[Mesa-dev] [PATCH 4/4] softpipe: add tgsi_exec support for new bit manipulation opcodes

Roland Scheidegger sroland at vmware.com
Fri Apr 25 14:44:54 PDT 2014


Am 25.04.2014 19:41, schrieb Ilia Mirkin:
> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> ---
>  src/gallium/auxiliary/tgsi/tgsi_exec.c | 188 +++++++++++++++++++++++++++++++++
>  src/gallium/auxiliary/util/u_math.h    |  11 ++
>  2 files changed, 199 insertions(+)
> 
> diff --git a/src/gallium/auxiliary/tgsi/tgsi_exec.c b/src/gallium/auxiliary/tgsi/tgsi_exec.c
> index 55da60a..2cc7884 100644
> --- a/src/gallium/auxiliary/tgsi/tgsi_exec.c
> +++ b/src/gallium/auxiliary/tgsi/tgsi_exec.c
> @@ -2603,6 +2603,40 @@ exec_vector_trinary(struct tgsi_exec_machine *mach,
>     }
>  }
>  
> +typedef void (* micro_quaternary_op)(union tgsi_exec_channel *dst,
> +                                     const union tgsi_exec_channel *src0,
> +                                     const union tgsi_exec_channel *src1,
> +                                     const union tgsi_exec_channel *src2,
> +                                     const union tgsi_exec_channel *src3);
> +
> +static void
> +exec_vector_quaternary(struct tgsi_exec_machine *mach,
> +                       const struct tgsi_full_instruction *inst,
> +                       micro_quaternary_op op,
> +                       enum tgsi_exec_datatype dst_datatype,
> +                       enum tgsi_exec_datatype src_datatype)
> +{
> +   unsigned int chan;
> +   struct tgsi_exec_vector dst;
> +
> +   for (chan = 0; chan < TGSI_NUM_CHANNELS; chan++) {
> +      if (inst->Dst[0].Register.WriteMask & (1 << chan)) {
> +         union tgsi_exec_channel src[4];
> +
> +         fetch_source(mach, &src[0], &inst->Src[0], chan, src_datatype);
> +         fetch_source(mach, &src[1], &inst->Src[1], chan, src_datatype);
> +         fetch_source(mach, &src[2], &inst->Src[2], chan, src_datatype);
> +         fetch_source(mach, &src[3], &inst->Src[3], chan, src_datatype);
> +         op(&dst.xyzw[chan], &src[0], &src[1], &src[2], &src[3]);
> +      }
> +   }
> +   for (chan = 0; chan < TGSI_NUM_CHANNELS; chan++) {
> +      if (inst->Dst[0].Register.WriteMask & (1 << chan)) {
> +         store_dest(mach, &dst.xyzw[chan], &inst->Dst[0], inst, chan, dst_datatype);
> +      }
> +   }
> +}
> +
>  static void
>  exec_dp3(struct tgsi_exec_machine *mach,
>           const struct tgsi_full_instruction *inst)
> @@ -3571,6 +3605,135 @@ micro_ucmp(union tgsi_exec_channel *dst,
>  }
>  
>  static void
> +micro_ibfe(union tgsi_exec_channel *dst,
> +           const union tgsi_exec_channel *src0,
> +           const union tgsi_exec_channel *src1,
> +           const union tgsi_exec_channel *src2)
> +{
> +   int i;
> +   for (i = 0; i < 4; i++) {
> +      int width = src2->i[i] & 0x1f;
> +      int offset = src1->i[i] & 0x1f;
> +      if (width == 0)
> +         dst->i[i] = 0;
> +      else if (width + offset < 32)
> +         dst->i[i] = (src0->i[i] << (32 - width - offset)) >> (32 - width);
> +      else
> +         dst->i[i] = src0->i[i] >> offset;
> +   }
> +}
> +
> +static void
> +micro_ubfe(union tgsi_exec_channel *dst,
> +           const union tgsi_exec_channel *src0,
> +           const union tgsi_exec_channel *src1,
> +           const union tgsi_exec_channel *src2)
> +{
> +   int i;
> +   for (i = 0; i < 4; i++) {
> +      int width = src2->u[i] & 0x1f;
> +      int offset = src1->u[i] & 0x1f;
> +      if (width == 0)
> +         dst->u[i] = 0;
> +      else if (width + offset < 32)
> +         dst->u[i] = (src0->u[i] << (32 - width - offset)) >> (32 - width);
> +      else
> +         dst->u[i] = src0->u[i] >> offset;
> +   }
> +}
> +
> +static void
> +micro_bfi(union tgsi_exec_channel *dst,
> +          const union tgsi_exec_channel *src0,
> +          const union tgsi_exec_channel *src1,
> +          const union tgsi_exec_channel *src2,
> +          const union tgsi_exec_channel *src3)
> +{
> +   int i;
> +   for (i = 0; i < 4; i++) {
> +      int width = src3->u[i] & 0x1f;
> +      int offset = src2->u[i] & 0x1f;
> +      int bitmask = ((1 << width) - 1) << offset;
> +      dst->u[i] = ((src1->u[i] << offset) & bitmask) | (src0->u[i] & ~bitmask);
> +   }
> +}
> +
> +static void
> +micro_brev(union tgsi_exec_channel *dst,
> +           const union tgsi_exec_channel *src)
> +{
> +   int i;
> +   static const unsigned reverse[16] = {
> +      [0x0] = 0x0,
> +      [0x1] = 0x8,
> +      [0x2] = 0x4,
> +      [0x3] = 0xc,
> +      [0x4] = 0x2,
> +      [0x5] = 0xa,
> +      [0x6] = 0x6,
> +      [0x7] = 0xe,
> +      [0x8] = 0x1,
> +      [0x9] = 0x9,
> +      [0xa] = 0x5,
> +      [0xb] = 0xd,
> +      [0xc] = 0x3,
> +      [0xd] = 0xb,
> +      [0xe] = 0x7,
> +      [0xf] = 0xf,
> +   };
> +   for (i = 0; i < 4; i++) {
> +      dst->u[i] = (reverse[(src->u[i] >> 0) & 0xf] << 28 |
> +                   reverse[(src->u[i] >> 4) & 0xf] << 24 |
> +                   reverse[(src->u[i] >> 8) & 0xf] << 20 |
> +                   reverse[(src->u[i] >> 12) & 0xf] << 16 |
> +                   reverse[(src->u[i] >> 16) & 0xf] << 12 |
> +                   reverse[(src->u[i] >> 20) & 0xf] << 8 |
> +                   reverse[(src->u[i] >> 24) & 0xf] << 4 |
> +                   reverse[(src->u[i] >> 28) & 0xf] << 0);
> +   }
> +}
Hmm looks like that opcode is slow even for softpipe's standards
(luckily llvmpipe should be able to exploit pshufb for a rather nice
implementation, though it will require ssse3...).
I think though something like
uint32_t reverse(uint32_t x)
{
    x = ((x >> 1) & 0x55555555u) | ((x & 0x55555555u) << 1);
    x = ((x >> 2) & 0x33333333u) | ((x & 0x33333333u) << 2);
    x = ((x >> 4) & 0x0f0f0f0fu) | ((x & 0x0f0f0f0fu) << 4);
    x = ((x >> 8) & 0x00ff00ffu) | ((x & 0x00ff00ffu) << 8);
    x = ((x >> 16) & 0xffffu) | ((x & 0xffffu) << 16);
    return x;
}

blatantly copied from
http://stackoverflow.com/questions/9144800/c-reverse-bits-in-unsigned-integer
should be faster. But whatever works...


> +
> +static void
> +micro_popc(union tgsi_exec_channel *dst,
> +           const union tgsi_exec_channel *src)
> +{
> +   dst->u[0] = util_bitcount(src->u[0]);
> +   dst->u[1] = util_bitcount(src->u[1]);
> +   dst->u[2] = util_bitcount(src->u[2]);
> +   dst->u[3] = util_bitcount(src->u[3]);
> +}
> +
> +static void
> +micro_lsb(union tgsi_exec_channel *dst,
> +          const union tgsi_exec_channel *src)
> +{
> +   dst->i[0] = ffs(src->u[0]) - 1;
> +   dst->i[1] = ffs(src->u[1]) - 1;
> +   dst->i[2] = ffs(src->u[2]) - 1;
> +   dst->i[3] = ffs(src->u[3]) - 1;
> +}
> +
> +static void
> +micro_imsb(union tgsi_exec_channel *dst,
> +           const union tgsi_exec_channel *src)
> +{
> +   dst->i[0] = util_last_bit_signed(src->i[0]) - 1;
> +   dst->i[1] = util_last_bit_signed(src->i[1]) - 1;
> +   dst->i[2] = util_last_bit_signed(src->i[2]) - 1;
> +   dst->i[3] = util_last_bit_signed(src->i[3]) - 1;
> +}
> +
> +static void
> +micro_umsb(union tgsi_exec_channel *dst,
> +           const union tgsi_exec_channel *src)
> +{
> +   dst->i[0] = util_last_bit(src->u[0]) - 1;
> +   dst->i[1] = util_last_bit(src->u[1]) - 1;
> +   dst->i[2] = util_last_bit(src->u[2]) - 1;
> +   dst->i[3] = util_last_bit(src->u[3]) - 1;
> +}
> +
> +static void
>  exec_instruction(
>     struct tgsi_exec_machine *mach,
>     const struct tgsi_full_instruction *inst,
> @@ -4417,6 +4580,31 @@ exec_instruction(
>        /* src[2] = sampler unit */
>        exec_tex(mach, inst, TEX_MODIFIER_EXPLICIT_LOD, 2);
>        break;
> +
> +   case TGSI_OPCODE_IBFE:
> +      exec_vector_trinary(mach, inst, micro_ibfe, TGSI_EXEC_DATA_INT, TGSI_EXEC_DATA_INT);
> +      break;
> +   case TGSI_OPCODE_UBFE:
> +      exec_vector_trinary(mach, inst, micro_ubfe, TGSI_EXEC_DATA_UINT, TGSI_EXEC_DATA_UINT);
> +      break;
> +   case TGSI_OPCODE_BFI:
> +      exec_vector_quaternary(mach, inst, micro_bfi, TGSI_EXEC_DATA_UINT, TGSI_EXEC_DATA_UINT);
> +      break;
> +   case TGSI_OPCODE_BREV:
> +      exec_vector_unary(mach, inst, micro_brev, TGSI_EXEC_DATA_UINT, TGSI_EXEC_DATA_UINT);
> +      break;
> +   case TGSI_OPCODE_POPC:
> +      exec_vector_unary(mach, inst, micro_popc, TGSI_EXEC_DATA_UINT, TGSI_EXEC_DATA_UINT);
> +      break;
> +   case TGSI_OPCODE_LSB:
> +      exec_vector_unary(mach, inst, micro_lsb, TGSI_EXEC_DATA_INT, TGSI_EXEC_DATA_UINT);
> +      break;
> +   case TGSI_OPCODE_IMSB:
> +      exec_vector_unary(mach, inst, micro_imsb, TGSI_EXEC_DATA_INT, TGSI_EXEC_DATA_INT);
> +      break;
> +   case TGSI_OPCODE_UMSB:
> +      exec_vector_unary(mach, inst, micro_umsb, TGSI_EXEC_DATA_INT, TGSI_EXEC_DATA_UINT);
> +      break;
>     default:
>        assert( 0 );
>     }
> diff --git a/src/gallium/auxiliary/util/u_math.h b/src/gallium/auxiliary/util/u_math.h
> index ec03e4e..5b811e3 100644
> --- a/src/gallium/auxiliary/util/u_math.h
> +++ b/src/gallium/auxiliary/util/u_math.h
> @@ -567,6 +567,17 @@ static INLINE unsigned util_last_bit(unsigned u)
>  #endif
>  }
>  
> +static INLINE unsigned util_last_bit_signed(int i)
Similar to my previous comment, I find that name confusing. Maybe
last_significant_bit_signed or something like that? No biggie though.
Otherwise looks good to me.

Roland

> +{
> +#if defined(__GNUC__) && ((__GNUC__ * 100 + __GNUC_MINOR__) >= 407)
> +   return 31 - __builtin_clrsb(i);
> +#else
> +   if (i >= 0)
> +      return util_last_bit(i);
> +   else
> +      return util_last_bit(~(unsigned)i);
> +#endif
> +}
>  
>  /* Destructively loop over all of the bits in a mask as in:
>   *
> 


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