On Tue, 24 Jul 2012, Richard Guenther wrote:
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. And sorry for forgetting to mention it was bootstrapped and
regtested.
Note that Andrew Pinski posted a patch:
http://gcc.gnu.org/ml/gcc-patches/2012-07/msg01167.html
which does something quite similar, so I will wait a bit before committing
anything.
--
Marc Glisse
