[Mesa-dev] [PATCH 3/5] llvmpipe: Optimize do_triangle_ccw for POWER8

[Oded Gabbay]

On Wed, Dec 30, 2015 at 1:17 AM, Roland Scheidegger <sroland at vmware.com> wrote:
> The idea looks right to me.
> Though frankly I don't like our current setup code too much - in
> particular the mix between c, assembly, and jit code, with some
> duplication (plus the lots of transpose everywhere). There's likely
> optimization potential to be found there.
>
> Roland

Agreed, if we can remove the transpose, that would be some 3-5% boost for sure.

     Oded

>
> Am 29.12.2015 um 17:12 schrieb Oded Gabbay:
>> This patch converts the SSE optimization done in do_triangle_ccw to
>> VMX/VSX.
>>
>> I measured the results on POWER8 machine with 32 cores at 3.4GHz and
>> 16GB of RAM.
>>
>>                       FPS/Score
>>   Name            Before     After    Delta
>> ------------------------------------------------
>> glmark2 (score)   136.6      139.8    2.34%
>> openarena         16.14      16.35    1.30%
>> xonotic           4.655      4.707    1.11%
>>
>> Signed-off-by: Oded Gabbay <oded.gabbay at gmail.com>
>> ---
>>  src/gallium/drivers/llvmpipe/lp_setup_tri.c | 96 +++++++++++++++++++++++++++++
>>  1 file changed, 96 insertions(+)
>>
>> diff --git a/src/gallium/drivers/llvmpipe/lp_setup_tri.c b/src/gallium/drivers/llvmpipe/lp_setup_tri.c
>> index b1671dd..cfa9874 100644
>> --- a/src/gallium/drivers/llvmpipe/lp_setup_tri.c
>> +++ b/src/gallium/drivers/llvmpipe/lp_setup_tri.c
>> @@ -46,6 +46,9 @@
>>
>>  #if defined(PIPE_ARCH_SSE)
>>  #include <emmintrin.h>
>> +#elif defined(_ARCH_PWR8)
>> +#include <altivec.h>
>> +#include "util/u_pwr8.h"
>>  #endif
>>
>>  static inline int
>> @@ -462,6 +465,99 @@ do_triangle_ccw(struct lp_setup_context *setup,
>>        STORE_PLANE(plane[2], p2);
>>  #undef STORE_PLANE
>>     } else
>> +#elif defined(_ARCH_PWR8)
>> +   if (setup->fb.width <= MAX_FIXED_LENGTH32 &&
>> +       setup->fb.height <= MAX_FIXED_LENGTH32 &&
>> +       (bbox.x1 - bbox.x0) <= MAX_FIXED_LENGTH32 &&
>> +       (bbox.y1 - bbox.y0) <= MAX_FIXED_LENGTH32) {
>> +      unsigned int bottom_edge;
>> +      __m128i vertx, verty;
>> +      __m128i shufx, shufy;
>> +      __m128i dcdx, dcdy, c;
>> +      __m128i unused;
>> +      __m128i dcdx_neg_mask;
>> +      __m128i dcdy_neg_mask;
>> +      __m128i dcdx_zero_mask;
>> +      __m128i top_left_flag;
>> +      __m128i c_inc_mask, c_inc;
>> +      __m128i eo, p0, p1, p2;
>> +      __m128i_union vshuf_mask;
>> +      __m128i zero = vec_splats((unsigned char) 0);
>> +      PIPE_ALIGN_VAR(16) int32_t temp_vec[4];
>> +
>> +#ifdef PIPE_ARCH_LITTLE_ENDIAN
>> +      vshuf_mask.i[0] = 0x07060504;
>> +      vshuf_mask.i[1] = 0x0B0A0908;
>> +      vshuf_mask.i[2] = 0x03020100;
>> +      vshuf_mask.i[3] = 0x0F0E0D0C;
>> +#else
>> +      vshuf_mask.i[0] = 0x00010203;
>> +      vshuf_mask.i[1] = 0x0C0D0E0F;
>> +      vshuf_mask.i[2] = 0x04050607;
>> +      vshuf_mask.i[3] = 0x08090A0B;
>> +#endif
>> +
>> +      /* vertex x coords */
>> +      vertx = vec_loadu_si128((const uint32_t *) position->x);
>> +      /* vertex y coords */
>> +      verty = vec_loadu_si128((const uint32_t *) position->y);
>> +
>> +      shufx = vec_perm (vertx, vertx, vshuf_mask.m128i);
>> +      shufy = vec_perm (verty, verty, vshuf_mask.m128i);
>> +
>> +      dcdx = vec_sub_epi32(verty, shufy);
>> +      dcdy = vec_sub_epi32(vertx, shufx);
>> +
>> +      dcdx_neg_mask = vec_srai_epi32(dcdx, 31);
>> +      dcdx_zero_mask = vec_cmpeq_epi32(dcdx, zero);
>> +      dcdy_neg_mask = vec_srai_epi32(dcdy, 31);
>> +
>> +      bottom_edge = (setup->bottom_edge_rule == 0) ? ~0 : 0;
>> +      top_left_flag = (__m128i) vec_splats(bottom_edge);
>> +
>> +      c_inc_mask = vec_or(dcdx_neg_mask,
>> +                                vec_and(dcdx_zero_mask,
>> +                                              vec_xor(dcdy_neg_mask,
>> +                                                            top_left_flag)));
>> +
>> +      c_inc = vec_srli_epi32(c_inc_mask, 31);
>> +
>> +      c = vec_sub_epi32(vec_mullo_epi32(dcdx, vertx),
>> +                        vec_mullo_epi32(dcdy, verty));
>> +
>> +      c = vec_add_epi32(c, c_inc);
>> +
>> +      /* Scale up to match c:
>> +       */
>> +      dcdx = vec_slli_epi32(dcdx, FIXED_ORDER);
>> +      dcdy = vec_slli_epi32(dcdy, FIXED_ORDER);
>> +
>> +      /* Calculate trivial reject values:
>> +       */
>> +      eo = vec_sub_epi32(vec_andc(dcdy_neg_mask, dcdy),
>> +                         vec_and(dcdx_neg_mask, dcdx));
>> +
>> +      /* ei = _mm_sub_epi32(_mm_sub_epi32(dcdy, dcdx), eo); */
>> +
>> +      /* Pointless transpose which gets undone immediately in
>> +       * rasterization:
>> +       */
>> +      transpose4_epi32(&c, &dcdx, &dcdy, &eo,
>> +                       &p0, &p1, &p2, &unused);
>> +
>> +#define STORE_PLANE(plane, vec) do {                  \
>> +         vec_store_si128((uint32_t *)&temp_vec, vec); \
>> +         plane.c    = (int64_t)temp_vec[0];           \
>> +         plane.dcdx = temp_vec[1];                    \
>> +         plane.dcdy = temp_vec[2];                    \
>> +         plane.eo   = temp_vec[3];                    \
>> +      } while(0)
>> +
>> +      STORE_PLANE(plane[0], p0);
>> +      STORE_PLANE(plane[1], p1);
>> +      STORE_PLANE(plane[2], p2);
>> +#undef STORE_PLANE
>> +   } else
>>  #endif
>>     {
>>        int i;
>>
>