On Sat, Nov 14, 2009 at 2:13 PM, Steven Bosscher <stevenb....@gmail.com> wrote: > On Sat, Nov 14, 2009 at 8:51 PM, Richard Guenther > <richard.guent...@gmail.com> wrote: >> Note that some optimizers (for example value-numbering) contain cut-offs >> so that they are turned off for large functions as otherwise compile-time >> issues appear as algorithms are non-linear in the size of the function. >> >> So it might even be not profitable in the end for size and speed reasons. > > ...where one should keep in mind, that this is one of those areas > where GCC is still at least a decade behind the best compilers in the > industry. Those optimizations, that cut themselves off, would work > just fine on regions instead of whole functions. Another thing that > might be helpful, is partial inlining (e.g. > http://www.csc.villanova.edu/~tway/publications/wayPDPTA02.pdf > although I suspect that for the code from Toon only whole-function > inlining is useful...?).
Indeed. For Tom it shouldn't really matter whether the functions are inlined or not - aliasing shouldn't be an issue here due to Fortran semantics. Maybe it's alignment ... With IPA-PTA aliasing shouldn't be an issue for C or C++ either, the alignment issue remains though. > Zadeck had code for structural analysis a couple of years ago. I don't > think anyone has seriously worked with that to experiment with region > based compilation. But I guess it will be the Next Big Challange for > GCC, after LTO. Yeah, I have some patches for the SSA propagators, but those are not the problematic ones with respect to compile-time. Value-numbering cut's itself off at a certain SCC size, which I suspect cannot be easily fixed with regions (regions probably can't really cross SCCs). I don't even remember which other passes have this kind of cut-offs .. Richard. > Ciao! > Steven >
