Community source repository for glibc add-on ports branch, master, updated. glibc-2.12-42-g2c20193
Wed Nov 24 23:24:00 GMT 2010

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- Log -----------------------------------------------------------------;a=commitdiff;h=2c2019389ef7286279edd1a120739906b1a61138

commit 2c2019389ef7286279edd1a120739906b1a61138
Author: Ken Werner <>
Date:   Wed Nov 24 23:23:48 2010 +0000

    Use __sync_* on ARM where supported by the compiler.

diff --git a/ChangeLog.arm b/ChangeLog.arm
index 08ed967..693d1e7 100644
--- a/ChangeLog.arm
+++ b/ChangeLog.arm
@@ -1,3 +1,9 @@
+2010-11-24  Ken Werner  <>
+	* sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h (atomic_full_barrier,
+	__arch_compare_and_exchange_val_32_acq): Use the atomic builtins
+	provided by GCC if __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 is defined.
 2010-11-22  Andreas Schwab  <>
 	* sysdeps/arm/preconfigure: Only modify CFLAGS when configuring
diff --git a/sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h b/sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h
index b0586ea..979db9f 100644
--- a/sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h
+++ b/sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h
@@ -37,7 +37,12 @@ typedef uintmax_t uatomic_max_t;
 void __arm_link_error (void);
-#ifdef __thumb2__
+/* Use the atomic builtins provided by GCC in case the backend provides
+   a pattern to do this efficiently.  */
+#define atomic_full_barrier() __sync_synchronize ()
+#elif defined __thumb2__
 #define atomic_full_barrier() \
      __asm__ __volatile__						      \
 	     ("movw\tip, #0x0fa0\n\t"					      \
@@ -64,11 +69,15 @@ void __arm_link_error (void);
 #define __arch_compare_and_exchange_val_16_acq(mem, newval, oldval) \
   ({ __arm_link_error (); oldval; })
+#define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \
+  __sync_val_compare_and_swap ((mem), (oldval), (newval))
 /* It doesn't matter what register is used for a_oldval2, but we must
    specify one to work around GCC PR rtl-optimization/21223.  Otherwise
    it may cause a_oldval or a_tmp to be moved to a different register.  */
-#ifdef __thumb2__
+#elif defined __thumb2__
 /* Thumb-2 has ldrex/strex.  However it does not have barrier instructions,
    so we still need to use the kernel helper.  */
 #define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \


Summary of changes:
 ChangeLog.arm                                  |    6 ++++++
 sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h |   13 +++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

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