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sys/bitcount.h: add __const_bitcount<n>

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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
Sponsored by:	The FreeBSD Foundation
Reviewed by:	brooks, emaste
Differential Revision: https://reviews.freebsd.org/D54301
This commit is contained in:
Bjoern A. Zeeb 2025-09-15 23:54:57 +00:00
parent 546d3d08e5
commit 27aa23cee8
1 changed files with 22 additions and 0 deletions
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22
sys/sys/bitcount.h
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@ -39,6 +39,28 @@
#include <sys/_types.h>
#define __const_bitcount8(x) ( \
!!((x) & (1 << 0)) + \
!!((x) & (1 << 1)) + \
!!((x) & (1 << 2)) + \
!!((x) & (1 << 3)) + \
!!((x) & (1 << 4)) + \
!!((x) & (1 << 5)) + \
!!((x) & (1 << 6)) + \
!!((x) & (1 << 7)))
#define __const_bitcount16(x) ( \
__const_bitcount8(x) + \
__const_bitcount8((x) >> 8))
#define __const_bitcount32(x) ( \
__const_bitcount16(x) + \
__const_bitcount16((x) >> 16))
#define __const_bitcount64(x) ( \
__const_bitcount32(x) + \
__const_bitcount32((x) >> 32))
#ifdef __POPCNT__
#define __bitcount64(x) __builtin_popcountll((__uint64_t)(x))
#define __bitcount32(x) __builtin_popcount((__uint32_t)(x))