Source/JavaScriptCore/b3/B3PatchpointValue.h

/*
 * Copyright (C) 2015-2016 Apple Inc. All rights reserved.
 *
 * 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
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 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 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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#pragma once

#if ENABLE(B3_JIT)

#include "B3Effects.h"
#include "B3StackmapValue.h"
#include "B3Value.h"

namespace JSC { namespace B3 {

class PatchpointValue : public StackmapValue {
public:
    typedef StackmapValue Base;
    
    static bool accepts(Kind kind) { return kind == Patchpoint; }

    ~PatchpointValue();

    // The effects of the patchpoint. This defaults to Effects::forCall(), but you can set it to anything.
    //
    // If there are no effects, B3 is free to assume any use of this PatchpointValue can be replaced with
    // a use of a different PatchpointValue, so long as the other one also has no effects and has the
    // same children. Note that this comparison ignores child constraints, the result constraint, and all
    // other StackmapValue meta-data. If there are read effects but not write effects, then this same sort
    // of substitution could be made so long as there are no interfering writes.
    Effects effects;

    // The input representation (i.e. constraint) of the return value. This defaults to WarmAny if the
    // type is Void and it defaults to SomeRegister otherwise. It's illegal to mess with this if the type
    // is Void. Otherwise you can set this to any input constraint.
    ValueRep resultConstraint;

    // The number of scratch registers that this patchpoint gets. The scratch register is guaranteed
    // to be different from any input register and the destination register. It's also guaranteed not
    // to be clobbered either early or late. These are 0 by default.
    uint8_t numGPScratchRegisters { 0 };
    uint8_t numFPScratchRegisters { 0 };

    B3_SPECIALIZE_VALUE_FOR_FINAL_SIZE_VARARGS_CHILDREN

protected:
    void dumpMeta(CommaPrinter&, PrintStream&) const override;

private:
    friend class Procedure;
    friend class Value;

    static Opcode opcodeFromConstructor(Type, Origin) { return Patchpoint; }
    JS_EXPORT_PRIVATE PatchpointValue(Type, Origin);
};

} } // namespace JSC::B3

#endif // ENABLE(B3_JIT)