[PATCH] PR libgcc/59714 complex division is surprising on aarch64

[Vladimir Mezentsev]

On 10/19/2017 06:37 AM, Richard Earnshaw (lists) wrote:
> On 19/10/17 14:07, Wilco Dijkstra wrote:
>> Vladimir wrote:
>>
>> +# Disable floating-point expression contraction
>> +LIBGCC2_FFP_CONTRAST_CFLAGS = -ffp-contract=off
>> +
>>
>> It looks like this disables fp-contract in all of libgcc...
>> What is the the number of FMAs in libgcc before/after?

   How can I find this number ?
dis <all functions in libgcc> | grep <all FMAs> | wc

Or are there the other simple ways ?

>>
>> If it disables anything other than the ones in complex division, it
>> would have an unintended performance impact. It's best to do
>> this just for complex division.
>>
>> Wilco
>>
> It's probably better to do this with an attribute
>
> 	__attribute__((optimize("fp-contract=off")))
>
> on the affected functions.

   I like your suggestion.

-Vladimir

>
> R.