On Mon, Jul 23, 2012 at 10:58 PM, Marc Glisse <marc.gli...@inria.fr> wrote: > On Wed, 20 Jun 2012, Richard Guenther wrote: > >> On Sun, Jun 10, 2012 at 4:16 PM, Marc Glisse <marc.gli...@inria.fr> wrote: >>> >>> Hello, >>> >>> currently, tree-ssa-ifcombine handles pairs of imbricated "if"s that >>> share >>> the same then branch, or the same else branch. There is no particular >>> reason >>> why it couldn't also handle the case where the then branch of one is the >>> else branch of the other, which is what I do here. >>> >>> Any comments? >> >> >> The general idea looks good, but I think the patch is too invasive. As >> far >> as I can see the only callers with a non-zero 'inv' argument come from >> ifcombine_ifnotorif and ifcombine_ifnotandif (and both with inv == 2). >> I would rather see a more localized patch that makes use of >> invert_tree_comparison to perform the inversion on the call arguments >> of maybe_fold_and/or_comparisons. > > > Hello, > > I finally went back to this version (which is where I started from, as shown > in the PR). It is not very satisfying because: > > * some bit tests could also be optimized (more generally, grouping a&&b and > !a&&b on one side and a||b and !a||b on the other side is rather arbitrary), > > * -ftrapping-math makes it useless for floating point, > > but I guess it is better than nothing. Handling traps correctly is > complicated because the current code is already a bit bogus (see > http://gcc.gnu.org/ml/gcc-patches/2012-07/msg00924.html for an example), and > even the definition of -ftrapping-math is not clear ( > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53805 ). > > If defaults are ever reconsidered, my default flags include -frounding-math > -fno-trapping-math. >
This patch is ok if bootstrapped / regtested properly. Thanks, Richard. > > 2012-06-10 Marc Glisse <marc.gli...@inria.fr> > > gcc/ > PR tree-optimization/51938 > * tree-ssa-ifcombine.c (ifcombine_ifandif): New parameter for > inverted outer condition. > (ifcombine_iforif): Likewise. > (tree_ssa_ifcombine_bb): Update calls to the above. Detect !a&&b > and !a||b patterns. > > > gcc/testsuite/ > PR tree-optimization/51938 > * gcc.dg/tree-ssa/ssa-ifcombine-8.c: New testcase. > * gcc.dg/tree-ssa/ssa-ifcombine-9.c: New testcase. > > -- > Marc Glisse
