Re: [PATCH 41/72] softfloat: Introduce sh[lr]_double primitives

[Alex Bennée]

Richard Henderson <richard.henderson@linaro.org> writes:

> Have x86_64 assembly for them, with a fallback.
> This avoids shuffling values through %cl in the x86 case.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/fpu/softfloat-macros.h |  36 ++++++++++++
>  fpu/softfloat.c                | 102 +++++++++++++++++++++++++--------
>  2 files changed, 115 insertions(+), 23 deletions(-)
>
> diff --git a/include/fpu/softfloat-macros.h b/include/fpu/softfloat-macros.h
> index 672c1db555..ec4e27a595 100644
> --- a/include/fpu/softfloat-macros.h
> +++ b/include/fpu/softfloat-macros.h
> @@ -85,6 +85,42 @@ this code that are retained.
>  #include "fpu/softfloat-types.h"
>  #include "qemu/host-utils.h"
>  
> +/**
> + * shl_double: double-word merging left shift
> + * @l: left or most-significant word
> + * @r: right or least-significant word
> + * @c: shift count
> + *
> + * Shift @l left by @c bits, shifting in bits from @r.
> + */
> +static inline uint64_t shl_double(uint64_t l, uint64_t r, int c)
> +{
> +#if defined(__x86_64__)
> +    asm("shld %b2, %1, %0" : "+r"(l) : "r"(r), "ci"(c));
> +    return l;
> +#else
> +    return c ? (l << c) | (r >> (64 - c)) : l;
> +#endif
> +}
> +
> +/**
> + * shr_double: double-word merging right shift
> + * @l: left or most-significant word
> + * @r: right or least-significant word
> + * @c: shift count
> + *
> + * Shift @r right by @c bits, shifting in bits from @l.
> + */
> +static inline uint64_t shr_double(uint64_t l, uint64_t r, int c)
> +{
> +#if defined(__x86_64__)
> +    asm("shrd %b2, %1, %0" : "+r"(r) : "r"(l), "ci"(c));
> +    return r;
> +#else
> +    return c ? (r >> c) | (l << (64 - c)) : r;
> +#endif
> +}
> +

I was pondering if these deserve to live in bitops but given they are
softfloat only for the time being and we don't do arch specific hacks in
there:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée