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-rw-r--r--libc/sysdeps/linux/arm/bits/atomic.h25
1 files changed, 17 insertions, 8 deletions
diff --git a/libc/sysdeps/linux/arm/bits/atomic.h b/libc/sysdeps/linux/arm/bits/atomic.h
index 8f63e2510..07101fbe8 100644
--- a/libc/sysdeps/linux/arm/bits/atomic.h
+++ b/libc/sysdeps/linux/arm/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. */
+
+#ifdef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
+#define atomic_full_barrier() __sync_synchronize ()
+#elif defined __thumb2__
#define atomic_full_barrier() \
__asm__ __volatile__ \
("movw\tip, #0x0fa0\n\t" \
@@ -64,17 +69,21 @@ void __arm_link_error (void);
#define __arch_compare_and_exchange_val_16_acq(mem, newval, oldval) \
({ __arm_link_error (); oldval; })
+#ifdef __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4
+#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) \
- ({ register __typeof (oldval) a_oldval __asm__ ("r0"); \
- register __typeof (oldval) a_newval __asm__ ("r1") = (newval); \
- register __typeof (mem) a_ptr __asm__ ("r2") = (mem); \
+ ({ register __typeof (oldval) a_oldval __asm__ ("r0"); \
+ register __typeof (oldval) a_newval __asm__ ("r1") = (newval); \
+ register __typeof (mem) a_ptr __asm__ ("r2") = (mem); \
register __typeof (oldval) a_tmp __asm__ ("r3"); \
register __typeof (oldval) a_oldval2 __asm__ ("r4") = (oldval); \
__asm__ __volatile__ \
@@ -95,9 +104,9 @@ void __arm_link_error (void);
a_tmp; })
#else
#define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \
- ({ register __typeof (oldval) a_oldval __asm__ ("r0"); \
- register __typeof (oldval) a_newval __asm__ ("r1") = (newval); \
- register __typeof (mem) a_ptr __asm__ ("r2") = (mem); \
+ ({ register __typeof (oldval) a_oldval __asm__ ("r0"); \
+ register __typeof (oldval) a_newval __asm__ ("r1") = (newval); \
+ register __typeof (mem) a_ptr __asm__ ("r2") = (mem); \
register __typeof (oldval) a_tmp __asm__ ("r3"); \
register __typeof (oldval) a_oldval2 __asm__ ("r4") = (oldval); \
__asm__ __volatile__ \