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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/64309] if (1 & (1 << n)) not simplified to if (n == 0) Date: Mon, 15 Dec 2014 20:46:00 -0000 [thread overview] Message-ID: <bug-64309-4-sMVH5RA8dX@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-64309-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64309 --- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (1 << n) & 5 != 0 -> n == 0 || n == 2 (not beneficial) Not only that, we actually emit similar comparisons as a bit test intentionally even if you write it in a switch or series of ifs that way, so undoing that optimization would be a bad idea.
next prev parent reply other threads:[~2014-12-15 20:46 UTC|newest] Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-12-15 2:49 [Bug rtl-optimization/64309] New: " olegendo at gcc dot gnu.org 2014-12-15 11:45 ` [Bug middle-end/64309] " mpolacek at gcc dot gnu.org 2014-12-15 13:23 ` mpolacek at gcc dot gnu.org 2014-12-15 19:08 ` olegendo at gcc dot gnu.org 2014-12-15 19:22 ` mpolacek at gcc dot gnu.org 2014-12-15 20:19 ` glisse at gcc dot gnu.org 2014-12-15 20:41 ` olegendo at gcc dot gnu.org 2014-12-15 20:46 ` mpolacek at gcc dot gnu.org 2014-12-15 20:46 ` jakub at gcc dot gnu.org [this message] 2014-12-15 20:49 ` mpolacek at gcc dot gnu.org 2014-12-15 21:06 ` glisse at gcc dot gnu.org 2014-12-15 21:11 ` glisse at gcc dot gnu.org 2014-12-16 8:54 ` rguenther at suse dot de 2014-12-16 18:29 ` mpolacek at gcc dot gnu.org 2014-12-16 18:30 ` mpolacek at gcc dot gnu.org
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