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From: "lis8215 at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/111835] New: Suboptimal codegen: zero extended load instead of sign extended one Date: Mon, 16 Oct 2023 14:46:49 +0000 [thread overview] Message-ID: <bug-111835-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111835 Bug ID: 111835 Summary: Suboptimal codegen: zero extended load instead of sign extended one Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end Assignee: unassigned at gcc dot gnu.org Reporter: lis8215 at gmail dot com Target Milestone: --- In this simplified example: int test (const uint8_t * src, uint8_t * dst) { int8_t tmp = (int8_t)*src; *dst = tmp; return tmp; } GCC prefers to use load with zero extension instead of more rational sign extended load. Then it needs to do explicit sign extension for making return value. I know there's a lot of bugs related to zero/sign ext, but I guessed it's rare special case, and it reproduces in any GCC version available at godbolt and any architecture except x86-64.
next reply other threads:[~2023-10-16 14:46 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-10-16 14:46 lis8215 at gmail dot com [this message] 2023-10-16 17:35 ` [Bug rtl-optimization/111835] " pinskia at gcc dot gnu.org 2023-10-31 22:07 ` pinskia at gcc dot gnu.org 2023-11-01 6:36 ` lis8215 at gmail dot com 2023-11-01 15:40 ` pinskia at gcc dot gnu.org
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