[PATCH] x86: Properly set x86 minimum ISA level [BZ #31883]

[Noah Goldstein]

On Tue, Jun 11, 2024 at 9:30 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> Properly set libc_cv_have_x86_isa_level in shell for MINIMUM_X86_ISA_LEVEL
> defined as
>
> (__X86_ISA_V1 + __X86_ISA_V2 + __X86_ISA_V3 + __X86_ISA_V4)
>
> Also set __X86_ISA_V2 to 1 for i386 if __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8
> is defined.  There are no changes in config.h nor in config.make on x86-64.
> On i386, -march=x86-64-v2 with GCC generates
>
>  #define MINIMUM_X86_ISA_LEVEL 2
>
> in config.h and
>
> have-x86-isa-level = 2
>
> in config.make.  This fixes BZ #31883.
>
> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
> ---
>  sysdeps/x86/configure    | 4 +++-
>  sysdeps/x86/configure.ac | 4 +++-
>  sysdeps/x86/isa-level.h  | 6 +++++-
>  3 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/sysdeps/x86/configure b/sysdeps/x86/configure
> index 1e2325d0d7..04c6ba3e6c 100644
> --- a/sysdeps/x86/configure
> +++ b/sysdeps/x86/configure
> @@ -141,8 +141,10 @@ libc_cv_have_x86_isa_level=3
>  libc_cv_have_x86_isa_level=2
>  #elif defined __x86_64__
>  libc_cv_have_x86_isa_level=baseline
> +#elif MINIMUM_X86_ISA_LEVEL == 1
> +libc_cv_have_x86_isa_level=1
>  #else
> -libc_cv_have_x86_isa_level=MINIMUM_X86_ISA_LEVEL
> +libc_cv_have_x86_isa_level=0
>  #endif
>  EOF
>                  eval `${CC-cc} $CFLAGS $CPPFLAGS $ISAFLAG -I$srcdir -E conftest.c | grep libc_cv_have_x86_isa_level`
> diff --git a/sysdeps/x86/configure.ac b/sysdeps/x86/configure.ac
> index 0b32fdfd4f..8a259d3971 100644
> --- a/sysdeps/x86/configure.ac
> +++ b/sysdeps/x86/configure.ac
> @@ -98,8 +98,10 @@ libc_cv_have_x86_isa_level=3
>  libc_cv_have_x86_isa_level=2
>  #elif defined __x86_64__
>  libc_cv_have_x86_isa_level=baseline
> +#elif MINIMUM_X86_ISA_LEVEL == 1
> +libc_cv_have_x86_isa_level=1
>  #else
> -libc_cv_have_x86_isa_level=MINIMUM_X86_ISA_LEVEL
> +libc_cv_have_x86_isa_level=0
>  #endif
>  EOF
>                  eval `${CC-cc} $CFLAGS $CPPFLAGS $ISAFLAG -I$srcdir -E conftest.c | grep libc_cv_have_x86_isa_level`
> diff --git a/sysdeps/x86/isa-level.h b/sysdeps/x86/isa-level.h
> index 2c7f74212b..fe1f0924e4 100644
> --- a/sysdeps/x86/isa-level.h
> +++ b/sysdeps/x86/isa-level.h
> @@ -35,7 +35,11 @@
>  # define __X86_ISA_V1 0
>  #endif
>
> -#if __X86_ISA_V1 && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16               \
> +#if __X86_ISA_V1                                                             \
> +    && ((defined __x86_64__                                                  \
> +        && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16)                      \
> +       || (!defined __x86_64__                                               \
> +           && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8))                   \
looks correct, but a bit ugly.

How about:
```
// X86_64
#if (defined __x86_64__) && (defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16)
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP 1
// X86
#elif !(defined __x86_64__) && (defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8)
#define __GCC_HAVE_SYNC_COMPARE_AND_SWAP 1
#endif

#if __X86_ISA_V1 && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP
...
```
?

>      && defined HAVE_X86_LAHF_SAHF && defined __POPCNT__ && defined __SSE3__   \
>      && defined __SSSE3__ && defined __SSE4_1__ && defined __SSE4_2__
>  /* NB: ISAs in x86-64 ISA level v2 are used.  */
> --
> 2.45.2
>