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From: "gabravier at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/104357] New: [Aarch64] Failure to use csinv instead of mvn+csel where possible Date: Wed, 02 Feb 2022 23:40:40 +0000 [thread overview] Message-ID: <bug-104357-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104357 Bug ID: 104357 Summary: [Aarch64] Failure to use csinv instead of mvn+csel where possible Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: gabravier at gmail dot com Target Milestone: --- unsigned char stbi__clamp(int x) { if ((unsigned)x > 255) { if (x < 0) return 0; if (x > 255) return 255; } return x; } With -O3, GCC outputs this (on aarch64): stbi__clamp(int): mvn w1, w0 cmp w0, 256 and w0, w0, 255 asr w1, w1, 31 and w1, w1, 255 csel w0, w0, w1, cc ret LLVM instead outputs this: stbi__clamp(int): asr w8, w0, #31 cmp w0, #255 csinv w0, w0, w8, ls ret I don't know if the `and`s are there because of ABI differences, but it seems to me like the `mvn` can definitely be replaced by using `csinv` instead of `csel`.
next reply other threads:[~2022-02-02 23:40 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-02-02 23:40 gabravier at gmail dot com [this message] 2022-02-02 23:51 ` [Bug tree-optimization/104357] " pinskia at gcc dot gnu.org 2022-02-03 0:02 ` pinskia at gcc dot gnu.org 2022-02-03 0:05 ` [Bug tree-optimization/104357] " pinskia at gcc dot gnu.org 2023-05-04 5:37 ` pinskia at gcc dot gnu.org
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