[Mesa-dev] [PATCH 4/9] gallium-tgsi: add TGSI_OPCODE_{FMA-POPCNT-MSB-LSB} description
Vadim Girlin
vadimgirlin at gmail.com
Tue Jan 7 18:46:46 PST 2014
On Tue, 2014-01-07 at 21:49 +0100, Marek Olšák wrote:
> FYI, Evergreen has dedicated instructions for both MAD and FMA. FMA
> seems to be available on DX11 chips only.
FWIW, not all evergreen chips support FMA, only high-end chips that
support FP64 (I guess cypress only), according to the isa docs:
> Instructions
> FMA
> Description
> Fused single-precision multiply-add. Only for double-precision parts.
> dst = src0 * src1 + src2
>
Vadim
>
> Marek
>
> On Tue, Jan 7, 2014 at 8:20 PM, Roland Scheidegger <sroland at 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.ledore at 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 <sroland at 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 <maraeo at 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.ledore at 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 at 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 at 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 at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
More information about the mesa-dev
mailing list