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From: "sebastiano.vigna at unimi dot it" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/66348] Simple loop has only lower half of the 64-bit counter initialized correctly Date: Tue, 02 Jun 2015 07:21:00 -0000 [thread overview] Message-ID: <bug-66348-4-509j3Qi9Cj@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-66348-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66348 --- Comment #5 from Sebastiano Vigna <sebastiano.vigna at unimi dot it> --- Fantastic tool! I didn't know about it. But it doesn't fire. There is no undefined behaviour in that code--it's just that the optimizer at -O1 does something wrong. I tried a binary search over the single options induced by -O1, but it turns out it's a combination of things--when I split the options in two half, the problem did not show up with either half. The code is 30-40 lines of assembly--I guess someone proficient with the output of the compiler could easily spot what's going wrong.
next prev parent reply other threads:[~2015-06-02 7:21 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-05-30 22:22 [Bug c/66348] New: Simple loop with 64-bit index has only lower half " sebastiano.vigna at unimi dot it 2015-05-30 22:46 ` [Bug c/66348] Simple loop has only lower half of the 64-bit counter " pinskia at gcc dot gnu.org 2015-05-30 23:00 ` sebastiano.vigna at unimi dot it 2015-05-30 23:01 ` sebastiano.vigna at unimi dot it 2015-06-01 8:19 ` rguenth at gcc dot gnu.org 2015-06-02 7:21 ` sebastiano.vigna at unimi dot it [this message] 2015-06-02 7:23 ` sebastiano.vigna at unimi dot it 2015-06-05 14:33 ` sebastiano.vigna at unimi dot it 2015-06-05 15:28 ` ubizjak at gmail dot com 2015-06-05 20:46 ` [Bug c/66348] Simple loop never exit with -O1, exits with -O0 sebastiano.vigna at unimi dot it 2015-06-05 22:14 ` [Bug c/66348] Simple loop never exits " miyuki at gcc dot gnu.org 2015-06-06 23:33 ` sebastiano.vigna at unimi dot it 2015-06-06 23:38 ` sebastiano.vigna at unimi dot it 2021-11-29 8:56 ` [Bug middle-end/66348] " sebastiano.vigna at unimi dot it
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