Evandro Menezes wrote:
On 03/23/16 11:24, Evandro Menezes wrote:
> On 03/17/16 15:09, Evandro Menezes wrote:
>> This patch implements FP division by an approximation using the Newton
>> series.
>>
>> With this patch, DF division is sped up by over 100% and SF division,
>> zilch, both on A57 and on M1.
Mentioning throughput is not useful given that the vectorized single precision
case will give most of the speedup in actual code.
> gcc/
> * config/aarch64/aarch64-tuning-flags.def
> (AARCH64_EXTRA_TUNE_APPROX_DIV_{SF,DF}: New tuning macros.
> * config/aarch64/aarch64-protos.h
> (AARCH64_EXTRA_TUNE_APPROX_DIV): New macro.
> (aarch64_emit_approx_div): Declare new function.
> * config/aarch64/aarch64.c
> (aarch64_emit_approx_div): Define new function.
> * config/aarch64/aarch64.md ("div<mode>3"): New expansion.
> * config/aarch64/aarch64-simd.md ("div<mode>3"): Likewise.
>
>
> This version of the patch cleans up the changes to the MD files and
> optimizes the division when the numerator is 1.0.
Adding support for plain recip is good. Having the enabling logic no longer in
the md file is an improvement, but I don't believe adding tuning flags for the
inner
mode is correct - we need a more generic solution like I mentioned in my other
mail.
The division variant should use the same latency reduction trick I mentioned
for sqrt.
Wilco
