http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45810
--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 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.
