https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104535
Bug ID: 104535
Summary: don't use fmod?
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: fx at gnu dot org
Target Milestone: ---
I was reminded by comments on the report I made about poor fmod performance on
x86 that I should have commented on the original observation.
I'd looked at one of the Polyhedron benchmarks which suffers badly from a
simple random number routine that calls DMOD. That gets compiled to fmod,
which is only inlined, albeit poorly on x86, with the relevant component(s) of
-ffast-math. It seems to me that MOD should compile to the arithmetical
expression in the standard, which doesn't have the complication of having to
treat errors. (When I defined DMOD as a statement function for it in that
routine, I got performance much closer to ifort. I should have kept the
profiles I compared, but could regenerate them.
Is there a good reason not to do that (and maybe similarly with other
intrinsics I haven't checked)? I could probably have a go at implementing it
if appropriate, though I don't know my way around now.
