--- Comment #4 from Richard Guenther <rguenth at gcc dot> 2010-09-28 
13:38:58 UTC ---
(In reply to comment #3)
> (In reply to comment #2)
> > For single-file programs -fwhole-program and -flto should be basically
> > equivalent if the Frontend provides correctly merged decls.  I suppose
> > it does not and thus we do less inlining with -fwhole-program compared
> > to -flto.
> It might well be the reason that one does less inlining without LTO - but

more inlining with LTO.  You read my stmt wrong.

> that's then not only a FE bug (not correctly merged decls) but also a 
> ME/target
> bug as the LTO program is _slower_.

Sure.  As with all performance related bugs this needs analysis and is
unlikely an "LTO" problem - LTO does not (not-)optimize, optimization
passes do.

> Cf. also PR 44334, which is about a -fwhole-program slowdown (w/ and w/o
> -flto). For the latter program, it helped to use "--param
> hot-bb-frequency-fraction=2000". However, for this PR, the option does not 
> seem
> to help.

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