Source/JavaScriptCore/b3/air/AirCCallSpecial.h

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#pragma once

#if ENABLE(B3_JIT)

#include "AirSpecial.h"

namespace JSC { namespace B3 { namespace Air {

// Use this special for constructing a C call. Arg 0 is of course a Special arg that refers to the
// CCallSpecial object. Arg 1 is the callee, and it can be an ImmPtr, a register, or an address. The
// next three args - arg 2, arg 3, and arg 4 - hold the return value GPRs and FPR. The remaining args
// are just the set of argument registers used by this call. For arguments that go to the stack, you
// have to do the grunt work of doing those stack stores. In fact, the only reason why we specify the
// argument registers as arguments to a call is so that the liveness analysis can see that they get
// used here. It would be wrong to automagically report all argument registers as being used because
// if we had a call that didn't pass them, then they'd appear to be live until some clobber point or
// the prologue, whichever happened sooner.

class CCallSpecial : public Special {
public:
    CCallSpecial();
    ~CCallSpecial();

    // You cannot use this register to pass arguments. It just so happens that this register is not
    // used for arguments in the C calling convention. By the way, this is the only thing that causes
    // this special to be specific to C calls.
    static constexpr GPRReg scratchRegister = GPRInfo::nonPreservedNonArgumentGPR0;

protected:
    void forEachArg(Inst&, const ScopedLambda<Inst::EachArgCallback>&) final;
    bool isValid(Inst&) final;
    bool admitsStack(Inst&, unsigned argIndex) final;
    bool admitsExtendedOffsetAddr(Inst&, unsigned) final;
    void reportUsedRegisters(Inst&, const RegisterSet&) final;
    CCallHelpers::Jump generate(Inst&, CCallHelpers&, GenerationContext&) final;
    RegisterSet extraEarlyClobberedRegs(Inst&) final;
    RegisterSet extraClobberedRegs(Inst&) final;

    void dumpImpl(PrintStream&) const final;
    void deepDumpImpl(PrintStream&) const final;

private:
    static constexpr unsigned specialArgOffset = 0;
    static constexpr unsigned numSpecialArgs = 1;
    static constexpr unsigned calleeArgOffset = numSpecialArgs;
    static constexpr unsigned numCalleeArgs = 1;
    static constexpr unsigned returnGPArgOffset = numSpecialArgs + numCalleeArgs;
    static constexpr unsigned numReturnGPArgs = 2;
    static constexpr unsigned returnFPArgOffset = numSpecialArgs + numCalleeArgs + numReturnGPArgs;
    static constexpr unsigned numReturnFPArgs = 1;
    static constexpr unsigned argArgOffset =
        numSpecialArgs + numCalleeArgs + numReturnGPArgs + numReturnFPArgs;
    
    RegisterSet m_clobberedRegs;
    RegisterSet m_emptyRegs;
};

} } } // namespace JSC::B3::Air

#endif // ENABLE(B3_JIT)