public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
* [Bug tree-optimization/110982] New: (unsigned)(signed_char) != (unsigned)-1 is never changed back into signed_char != -1 @ 2023-08-11 3:25 pinskia at gcc dot gnu.org 2023-08-11 8:53 ` [Bug tree-optimization/110982] " pinskia at gcc dot gnu.org 2023-09-25 8:52 ` pinskia at gcc dot gnu.org 0 siblings, 2 replies; 3+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-08-11 3:25 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110982 Bug ID: 110982 Summary: (unsigned)(signed_char) != (unsigned)-1 is never changed back into signed_char != -1 Product: gcc Version: 14.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: pinskia at gcc dot gnu.org Target Milestone: --- While looking into a failure after improving VRP, I see we never translate this: ``` bool f(signed char t) { unsigned int t1 = t; return t1 != (unsigned int)-1; } ``` into: ``` bool f0(signed char t) { return t != -1; } ``` ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/110982] (unsigned)(signed_char) != (unsigned)-1 is never changed back into signed_char != -1 2023-08-11 3:25 [Bug tree-optimization/110982] New: (unsigned)(signed_char) != (unsigned)-1 is never changed back into signed_char != -1 pinskia at gcc dot gnu.org @ 2023-08-11 8:53 ` pinskia at gcc dot gnu.org 2023-09-25 8:52 ` pinskia at gcc dot gnu.org 1 sibling, 0 replies; 3+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-08-11 8:53 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110982 --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- The basic issue is int_fits_type_p does not work the way folks think it works for casting from signed to unsigned and then casting back ... ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/110982] (unsigned)(signed_char) != (unsigned)-1 is never changed back into signed_char != -1 2023-08-11 3:25 [Bug tree-optimization/110982] New: (unsigned)(signed_char) != (unsigned)-1 is never changed back into signed_char != -1 pinskia at gcc dot gnu.org 2023-08-11 8:53 ` [Bug tree-optimization/110982] " pinskia at gcc dot gnu.org @ 2023-09-25 8:52 ` pinskia at gcc dot gnu.org 1 sibling, 0 replies; 3+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-09-25 8:52 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110982 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Ever confirmed|0 |1 Last reconfirmed| |2023-09-25 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Another case where int_fits_type_p use causes an missed optimization is: ``` unsigned f(int a) { unsigned t = a; if (a == -1) return t; return 0; } ``` This should be caught in phiopt2 but currently is not due to the int_fits_type_p usage. I noticed this in PR 110131 . ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-09-25 8:52 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-08-11 3:25 [Bug tree-optimization/110982] New: (unsigned)(signed_char) != (unsigned)-1 is never changed back into signed_char != -1 pinskia at gcc dot gnu.org 2023-08-11 8:53 ` [Bug tree-optimization/110982] " pinskia at gcc dot gnu.org 2023-09-25 8:52 ` pinskia 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).