Re: [PATCH v2 37/69] target/arm: Handle FPCR.AH in negation steps in SVE FCADD

[Richard Henderson <richard.henderson@linaro.org>]

On 2/1/25 08:39, Peter Maydell wrote:
> The negation steps in FCADD must honour FPCR.AH's "don't change the
> sign of a NaN" semantics.  Implement this in the same way we did for
> the base ASIMD FCADD, by encoding FPCR.AH into the SIMD data field
> passed to the helper and using that to decide whether to negate the
> values.
> 
> The construction of neg_imag and neg_real were done to make it easy
> to apply both in parallel with two simple logical operations.  This
> changed with FPCR.AH, which is more complex than that. Switch to
> an approach that follows the pseudocode more closely, by extracting
> the 'rot=1' parameter from the SIMD data field and changing the
> sign of the appropriate input value.
> 
> Note that there was a naming issue with neg_imag and neg_real.
> They were named backward, with neg_imag being non-zero for rot=1,
> and vice versa.  This was combined with reversed usage within the
> loop, so that the negation in the end turned out correct.
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
> v2: Squashed in changes from RTH's patchset
> ---
>   target/arm/tcg/vec_internal.h  | 17 ++++++++++++++
>   target/arm/tcg/sve_helper.c    | 42 ++++++++++++++++++++++++----------
>   target/arm/tcg/translate-sve.c |  2 +-
>   3 files changed, 48 insertions(+), 13 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~