Source/JavaScriptCore/b3/B3LegalizeMemoryOffsets.cpp

/*
 * Copyright (C) 2015-2017 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    notice, this list of conditions and the following disclaimer in the
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
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#include "config.h"
#include "B3LegalizeMemoryOffsets.h"

#if ENABLE(B3_JIT)

#include "B3InsertionSetInlines.h"
#include "B3MemoryValueInlines.h"
#include "B3PhaseScope.h"
#include "B3ProcedureInlines.h"
#include "B3ValueInlines.h"

namespace JSC { namespace B3 {

namespace {

class LegalizeMemoryOffsets {
public:
    LegalizeMemoryOffsets(Procedure& proc)
        : m_proc(proc)
        , m_insertionSet(proc)
    {
    }

    void run()
    {
        // FIXME: Perhaps this should be moved to lowerMacros, and quirks mode can impose the requirement
        // that the offset is legal. But for now this is sort of OK because we run pureCSE after. Also,
        // we should probably have something better than just pureCSE to clean up the code that this
        // introduces.
        // https://bugs.webkit.org/show_bug.cgi?id=169246
        
        for (BasicBlock* block : m_proc) {
            for (unsigned index = 0; index < block->size(); ++index) {
                MemoryValue* memoryValue = block->at(index)->as<MemoryValue>();
                if (!memoryValue)
                    continue;
                
                if (!memoryValue->isLegalOffset(memoryValue->offset())) {
                    Value* base = memoryValue->lastChild();
                    Value* offsetValue = m_insertionSet.insertIntConstant(index, memoryValue->origin(), pointerType(), memoryValue->offset());
                    Value* resolvedAddress = m_proc.add<Value>(Add, memoryValue->origin(), base, offsetValue);
                    m_insertionSet.insertValue(index, resolvedAddress);

                    memoryValue->lastChild() = resolvedAddress;
                    memoryValue->setOffset(0);
                }
            }
            m_insertionSet.execute(block);
        }
    }

    Procedure& m_proc;
    InsertionSet m_insertionSet;
};

} // anonymous namespace

void legalizeMemoryOffsets(Procedure& proc)
{
    PhaseScope phaseScope(proc, "legalizeMemoryOffsets");
    LegalizeMemoryOffsets legalizeMemoryOffsets(proc);
    legalizeMemoryOffsets.run();
}

} } // namespace JSC::B3

#endif // ENABLE(B3_JIT)