gcc/testsuite/gcc.dg/graphite/pr42211.c

/* { dg-options "-O3 -floop-nest-optimize" } */

typedef unsigned char uint8_t;

void border_mirror(uint8_t *outer_img, int w, int h, int rb, int border)
{
  uint8_t *img = outer_img + border * rb + border;
  int x, y;

  for (y = -border; y < 0; y++) {
    for (x = -border; x < 0; x++)
      img[y*rb + x] = img[(-y)*rb + (-x)];

    for (x = 0; x < w; x++)
      img[y*rb + x] = img[(-y)*rb + x];
  }
}

void border_mirror_480(uint8_t *outer_img)
{
  border_mirror(outer_img, 640, 480, 640 + 16*2, 16);
}