------- Comment #14 from rguenther at suse dot de 2010-05-25 08:11 -------
Subject: Re: Multiple comparisons are not simplified
On Mon, 24 May 2010, sandra at codesourcery dot com wrote:
> ------- Comment #13 from sandra at codesourcery dot com 2010-05-24 13:21
> -------
> I'm working on a patch that fixes the test case in comment #5 (originally
> filed
> as PR 39874) and some other test cases by improving the comparison combination
> logic in both tree-ssa-ifcombine and tree-ssa-reassoc.
>
> The test case in comment #4 is a somewhat different problem -- maybe it is a
> VRP failure? The problem is figuring out the right place to attempt to
> combine
> the comparisons....
In this case it is probably phiopt that could recognize this (though
it does not do the kind of transformation). It could transform
<bb 2>:
eq_5 = a_2(D) == b_3(D);
if (a_2(D) < b_3(D))
goto <bb 4>;
else
goto <bb 3>;
<bb 3>:
<bb 4>:
# eq_1 = PHI <1(2), eq_5(3)>
return eq_1;
to
<bb 2>:
if (a_2(D) <= b_3(D))
goto <bb 4>;
else
goto <bb 3>;
<bb 3>:
<bb 4>:
# eq_1 = PHI <1(2), 0(3)>
return eq_1;
and eventually further if-convert that.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28685
