[PATCH 28/59] x86: Use -msse2avx iff compiler supports it

[H.J. Lu]

On Sat, Oct 18, 2025 at 3:51 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> clang supports it from version 19 and onwards, but it should be gated
> as an option to assembler (either with -Wa or -Xassembler).  Aadd a
> test for -Wa as well if -msse2avx fully supported by the compiler.
> ---
>  sysdeps/x86_64/configure              | 24 ++++++++++++++++++++++++
>  sysdeps/x86_64/configure.ac           | 11 +++++++++++
>  sysdeps/x86_64/fpu/multiarch/Makefile | 14 +++++++-------
>  3 files changed, 42 insertions(+), 7 deletions(-)
>
> diff --git a/sysdeps/x86_64/configure b/sysdeps/x86_64/configure
> index 32324f62da..9dd2e4a179 100644
> --- a/sysdeps/x86_64/configure
> +++ b/sysdeps/x86_64/configure
> @@ -210,6 +210,30 @@ fi
>  config_vars="$config_vars
>  enable-cet = $enable_cet"
>
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking -msse2avx" >&5
> +printf %s "checking -msse2avx... " >&6; }
> +if test ${libc_cv_cc_msse2avx+y}
> +then :
> +  printf %s "(cached) " >&6
> +else case e in #(
> +  e)   for opt in "-msse2avx" "-Wa,-msse2avx"; do
> +    if { ac_try='${CC-cc} $CFLAGS -c -xc /dev/null -o /dev/null -c "$opt" 1>&5'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; }; then
> +      libc_cv_cc_msse2avx="$opt"; break;
> +    fi
> +  done
> + ;;
> +esac
> +fi
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_cc_msse2avx" >&5
> +printf "%s\n" "$libc_cv_cc_msse2avx" >&6; }
> +config_vars="$config_vars
> +config-cflags-msse2avx = $libc_cv_cc_msse2avx"
> +
>  # Check if -mamx-tile works properly.
>
>  cat > conftest.c <<EOF
> diff --git a/sysdeps/x86_64/configure.ac b/sysdeps/x86_64/configure.ac
> index a00958e219..d1bcfd7ca4 100644
> --- a/sysdeps/x86_64/configure.ac
> +++ b/sysdeps/x86_64/configure.ac
> @@ -67,6 +67,17 @@ elif test $enable_cet = permissive; then
>  fi
>  LIBC_CONFIG_VAR([enable-cet], [$enable_cet])
>
> +dnl Check if compiler supports -msse2avx or -Wa,-msse2avx
> +AC_CACHE_CHECK(-msse2avx, libc_cv_cc_msse2avx, [dnl
> +  for opt in "-msse2avx" "-Wa,-msse2avx"; do
> +    if AC_TRY_COMMAND(${CC-cc} $CFLAGS -c -xc /dev/null -o /dev/null -c "$opt" 1>&AS_MESSAGE_LOG_FD); then
> +      libc_cv_cc_msse2avx="$opt"; break;
> +    fi
> +  done
> +])
> +LIBC_CONFIG_VAR([config-cflags-msse2avx],
> +               [$libc_cv_cc_msse2avx])
> +
>  # Check if -mamx-tile works properly.
>  LIBC_TRY_TEST_CC_COMMAND([whether -mamx-tile works properly],
>    [#include <x86intrin.h>],
> diff --git a/sysdeps/x86_64/fpu/multiarch/Makefile b/sysdeps/x86_64/fpu/multiarch/Makefile
> index 708b14297f..50b66509f9 100644
> --- a/sysdeps/x86_64/fpu/multiarch/Makefile
> +++ b/sysdeps/x86_64/fpu/multiarch/Makefile
> @@ -150,13 +150,13 @@ CFLAGS-s_sin-fma4.c = -mfma4
>  CFLAGS-s_tan-fma4.c = -mfma4
>  CFLAGS-s_sincos-fma4.c = -mfma4
>
> -CFLAGS-e_atan2-avx.c = -msse2avx -DSSE2AVX
> -CFLAGS-e_exp-avx.c = -msse2avx -DSSE2AVX
> -CFLAGS-e_log-avx.c = -msse2avx -DSSE2AVX
> -CFLAGS-s_atan-avx.c = -msse2avx -DSSE2AVX
> -CFLAGS-s_sin-avx.c = -msse2avx -DSSE2AVX
> -CFLAGS-s_tan-avx.c = -msse2avx -DSSE2AVX
> -CFLAGS-s_sincos-avx.c = -msse2avx -DSSE2AVX
> +CFLAGS-e_atan2-avx.c = $(config-cflags-msse2avx) -DSSE2AVX
> +CFLAGS-e_exp-avx.c = $(config-cflags-msse2avx) -DSSE2AVX
> +CFLAGS-e_log-avx.c = $(config-cflags-msse2avx) -DSSE2AVX
> +CFLAGS-s_atan-avx.c = $(config-cflags-msse2avx) -DSSE2AVX
> +CFLAGS-s_sin-avx.c = $(config-cflags-msse2avx) -DSSE2AVX
> +CFLAGS-s_tan-avx.c = $(config-cflags-msse2avx) -DSSE2AVX
> +CFLAGS-s_sincos-avx.c = $(config-cflags-msse2avx) -DSSE2AVX

Why not simply compile them with -mavx2?

>  CFLAGS-s_modf-sse4_1.c = -msse4.1 -fno-builtin-modff32x -fno-builtin-modff64
>  CFLAGS-s_modff-sse4_1.c = -msse4.1 -fno-builtin-modff32
> --
> 2.43.0
>


-- 
H.J.