------- Comment #5 from steven at gcc dot gnu dot org 2006-04-27 20:46 -------
So I asked myself, why are we not catching this in vrp? I know we can derive
ranges from types, so why don't we derive a [0,1] range from the bitfield load?
It turns out that we make _all_ loads VARYING right away, so we end up with:
Value ranges after VRP:
b_1: ~[0B, 0B] EQUIVALENCES: { b_2 } (1 elements)
b_2: VARYING
D.1882_3: VARYING
D.1883_4: [0, 1] EQUIVALENCES: { } (0 elements)
D.1884_5: [0, +INF] EQUIVALENCES: { } (0 elements)
D.1885_6: [0, 127] EQUIVALENCES: { } (0 elements)
D.1886_7: [0, +INF] EQUIVALENCES: { } (0 elements)
ior (b)
{
<unnamed type> D.1886;
unsigned char D.1885;
signed char D.1884;
signed char D.1883;
<unnamed type> D.1882;
<bb 2>:
D.1882_3 = b_2->bit;
D.1883_4 = (signed char) D.1882_3;
D.1884_5 = D.1883_4 | 1;
D.1885_6 = (unsigned char) D.1884_5;
D.1886_7 = (<unnamed type>) D.1885_6;
b_2->bit = D.1886_7;
return;
}
where, at least so it seems to me, we could find something like,
D.1882_3: [0, 1] (etc.)
--
steven at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2006-02-18 18:24:49 |2006-04-27 20:46:04
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18031
