public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
* [Bug tree-optimization/116826] New: Optimise log (1.0 / x) into -log (x)
@ 2024-09-24 8:14 ktkachov at gcc dot gnu.org
2024-09-24 9:56 ` [Bug tree-optimization/116826] " jschmitz at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: ktkachov at gcc dot gnu.org @ 2024-09-24 8:14 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116826
Bug ID: 116826
Summary: Optimise log (1.0 / x) into -log (x)
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ktkachov at gcc dot gnu.org
Target Milestone: ---
float
foo (float a)
{
return __builtin_logf (1.0f / a);
}
We can avoid the division by folding it into -__builtin_logf (a);
under the usual -funsafe-math-optimizations group for all the various standard
logs.
More generally, log (CST / a) could be folded into log (CST) - log (a).
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug tree-optimization/116826] Optimise log (1.0 / x) into -log (x) 2024-09-24 8:14 [Bug tree-optimization/116826] New: Optimise log (1.0 / x) into -log (x) ktkachov at gcc dot gnu.org @ 2024-09-24 9:56 ` jschmitz at gcc dot gnu.org 2024-09-24 18:13 ` pinskia at gcc dot gnu.org 2024-09-25 6:45 ` ktkachov at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: jschmitz at gcc dot gnu.org @ 2024-09-24 9:56 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116826 Jennifer Schmitz <jschmitz at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2024-09-24 Status|UNCONFIRMED |ASSIGNED Ever confirmed|0 |1 CC| |jschmitz at gcc dot gnu.org Assignee|unassigned at gcc dot gnu.org |jschmitz at gcc dot gnu.org --- Comment #1 from Jennifer Schmitz <jschmitz at gcc dot gnu.org> --- . ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/116826] Optimise log (1.0 / x) into -log (x) 2024-09-24 8:14 [Bug tree-optimization/116826] New: Optimise log (1.0 / x) into -log (x) ktkachov at gcc dot gnu.org 2024-09-24 9:56 ` [Bug tree-optimization/116826] " jschmitz at gcc dot gnu.org @ 2024-09-24 18:13 ` pinskia at gcc dot gnu.org 2024-09-25 6:45 ` ktkachov at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-09-24 18:13 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116826 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Note PR 86710 lists the opposite (except without being a CST for the division). Just like PR 86710, this applies for log, log10 and log2 too (and the type variants too). ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/116826] Optimise log (1.0 / x) into -log (x) 2024-09-24 8:14 [Bug tree-optimization/116826] New: Optimise log (1.0 / x) into -log (x) ktkachov at gcc dot gnu.org 2024-09-24 9:56 ` [Bug tree-optimization/116826] " jschmitz at gcc dot gnu.org 2024-09-24 18:13 ` pinskia at gcc dot gnu.org @ 2024-09-25 6:45 ` ktkachov at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: ktkachov at gcc dot gnu.org @ 2024-09-25 6:45 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116826 --- Comment #3 from ktkachov at gcc dot gnu.org --- (In reply to Andrew Pinski from comment #2) > Note PR 86710 lists the opposite (except without being a CST for the > division). > > Just like PR 86710, this applies for log, log10 and log2 too (and the type > variants too). Thanks for the reference. Yeah, splitting up one log call to two log calls is not a good idea for variable arguments, but when we can calculate the log (CST) at compile-time it should be a win. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-09-25 6:45 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-09-24 8:14 [Bug tree-optimization/116826] New: Optimise log (1.0 / x) into -log (x) ktkachov at gcc dot gnu.org 2024-09-24 9:56 ` [Bug tree-optimization/116826] " jschmitz at gcc dot gnu.org 2024-09-24 18:13 ` pinskia at gcc dot gnu.org 2024-09-25 6:45 ` ktkachov at gcc dot gnu.org
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).