[Mesa-dev] [PATCH 4/9] gallium-tgsi: add TGSI_OPCODE_{FMA-POPCNT-MSB-LSB} description
Maxence Le Doré
maxence.ledore at gmail.com
Tue Jan 7 10:24:41 PST 2014
I forgot the link :
http://www.geeks3d.com/20120106/precise-qualifier-in-glsl-and-nvidia-geforce-cards/
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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