DFGArithMode.h   [plain text]

/*
 * Copyright (C) 2014 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
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 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#ifndef DFGArithMode_h
#define DFGArithMode_h

#if ENABLE(DFG_JIT)

namespace JSC { namespace DFG {

// Arith::Mode describes the mode of an arithmetic operation that speculates integer.
// Note that not all modes are valid for all operations.
namespace Arith {
enum Mode {
    NotSet, // Arithmetic mode is either not relevant because we're using doubles anyway or we are at a phase in compilation where we don't know what we're doing, yet. Should never see this after FixupPhase except for nodes that take doubles as inputs already.
    Unchecked, // Don't check anything and just do the direct hardware operation.
    CheckOverflow, // Check for overflow but don't bother with negative zero.
    CheckOverflowAndNegativeZero, // Check for both overflow and negative zero.
    DoOverflow // Up-convert to the smallest type that soundly represents all possible results after input type speculation.
};

// Define the type of operation the rounding operation will perform.
enum class RoundingMode {
    Int32, // The round operation produces a integer and -0 is considered as 0.
    Int32WithNegativeZeroCheck, // The round operation produces a integer and checks for -0.
    Double // The round operation produce a double. The result can be -0, NaN or (+/-)Infinity.
};

} // namespace Arith

inline bool doesOverflow(Arith::Mode mode)
{
    switch (mode) {
    case Arith::NotSet:
        ASSERT_NOT_REACHED();
#if ASSERT_DISABLED
        FALLTHROUGH;
#endif
    case Arith::Unchecked:
    case Arith::CheckOverflow:
    case Arith::CheckOverflowAndNegativeZero:
        return false;
    case Arith::DoOverflow:
        return true;
    }
    ASSERT_NOT_REACHED();
    return true;
}

// It's only valid to call this once you've determined that you don't need to *do*
// overflow. For most nodes, that's implicit.
inline bool shouldCheckOverflow(Arith::Mode mode)
{
    switch (mode) {
    case Arith::NotSet:
    case Arith::DoOverflow:
        ASSERT_NOT_REACHED();
        return true;
    case Arith::Unchecked:
        return false;
    case Arith::CheckOverflow:
    case Arith::CheckOverflowAndNegativeZero:
        return true;
    }
    ASSERT_NOT_REACHED();
    return true;
}

inline bool shouldCheckNegativeZero(Arith::Mode mode)
{
    switch (mode) {
    case Arith::NotSet:
    case Arith::DoOverflow:
        ASSERT_NOT_REACHED();
        return true;
    case Arith::Unchecked:
    case Arith::CheckOverflow:
        return false;
    case Arith::CheckOverflowAndNegativeZero:
        return true;
    }
    ASSERT_NOT_REACHED();
    return true;
}

inline bool subsumes(Arith::Mode earlier, Arith::Mode later)
{
    switch (earlier) {
    case Arith::CheckOverflow:
        switch (later) {
        case Arith::Unchecked:
        case Arith::CheckOverflow:
            return true;
        default:
            return false;
        }
    case Arith::CheckOverflowAndNegativeZero:
        switch (later) {
        case Arith::Unchecked:
        case Arith::CheckOverflow:
        case Arith::CheckOverflowAndNegativeZero:
            return true;
        default:
            return false;
        }
    default:
        return earlier == later;
    }
}

inline bool producesInteger(Arith::RoundingMode mode)
{
    return mode == Arith::RoundingMode::Int32WithNegativeZeroCheck || mode == Arith::RoundingMode::Int32;
}

inline bool shouldCheckNegativeZero(Arith::RoundingMode mode)
{
    return mode == Arith::RoundingMode::Int32WithNegativeZeroCheck;
}

} } // namespace JSC::DFG

namespace WTF {

class PrintStream;
void printInternal(PrintStream&, JSC::DFG::Arith::Mode);

} // namespace WTF

#endif // ENABLE(DFG_JIT)

#endif // DFGArithMode_h