https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98854
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, one can see it with BB vectorization enabled vs. disabled.
Bad:
Samples: 7K of event 'cycles:u', Event count (approx.): 7540324763
Overhead Samples Command Shared Object Symbol
53.11% 3711 a.out a.out [.] shade
25.39% 1774 a.out a.out [.] trace
18.16% 1271 a.out a.out [.] render_scanline
1.56% 109 a.out libm-2.26.so [.] __ieee754_pow_sse2
Good:
Samples: 6K of event 'cycles:u', Event count (approx.): 6673802579
Overhead Samples Command Shared Object Symbol
61.21% 3857 a.out a.out [.] shade
20.44% 1288 a.out a.out [.] trace
14.42% 912 a.out a.out [.] render_scanline
1.81% 114 a.out libm-2.26.so [.] __ieee754_pow_sse2
With added -fwhole-program we have
c-ray-mt.c:624:18: optimized: basic block part vectorized using 32 byte vectors
c-ray-mt.c:372:13: optimized: basic block part vectorized using 32 byte vectors
c-ray-mt.c:372:13: optimized: basic block part vectorized using 32 byte vectors
c-ray-mt.c:432:9: optimized: basic block part vectorized using 32 byte vectors
c-ray-mt.c:656:7: optimized: basic block part vectorized using 32 byte vectors
c-ray-mt.c:656:7: optimized: basic block part vectorized using 32 byte vectors
c-ray-mt.c:265:23: optimized: basic block part vectorized using 32 byte vectors
:372 is bad and then :656
For the first we vectorize a store
<bb 26> [local count: 31445960]:
# nearest_obj_239 = PHI <nearest_obj_11(17), nearest_obj_11(25),
iter_363(24), nearest_obj_11(19), nearest_obj_11(18), iter_363(23)>
...
_816 = {nearest_sp_pos_x_lsm.258_78, nearest_sp_pos_y_lsm.259_174,
nearest_sp_pos_z_lsm.260_201, nearest_sp_normal_x_lsm.261_200};
_820 = {nearest_sp_normal_y_lsm.262_122, nearest_sp_normal_z_lsm.263_293,
nearest_sp_vref_x_lsm.264_124, nearest_sp_vref_y_lsm.265_148};
iter_231 = iter_363->next;
if (iter_231 != 0B)
goto <bb 33>; [89.00%]
else
goto <bb 27>; [11.00%]
<bb 33> [local count: 27986904]:
goto <bb 17>; [100.00%]
<bb 27> [local count: 3459055]:
# nearest_sp_dist_lsm.257_228 = PHI <nearest_sp_dist_lsm.257_66(26)>
# nearest_sp_pos_x_lsm.258_226 = PHI <nearest_sp_pos_x_lsm.258_78(26)>
# nearest_sp_normal_y_lsm.262_343 = PHI <nearest_sp_normal_y_lsm.262_122(26)>
# nearest_sp_vref_x_lsm.264_238 = PHI <nearest_sp_vref_x_lsm.264_124(26)>
# nearest_sp_vref_y_lsm.265_237 = PHI <nearest_sp_vref_y_lsm.265_148(26)>
# nearest_sp_vref_z_lsm.266_236 = PHI <nearest_sp_vref_z_lsm.266_152(26)>
# nearest_sp_pos_y_lsm.259_342 = PHI <nearest_sp_pos_y_lsm.259_174(26)>
# nearest_sp_normal_x_lsm.261_351 = PHI <nearest_sp_normal_x_lsm.261_200(26)>
# nearest_sp_pos_z_lsm.260_304 = PHI <nearest_sp_pos_z_lsm.260_201(26)>
# nearest_obj_197 = PHI <nearest_obj_239(26)>
# nearest_sp_normal_z_lsm.263_821 = PHI <nearest_sp_normal_z_lsm.263_293(26)>
# vect_nearest_sp_pos_x_lsm.258_226.268_815 = PHI <_816(26)>
# vect_nearest_sp_pos_x_lsm.258_226.268_814 = PHI <_820(26)>
nearest_sp.vref.z = nearest_sp_vref_z_lsm.266_236;
MEM <vector(4) double> [(double *)&nearest_sp] =
vect_nearest_sp_pos_x_lsm.258_226.268_815;
_812 = &nearest_sp.pos.x + 32;
MEM <vector(4) double> [(double *)_812] =
vect_nearest_sp_pos_x_lsm.258_226.268_814;
but we insert the vector CTOR on a path that's more often executed than
the use. And since there's no sinking pass after vectorization nothing
fixes this up.
