[Mesa-dev] [PATCH 4/9] gallium-tgsi: add TGSI_OPCODE_{FMA-POPCNT-MSB-LSB} description
Marek Olšák
maraeo at gmail.com
Tue Jan 7 12:49:48 PST 2014
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 <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
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>> mesa-dev at lists.freedesktop.org
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>>>>> _______________________________________________
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>>>>>
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