[PATCH v1 3/7] x86: Add macro for NOT of a cpu arch feature and improve comments

[H.J. Lu]

On Thu, Jun 23, 2022 at 11:37 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> Some ARCH_P features such as Prefer_No_VZEROUPPER used to disable
> implementations if true as opposed fo the majority of features
> such as AVX2 which are used to enabled features.
>
> Different ISA build levels want override certain disabling
> features. For example ISA build level >= 3 should ignore
> Prefer_No_VZEROUPPER which means converting the check to
> false (as opposed to true for a feature like AVX2).
> ---
>  sysdeps/x86/isa-ifunc-macros.h | 4 ++++
>  sysdeps/x86/isa-level.h        | 7 ++++---
>  2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/sysdeps/x86/isa-ifunc-macros.h b/sysdeps/x86/isa-ifunc-macros.h
> index ba6826d518..e229e612a4 100644
> --- a/sysdeps/x86/isa-ifunc-macros.h
> +++ b/sysdeps/x86/isa-ifunc-macros.h
> @@ -67,4 +67,8 @@
>    (X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED (name)                      \
>     || CPU_FEATURES_ARCH_P (ptr, name))
>
> +#define X86_ISA_CPU_FEATURES_ARCH_P_NOT(ptr, name)                            \
> +  (!X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED (name)                           \
> +     && !CPU_FEATURES_ARCH_P (ptr, name))
> +
>  #endif
> diff --git a/sysdeps/x86/isa-level.h b/sysdeps/x86/isa-level.h
> index 7cae11c228..e1a30ed83e 100644
> --- a/sysdeps/x86/isa-level.h
> +++ b/sysdeps/x86/isa-level.h
> @@ -66,10 +66,10 @@
>
>
>  /*
> - * CPU Features that are hard coded as enabled depending on ISA build
> - *   level.
> + * CPU Features that are hard coded as enabled/disabled depending on
> + * ISA build level.
>   *    - Values > 0 features are always ENABLED if:
> - *          Value >= MINIMUM_X86_ISA_LEVEL
> + *          Value <= MINIMUM_X86_ISA_LEVEL
>   */
>
>
> @@ -92,6 +92,7 @@
>  /*
>   * KNL (the only cpu that sets this supported in cpu-features.h)
>   * builds with ISA V1 so this shouldn't harm any architectures.
> + * NB: Only use this feature with the ARCH_P_NOT macro.
>   */
>  #define Prefer_No_VZEROUPPER_X86_ISA_LEVEL 3
>
> --
> 2.34.1
>

This is a bug fix.  Please make it a separate patch set.   Please also
send individual patches,
instead of a set, if there are no dependencies between patches.

Thanks.

-- 
H.J.