-ffloat-store behavior (Re: Susprising behavior of gcc on x86 (-m32))

[Mathieu Malaterre]

Manuel,

On Tue, Sep 8, 2015 at 11:31 PM, Manuel López-Ibáñez
<lopezibanez@gmail.com> wrote:
> On 08/09/15 22:05, Mathieu Malaterre wrote:
>>
>>
>> Ok, I think I understand now. -O0 did produce code that is compatible
>> with -ffloat-store. However I am still required to use -ffloat-store
>> (explicitly) for any other optimization (at least required with -O2 in
>> my case).
>
>
> You are not required to use -ffloat-store, neither is -ffloat-store
> guaranteed to work. Please read https://gcc.gnu.org/wiki/FAQ#PR323
>
> (If there is something that is not explained there, it would be better to
> expand the answer rather than reply here with bits of info.)

Thanks for the link. However -in my case- the compile option
`-fexcess-precision=standard` does produce the same code as
`-ffloat-store`. At least for

[...]
double div; /* OPJ_FLOAT64 */
div = dd / dr;
if (div >= thresh)
[...]

Is there a longer description for `-fexcess-precision=standard` which
explains case of failures ?

Thanks again,