Bernd Schmidt wrote: > >>> +ACCUM_MODE (HA, 2, 8, 7); /* s8.7 */ > >>> +ACCUM_MODE (SA, 4, 16, 15); /* s16.15 */ > >>> +ACCUM_MODE (DA, 8, 32, 31); /* s32.31 */ > >>> +ACCUM_MODE (TA, 16, 64, 63); /* s64.63 */ > >> Lots of predefined types and modes in this patch. What > about targets > >> with other requirements (the Blackfin has 40 bit (8 + 32) > >> accumulators)? > > > > In "bfin-modes.def", we can adjust the DA mode to (s7.32) by using > > ADJUST_IBIT(DA, 7) > > ADJUST_FBIT(DA, 32) > > > >> For vectors, we let the targets define the supported > modes. Why do we > >> want something else for fractional support? > > > > I am not clear about this question. The new modes > (FRACT, UFRACT, ACCUM, > > and UACCUM) enables GCC to recognize the formats of the > underlying values > > to perform constant folding (e.g., + - * /). > > To use the DA mode for vector, we can use: > > VECTOR_MODE (ACCUM, DA, 2); > > No, I was trying to make an analogy of how ports explicitly > define the > modes their hardware supports, e.g. for arm: > > /* Vector modes. */ > VECTOR_MODES (INT, 4); /* V4QI V2HI */ > VECTOR_MODES (INT, 8); /* V8QI V4HI V2SI */ > VECTOR_MODES (INT, 16); /* V16QI V8HI V4SI V2DI */ > VECTOR_MODES (FLOAT, 8); /* V4HF V2SF */ > VECTOR_MODES (FLOAT, 16); /* V8HF V4SF V2DF */ > > I'm wondering whether it's a good idea to have a lot of pre-defined > fractional modes and types that may or may not match the target > hardware. Not saying it's necessarily wrong; I'm just interested to > hear why you chose to do it this way. (I also just noticed > that things > like SHORT_ACCUM_TYPE_SIZE are used but apparently not defined in the > patch - does it actually compile?) >
Ok. I got it. Maybe we treat fixed-point modes as the first class modes like other scalar modes (integer, floating, etc.), so we pre-define them. We can argue that how about making machine modes (ex: floating-point, decimal floating-point) not pre-defined, similar to vector modes. I think, the default fixed-point formats are the efficient ones for 32-bit/64-bit processors (with or without hardware supports). One of the goals for the fixed-point extension is that all targets in GCC will enable the extension, so efficient formats may be set by default. We have all FRACT and ACCUM sizes in defaults.h. Thanks! #ifndef SHORT_FRACT_TYPE_SIZE #define SHORT_FRACT_TYPE_SIZE BITS_PER_UNIT #endif #ifndef FRACT_TYPE_SIZE #define FRACT_TYPE_SIZE (BITS_PER_UNIT * 2) #endif #ifndef LONG_FRACT_TYPE_SIZE #define LONG_FRACT_TYPE_SIZE (BITS_PER_UNIT * 4) #endif #ifndef LONG_LONG_FRACT_TYPE_SIZE #define LONG_LONG_FRACT_TYPE_SIZE (BITS_PER_UNIT * 8) #endif #ifndef SHORT_ACCUM_TYPE_SIZE #define SHORT_ACCUM_TYPE_SIZE (SHORT_FRACT_TYPE_SIZE * 2) #endif #ifndef ACCUM_TYPE_SIZE #define ACCUM_TYPE_SIZE (FRACT_TYPE_SIZE * 2) #endif #ifndef LONG_ACCUM_TYPE_SIZE #define LONG_ACCUM_TYPE_SIZE (LONG_FRACT_TYPE_SIZE * 2) #endif #ifndef LONG_LONG_ACCUM_TYPE_SIZE #define LONG_LONG_ACCUM_TYPE_SIZE (LONG_LONG_FRACT_TYPE_SIZE * 2) #endif Regards, Chao-ying
