[PATCH v3 1/2] x86: Skip XSAVE state size reset if ISA level requires XSAVE

[Florian Weimer]

* Florian Weimer:

> If we have to use XSAVE or XSAVEC trampolines, do not adjust the size
> information they need.  Technically, it is an operator error to try to
> run with -XSAVE,-XSAVEC on such builds, but this change here disables
> some unnecessary code with higher ISA levels and simplifies testing.
>
> Related to commit befe2d3c4dec8be2cdd01a47132e47bdb7020922
> ("x86-64: Don't use SSE resolvers for ISA level 3 or above").
> ---
> v3: Use AVX build flag for the decision, not ISA level.
>
>  sysdeps/x86/cpu-features.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
> index 27abaca8b7..6dfb112038 100644
> --- a/sysdeps/x86/cpu-features.c
> +++ b/sysdeps/x86/cpu-features.c
> @@ -24,6 +24,7 @@
>  #include <dl-cacheinfo.h>
>  #include <dl-minsigstacksize.h>
>  #include <dl-hwcap2.h>
> +#include <gcc-macros.h>
>  
>  extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *)
>    attribute_hidden;
> @@ -1159,6 +1160,9 @@ no_cpuid:
>  	       TUNABLE_CALLBACK (set_prefer_map_32bit_exec));
>  #endif
>  
> +  /* Do not add the logic to disable XSAVE/XSAVEC if this glibc build
> +     requires AVX and therefore XSAVE or XSAVEC support.  */
> +#ifndef GCCMACRO__AVX__
>    bool disable_xsave_features = false;
>  
>    if (!CPU_FEATURE_USABLE_P (cpu_features, OSXSAVE))
> @@ -1212,6 +1216,7 @@ no_cpuid:
>  
>        CPU_FEATURE_UNSET (cpu_features, FMA4);
>      }
> +#endif

Hmph, this doesn't work, it disables the x86-64-v3 compatibility
detection in ld.so.

Florian