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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/109038] New: Miss optimization to simplify bit_and + rotate to shift Date: Mon, 06 Mar 2023 09:55:49 +0000 [thread overview] Message-ID: <bug-109038-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109038 Bug ID: 109038 Summary: Miss optimization to simplify bit_and + rotate to shift Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end Assignee: unassigned at gcc dot gnu.org Reporter: crazylht at gmail dot com Target Milestone: --- Target: x86_64-*-* i?86-*-* unsigned foo (unsigned int a) { unsigned int b = a & 0x00FFFFFF; unsigned int c = ((b & 0x000000FF) << 8 | (b & 0x0000FF00) << 8 | (b & 0x00FF0000) << 8 | (b & 0xFF000000) >> 24); return c; } gcc generates foo: mov eax, edi and eax, 16777215 rol eax, 8 ret But it can be optimized as below foo: # @foo mov eax, edi shl eax, 8 ret
next reply other threads:[~2023-03-06 9:55 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-03-06 9:55 crazylht at gmail dot com [this message] 2023-03-06 17:46 ` [Bug middle-end/109038] " pinskia at gcc dot gnu.org 2023-05-19 23:29 ` [Bug tree-optimization/109038] " pinskia at gcc dot gnu.org
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