https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94364
Bug ID: 94364
Summary: 505.mcf_r is 8% faster when compiled with
-mprefer-vector-width=128
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jamborm at gcc dot gnu.org
Blocks: 26163
Target Milestone: ---
Host: x86_64-linux
Target: x86_64-linux
SPEC 2017 INTrate benchmark 505.mcf_r, when compiled with options
-Ofast -march=native -mtune=native, is 8% slower than when we also use
option -mprefer-vector-width=128. I have observed it on both AMD Zen2
and Intel Cascade Lake Server CPUs (using master revision 26b3e568a60).
Better vector width selection would therefore bring about noticeable
speed-up.
Symbol profiles (collected on AMD Rome):
-Ofast -march=native -mtune=native:
Overhead Samples Shared Object Symbol
........ ............ ............... ................................
28.64% 462302 mcf_r_peak.mine spec_qsort
21.58% 348703 mcf_r_peak.mine cost_compare
15.81% 255029 mcf_r_peak.mine primal_bea_mpp
15.58% 251176 mcf_r_peak.mine replace_weaker_arc
7.37% 118646 mcf_r_peak.mine arc_compare
6.53% 105337 mcf_r_peak.mine price_out_impl
1.38% 22276 mcf_r_peak.mine update_tree
-Ofast -march=native -mtune=native -mprefer-vector-width=128:
Overhead Samples Shared Object Symbol
........ ............ ............... ................................
23.57% 354536 mcf_r_peak.mine spec_qsort
23.51% 353767 mcf_r_peak.mine cost_compare
16.98% 255104 mcf_r_peak.mine primal_bea_mpp
16.65% 249891 mcf_r_peak.mine replace_weaker_arc
7.29% 109267 mcf_r_peak.mine arc_compare
7.09% 106380 mcf_r_peak.mine price_out_impl
1.53% 22968 mcf_r_peak.mine update_tree
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2k17, 2k and 2k6 and 95)
