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Re: [PATCH 2/8] softfloat: Use int128.h for some operations
From: |
David Hildenbrand |
Subject: |
Re: [PATCH 2/8] softfloat: Use int128.h for some operations |
Date: |
Thu, 24 Sep 2020 09:35:48 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
On 24.09.20 03:24, Richard Henderson wrote:
> Use our Int128, which wraps the compiler's __int128_t,
> instead of open-coding left shifts and arithmetic.
> We'd need to extend Int128 to have unsigned operations
> to replace more than these three.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> include/fpu/softfloat-macros.h | 39 +++++++++++++++++-----------------
> 1 file changed, 20 insertions(+), 19 deletions(-)
>
> diff --git a/include/fpu/softfloat-macros.h b/include/fpu/softfloat-macros.h
> index 57845f8af0..95d88d05b8 100644
> --- a/include/fpu/softfloat-macros.h
> +++ b/include/fpu/softfloat-macros.h
> @@ -84,6 +84,7 @@ this code that are retained.
>
> #include "fpu/softfloat-types.h"
> #include "qemu/host-utils.h"
> +#include "qemu/int128.h"
>
>
> /*----------------------------------------------------------------------------
> | Shifts `a' right by the number of bits given in `count'. If any nonzero
> @@ -352,13 +353,11 @@ static inline void shortShift128Left(uint64_t a0,
> uint64_t a1, int count,
> static inline void shift128Left(uint64_t a0, uint64_t a1, int count,
> uint64_t *z0Ptr, uint64_t *z1Ptr)
> {
> - if (count < 64) {
> - *z1Ptr = a1 << count;
> - *z0Ptr = count == 0 ? a0 : (a0 << count) | (a1 >> (-count & 63));
> - } else {
> - *z1Ptr = 0;
> - *z0Ptr = a1 << (count - 64);
> - }
> + Int128 a = int128_make128(a1, a0);
> + Int128 z = int128_lshift(a, count);
> +
> + *z0Ptr = int128_gethi(z);
> + *z1Ptr = int128_getlo(z);
> }
>
>
> /*----------------------------------------------------------------------------
> @@ -405,15 +404,15 @@ static inline void
>
> *----------------------------------------------------------------------------*/
>
> static inline void
> - add128(
> - uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1, uint64_t *z0Ptr,
> uint64_t *z1Ptr )
> +add128(uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1,
> + uint64_t *z0Ptr, uint64_t *z1Ptr)
> {
> - uint64_t z1;
> -
> - z1 = a1 + b1;
> - *z1Ptr = z1;
> - *z0Ptr = a0 + b0 + ( z1 < a1 );
> + Int128 a = int128_make128(a1, a0);
> + Int128 b = int128_make128(b1, b0);
> + Int128 z = int128_add(a, b);
>
> + *z0Ptr = int128_gethi(z);
> + *z1Ptr = int128_getlo(z);
> }
>
>
> /*----------------------------------------------------------------------------
> @@ -463,13 +462,15 @@ static inline void
>
> *----------------------------------------------------------------------------*/
>
> static inline void
> - sub128(
> - uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1, uint64_t *z0Ptr,
> uint64_t *z1Ptr )
> +sub128(uint64_t a0, uint64_t a1, uint64_t b0, uint64_t b1,
> + uint64_t *z0Ptr, uint64_t *z1Ptr)
> {
> + Int128 a = int128_make128(a1, a0);
> + Int128 b = int128_make128(b1, b0);
> + Int128 z = int128_sub(a, b);
>
> - *z1Ptr = a1 - b1;
> - *z0Ptr = a0 - b0 - ( a1 < b1 );
> -
> + *z0Ptr = int128_gethi(z);
> + *z1Ptr = int128_getlo(z);
> }
>
>
> /*----------------------------------------------------------------------------
>
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
- [PATCH 0/8] softfloat: Implement float128_muladd, Richard Henderson, 2020/09/23
- [PATCH 1/8] softfloat: Use mulu64 for mul64To128, Richard Henderson, 2020/09/23
- [PATCH 2/8] softfloat: Use int128.h for some operations, Richard Henderson, 2020/09/23
- Re: [PATCH 2/8] softfloat: Use int128.h for some operations,
David Hildenbrand <=
- [PATCH 3/8] softfloat: Tidy a * b + inf return, Richard Henderson, 2020/09/23
- [PATCH 4/8] softfloat: Add float_cmask and constants, Richard Henderson, 2020/09/23
- [PATCH 5/8] softfloat: Inline pick_nan_muladd into its caller, Richard Henderson, 2020/09/23
- [PATCH 6/8] softfloat: Implement float128_muladd, Richard Henderson, 2020/09/23