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From: "malat at debian dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/110622] New: x86: Miscompilation at O1 level (O0 is working) Date: Tue, 11 Jul 2023 06:28:29 +0000 [thread overview] Message-ID: <bug-110622-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110622 Bug ID: 110622 Summary: x86: Miscompilation at O1 level (O0 is working) Product: gcc Version: 13.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: malat at debian dot org Target Milestone: --- I can trigger an assertion in highway unit test suite on Debian/i386 when using -O1 (does not happen at -O0). Symptoms: [...] f32x2: Log1p(5.5968112995194757e-20) expected 5.5968112995194757e-20 actual 0 ulp 5.28754e+08 max ulp 3 [...] For some reason the code return exactly zero (0) during a math computation of a log1p function. The code runs fine at O2 on all other Debian arches (amd64, mipsel, armel, ppc32 ...). Since the return value is exactly 0, I suspect this is not a case of excess precision (x87). This is not a hardware issue as I can reproduce it on multiple hosts (Debian buildds machine, and x86 porterbox). If I extract the math logic and call it in a `main` function, then the compiler is able to optimize the code correctly (even at O2) and return appropriate result (correct tolerance). I did not observe any suspicious behavior under valgrind and/or -fsanitize.
next reply other threads:[~2023-07-11 6:28 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-07-11 6:28 malat at debian dot org [this message] 2023-07-11 6:29 ` [Bug c++/110622] " malat at debian dot org 2023-07-11 6:30 ` malat at debian dot org 2023-07-11 6:31 ` pinskia at gcc dot gnu.org 2023-07-11 6:33 ` malat at debian dot org 2023-07-11 6:33 ` malat at debian dot org 2023-07-11 6:38 ` pinskia at gcc dot gnu.org 2023-07-11 6:44 ` [Bug target/110622] " malat at debian dot org 2023-07-11 8:25 ` malat at debian dot org 2023-09-21 9:44 ` malat at debian dot org 2023-09-21 9:48 ` [Bug target/110622] x87: Miscompilation at O2 level (O1 " malat at debian dot org 2023-09-21 9:51 ` malat at debian dot org 2023-09-21 9:56 ` malat at debian dot org 2023-09-21 13:33 ` pinskia at gcc dot gnu.org 2023-09-21 13:42 ` malat at debian dot org 2023-09-21 13:45 ` xry111 at gcc dot gnu.org 2023-09-21 14:29 ` malat at debian dot org
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