Yes, and I guess just about all GPUs can do that. For llvmpipe we'd be vaguely interested in being able to do opencl-style MAD with undefined rounding as FMA since (x86) cpus never have MAD but may have FMA. I am not sure actually though this is ok for d3d10 - interestingly d3d10 has only MAD for SP (saying it's just mul+add but I'm unsure if that really means skipping the intermediate rounding is prohibited), but only FMA for DP...
Roland Am 07.01.2014 21:49, schrieb Marek Olšák: > FYI, Evergreen has dedicated instructions for both MAD and FMA. FMA > seems to be available on DX11 chips only. > > Marek > > On Tue, Jan 7, 2014 at 8:20 PM, Roland Scheidegger <srol...@vmware.com> wrote: >> Yes that is certainly related. I'm actually not entirely sure what is >> allowed in glsl by default as OpenGL seems to have some lax rules >> regarding precision in any case (float calculations not required but >> allowed to use denorms, at least earlier versions weren't required to >> support Infs neither and so on). >> It is quite possible the "MAD" we were always using would have been >> allowed to really do fma (at least with OpenGL), unless the "precise" >> qualifier was used (which isn't supported yet?). >> TGSI also isn't really watertight about such issues neither (that is if >> you use it with hw such as r300 then you certainly don't expect ieee754 >> rules to be followed but if you've got a d3d10-capable backend then you >> are expected to follow rules specified there which are _mostly_ >> ieee754-2008). >> So I'm not really sure if TGSI MAD should be allowed to do either >> rounding or not, but someday it should be figured out and spelled out >> explicitly in docs. >> >> Roland >> >> >> Am 07.01.2014 19:24, schrieb Maxence Le Doré: >>> I forgot the link : >>> >>> https://urldefense.proofpoint.com/v1/url?u=http://www.geeks3d.com/20120106/precise-qualifier-in-glsl-and-nvidia-geforce-cards/&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=F4msKE2WxRzA%2BwN%2B25muztFm5TSPwE8HKJfWfR2NgfY%3D%0A&m=%2FzSAl55KOH0z7T5qkRj6BX164wf6QpYOnJLIzojXBQc%3D%0A&s=0ac5e0fbd69867705f0c52090c9ddf84e7832be80e724a0983c5aa2f5dde72e0 >>> >>> 2014/1/7 Maxence Le Doré <maxence.led...@gmail.com>: >>>> For this reason, GLSL 4.0 introduces the 'precise' qualifier. I invite >>>> you to take a look at this article. >>>> >>>> 2014/1/6 Roland Scheidegger <srol...@vmware.com>: >>>>> 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
