sparc: Use atomic compiler builtins on sparc

This patch removes the arch-specific atomic instruction, relying on
compiler builtins.  The __sparc32_atomic_locks support is removed
and a configure check is added to check if compiler uses libatomic
to implement CAS.

It also removes the sparc specific sem_* and pthread_barrier_*
implementations.  It in turn allows buidling against a LEON3/LEON4
sparcv8 target, although it will still be incompatible with generic
sparcv9.

Checked on sparcv9-linux-gnu and sparc64-linux-gnu.  I also checked
with build against sparcv8-linux-gnu with -mcpu=leon3.

Tested-by: Andreas Larsson <andreas@gaisler.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/sysdeps/sparc/cpu_relax.c b/sysdeps/sparc/cpu_relax.c
new file mode 100644
index 0000000000..973dfb5935
--- /dev/null
+++ b/sysdeps/sparc/cpu_relax.c
@@ -0,0 +1,40 @@
+/* CPU strand yielding for busy loops.  Linux/sparc version.
+   Copyright (C) 2017-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sparc-ifunc.h>
+
+#ifdef __sparc_v9__
+static void
+__cpu_relax_generic (void)
+{
+  asm volatile ("rd %ccr, %g0;"
+		"rd %ccr, %g0;"
+		"rd %ccr, %g0");
+}
+
+static void
+__cpu_relax_pause (void)
+{
+  asm volatile ("wr %g0, 128, %asr27");
+}
+
+sparc_libc_ifunc (__cpu_relax,
+		  hwcap & HWCAP_SPARC_PAUSE
+		  ? __cpu_relax_pause
+		  : __cpu_relax_generic)
+#endif