git: 53fe018630d0 - main - amd64: gate WRMSRNS immediate form on compiler support

The branch main has been updated by brooks:

URL: https://cgit.FreeBSD.org/src/commit/?id=53fe018630d06eeef6791cfacaa6dc9acdf4d669

commit 53fe018630d06eeef6791cfacaa6dc9acdf4d669
Author:     Brooks Davis <brooks@FreeBSD.org>
AuthorDate: 2026-09-26 11:43:34 +0000
Commit:     Brooks Davis <brooks@FreeBSD.org>
CommitDate: 2026-09-26 11:43:34 +0000

    amd64: gate WRMSRNS immediate form on compiler support
    
    This support was introduced in LLVM 20 and we still support releases
    with LLVM 19 so it's too early to require LLVM 20.  Decay to the
    non-immediate form when the compiler it too old.  This makes the ifunc
    pointless, but limits the need for other ifdefs.
    
    Reviewed by:    kib
    Sponsored by:   Innovate UK
    Differential Revision:  https://reviews.freebsd.org/D60023
---
 sys/amd64/include/cpufunc.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sys/amd64/include/cpufunc.h b/sys/amd64/include/cpufunc.h
index 38dfbf2a493b..f56a7e763158 100644
--- a/sys/amd64/include/cpufunc.h
+++ b/sys/amd64/include/cpufunc.h
@@ -390,8 +390,18 @@ wrmsrns(u_int msr, uint64_t newval)
 	__asm __volatile("wrmsrns" : : "a" (low), "d" (high), "c" (msr));
 }
 
+#if defined(__clang__) && \
+    (__clang_major__ > 20 || (__clang_major__ == 20 && __clang_minor__ >= 1))
 #define	wrmsr_imm(msr, val) \
     __asm __volatile("wrmsrns %0, %1" : : "r" (val), "i" (msr))
+#else
+/*
+ * When Clang does not support the immediate form of wrmsr, decay it
+ * to plain wrmsr.
+ */
+#define	wrmsr_imm(msr, val) \
+    wrmsr((msr), (val));
+#endif
 
 static __inline void
 load_cr0(u_long data)