On 09/17/2018 11:15 PM, Marc Glisse wrote:
On Mon, 17 Sep 2018, François Dumont wrote:
We talk about it a while back.
I've run testsuite several times since I have this patch on my local
copy. Note that when I implemented it the wrong way tests started to
fail so it is clearly having an effect on the generated code.
* include/bits/c++config [__OPTIMIZE__](__glibcxx_assert): Define as
optimization hint
using __builtin_unreachable.
Ok to commit ?
I see for instance in bits/regex_automaton.tcc:
__glibcxx_assert(__m.count(__ref._M_next) > 0);
where __m is a map, which does not look so well suited for a
__builtin_unreachable. Is it using the wrong macro?
I don't know if this particular code is well covered by the testsuite.
So I tweaked several tests in 23_containers/map and the code compiles
just fine if it is your concern.
If your concern is rather that the condition got evaluated which will
eventually slow down execution then I need to check generated code. Any
good link explaining how to have a clear view on the generated code ?
Maybe a 'if __builtin_constant_p(_Condition)' could help if gcc doesn't
do it itself already.
