darling-JavaScriptCore/dfg/DFGOSRAvailabilityAnalysisPhase.cpp

/*
 * Copyright (C) 2013-2015 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    notice, this list of conditions and the following disclaimer in the
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#include "config.h"
#include "DFGOSRAvailabilityAnalysisPhase.h"

#if ENABLE(DFG_JIT)

#include "DFGBlockMapInlines.h"
#include "DFGMayExit.h"
#include "DFGPhase.h"
#include "JSCJSValueInlines.h"
#include "OperandsInlines.h"

namespace JSC { namespace DFG {

template<typename HeadFunctor, typename TailFunctor>
class OSRAvailabilityAnalysisPhase : public Phase {
    static constexpr bool verbose = false;
public:
    OSRAvailabilityAnalysisPhase(Graph& graph, HeadFunctor& availabilityAtHead, TailFunctor& availabilityAtTail)
        : Phase(graph, "OSR availability analysis")
        , availabilityAtHead(availabilityAtHead)
        , availabilityAtTail(availabilityAtTail)
    {
    }
    
    bool run()
    {
        ASSERT(m_graph.m_form == SSA);
        
        for (BlockIndex blockIndex = m_graph.numBlocks(); blockIndex--;) {
            BasicBlock* block = m_graph.block(blockIndex);
            if (!block)
                continue;
            availabilityAtHead(block).clear();
            availabilityAtTail(block).clear();
        }
        
        BasicBlock* root = m_graph.block(0);
        availabilityAtHead(root).m_locals.fill(Availability::unavailable());

        for (unsigned argument = 0; argument < m_graph.block(0)->valuesAtHead.numberOfArguments(); ++argument)
            availabilityAtHead(root).m_locals.argument(argument) = Availability(FlushedAt(FlushedJSValue, virtualRegisterForArgumentIncludingThis(argument)));

        // This could be made more efficient by processing blocks in reverse postorder.
        
        auto dumpAvailability = [&] (BasicBlock* block) {
            dataLogLn("Head: ", availabilityAtHead(block));
            dataLogLn("Tail: ", availabilityAtTail(block));
        };

        auto dumpBytecodeLivenessAtHead = [&] (BasicBlock* block) {
            dataLog("Live: ");
            m_graph.forAllLiveInBytecode(
                block->at(0)->origin.forExit,
                [&] (Operand operand) {
                    dataLog(operand, " ");
                });
            dataLogLn("");
        };

        LocalOSRAvailabilityCalculator calculator(m_graph);
        bool changed;
        do {
            changed = false;
            
            for (BasicBlock* block : m_graph.blocksInNaturalOrder()) {
                if (verbose) {
                    dataLogLn("Before changing Block #", block->index);
                    dumpAvailability(block);
                }

                calculator.m_availability = availabilityAtHead(block);
                
                for (unsigned nodeIndex = 0; nodeIndex < block->size(); ++nodeIndex)
                    calculator.executeNode(block->at(nodeIndex));
                
                if (calculator.m_availability == availabilityAtTail(block))
                    continue;
                
                availabilityAtTail(block) = calculator.m_availability;
                changed = true;

                if (verbose) {
                    dataLogLn("After changing Block #", block->index);
                    dumpAvailability(block);
                }

                for (unsigned successorIndex = block->numSuccessors(); successorIndex--;) {
                    BasicBlock* successor = block->successor(successorIndex);
                    availabilityAtHead(successor).merge(calculator.m_availability);
                }

                for (unsigned successorIndex = block->numSuccessors(); successorIndex--;) {
                    BasicBlock* successor = block->successor(successorIndex);
                    availabilityAtHead(successor).pruneByLiveness(
                        m_graph, successor->at(0)->origin.forExit);
                    if (verbose) {
                        dataLogLn("After pruning Block #", successor->index);
                        dumpAvailability(successor);
                        dumpBytecodeLivenessAtHead(successor);
                    }
                }
            }
        } while (changed);

        if (validationEnabled()) {

            for (BasicBlock* block : m_graph.blocksInNaturalOrder()) {
                calculator.m_availability = availabilityAtHead(block);
                
                for (unsigned nodeIndex = 0; nodeIndex < block->size(); ++nodeIndex) {
                    Node* node = block->at(nodeIndex);
                    if (node->origin.exitOK) {
                        // If we're allowed to exit here, the heap must be in a state
                        // where exiting wouldn't crash. These particular fields are
                        // required for correctness because we use them during OSR exit
                        // to do meaningful things. It would be wrong for any of them
                        // to be dead.

                        CodeOrigin exitOrigin = node->origin.forExit;
                        // FIXME: availabilityMap seems like it should be able to be a reference to the calculator's map. https://bugs.webkit.org/show_bug.cgi?id=215675
                        AvailabilityMap availabilityMap = calculator.m_availability;
                        availabilityMap.pruneByLiveness(m_graph, exitOrigin);

                        for (auto heapPair : availabilityMap.m_heap) {
                            switch (heapPair.key.kind()) {
                            case ActivationScopePLoc:
                            case ActivationSymbolTablePLoc:
                            case FunctionActivationPLoc:
                            case FunctionExecutablePLoc:
                            case StructurePLoc:
                                if (heapPair.value.isDead()) {
                                    dataLogLn("PromotedHeapLocation is dead, but should not be: ", heapPair.key);
                                    availabilityMap.dump(WTF::dataFile());
                                    CRASH();
                                }
                                break;

                            default:
                                break;
                            }
                        }

                        // FIXME: It seems like we should be able to do at least some validation when OSR entering. https://bugs.webkit.org/show_bug.cgi?id=215511
                        if (m_graph.m_plan.mode() != FTLForOSREntryMode) {
                            for (size_t i = 0; i < availabilityMap.m_locals.size(); ++i) {
                                Operand operand = availabilityMap.m_locals.operandForIndex(i);
                                Availability availability = availabilityMap.m_locals[i];
                                if (availability.isDead() && m_graph.isLiveInBytecode(operand, exitOrigin))
                                    DFG_CRASH(m_graph, node, toCString("Live bytecode local not available: operand = ", operand, ", availabilityMap = ", availabilityMap, ", origin = ", exitOrigin).data());
                            }
                        }
                    }

                    calculator.executeNode(block->at(nodeIndex));
                }
            }
        }
        
        return true;
    }

    HeadFunctor& availabilityAtHead;
    TailFunctor& availabilityAtTail;
};

bool performOSRAvailabilityAnalysis(Graph& graph)
{
    auto availabilityAtHead = [&] (BasicBlock* block) -> AvailabilityMap& { return block->ssa->availabilityAtHead; };
    auto availabilityAtTail = [&] (BasicBlock* block) -> AvailabilityMap& { return block->ssa->availabilityAtTail; };
    return runPhase<OSRAvailabilityAnalysisPhase<decltype(availabilityAtHead), decltype(availabilityAtTail)>>(graph, availabilityAtHead, availabilityAtTail);
}

void validateOSRExitAvailability(Graph& graph)
{
    BlockMap<AvailabilityMap> availabilityMapAtHead(graph);
    BlockMap<AvailabilityMap> availabilityMapAtTail(graph);

    for (BasicBlock* block : graph.blocksInNaturalOrder()) {
        availabilityMapAtHead[block] = AvailabilityMap(block->ssa->availabilityAtHead);
        availabilityMapAtTail[block] = AvailabilityMap(block->ssa->availabilityAtTail);
    }

    auto availabilityAtHead = [&] (BasicBlock* block) -> AvailabilityMap& { return availabilityMapAtHead[block]; };
    auto availabilityAtTail = [&] (BasicBlock* block) -> AvailabilityMap& { return availabilityMapAtTail[block]; };
    OSRAvailabilityAnalysisPhase phase(graph, availabilityAtHead, availabilityAtTail);
    phase.run();
}

LocalOSRAvailabilityCalculator::LocalOSRAvailabilityCalculator(Graph& graph)
    : m_graph(graph)
{
}

LocalOSRAvailabilityCalculator::~LocalOSRAvailabilityCalculator()
{
}

void LocalOSRAvailabilityCalculator::beginBlock(BasicBlock* block)
{
    m_availability = block->ssa->availabilityAtHead;
}

void LocalOSRAvailabilityCalculator::endBlock(BasicBlock* block)
{
    m_availability = block->ssa->availabilityAtTail;
}

void LocalOSRAvailabilityCalculator::executeNode(Node* node)
{
    switch (node->op()) {

    // It's somewhat subtle why we cannot use the node for the GetStack itself in the Availability's node field. The reason is that if we did we would need to make any phase that converts nodes to GetStack availability aware. For instance a place where this could come up is if you had a graph like:

    // BB#1:
    // @1: NewObject()
    // @2: MovHint(@1, inline-arg1)
    // @3: Jump(#2, #3)

    // BB#2:
    // @4: PutStack(@1, inline-arg1)
    // @5: GetMyArgumentByVal(inline-arg1)
    // @6: Jump(#3)

    // BB#3:
    // @7: InvalidationPoint()

    // If constant folding converts @5 to a GetStack then at @7 inline-arg1 won't be available since at the end of BB#1 our availability is (@1, DeadFlush) and (@5, FlushedAt(inline-arg1)). When that gets merged at BB#3 then the availability will be (nullptr, ConflictingFlush).
    case GetStack:
    case PutStack: {
        StackAccessData* data = node->stackAccessData();
        m_availability.m_locals.operand(data->operand).setFlush(data->flushedAt());
        break;
    }
        
    case KillStack: {
        m_availability.m_locals.operand(node->unlinkedOperand()).setFlush(FlushedAt(ConflictingFlush));
        break;
    }

    case MovHint: {
        m_availability.m_locals.operand(node->unlinkedOperand()).setNode(node->child1().node());
        break;
    }

    case InitializeEntrypointArguments: {
        unsigned entrypointIndex = node->entrypointIndex();
        const Vector<FlushFormat>& argumentFormats = m_graph.m_argumentFormats[entrypointIndex];
        for (unsigned argument = argumentFormats.size(); argument--; ) {
            FlushedAt flushedAt = FlushedAt(argumentFormats[argument], virtualRegisterForArgumentIncludingThis(argument));
            m_availability.m_locals.argument(argument) = Availability(flushedAt);
        }
        break;
    }

    case VarargsLength: {
        break;
    }

    case LoadVarargs:
    case ForwardVarargs: {
        LoadVarargsData* data = node->loadVarargsData();
        m_availability.m_locals.operand(data->count) = Availability(FlushedAt(FlushedInt32, data->machineCount));
        for (unsigned i = data->limit; i--;) {
            m_availability.m_locals.operand(data->start + i) =
                Availability(FlushedAt(FlushedJSValue, data->machineStart.isValid() ? (data->machineStart + i) : VirtualRegister()));
        }
        break;
    }
    
    case PhantomCreateRest:
    case PhantomDirectArguments:
    case PhantomClonedArguments: {
        InlineCallFrame* inlineCallFrame = node->origin.semantic.inlineCallFrame();
        if (!inlineCallFrame) {
            // We don't need to record anything about how the arguments are to be recovered. It's just a
            // given that we can read them from the stack.
            break;
        }

        unsigned numberOfArgumentsToSkip = 0;
        if (node->op() == PhantomCreateRest)
            numberOfArgumentsToSkip = node->numberOfArgumentsToSkip();
        
        if (inlineCallFrame->isVarargs()) {
            // Record how to read each argument and the argument count.
            Availability argumentCount =
                m_availability.m_locals.operand(VirtualRegister(inlineCallFrame->stackOffset + CallFrameSlot::argumentCountIncludingThis));
            
            m_availability.m_heap.set(PromotedHeapLocation(ArgumentCountPLoc, node), argumentCount);
        }
        
        if (inlineCallFrame->isClosureCall) {
            Availability callee = m_availability.m_locals.operand(
                VirtualRegister(inlineCallFrame->stackOffset + CallFrameSlot::callee));
            m_availability.m_heap.set(PromotedHeapLocation(ArgumentsCalleePLoc, node), callee);
        }
        
        for (unsigned i = numberOfArgumentsToSkip; i < static_cast<unsigned>(inlineCallFrame->argumentCountIncludingThis - 1); ++i) {
            Availability argument = m_availability.m_locals.operand(
                VirtualRegister(inlineCallFrame->stackOffset + CallFrame::argumentOffset(i)));
            
            m_availability.m_heap.set(PromotedHeapLocation(ArgumentPLoc, node, i), argument);
        }
        break;
    }
        
    case PutHint: {
        m_availability.m_heap.set(
            PromotedHeapLocation(node->child1().node(), node->promotedLocationDescriptor()),
            Availability(node->child2().node()));
        break;
    }

    case PhantomSpread:
        m_availability.m_heap.set(PromotedHeapLocation(SpreadPLoc, node), Availability(node->child1().node()));
        break;

    case PhantomNewArrayWithSpread:
        for (unsigned i = 0; i < node->numChildren(); i++) {
            Node* child = m_graph.varArgChild(node, i).node();
            m_availability.m_heap.set(PromotedHeapLocation(NewArrayWithSpreadArgumentPLoc, node, i), Availability(child));
        }
        break;

    case PhantomNewArrayBuffer:
        m_availability.m_heap.set(PromotedHeapLocation(NewArrayBufferPLoc, node), Availability(node->child1().node()));
        break;
        
    default:
        break;
    }
}

} } // namespace JSC::DFG

#endif // ENABLE(DFG_JIT)