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From: "richard.yao at alumni dot stonybrook.edu" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/110007] New: Implement support for Clang’s __builtin_unpredictable() Date: Sat, 27 May 2023 17:54:06 +0000 [thread overview] Message-ID: <bug-110007-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110007 Bug ID: 110007 Summary: Implement support for Clang’s __builtin_unpredictable() Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: richard.yao at alumni dot stonybrook.edu Target Milestone: --- Having the ability to specify __builtin_unpredictable() as a hint to encourage the compiler to use cmov would be useful for implementing algorithms like binary search that have unpredictable branches. __builtin_expect_with_probability() looks like a possible substitute, but Clang does not support it and it does not always work as described in #110001. Combining this with C’s ternary operator should make the proposed cmov builtin from #98801 unnecessary. Note that while clang implements __builtin_unpredictable(), it does not currently pass that information to the backend: https://github.com/llvm/llvm-project/issues/62790#issuecomment-1552671099
next reply other threads:[~2023-05-27 17:54 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-27 17:54 richard.yao at alumni dot stonybrook.edu [this message] 2023-05-27 17:59 ` [Bug c/110007] " pinskia at gcc dot gnu.org 2023-05-27 18:01 ` pinskia at gcc dot gnu.org 2023-05-27 18:19 ` richard.yao at alumni dot stonybrook.edu 2023-05-27 18:25 ` pinskia at gcc dot gnu.org 2023-05-27 20:26 ` richard.yao at alumni dot stonybrook.edu 2023-05-28 5:42 ` amonakov at gcc dot gnu.org 2023-05-28 16:21 ` hubicka at gcc dot gnu.org 2023-05-28 21:37 ` richard.yao at alumni dot stonybrook.edu 2023-05-30 7:49 ` rguenth at gcc dot gnu.org
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