Date: Tue, 28 May 2024 05:28:15 +0000 From: bugzilla-noreply@freebsd.org To: toolchain@FreeBSD.org Subject: [Bug 278908] Upcoming 14.1-RELEASE LLVM -> Worse runtime performance on Zen CPU when optimizing for Zen Message-ID: <bug-278908-29464-G8a3aZqWNy@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-278908-29464@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=278908 --- Comment #5 from commit-hook@FreeBSD.org --- A commit in branch stable/14 references this bug: URL: https://cgit.FreeBSD.org/src/commit/?id=ec38746722a15b4376bed274e96ff7b8c31804e1 commit ec38746722a15b4376bed274e96ff7b8c31804e1 Author: Dimitry Andric <dim@FreeBSD.org> AuthorDate: 2024-05-25 17:52:15 +0000 Commit: Dimitry Andric <dim@FreeBSD.org> CommitDate: 2024-05-28 05:25:49 +0000 Merge commit d0be944aa511 from llvm-project (by Simon Pilgrim): [X86] Add slow div64 tuning flag to Nehalem target (#91129) This appears to have been missed because later cpus don't inherit from Nehalem tuning much. Noticed while cleaning up for #90985 Merge commit 8b400de79eff from llvm-project (by Simon Pilgrim): [X86] Enable TuningSlowDivide64 on Barcelona/Bobcat/Bulldozer/Ryzen Families (#91277) Despite most AMD cpus having a lower latency for i64 divisions that converge early, we are still better off testing for values representable as i32 and performing a i32 division if possible. All AMD cpus appear to have been missed when we added the "idivq-to-divl" attribute - this patch now matches Intel cpu behaviour (and the x86-64/v2/3/4 levels). Unfortunately the difference in code scheduling means I've had to stop using the update_llc_test_checks script and just use old-fashioned CHECK-DAG checks for divl/divq pairs. Fixes #90985 This fixes possibly worse runtime performance on AMD Zen hardware, when using -march=znver4 (or any other znver), as opposed to -march=x86-64-v4 or the baseline -march=x86-64. A similar fix is applied for Nehalem. PR: 278908 MFC after: 3 days (cherry picked from commit cadd2ca21765ebcb95b77ec94977b4e74e1edc1b) contrib/llvm-project/llvm/lib/Target/X86/X86.td | 6 ++++++ 1 file changed, 6 insertions(+) -- You are receiving this mail because: You are the assignee for the bug.help
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