[gcc r12-6601] libgcc: Fix __gthr_i486_lock_cmp_xchg clobber for Windows

[Jonathan Yong <jyong@gcc.gnu.org>]

https://gcc.gnu.org/g:dcf8fe1eeab668a4d24bcc4baa3ad185dbf1b5e0

commit r12-6601-gdcf8fe1eeab668a4d24bcc4baa3ad185dbf1b5e0
Author: Jonathan Yong <10walls@gmail.com>
Date:   Sat Jan 15 13:24:33 2022 +0000

    libgcc: Fix __gthr_i486_lock_cmp_xchg clobber for Windows
    
    2022-01-14  David  <gccbugzilla@limegreensocks.com>
    
    libgcc/
            * config/i386/gthr-win32.c (__gthr_i486_lock_cmp_xchg):
            Remove inlined version, Windows 95 is no longer relevant.
            * config/i386/gthr-win32.h
            (__GTHREAD_I486_INLINE_LOCK_PRIMITIVES): unset.

Diff:
---
 libgcc/config/i386/gthr-win32.c |  2 --
 libgcc/config/i386/gthr-win32.h | 23 ++---------------------
 2 files changed, 2 insertions(+), 23 deletions(-)

diff --git a/libgcc/config/i386/gthr-win32.c b/libgcc/config/i386/gthr-win32.c
index 0ad29bea6da..fad8f8aca1e 100644
--- a/libgcc/config/i386/gthr-win32.c
+++ b/libgcc/config/i386/gthr-win32.c
@@ -31,8 +31,6 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #ifndef __GTHREAD_HIDE_WIN32API
 # define __GTHREAD_HIDE_WIN32API 1
 #endif
-#undef  __GTHREAD_I486_INLINE_LOCK_PRIMITIVES
-#define __GTHREAD_I486_INLINE_LOCK_PRIMITIVES
 #include "gthr-win32.h"
 
 /* Windows32 threads specific definitions. The windows32 threading model
diff --git a/libgcc/config/i386/gthr-win32.h b/libgcc/config/i386/gthr-win32.h
index cbc7a2dae15..6f70e9b9dea 100644
--- a/libgcc/config/i386/gthr-win32.h
+++ b/libgcc/config/i386/gthr-win32.h
@@ -374,28 +374,9 @@ extern int _CRT_MT;
 extern int __mingwthr_key_dtor (unsigned long, void (*) (void *));
 #endif /* _WIN32 && !__CYGWIN__ */
 
-/* The Windows95 kernel does not export InterlockedCompareExchange.
-   This provides a substitute.   When building apps that reference
-   gthread_mutex_try_lock, the  __GTHREAD_I486_INLINE_LOCK_PRIMITIVES
-   macro  must be defined if Windows95 is a target.  Currently
-   gthread_mutex_try_lock is not referenced by libgcc or libstdc++.  */
-#ifdef __GTHREAD_I486_INLINE_LOCK_PRIMITIVES
-static inline long
-__gthr_i486_lock_cmp_xchg(long *__dest, long __xchg, long __comperand)
-{
-  long result;
-  __asm__ __volatile__ ("\n\
-	lock\n\
-	cmpxchg{l} {%4, %1|%1, %4}\n"
-	: "=a" (result), "=m" (*__dest)
-	: "0" (__comperand), "m" (*__dest), "r" (__xchg)
-	: "cc");
-  return result;
-}
-#define __GTHR_W32_InterlockedCompareExchange __gthr_i486_lock_cmp_xchg
-#else  /* __GTHREAD_I486_INLINE_LOCK_PRIMITIVES */
+/* __GTHR_W32_InterlockedCompareExchange is left over from win95,
+   which did not support InterlockedCompareExchange. */
 #define __GTHR_W32_InterlockedCompareExchange InterlockedCompareExchange
-#endif /* __GTHREAD_I486_INLINE_LOCK_PRIMITIVES */
 
 static inline int
 __gthread_active_p (void)