Machine Modes Used in C Attributes

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    DevynCJohnson
    DevynCJohnson
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    Some compilers (such as GNU-GCC) support the mode attribute (__attribute__((mode(X)))). The mode attribute and the various machine-mode parameters can be used to create various datatypes. For instance, on an x86-64 system, 128-bit integers and Decimal-Floats can be created using the below code.

    typedef signed int __attribute__((mode(TI)))   int128_t;
    typedef unsigned int __attribute__((mode(TI)))   uint128_t;
    typedef float __attribute__((__mode__(__SD__)))   _Decimal32;
    typedef float __attribute__((__mode__(__DD__)))   _Decimal64;
    typedef float __attribute__((__mode__(__TD__)))   _Decimal128;

    The below list describes all of the possible parameters used by the mode attribute.

    • BI - 1 Bit
    • QI - Quarter Integer; 1 byte
    • HI - Half Integer; 2 bytes
    • PSI - Partial Single Integer; 4 bytes; not all bits used
    • SI - Single Integer; 4 bytes
    • PDI - Partial Double Integer; 8 bytes; not all bits used
    • DI - Double Integer; 8 bytes (64-bits)
    • TI - Tetra Integer; 16 bytes (128-bits)
    • OI - Octa Integer; 32 bytes (256-bits)
    • XI - Hexadeca Integer; 64 bytes (512-bits)
    • QF - Quarter Floating; 1 byte quarter-precision float-point
    • HF - Half Floating; 2 byte half-precision float-point
    • TQF - Three Quarter Floating; 3 byte three-quarter-precision float-point
    • SF - Single Floating; 4 byte single-precision float-point
    • DF - Double Floating; 8 byte double-precision float-point
    • XF - Extended Floating; 12 byte extended-precision float-point
    • TF - Tetra Floating; 16 byte tetra-precision float-point
    • SD - Single Decimal Floating; 4 byte (32-bit) decimal float-point
    • DD - Double Decimal Floating; 8 byte (64-bit) decimal float-point
    • TD - Tetra Decimal Floating; 4 byte (128-bit) decimal float-point
    • CQI - Complex Quarter Integer; 1 byte
    • CHI - Complex Half Integer; 2 bytes
    • CSI - Complex Single Integer; 4 bytes
    • CDI - Complex Double Integer; 8 bytes
    • CTI - Complex Tetra Integer; 16 bytes
    • COI - Complex Octa Integer; 32 bytes
    • QC - Quarter Complex; 1 byte quarter-precision complex float-point
    • HC - Half Complex; 2 byte half-precision complex float-point
    • SC - Single Complex; 4 byte single-precision complex float-point
    • DC - Double Complex; 8 byte double-precision complex float-point
    • XC - Extended Complex; 12 byte extended-precision complex float-point
    • TC - Tetra Complex; 16 byte tetra-precision complex float-point
    • QQ - Quarter-Fractional; 1-byte signed fractional number
    • HQ - Half-Fractional; 2-byte signed fractional number
    • SQ - Single-Fractional; 4-byte (32-bit) signed fractional number
    • DQ - Double-Fractional; 8-byte (64-bit) signed fractional number
    • TQ - Tetra-Fractional; 16-byte (128-bit) signed fractional number
    • UQQ - Unsigned Quarter-Fractional; 1-byte unsigned fractional number
    • UHQ - Unsigned Half-Fractional; 2-byte unsigned fractional number
    • USQ - Unsigned Single-Fractional; 4-byte (32-bit) unsigned fractional number
    • UDQ - Unsigned Double-Fractional; 8-byte (64-bit) unsigned fractional number
    • UTQ - Unsigned Tetra-Fractional; 16-byte (128-bit) unsigned fractional number
    • HA - Half-Accumulator; 2-byte (16-bit) signed accumulator
    • SA - Single-Accumulator; 4-byte (32-bit) signed accumulator
    • DA - Double-Accumulator; 8-byte (64-bit) signed accumulator
    • TA - Tetra-Accumulator; 16-byte (128-bit) signed accumulator
    • UHA - Unsigned Half-Accumulator; 2-byte (16-bit) unsigned accumulator
    • USA - Unsigned Single-Accumulator; 4-byte (32-bit) unsigned accumulator
    • UDA - Unsigned Double-Accumulator; 8-byte (64-bit) unsigned accumulator
    • UTA - Unsigned Tetra-Accumulator; 16-byte (128-bit) unsigned accumulator
    • CC - Condition Code
    • BLK - Block
    • VOID - Void
    • P - Address mode
    • V4SI - Vector; 4 single integers
    • V8QI - Vector; 8 single-byte integers
    • BND32 - 32-bit pointer bound
    • BND64 - 32-bit pointer bound

    Further Reading

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