[Bf-blender-cvs] [81c9e0d] master: Cycles: Avoid branching in SSE version of intersection pre-calculation
Sergey Sharybin
noreply at git.blender.org
Tue Oct 25 15:34:28 CEST 2016
Commit: 81c9e0d2958a1274f8cb76386a3bafc08a181eed
Author: Sergey Sharybin
Date: Tue Oct 25 14:18:32 2016 +0200
Branches: master
https://developer.blender.org/rB81c9e0d2958a1274f8cb76386a3bafc08a181eed
Cycles: Avoid branching in SSE version of intersection pre-calculation
Similar to the previous commit, avoid negative effect of bad branch prediction.
Gives measurable performance up to ~2% in tests here.
Once again, thanks to Maxym Dmytrychenko!
===================================================================
M intern/cycles/kernel/geom/geom_triangle_intersect.h
===================================================================
diff --git a/intern/cycles/kernel/geom/geom_triangle_intersect.h b/intern/cycles/kernel/geom/geom_triangle_intersect.h
index 8d17e12..5d76fc3 100644
--- a/intern/cycles/kernel/geom/geom_triangle_intersect.h
+++ b/intern/cycles/kernel/geom/geom_triangle_intersect.h
@@ -59,21 +59,33 @@ void triangle_intersect_precalc(float3 dir,
IsectPrecalc *isect_precalc)
{
/* Calculate dimension where the ray direction is maximal. */
+#ifndef __KERNEL_SSE__
int kz = util_max_axis(make_float3(fabsf(dir.x),
fabsf(dir.y),
fabsf(dir.z)));
int kx = kz + 1; if(kx == 3) kx = 0;
int ky = kx + 1; if(ky == 3) ky = 0;
+#else
+ int kx, ky, kz;
+ /* Avoiding mispredicted branch on direction. */
+ kz = util_max_axis(fabs(dir));
+ static const char inc_xaxis[] = {1, 2, 0, 55};
+ static const char inc_yaxis[] = {2, 0, 1, 55};
+ kx = inc_xaxis[kz];
+ ky = inc_yaxis[kz];
+#endif
+
+ float dir_kz = IDX(dir, kz);
/* Swap kx and ky dimensions to preserve winding direction of triangles. */
- if(IDX(dir, kz) < 0.0f) {
+ if(dir_kz < 0.0f) {
int tmp = kx;
kx = ky;
ky = tmp;
}
/* Calculate the shear constants. */
- float inv_dir_z = 1.0f / IDX(dir, kz);
+ float inv_dir_z = 1.0f / dir_kz;
isect_precalc->Sx = IDX(dir, kx) * inv_dir_z;
isect_precalc->Sy = IDX(dir, ky) * inv_dir_z;
isect_precalc->Sz = inv_dir_z;
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