Re: [PATCH 1/8] softfloat: Use mulu64 for mul64To128

[David Hildenbrand]

On 24.09.20 03:24, Richard Henderson wrote:
> Via host-utils.h, we use a host widening multiply for
> 64-bit hosts, and a common subroutine for 32-bit hosts.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/fpu/softfloat-macros.h | 24 ++++--------------------
>  1 file changed, 4 insertions(+), 20 deletions(-)
> 
> diff --git a/include/fpu/softfloat-macros.h b/include/fpu/softfloat-macros.h
> index a35ec2893a..57845f8af0 100644
> --- a/include/fpu/softfloat-macros.h
> +++ b/include/fpu/softfloat-macros.h
> @@ -83,6 +83,7 @@ this code that are retained.
>  #define FPU_SOFTFLOAT_MACROS_H
>  
>  #include "fpu/softfloat-types.h"
> +#include "qemu/host-utils.h"
>  
>  
> /*----------------------------------------------------------------------------
>  | Shifts `a' right by the number of bits given in `count'.  If any nonzero
> @@ -515,27 +516,10 @@ static inline void
>  | `z0Ptr' and `z1Ptr'.
>  
> *----------------------------------------------------------------------------*/
>  
> -static inline void mul64To128( uint64_t a, uint64_t b, uint64_t *z0Ptr, 
> uint64_t *z1Ptr )
> +static inline void
> +mul64To128(uint64_t a, uint64_t b, uint64_t *z0Ptr, uint64_t *z1Ptr)
>  {
> -    uint32_t aHigh, aLow, bHigh, bLow;
> -    uint64_t z0, zMiddleA, zMiddleB, z1;
> -
> -    aLow = a;
> -    aHigh = a>>32;
> -    bLow = b;
> -    bHigh = b>>32;
> -    z1 = ( (uint64_t) aLow ) * bLow;
> -    zMiddleA = ( (uint64_t) aLow ) * bHigh;
> -    zMiddleB = ( (uint64_t) aHigh ) * bLow;
> -    z0 = ( (uint64_t) aHigh ) * bHigh;
> -    zMiddleA += zMiddleB;
> -    z0 += ( ( (uint64_t) ( zMiddleA < zMiddleB ) )<<32 ) + ( zMiddleA>>32 );
> -    zMiddleA <<= 32;
> -    z1 += zMiddleA;
> -    z0 += ( z1 < zMiddleA );
> -    *z1Ptr = z1;
> -    *z0Ptr = z0;
> -
> +    mulu64(z1Ptr, z0Ptr, a, b);
>  }
>  
>  
> /*----------------------------------------------------------------------------
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb