Hi Josef, Martin & Honza, hello world,
Josef Melcr wrote:
this is the fourth version of this patch
I have some questions below - as a mere user.
Disclaimer: I presume that there are good reasons for the
current behavior and I know that there is always room for
improvement - and my puzzled questions shouldn't delay
the landing of the patch. (Additionally, I have no idea
how GCC's IPA internally works and I only glanced at the
patch. Still, am a bit puzzled.)
* * *
I tried the following test case:
------------------
int f()
{
int x = 1;
int res;
#pragma omp parallel
if (x > 0)
res = 55;
else
res = 33;
return res;
}
------------------
But, using gcc -fopenmp -O3 -fdump-tree-optimized, I still see
the condition in the dump/assembly.
What puzzled me a bit with the examples is that all of them use
LTO. Shouldn't the optimization not always be in place? In particular,
the generated f._omp_fn.0 is/should be static, i.e. issues like code
side growth or use outside of the TU shouldn't apply?
If I add 'int main() { return f(); }' and compile with -flto, I see
that the condition is gone.
Secondly, as the function is static, I would have expected that -O2
(implies -fipa-cp) is enough; however, I see that -fipa-cp-clone
(implied by -O3) is required. - I understand that internally cloning
is easier, but I wonder whether we it could still enable this with
-O2, given that the func is static and has a single caller, only.
But also if it weren't static (or had multiple caller), for -O3 I'd
expect the cloning in this case (assuming that it is profitable by
whatever measure the compiler has).
Thanks again for the patch and all others involved in reviewing
creating, it.
Tobias
