeGenerator::emitCatch(RegisterID* targetRegister, Label* start, Label* end)
{
#if ENABLE(JIT)
    HandlerInfo info = { start->offsetFrom(0), end->offsetFrom(0), instructions().size(), m_dynamicScopeDepth + m_baseScopeDepth, MacroAssembler::CodeLocationLabel() };
#else
    HandlerInfo info = { start->offsetFrom(0), end->offsetFrom(0), instructions().size(), m_dynamicScopeDepth + m_baseScopeDepth };
#endif

    m_codeBlock->addExceptionHandler(info);
    emitOpcode(op_catch);
    instructions().append(targetRegister->index());
    return targetRegister;
}

RegisterID* BytecodeGenerator::emitNewError(RegisterID* dst, ErrorType type, JSValuePtr message)
{
    emitOpcode(op_new_error);
    instructions().append(dst->index());
    instructions().append(static_cast<int>(type));
    instructions().append(addUnexpectedConstant(message));
    return dst;
}

PassRefPtr<Label> BytecodeGenerator::emitJumpSubroutine(RegisterID* retAddrDst, Label* finally)
{
    emitOpcode(op_jsr);
    instructions().append(retAddrDst->index());
    instructions().append(finally->offsetFrom(instructions().size()));
    return finally;
}

void BytecodeGenerator::emitSubroutineReturn(RegisterID* retAddrSrc)
{
    emitOpcode(op_sret);
    instructions().append(retAddrSrc->index());
}

void BytecodeGenerator::emitPushNewScope(RegisterID* dst, Identifier& property, RegisterID* value)
{
    ControlFlowContext context;
    context.isFinallyBlock = false;
    m_scopeContextStack.append(context);
    m_dynamicScopeDepth++;
    
    emitOpcode(op_push_new_scope);
    instructions().append(dst->index());
    instructions().append(addConstant(property));
    instructions().append(value->index());
}

void BytecodeGenerator::beginSwitch(RegisterID* scrutineeRegister, SwitchInfo::SwitchType type)
{
    SwitchInfo info = { instructions().size(), type };
    switch (type) {
        case SwitchInfo::SwitchImmediate:
            emitOpcode(op_switch_imm);
            break;
        case SwitchInfo::SwitchCharacter:
            emitOpcode(op_switch_char);
            break;
        case SwitchInfo::SwitchString:
            emitOpcode(op_switch_string);
            break;
        default:
            ASSERT_NOT_REACHED();
    }

    instructions().append(0); // place holder for table index
    instructions().append(0); // place holder for default target    
    instructions().append(scrutineeRegister->index());
    m_switchContextStack.append(info);
}

static int32_t keyForImmediateSwitch(ExpressionNode* node, int32_t min, int32_t max)
{
    UNUSED_PARAM(max);
    ASSERT(node->isNumber());
    double value = static_cast<NumberNode*>(node)->value();
    int32_t key = static_cast<int32_t>(value);
    ASSERT(JSValuePtr::makeInt32Fast(key) && (JSValuePtr::makeInt32Fast(key).getInt32Fast() == value));
    ASSERT(key == value);
    ASSERT(key >= min);
    ASSERT(key <= max);
    return key - min;
}

static void prepareJumpTableForImmediateSwitch(SimpleJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, int32_t min, int32_t max)
{
    jumpTable.min = min;
    jumpTable.branchOffsets.resize(max - min + 1);
    jumpTable.branchOffsets.fill(0);
    for (uint32_t i = 0; i < clauseCount; ++i) {
        // We're emitting this after the clause labels should have been fixed, so 
        // the labels should not be "forward" references
        ASSERT(!labels[i]->isForward());
        jumpTable.add(keyForImmediateSwitch(nodes[i], min, max), labels[i]->offsetFrom(switchAddress)); 
    }
}

static int32_t keyForCharacterSwitch(ExpressionNode* node, int32_t min, int32_t max)
{
    UNUSED_PARAM(max);
    ASSERT(node->isString());
    UString::Rep* clause = static_cast<StringNode*>(node)->value().ustring().rep();
    ASSERT(clause->size() == 1);
    
    int32_t key = clause->data()[0];
    ASSERT(key >= min);
    ASSERT(key <= max);
    return key - min;
}

static void prepareJumpTableForCharacterSwitch(SimpleJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, int32_t min, int32_t max)
{
    jumpTable.min = min;
    jumpTable.branchOffsets.resize(max - min + 1);
    jumpTable.branchOffsets.fill(0);
    for (uint32_t i = 0; i < clauseCount; ++i) {
        // We're emitting this after the clause labels should have been fixed, so 
        // the labels should not be "forward" references
        ASSERT(!labels[i]->isForward());
        jumpTable.add(keyForCharacterSwitch(nodes[i], min, max), labels[i]->offsetFrom(switchAddress)); 
    }
}

static void prepareJumpTableForStringSwitch(StringJumpTable& jumpTable, int32_t switchAddress, uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes)
{
    for (uint32_t i = 0; i < clauseCount; ++i) {
        // We're emitting this after the clause labels should have been fixed, so 
        // the labels should not be "forward" references
        ASSERT(!labels[i]->isForward());
        
        ASSERT(nodes[i]->isString());
        UString::Rep* clause = static_cast<StringNode*>(nodes[i])->value().ustring().rep();
        OffsetLocation location;
        location.branchOffset = labels[i]->offsetFrom(switchAddress);
        jumpTable.offsetTable.add(clause, location);
    }
}

void BytecodeGenerator::endSwitch(uint32_t clauseCount, RefPtr<Label>* labels, ExpressionNode** nodes, Label* defaultLabel, int32_t min, int32_t max)
{
    SwitchInfo switchInfo = m_switchContextStack.last();
    m_switchContextStack.removeLast();
    if (switchInfo.switchType == SwitchInfo::SwitchImmediate) {
        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfImmediateSwitchJumpTables();
        instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->offsetFrom(switchInfo.bytecodeOffset + 3);

        SimpleJumpTable& jumpTable = m_codeBlock->addImmediateSwitchJumpTable();
        prepareJumpTableForImmediateSwitch(jumpTable, switchInfo.bytecodeOffset + 3, clauseCount, labels, nodes, min, max);
    } else if (switchInfo.switchType == SwitchInfo::SwitchCharacter) {
        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfCharacterSwitchJumpTables();
        instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->offsetFrom(switchInfo.bytecodeOffset + 3);
        
        SimpleJumpTable& jumpTable = m_codeBlock->addCharacterSwitchJumpTable();
        prepareJumpTableForCharacterSwitch(jumpTable, switchInfo.bytecodeOffset + 3, clauseCount, labels, nodes, min, max);
    } else {
        ASSERT(switchInfo.switchType == SwitchInfo::SwitchString);
        instructions()[switchInfo.bytecodeOffset + 1] = m_codeBlock->numberOfStringSwitchJumpTables();
        instructions()[switchInfo.bytecodeOffset + 2] = defaultLabel->offsetFrom(switchInfo.bytecodeOffset + 3);

        StringJumpTable& jumpTable = m_codeBlock->addStringSwitchJumpTable();
        prepareJumpTableForStringSwitch(jumpTable, switchInfo.bytecodeOffset + 3, clauseCount, labels, nodes);
    }
}

RegisterID* BytecodeGenerator::emitThrowExpressionTooDeepException()
{
    // It would be nice to do an even better job of identifying exactly where the expression is.
    // And we could make the caller pass the node pointer in, if there was some way of getting
    // that from an arbitrary node. However, calling emitExpressionInfo without any useful data
    // is still good enough to get us an accurate line number.
    emitExpressionInfo(0, 0, 0);
    RegisterID* exception = emitNewError(newTemporary(), SyntaxError, jsString(globalData(), "Expression too deep"));
    emitThrow(exception);
    return exception;
}

} // namespace JSC