git: 9755a8036354 - stable/15 - LinuxKPI: bitcount fix builds with gcc and older llvm

The branch stable/15 has been updated by bz:

URL: https://cgit.FreeBSD.org/src/commit/?id=9755a80363549cc5504b4bb2d18a4a12e34ded28

commit 9755a80363549cc5504b4bb2d18a4a12e34ded28
Author:     Bjoern A. Zeeb <bz@FreeBSD.org>
AuthorDate: 2025-09-15 23:52:13 +0000
Commit:     Bjoern A. Zeeb <bz@FreeBSD.org>
CommitDate: 2026-01-16 08:48:47 +0000

    LinuxKPI: bitcount fix builds with gcc and older llvm
    
    LLVM before 19 and gcc before 14 do not support __builtin_popcountg().
    Use __const_bitcount<n> from sys/bitcount.h as a replacement in these
    cases.  This should still allow drm-kmod to build where the size needs
    to be known at compile-time.
    
    Remove the conditional for gcc around the iwlwifi modules build,
    which was collateral damage in all this.
    
    Sponsored by:   The FreeBSD Foundation
    Fixes:          7cbc4d875971, 5e0a4859f28a
    Reviewed by:    brooks, emaste (without the sys/modules/Makefile change)
    Differential Revision: https://reviews.freebsd.org/D54297
    
    (cherry picked from commit 34892a8e30055000352d9612ad985be550c82bea)
---
 sys/compat/linuxkpi/common/include/linux/bitops.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sys/compat/linuxkpi/common/include/linux/bitops.h b/sys/compat/linuxkpi/common/include/linux/bitops.h
index a5a7abd55287..8fac80820f30 100644
--- a/sys/compat/linuxkpi/common/include/linux/bitops.h
+++ b/sys/compat/linuxkpi/common/include/linux/bitops.h
@@ -57,10 +57,18 @@
 #define	hweight64(x)	bitcount64(x)
 #define	hweight_long(x)	bitcountl(x)
 
+#if __has_builtin(__builtin_popcountg)
 #define	HWEIGHT8(x)	(__builtin_popcountg((uint8_t)(x)))
 #define	HWEIGHT16(x)	(__builtin_popcountg((uint16_t)(x)))
 #define	HWEIGHT32(x)	(__builtin_popcountg((uint32_t)(x)))
 #define	HWEIGHT64(x)	(__builtin_popcountg((uint64_t)(x)))
+#else
+/* LLVM before 19, gcc before 14. */
+#define	HWEIGHT8(x)	(__const_bitcount8((uint8_t)(x)))
+#define	HWEIGHT16(x)	(__const_bitcount16((uint16_t)(x)))
+#define	HWEIGHT32(x)	(__const_bitcount32((uint32_t)(x)))
+#define	HWEIGHT64(x)	(__const_bitcount64((uint64_t)(x)))
+#endif
 
 static inline int
 __ffs(int mask)