[Mesa-dev] [PATCH 4/9] gallium-tgsi: add TGSI_OPCODE_{FMA-POPCNT-MSB-LSB} description
Roland Scheidegger
sroland at vmware.com
Mon Jan 6 07:56:48 PST 2014
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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