[Mesa-dev] [PATCH 4/9] gallium-tgsi: add TGSI_OPCODE_{FMA-POPCNT-MSB-LSB} description

[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.



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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