Default std::vector<bool> default and move constructor

[François Dumont]

On 15/05/2017 21:31, Marc Glisse wrote:
> On Mon, 15 May 2017, François Dumont wrote:
>
>>    I also added some optimizations. Especially replacement of 
>> std::fill with calls to __builtin_memset. Has anyone ever proposed to 
>> optimize std::fill in such a way ? It would require a test on the 
>> value used to fill the range but it might worth this additional 
>> runtime check, no ?
>
> Note that with -O3, gcc recognizes the pattern in std::fill and 
> generates a call to memset (there is a bit too much extra code around 
> the memset, but a couple match.pd transformations should fix that).

Good to know, at least g++ will be able to spend more time on other 
optimizations :-) What is match.pd ?

> That doesn't mean we can't save it the work. If you want to save the 
> runtime check, there is always __builtin_constant_p...

Good point, I will give it a try.

>
> The __fill_bvector part of the fill overload for vector<bool> could do 
> with some improvements as well. Looping is unnecessary, one just needs 
> to produce the right mask and and or or with it, that shouldn't take 
> more than 4 instructions or so.
Yes, good idear, I'll submit another patch after this one.
>
> There was a time when I suggested overloading std::count and std::find 
> in order to use __builtin_popcount, etc. But from what I've seen of 
> committee discussions, I expect that there will be specialized 
> algorithms (possibly member functions) eventually, making the overload 
> less useful.
>
ok, thanks for those feedbacks.

François