Re: [PATCH 1/5] config: Added HAVE_SVE_ASM_SUPPORT for aarch64

[Szabolcs Nagy via Libc-alpha <libc-alpha@sourceware.org>]

The 03/17/2021 02:33, Naohiro Tamura wrote:
> From: Naohiro Tamura <naohirot@jp.fujitsu.com>
> 
> This patch checks if assembler supports '-march=armv8.2-a+sve' to
> generate SVE code or not, and then define HAVE_SVE_ASM_SUPPORT macro.
> ---
>  config.h.in                  |  3 +++
>  sysdeps/aarch64/configure    | 28 ++++++++++++++++++++++++++++
>  sysdeps/aarch64/configure.ac | 15 +++++++++++++++
>  3 files changed, 46 insertions(+)
> 
> diff --git a/config.h.in b/config.h.in
> index f21bf04e47..2073816af8 100644
> --- a/config.h.in
> +++ b/config.h.in
> @@ -118,6 +118,9 @@
>  /* AArch64 PAC-RET code generation is enabled.  */
>  #define HAVE_AARCH64_PAC_RET 0
>  
> +/* Assembler support ARMv8.2-A SVE */
> +#define HAVE_SVE_ASM_SUPPORT 0
> +

i prefer to use HAVE_AARCH64_ prefix for aarch64 specific
macros in the global config.h, e.g. HAVE_AARCH64_SVE_ASM

and i'd like to have a comment here or in configue.ac with the
binutils version where this becomes obsolete (binutils 2.28 i
think). right now the minimum required version is 2.25, but
glibc may increase that soon to above 2.28.

> diff --git a/sysdeps/aarch64/configure.ac b/sysdeps/aarch64/configure.ac
> index 66f755078a..389a0b4e8d 100644
> --- a/sysdeps/aarch64/configure.ac
> +++ b/sysdeps/aarch64/configure.ac
> @@ -90,3 +90,18 @@ EOF
>    fi
>    rm -rf conftest.*])
>  LIBC_CONFIG_VAR([aarch64-variant-pcs], [$libc_cv_aarch64_variant_pcs])
> +
> +# Check if asm support armv8.2-a+sve
> +AC_CACHE_CHECK(for SVE support in assembler, libc_cv_asm_sve, [dnl
> +cat > conftest.s <<\EOF
> +        ptrue p0.b
> +EOF
> +if AC_TRY_COMMAND(${CC-cc} -c -march=armv8.2-a+sve conftest.s 1>&AS_MESSAGE_LOG_FD); then
> +  libc_cv_asm_sve=yes
> +else
> +  libc_cv_asm_sve=no
> +fi
> +rm -f conftest*])
> +if test $libc_cv_asm_sve = yes; then
> +  AC_DEFINE(HAVE_SVE_ASM_SUPPORT)
> +fi

i would use libc_cv_aarch64_sve_asm to make it obvious
that it's aarch64 specific setting.

otherwise OK.