arm: Enable USE_ATOMIC_COMPILER_BUILTINS (BZ #24774)
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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.
---
sysdeps/arm/atomic-machine.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Comments
Ping.
On 29/09/2021 16:14, Adhemerval Zanella wrote:
> 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.
> ---
> sysdeps/arm/atomic-machine.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sysdeps/arm/atomic-machine.h b/sysdeps/arm/atomic-machine.h
> index 7928ff29d8..0275fcd2f7 100644
> --- a/sysdeps/arm/atomic-machine.h
> +++ b/sysdeps/arm/atomic-machine.h
> @@ -34,7 +34,7 @@ typedef intmax_t atomic_max_t;
> typedef uintmax_t uatomic_max_t;
>
> #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);
On 2021-09-29 16:14, Adhemerval Zanella via Libc-alpha wrote:
> 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.
> ---
> sysdeps/arm/atomic-machine.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/sysdeps/arm/atomic-machine.h b/sysdeps/arm/atomic-machine.h
> index 7928ff29d8..0275fcd2f7 100644
> --- a/sysdeps/arm/atomic-machine.h
> +++ b/sysdeps/arm/atomic-machine.h
> @@ -34,7 +34,7 @@ typedef intmax_t atomic_max_t;
> typedef uintmax_t uatomic_max_t;
>
> #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);
> --
I have just found your patch after I stumbled on BZ #24774. I confirm it
fixes this bug and also the flaky nptl/tst-rwlock9 test on arm. I did
not find any regression on the testsuite on Debian armel
(armv5-linux-gnueabi) and Debian armhf (armv7-linux-gnueabihf), using
GCC 11.
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>
@@ -34,7 +34,7 @@ typedef intmax_t atomic_max_t;
typedef uintmax_t uatomic_max_t;
#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);