Re: [PATCH 1/8] x86: Add macros to implement ifunce selection in C

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Jun 2, 2017 at 12:42 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> Should they go into include/libc-symbols.h so that they are available
> everywhere?
>
> H.J.
> ---
> These macros are used to implement ifunc selection in C.  To implement
> an ifunc function, foo, which returns the address of __foo_sse2 or
> __foo_avx2:
>
>    __foo_avx2:
>
>    #define foo __redirect_foo
>    #define __foo __redirect___foo
>    #include <foo.h>
>    #undef foo
>    #undef __foo
>    #define SYMBOL_NAME foo
>    #include <init-arch.h>
>
>    extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
>    extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
>
>    static inline void *
>    foo_selector (void)
>    {
>      if (use AVX2)
>       return OPTIMIZE (avx2);
>
>      return OPTIMIZE (sse2);
>    }
>
>    libc_ifunc_redirected (__redirect_foo, foo, foo_selector ());
>
> 2017-06-02  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
>             H.J. Lu  <hongjiu.lu@intel.com>
>
>         * sysdeps/x86/init-arch.h (PASTER1): New.
>         (EVALUATOR1): Likewise.
>         (PASTER2): Likewise.
>         (EVALUATOR2): Likewise.
>         (REDIRECT_NAME): Likewise.
>         (OPTIMIZE): Likewise.
>         (IFUNC_SELECTOR): Likewise.
> ---
>  sysdeps/x86/init-arch.h | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
>
> diff --git a/sysdeps/x86/init-arch.h b/sysdeps/x86/init-arch.h
> index 6cbc16b..15d3f09 100644
> --- a/sysdeps/x86/init-arch.h
> +++ b/sysdeps/x86/init-arch.h
> @@ -21,6 +21,46 @@
>  # include <ldsodefs.h>
>  #endif
>
> +/* These macros are used to implement ifunc selection in C.  To implement
> +   an ifunc function, foo, which returns the address of __foo_sse2 or
> +   __foo_avx2:
> +
> +   #define foo __redirect_foo
> +   #define __foo __redirect___foo
> +   #include <foo.h>
> +   #undef foo
> +   #undef __foo
> +   #define SYMBOL_NAME foo
> +   #include <init-arch.h>
> +
> +   extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> +   extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> +
> +   static inline void *
> +   foo_selector (void)
> +   {
> +     if (use AVX2)
> +      return OPTIMIZE (avx2);
> +
> +     return OPTIMIZE (sse2);
> +   }
> +
> +   libc_ifunc_redirected (__redirect_foo, foo, foo_selector ());
> +
> +*/
> +
> +#define PASTER1(x,y)   x##_##y
> +#define EVALUATOR1(x,y)        PASTER1 (x,y)
> +#define PASTER2(x,y)   __##x##_##y
> +#define EVALUATOR2(x,y)        PASTER2 (x,y)
> +
> +/* Basically set '__redirect_<symbol>' to use as type definition,
> +   '__<symbol>_<variant>' as the optimized implementation and
> +   '<symbol>_ifunc_selector' as the IFUNC selector.  */
> +#define REDIRECT_NAME  EVALUATOR1 (__redirect, SYMBOL_NAME)
> +#define OPTIMIZE(name) EVALUATOR2 (SYMBOL_NAME, name)
> +#define IFUNC_SELECTOR EVALUATOR1 (SYMBOL_NAME, ifunc_selector)
> +
>  #ifndef __x86_64__
>  /* Due to the reordering and the other nifty extensions in i686, it is
>     not really good to use heavily i586 optimized code on an i686.  It's
> --
> 2.9.4
>

I will check it in today to unblock my AVX2 patches.


-- 
H.J.