Am 05.01.2014 01:34, schrieb Maxence Le Doré: > FMA(a,b,c) keeps extra precision (usually 1 more bit of mantissa, > afaik) for the result a*b and add this to c, to finally produce a > IEEE754 32bit float result. > > MAD(a,b,c) product a IEEE754 32bit float product a*b and add it to C. > > So, fma can be slightly more accurate. An accuracy that is something > very appreciate.
Actually in "newer" languages (such as opencl) "mad" is used to indicate intermediate rounding does not matter, so if your cpu can do fma but not mul+add in a single cycle it is allowed to use fma instead. FMA OTOH of course forces no intermediate rounding. Our tgsi definitions certainly initially were meaning intermediate rounding should take place, I don't know if we need to keep it that way or could repurpose that slightly (so if you require the intermediate rounding you'd just use mul+add). Roland > > > 2014/1/5 Marek Olšák <mar...@gmail.com>: >> How is FMA different from MAD? >> >> Please document the new opcodes in src/gallium/docs/source/tgsi.rst. >> >> Marek >> >> On Sun, Jan 5, 2014 at 12:42 AM, Maxence Le Doré >> <maxence.led...@gmail.com> wrote: >>> From: Maxence Le Doré <Maxence Le Doré> >>> >>> --- >>> src/gallium/auxiliary/tgsi/tgsi_info.c | 16 ++++++++++++++++ >>> src/gallium/auxiliary/tgsi/tgsi_opcode_tmp.h | 6 ++++++ >>> src/gallium/include/pipe/p_shader_tokens.h | 9 ++++++++- >>> 3 files changed, 30 insertions(+), 1 deletion(-) >>> >>> diff --git a/src/gallium/auxiliary/tgsi/tgsi_info.c >>> b/src/gallium/auxiliary/tgsi/tgsi_info.c >>> index 0beef44..ed55940 100644 >>> --- a/src/gallium/auxiliary/tgsi/tgsi_info.c >>> +++ b/src/gallium/auxiliary/tgsi/tgsi_info.c >>> @@ -221,6 +221,12 @@ static const struct tgsi_opcode_info >>> opcode_info[TGSI_OPCODE_LAST] = >>> { 1, 3, 1, 0, 0, 0, OTHR, "TXL2", TGSI_OPCODE_TXL2 }, >>> { 1, 2, 0, 0, 0, 0, COMP, "IMUL_HI", TGSI_OPCODE_IMUL_HI }, >>> { 1, 2, 0, 0, 0, 0, COMP, "UMUL_HI", TGSI_OPCODE_UMUL_HI }, >>> + { 1, 3, 0, 0, 0, 0, COMP, "FMA", TGSI_OPCODE_FMA }, >>> + { 1, 1, 0, 0, 0, 0, COMP, "POPCNT", TGSI_OPCODE_POPCNT }, >>> + { 1, 1, 0, 0, 0, 0, COMP, "IMSB", TGSI_OPCODE_IMSB }, >>> + { 1, 1, 0, 0, 0, 0, COMP, "ILSB", TGSI_OPCODE_ILSB }, >>> + { 1, 1, 0, 0, 0, 0, COMP, "UMSB", TGSI_OPCODE_UMSB }, >>> + { 1, 1, 0, 0, 0, 0, COMP, "ULSB", TGSI_OPCODE_ULSB }, >>> }; >>> >>> const struct tgsi_opcode_info * >>> @@ -321,6 +327,11 @@ tgsi_opcode_infer_type( uint opcode ) >>> case TGSI_OPCODE_IABS: >>> case TGSI_OPCODE_ISSG: >>> case TGSI_OPCODE_IMUL_HI: >>> + case TGSI_OPCODE_POPCNT: >>> + case TGSI_OPCODE_ILSB: >>> + case TGSI_OPCODE_IMSB: >>> + case TGSI_OPCODE_ULSB: >>> + case TGSI_OPCODE_UMSB: >>> return TGSI_TYPE_SIGNED; >>> default: >>> return TGSI_TYPE_FLOAT; >>> @@ -344,9 +355,14 @@ tgsi_opcode_infer_src_type( uint opcode ) >>> case TGSI_OPCODE_SAMPLE_I: >>> case TGSI_OPCODE_SAMPLE_I_MS: >>> case TGSI_OPCODE_UMUL_HI: >>> + case TGSI_OPCODE_POPCNT: >>> + case TGSI_OPCODE_ULSB: >>> + case TGSI_OPCODE_UMSB: >>> return TGSI_TYPE_UNSIGNED; >>> case TGSI_OPCODE_IMUL_HI: >>> case TGSI_OPCODE_I2F: >>> + case TGSI_OPCODE_ILSB: >>> + case TGSI_OPCODE_IMSB: >>> return TGSI_TYPE_SIGNED; >>> case TGSI_OPCODE_ARL: >>> case TGSI_OPCODE_ARR: >>> diff --git a/src/gallium/auxiliary/tgsi/tgsi_opcode_tmp.h >>> b/src/gallium/auxiliary/tgsi/tgsi_opcode_tmp.h >>> index 1ef78dd..cba0975 100644 >>> --- a/src/gallium/auxiliary/tgsi/tgsi_opcode_tmp.h >>> +++ b/src/gallium/auxiliary/tgsi/tgsi_opcode_tmp.h >>> @@ -206,6 +206,12 @@ OP13(UCMP) >>> >>> OP12(IMUL_HI) >>> OP12(UMUL_HI) >>> +OP13(FMA) >>> +OP11(POPCNT) >>> +OP11(IMSB) >>> +OP11(ILSB) >>> +OP11(UMSB) >>> +OP11(ULSB) >>> >>> #undef OP00 >>> #undef OP01 >>> diff --git a/src/gallium/include/pipe/p_shader_tokens.h >>> b/src/gallium/include/pipe/p_shader_tokens.h >>> index 8010902..5ed0c34 100644 >>> --- a/src/gallium/include/pipe/p_shader_tokens.h >>> +++ b/src/gallium/include/pipe/p_shader_tokens.h >>> @@ -453,7 +453,14 @@ struct tgsi_property_data { >>> #define TGSI_OPCODE_IMUL_HI 180 >>> #define TGSI_OPCODE_UMUL_HI 181 >>> >>> -#define TGSI_OPCODE_LAST 182 >>> +#define TGSI_OPCODE_FMA 182 >>> +#define TGSI_OPCODE_POPCNT 183 >>> +#define TGSI_OPCODE_IMSB 184 >>> +#define TGSI_OPCODE_ILSB 185 >>> +#define TGSI_OPCODE_UMSB 186 >>> +#define TGSI_OPCODE_ULSB 187 >>> + >>> +#define TGSI_OPCODE_LAST 188 >>> >>> #define TGSI_SAT_NONE 0 /* do not saturate */ >>> #define TGSI_SAT_ZERO_ONE 1 /* clamp to [0,1] */ >>> -- >>> 1.8.5.2 >>> >>> _______________________________________________ >>> mesa-dev mailing list >>> mesa-dev@lists.freedesktop.org >>> https://urldefense.proofpoint.com/v1/url?u=http://lists.freedesktop.org/mailman/listinfo/mesa-dev&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=F4msKE2WxRzA%2BwN%2B25muztFm5TSPwE8HKJfWfR2NgfY%3D%0A&m=UbogYegyhJOd8MD5pXDHVLpkdfH0gvvci5OW50vTexw%3D%0A&s=4da499b672e3e50826f923f340c51cfaa5c79830951ccc3034abd52a1b7402a8 > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://urldefense.proofpoint.com/v1/url?u=http://lists.freedesktop.org/mailman/listinfo/mesa-dev&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=F4msKE2WxRzA%2BwN%2B25muztFm5TSPwE8HKJfWfR2NgfY%3D%0A&m=UbogYegyhJOd8MD5pXDHVLpkdfH0gvvci5OW50vTexw%3D%0A&s=4da499b672e3e50826f923f340c51cfaa5c79830951ccc3034abd52a1b7402a8 > _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev