Re: [PATCH v2 04/69] fpu: Implement float_flag_input_denormal_used

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

On 2/1/25 08:39, Peter Maydell wrote:
> For the x86 and the Arm FEAT_AFP semantics, we need to be able to
> tell the target code that the FPU operation has used an input
> denormal.  Implement this; when it happens we set the new
> float_flag_denormal_input_used.
> 
> Note that we only set this when an input denormal is actually used by
> the operation: if the operation results in Invalid Operation or
> Divide By Zero or the result is a NaN because some other input was a
> NaN then we never needed to look at the input denormal and do not set
> denormal_input_used.
> 
> We mostly do not need to adjust the hardfloat codepaths to deal with
> this flag, because almost all hardfloat operations are already gated
> on the input not being a denormal, and will fall back to softfloat
> for a denormal input.  The only exception is the comparison
> operations, where we need to add the check for input denormals, which
> must now fall back to softfloat where they did not before.
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
> v2: drop the now-unnecessary float*_input_flush2() calls in
> the float*_hs_compare() functions
> ---
>   include/fpu/softfloat-types.h |  7 ++++
>   fpu/softfloat.c               | 38 +++++++++++++++++---
>   fpu/softfloat-parts.c.inc     | 68 ++++++++++++++++++++++++++++++++++-
>   3 files changed, 107 insertions(+), 6 deletions(-)

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

r~