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Authored by bz on Thu, Dec 18, 10:51 PM.

Details

Reviewers

dumbbell
obiwac
imp
brooks
emaste

Group Reviewers

linuxkpi

Commits

rG27aa23cee810: sys/bitcount.h: add __const_bitcount<n>

Summary

Add a version of const_bitcount<n> which can be used to get the
numbers at compile-time when builtin_popcountg() is not available
(see sys/compat/linuxkpi/common/include/linux/bitops.h for LLVM before
19 and gcc before 14).

Obtained from: https://reviews.freebsd.org/D50995#1174884 by obiwac

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Passed

Unit

No Test Coverage

Build Status

Buildable 69389
Build 66272: arc lint + arc unit

Event Timeline

bz requested review of this revision.Thu, Dec 18, 10:51 PM

bz created this revision.

Harbormaster completed remote builds in B69389: Diff 168375.Thu, Dec 18, 10:51 PM

bz added a parent revision: D54297: LinuxKPI: bitcount fix gcc and older llvm builds.Thu, Dec 18, 10:52 PM

bz mentioned this in D54297: LinuxKPI: bitcount fix gcc and older llvm builds.

Adding @emaste as I found @dumbbell 's version through the stack of local changes you carry.

LGTM. Out of paranoia, I verified using compiler explorer that it's reliably const enough to use in a macro even at -O0 with an old clang.

This revision is now accepted and ready to land.Fri, Dec 19, 9:55 AM

brooks mentioned this in D54266: iwlwifi: Don't compile for clang before 19.Fri, Dec 19, 9:56 AM

emaste accepted this revision as: emaste.Fri, Dec 19, 8:03 PM

In D54301#1241028, @brooks wrote:

LGTM. Out of paranoia, I verified using compiler explorer that it's reliably const enough to use in a macro even at -O0 with an old clang.

Neat tool. Didn't know about that. Thank you!

Closed by commit rG27aa23cee810: sys/bitcount.h: add __const_bitcount<n> (authored by bz). · Explain WhyFri, Dec 19, 9:17 PM

This revision was automatically updated to reflect the committed changes.

bz added a commit: rG27aa23cee810: sys/bitcount.h: add __const_bitcount<n>.