https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86424
Bug ID: 86424
Summary: Milc is slower on PowerPC using -ffast-math than
without using -ffast-math
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: meissner at gcc dot gnu.org
Target Milestone: ---
I did some Spec 2006 runs, and one of the runs I was comparing normal speed
with -ffast-math. As expected a lot of SpecFP benchmarks were faster using the
-ffast-math option. However, 3 of the benchmarks were slower, including milc.
The two hotest functions seem to be slower using -ffast-math:
slowmath fastmath | slowmath fastmath | Function
======== ======== | ======== ======== | ========
17.5310% 17.4259% | 5,489,872 5,580,840 | mult_su3_na
13.4533% 15.6660% | 4,212,953 5,017,232 | mult_adj_su3_mat_vec
Function mult_su3_na, 17.43 - 17.53% of total in 2 files
--------------------------------------------------------
Percent Percent | Samples Samples | Line # Filename
slowmath fastmath | slowmath fastmath | Line # Filename
-------- -------- | --------- --------- | ------ ----------
9.8993% 75.9216% | 543,453 4,237,070 | 38 m_mat_na.c
65.7913% 2.8468% | 3,611,855 158,877 | 33 m_mat_na.c
6.9169% | 386,020 | 40 m_mat_na.c
1.1277% 6.8534% | 61,915 382,477 | 48 m_mat_na.c
5.6730% | 311,441 | 49 m_mat_na.c
3.8513% 2.1642% | 211,433 120,784 | 46 m_mat_na.c
3.5253% | 193,542 | 45 m_mat_na.c
2.8633% | 157,188 | 41 m_mat_na.c
2.1619% | 118,689 | 39 m_mat_na.c
1.4727% | 80,847 | 43 m_mat_na.c
1.1929% | 65,486 | 36 m_mat_na.c
1.1072% | 61,790 | 44 m_mat_na.c
Function mult_adj_su3_mat_vec, 13.45 - 15.67% of total in 2 files
-----------------------------------------------------------------
Percent Percent | Samples Samples | Line # Filename
slowmath fastmath | slowmath fastmath | Line # Filename
-------- -------- | --------- --------- | ------ -----------
71.3008% 77.9373% | 3,003,867 3,910,288 | 116 m_amatvec.c
12.1258% 13.8781% | 510,853 696,296 | 126 m_amatvec.c
11.0201% | 464,272 | 121 m_amatvec.c
3.4868% | 174,944 | 123 m_amatvec.c
2.1345% 1.4971% | 89,925 75,109 | 129 m_amatvec.c
1.3833% | 58,278 | 132 m_amatvec.c
