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[Bug tree-optimization/66512] PRE fails to optimize calls to pure functions in C++, ok in C
- From: "amonakov at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Mon, 15 Jun 2015 10:33:19 +0000
- Subject: [Bug tree-optimization/66512] PRE fails to optimize calls to pure functions in C++, ok in C
- Auto-submitted: auto-generated
- References: <bug-66512-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66512
--- Comment #2 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
In that case I'd like to contribute a documentation patch to make that clear in
the pure/const attribute information, but I need more explanation. I see that
int p(void) __attribute__((const));
void f()
{
p();
p();
}
is optimized to an empty function, even though p may throw. Is that not a bug?
Also, could you please expand your explanation in the first paragraph, i.e.
this:
What we miss here is the fact that it should only matter
if p throws internally for IL consistency. Of course it
still matters for observing other side-effects if p throws
and after the transform now does so before side-effects
that should be observed otherwise.
I'm probably missing a lot of contextual knowledge to understand that. TIA.