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commit f9646d138f568ced95b29c20efdf902063c7ea96
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Tue Sep 28 17:53:28 2021 +0000
arm: Enable USE_ATOMIC_COMPILER_BUILTINS (BZ #24774)
As per other architectures. I have checked on a armv8 hardware with
the following configurations:
arm-linux-gnueabihf (gcc built with --with-float=hard --with-cpu=arm926ej-s)
armv5-linux-gnueabihf (-march=armv5te -mfpu=vfpv3)
armv7-linux-gnueabihf (-march=armv7-a -mfpu=vfpv3)
armv7-thumb-linux-gnueabihf (-march=armv7-a -mfpu=vfpv3 -mthumb)
armv7-neon-linux-gnueabihf (-march=armv7-a -mfpu=neon)
armv7-neonhard-linux-gnueabihf (-march=armv7-a -mfpu=neon -mfloat-abi=hard)
Without any regression.
I haven't dig into the code, but since Linux atomic-machine.h handle
pre-ARMv6 and ARMv6 I expect the compiler might have some small room
to optimize.
The code size also improves is most of the configurations:
* master
text data bss dec hex filename
1727801 9720 37928 1775449 1b1759 arm-linux-gnueabihf/libc.so
1691729 9720 37928 1739377 1a8a71 arm-linux-gnueabihf-armv7-disable-multi-arch/libc.so
1725509 9720 37928 1773157 1b0e65 armv5-linux-gnueabihf/libc.so
1700757 9720 37928 1748405 1aadb5 armv6-linux-gnueabihf/libc.so
1698973 9720 37928 1746621 1aa6bd armv6t2-linux-gnueabihf/libc.so
1695481 9752 37928 1743161 1a9939 armv7-linux-gnueabihf/libc.so
1692917 9744 37928 1740589 1a8f2d armv7-neonhard-linux-gnueabihf/libc.so
1692917 9744 37928 1740589 1a8f2d armv7-neon-linux-gnueabihf/libc.so
1225353 9752 37928 1273033 136cc9 armv7-thumb-linux-gnueabihf/libc.so
* patched
text data bss dec hex filename
1726805 9720 37928 1774453 1b1375 arm-linux-gnueabihf/libc.so
1689321 9720 37928 1736969 1a8109 arm-linux-gnueabihf-armv7-disable-multi-arch/libc.so
1724433 9720 37928 1772081 1b0a31 armv5-linux-gnueabihf/libc.so
1698301 9720 37928 1745949 1aa41d armv6-linux-gnueabihf/libc.so
1696525 9720 37928 1744173 1a9d2d armv6t2-linux-gnueabihf/libc.so
1693009 9752 37928 1740689 1a8f91 armv7-linux-gnueabihf/libc.so
1690493 9744 37928 1738165 1a85b5 armv7-neonhard-linux-gnueabihf/libc.so
1690493 9744 37928 1738165 1a85b5 armv7-neon-linux-gnueabihf/libc.so
1223837 9752 37928 1271517 1366dd armv7-thumb-linux-gnueabihf/libc.so
The idea is eventually move all architectures to use compiler builtins.
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/sysdeps/arm/atomic-machine.h b/sysdeps/arm/atomic-machine.h
index 9524043797..e1f7731df0 100644
--- a/sysdeps/arm/atomic-machine.h
+++ b/sysdeps/arm/atomic-machine.h
@@ -17,7 +17,7 @@
<https://www.gnu.org/licenses/>. */
#define __HAVE_64B_ATOMICS 0
-#define USE_ATOMIC_COMPILER_BUILTINS 0
+#define USE_ATOMIC_COMPILER_BUILTINS 1
#define ATOMIC_EXCHANGE_USES_CAS 1
void __arm_link_error (void);
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