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* [Bug middle-end/46554] New: Less inlining leads to CSiBE regression @ 2010-11-19 8:27 hubicka at gcc dot gnu.org 2010-11-19 10:55 ` [Bug middle-end/46554] " rguenth at gcc dot gnu.org ` (2 more replies) 0 siblings, 3 replies; 5+ messages in thread From: hubicka at gcc dot gnu.org @ 2010-11-19 8:27 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46554 Summary: Less inlining leads to CSiBE regression Product: gcc Version: 4.6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end AssignedTo: unassigned@gcc.gnu.org ReportedBy: hubicka@gcc.gnu.org Created attachment 22451 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22451 testcase flex-2.5.31/regex.c The loss here is not inlining regmatch_len. The catch is that the test if (m == ((void *)0) || m->rm_so < 0) is tested before all uses of regmatch_len and thus optimized out. So it simplifies into m->rm_so < 0 test and arithmetic that ends up being cheaper than call. int regmatch_len (regmatch_t * m) { if (m == ((void *)0) || m->rm_so < 0) { return 0; } return m->rm_eo - m->rm_so; } It is used as: if (m == ((void *)0) || m->rm_so < 0) return 0; if (regmatch_len (m) < 20) s = regmatch_cpy (m, buf, src); else s = regmatch_dup (m, src); Tricky. Inliner sees it as: Analyzing function body size: regmatch_len freq: 1000 size: 2 time: 2 if (m_2(D) == 0B) freq: 898 size: 1 time: 1 D.7268_3 = m_2(D)->rm_so; 50% will be eliminated by inlining freq: 898 size: 2 time: 2 if (D.7268_3 < 0) freq: 726 size: 1 time: 1 D.7270_4 = m_2(D)->rm_eo; 50% will be eliminated by inlining freq: 726 size: 1 time: 1 D.7268_5 = m_2(D)->rm_so; 50% will be eliminated by inlining freq: 726 size: 1 time: 1 D.7269_6 = D.7270_4 - D.7268_5; freq: 1000 size: 1 time: 2 return D.7269_1; will eliminated by inlining Overall function body time: 9-3 size: 11-5 With function call overhead time: 9-15 size: 11-8 I can imagine we can try to get summary based on value ranges, instead of known constants, do early VRP and work out first test well. Even optimizing the first conditoinal away won't make it inlined, it will be still considered to have size 9, so code will be expected to grow by 1 byte. Optimizing second conditoinal is even trickier. The code can be optimized away by IP-value range propagation that would be interesting optimization to have... ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/46554] Less inlining leads to CSiBE regression 2010-11-19 8:27 [Bug middle-end/46554] New: Less inlining leads to CSiBE regression hubicka at gcc dot gnu.org @ 2010-11-19 10:55 ` rguenth at gcc dot gnu.org 2010-11-19 10:58 ` Jan Hubicka 2010-11-19 11:14 ` hubicka at ucw dot cz 2021-11-29 2:16 ` [Bug ipa/46554] " pinskia at gcc dot gnu.org 2 siblings, 1 reply; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2010-11-19 10:55 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46554 Richard Guenther <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2010.11.19 10:52:53 Ever Confirmed|0 |1 --- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-19 10:52:53 UTC --- I thought partial inlining would maybe fix this? Otherwise it's really a case that needs IP analysis. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Bug middle-end/46554] Less inlining leads to CSiBE regression 2010-11-19 10:55 ` [Bug middle-end/46554] " rguenth at gcc dot gnu.org @ 2010-11-19 10:58 ` Jan Hubicka 0 siblings, 0 replies; 5+ messages in thread From: Jan Hubicka @ 2010-11-19 10:58 UTC (permalink / raw) To: rguenth at gcc dot gnu.org; +Cc: gcc-bugs > I thought partial inlining would maybe fix this? Otherwise it's really a > case that needs IP analysis. Not with -Os, we really know that it will optimize away. Honza ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/46554] Less inlining leads to CSiBE regression 2010-11-19 8:27 [Bug middle-end/46554] New: Less inlining leads to CSiBE regression hubicka at gcc dot gnu.org 2010-11-19 10:55 ` [Bug middle-end/46554] " rguenth at gcc dot gnu.org @ 2010-11-19 11:14 ` hubicka at ucw dot cz 2021-11-29 2:16 ` [Bug ipa/46554] " pinskia at gcc dot gnu.org 2 siblings, 0 replies; 5+ messages in thread From: hubicka at ucw dot cz @ 2010-11-19 11:14 UTC (permalink / raw) To: gcc-bugs http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46554 --- Comment #2 from Jan Hubicka <hubicka at ucw dot cz> 2010-11-19 10:57:57 UTC --- > I thought partial inlining would maybe fix this? Otherwise it's really a > case that needs IP analysis. Not with -Os, we really know that it will optimize away. Honza ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug ipa/46554] Less inlining leads to CSiBE regression 2010-11-19 8:27 [Bug middle-end/46554] New: Less inlining leads to CSiBE regression hubicka at gcc dot gnu.org 2010-11-19 10:55 ` [Bug middle-end/46554] " rguenth at gcc dot gnu.org 2010-11-19 11:14 ` hubicka at ucw dot cz @ 2021-11-29 2:16 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-11-29 2:16 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46554 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Component|middle-end |ipa Keywords| |missed-optimization CC| |marxin at gcc dot gnu.org --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Many things has changed since GCC 4.6 with respect to the inliner, has this been fixed? ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-11-29 2:16 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2010-11-19 8:27 [Bug middle-end/46554] New: Less inlining leads to CSiBE regression hubicka at gcc dot gnu.org 2010-11-19 10:55 ` [Bug middle-end/46554] " rguenth at gcc dot gnu.org 2010-11-19 10:58 ` Jan Hubicka 2010-11-19 11:14 ` hubicka at ucw dot cz 2021-11-29 2:16 ` [Bug ipa/46554] " pinskia at gcc dot gnu.org
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