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Re: 100x perfomance regression between gcc 3.4.5 and gcc 4.X


On 3/13/06, tbp <tbptbp@gmail.com> wrote:
> On 3/13/06, Richard Guenther <richard.guenther@gmail.com> wrote:
>  > Starting with gcc 4.1.0 we have inline heuristics in place that will _always_
> > inline such simple "wrappers".  So, if this still happens, there is a bug in the
> > heuristics and that should be reported.  Before 4.1.0 the heuristics were bogus
> > and wrappers were not inlined all the time.
> > So, can you verify you are happy with the heuristics in 4.1.0
> No i'm not, and i've used a pristine 4.1.0 in
> http://gcc.gnu.org/ml/gcc/2006-03/msg00410.html

For the testcase in this message, I get (I removed the always_inline)
all wrappers inlined to bloatit.  Of course bloatit does not get inlined
w/o always_inline - it's a huge function and not a simple wrapper.  With
always_inline on it, the wrappers are no longer inlined - this is a bug and
should be reported.  Of course from 4.1.0 on you can easier stick an
__attribute__((flatten)) on the function you want everything inlined to
(finalblow) and get everything inlined into it.

Can you report a bugzilla for the bad interaction between always_inline
and inlining of simple wrappers?

Thanks,
Richard.


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