Date: Mon, 10 Feb 2025 11:15:18 GMT From: Doug Moore <dougm@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 7bcc7a0b88cc - stable/14 - libkern: avoid local var in order_base_2() Message-ID: <202502101115.51ABFISj016298@gitrepo.freebsd.org>
next in thread | raw e-mail | index | archive | help
The branch stable/14 has been updated by dougm: URL: https://cgit.FreeBSD.org/src/commit/?id=7bcc7a0b88ccb5e1fe31de88ab9a17e46859318b commit 7bcc7a0b88ccb5e1fe31de88ab9a17e46859318b Author: Doug Moore <dougm@FreeBSD.org> AuthorDate: 2024-09-27 23:43:07 +0000 Commit: Doug Moore <dougm@FreeBSD.org> CommitDate: 2025-02-10 10:30:05 +0000 libkern: avoid local var in order_base_2() order_base_2(n) is implemented with a variable, which keeps it from being used at file scope. Implement it instead as ilog2(2*n-1), which produces a different result when 2*n overflows, which appears unlikely in practice. Reviewed by: bz Differential Revision: https://reviews.freebsd.org/D46826 (cherry picked from commit b7cbf741d55468ba34305a14ac3acc1c286af034) --- sys/sys/libkern.h | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/sys/sys/libkern.h b/sys/sys/libkern.h index a10289d72dc7..835e5ffaf0b7 100644 --- a/sys/sys/libkern.h +++ b/sys/sys/libkern.h @@ -229,10 +229,7 @@ ilog2_long_long(long long n) #define ilog2(n) (__builtin_constant_p(n) ? ilog2_const(n) : ilog2_var(n)) #define rounddown_pow_of_two(n) ((__typeof(n))1 << ilog2(n)) -#define order_base_2(n) ({ \ - __typeof(n) _n = (n); \ - _n == 1 ? 0 : 1 + ilog2(_n - 1); \ -}) +#define order_base_2(n) ilog2(2*(n)-1) #define roundup_pow_of_two(n) ((__typeof(n))1 << order_base_2(n)) #define bitcount64(x) __bitcount64((uint64_t)(x))
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202502101115.51ABFISj016298>