Machine Modes Used in C Attributes

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 - 64-bit pointer bound

Further Reading

• Programming and Development (Article Index) - https://dcjtech.info/topic/programming-and-development/
• C Programming Article Forum - https://dcjtech.info/forum/articles/programming/c-c-and-c/
• Type Qualifiers in C - https://dcjtech.info/topic/type-qualifiers-in-c/