xref: /xsrc/external/mit/MesaLib.old/dist/src/mesa/main/sse_minmax.c

/*
 * Copyright © 2014 Timothy Arceri
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 * Author:
 *    Timothy Arceri <t_arceri@yahoo.com.au>
 *
 */

#include "main/sse_minmax.h"
#include <smmintrin.h>
#include <stdint.h>

void
_mesa_uint_array_min_max(const unsigned *ui_indices, unsigned *min_index,
                         unsigned *max_index, const unsigned count)
{
   unsigned max_ui = 0;
   unsigned min_ui = ~0U;
   unsigned i = 0;
   unsigned aligned_count = count;

   /* handle the first few values without SSE until the pointer is aligned */
   while (((uintptr_t)ui_indices & 15) && aligned_count) {
      if (*ui_indices > max_ui)
         max_ui = *ui_indices;
      if (*ui_indices < min_ui)
         min_ui = *ui_indices;

      aligned_count--;
      ui_indices++;
   }

   /* TODO: The actual threshold for SSE begin useful may be higher than 8.
    * Some careful microbenchmarks and measurement are required to
    * find the actual tipping point.
    */
   if (aligned_count >= 8) {
      unsigned max_arr[4] __attribute__ ((aligned (16)));
      unsigned min_arr[4] __attribute__ ((aligned (16)));
      unsigned vec_count;
      __m128i max_ui4 = _mm_setzero_si128();
      __m128i min_ui4 = _mm_set1_epi32(~0U);
      __m128i ui_indices4;
      __m128i *ui_indices_ptr;

      vec_count = aligned_count & ~0x3;
      ui_indices_ptr = (__m128i *)ui_indices;
      for (i = 0; i < vec_count / 4; i++) {
         ui_indices4 = _mm_load_si128(&ui_indices_ptr[i]);
         max_ui4 = _mm_max_epu32(ui_indices4, max_ui4);
         min_ui4 = _mm_min_epu32(ui_indices4, min_ui4);
      }

      _mm_store_si128((__m128i *)max_arr, max_ui4);
      _mm_store_si128((__m128i *)min_arr, min_ui4);

      for (i = 0; i < 4; i++) {
         if (max_arr[i] > max_ui)
            max_ui = max_arr[i];
         if (min_arr[i] < min_ui)
            min_ui = min_arr[i];
      }
      i = vec_count;
   }

   for (; i < aligned_count; i++) {
      if (ui_indices[i] > max_ui)
         max_ui = ui_indices[i];
      if (ui_indices[i] < min_ui)
         min_ui = ui_indices[i];
   }

   *min_index = min_ui;
   *max_index = max_ui;
}