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* [Bug ipa/114703] New: Missed devirtualization in rather simple case @ 2024-04-12 13:57 konstantin.vladimirov at gmail dot com 2024-04-12 22:01 ` [Bug ipa/114703] " pinskia at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: konstantin.vladimirov at gmail dot com @ 2024-04-12 13:57 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114703 Bug ID: 114703 Summary: Missed devirtualization in rather simple case Product: gcc Version: 13.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: ipa Assignee: unassigned at gcc dot gnu.org Reporter: konstantin.vladimirov at gmail dot com Target Milestone: --- See code here: https://godbolt.org/z/T9Ma7qe3E struct A { virtual int foo() { return 1; } }; struct B : A { int foo() override { return 2; } virtual int foo(int i) { return i + 1; } }; int use(int, int, int); int main() { B *p = new B; #if 0 A* q = p; #else A* q = new B; #endif int result1 = p->foo(1); int result2 = p->foo(); int result3 = q->foo(); use(result1, result2, result3); } clang devirtualizes just fine, gcc lacks this one. Interesting that if you flip preprocessor switch, everything works with gcc either. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug ipa/114703] Missed devirtualization in rather simple case 2024-04-12 13:57 [Bug ipa/114703] New: Missed devirtualization in rather simple case konstantin.vladimirov at gmail dot com @ 2024-04-12 22:01 ` pinskia at gcc dot gnu.org 2024-04-12 22:11 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-04-12 22:01 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114703 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Last reconfirmed| |2024-04-12 Status|UNCONFIRMED |NEW --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- The problem I think is we don't realize that `operator new` can't touch the other memory that was just allocated partly because the escape analysis is not flow sensitive . ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug ipa/114703] Missed devirtualization in rather simple case 2024-04-12 13:57 [Bug ipa/114703] New: Missed devirtualization in rather simple case konstantin.vladimirov at gmail dot com 2024-04-12 22:01 ` [Bug ipa/114703] " pinskia at gcc dot gnu.org @ 2024-04-12 22:11 ` pinskia at gcc dot gnu.org 2024-04-15 7:53 ` rguenth at gcc dot gnu.org 2024-04-15 10:20 ` hubicka at ucw dot cz 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-04-12 22:11 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114703 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Severity|normal |enhancement ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug ipa/114703] Missed devirtualization in rather simple case 2024-04-12 13:57 [Bug ipa/114703] New: Missed devirtualization in rather simple case konstantin.vladimirov at gmail dot com 2024-04-12 22:01 ` [Bug ipa/114703] " pinskia at gcc dot gnu.org 2024-04-12 22:11 ` pinskia at gcc dot gnu.org @ 2024-04-15 7:53 ` rguenth at gcc dot gnu.org 2024-04-15 10:20 ` hubicka at ucw dot cz 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2024-04-15 7:53 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114703 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |hubicka at gcc dot gnu.org --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- Yep, 'new' memory escapes. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug ipa/114703] Missed devirtualization in rather simple case 2024-04-12 13:57 [Bug ipa/114703] New: Missed devirtualization in rather simple case konstantin.vladimirov at gmail dot com ` (2 preceding siblings ...) 2024-04-15 7:53 ` rguenth at gcc dot gnu.org @ 2024-04-15 10:20 ` hubicka at ucw dot cz 3 siblings, 0 replies; 5+ messages in thread From: hubicka at ucw dot cz @ 2024-04-15 10:20 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114703 --- Comment #3 from Jan Hubicka <hubicka at ucw dot cz> --- > Yep, 'new' memory escapes. Yep, this is blocking a lot of propagation in common C++ code. Here it may help to do speculative devirtualization during IPA stage that will let the late optimization to get rid of the speculation (since after inlning we will know that the virtual call does not overwrite virtual table pointer). This is technically not too hard to add. We can optimistically rule out (some) may aliases while walking the alias oracle. I will take a look next stage1. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-04-15 10:20 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-04-12 13:57 [Bug ipa/114703] New: Missed devirtualization in rather simple case konstantin.vladimirov at gmail dot com 2024-04-12 22:01 ` [Bug ipa/114703] " pinskia at gcc dot gnu.org 2024-04-12 22:11 ` pinskia at gcc dot gnu.org 2024-04-15 7:53 ` rguenth at gcc dot gnu.org 2024-04-15 10:20 ` hubicka at ucw dot cz
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