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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/104265] New: Missed vectorization in
 526.blender_r
Date: Fri, 28 Jan 2022 07:05:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104265

            Bug ID: 104265
           Summary: Missed vectorization in 526.blender_r
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

Blenders hottest spot is rayobject_bb_intersect_test which can be summarize=
d as

struct Isect {
    float start[3];
    float dir[3];
    float dist;
    float origstart[3];
    float origdir[3];
    int bv_index[6];
    float idot_axis[3];
    /* More stuff.  */
    void *userdata; /* aligns it to 8 */
};

int rayobject_bb_intersect_test (struct Isect *isec, const float *bb)
{
  float t1x =3D (bb[isec->bv_index[0]] - isec->start[0]) * isec->idot_axis[=
0];
  float t2x =3D (bb[isec->bv_index[1]] - isec->start[0]) * isec->idot_axis[=
0];
  float t1y =3D (bb[isec->bv_index[2]] - isec->start[1]) * isec->idot_axis[=
1];
  float t2y =3D (bb[isec->bv_index[3]] - isec->start[1]) * isec->idot_axis[=
1];
  float t1z =3D (bb[isec->bv_index[4]] - isec->start[2]) * isec->idot_axis[=
2];
  float t2z =3D (bb[isec->bv_index[5]] - isec->start[2]) * isec->idot_axis[=
2];

  if (t1x > t2y  || t2x < t1y  || t1x > t2z || t2x < t1z || t1y > t2z || t2=
y <
t1z) return 0;
  if (t2x < 0.0f || t2y < 0.0f || t2z < 0.0f) return 0;
  if (t1x > isec->dist || t1y > isec->dist || t1z > isec->dist) return 0;
  return 1;
}

at least on x86 with SSE4 (for some extra permutes) we can vectorize the
comparisons, carefully filling extra lanes of V4SF vectors with redundant
data from another lane starting with {t1x,t1y,t1z,} {t2x,t2y,t2z,}
vectors.  AOCC does this kind of vectorization and receives a nice 25%
uplift in performance from it.=