[Bug libstdc++/11706] std::pow(T, int) implementation pessimizes code

["pcarlini at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From pcarlini at suse dot de  2004-03-10 20:01 -------
Subject: Re:  std::pow(T, int) implementation pessimizes
 code

gdr at integrable-solutions dot net wrote:

>| >The issue is actually solved in tree--ssa (or was reported as
>| >such at some point in the past).  I believe this should be targetted
>| >for 3.5.0.  It really is compiler-optimization issue even though it is
>| >not labelled as scuh.
>| >  
>| >
>| This is very good to know, if confirmed: do you have a pointer?
>
>Don't have a pointer handy but, google for messages from Richard G. with the
>complain that the ::pow() is no longer "inlined".
>  
>
Anyway, the issue is *not* solved in tree-ssa, because __cmath_power 
cannot be
unrolled due to its non-linear iv. The blocker is the unroller not the 
inliner, see
PR 11710. Zdenek confirmed in private email that the unroller *could* be 
fixed,
in principle, but nobody is working on the issue.

Short-term the only feasible approach seems the one outlined by Richard 
here:

    http://gcc.gnu.org/ml/gcc/2003-07/msg01950.html

Luckily, I have plenty of time, since for this PR "rush" is defined as 
something of
order 1-2 months :-P

Paolo.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11706