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From: "amylaar at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/52267] a&~N where N has all the bits set up till a specific point can be folded to ((unsigned)a) < N
Date: Sat, 29 Jun 2013 20:08:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52267

--- Comment #9 from Jorn Wolfgang Rennecke <amylaar at gcc dot gnu.org> ---
(In reply to Jorn Wolfgang Rennecke from comment #8)
> (In reply to Georg-Johann Lay from comment #7)
> 
> > I just rediced the test case to find this thinko; I don't know if there are
> > more because of the sheer amount of values in this program.
> 
> Here is a summary of the failing subtests / iteration counts:
> f2,f1: i == 6,7
> f4,f5,f3: i == 13,15,16,24,25,31
> f7,f8,f6: i == 10..12,23
> f11,f9: i == 11,13,15,24,25,31
> f12,f10: i == 11,13,15,24,25,26,31
> f17: i == 12,13
> f21: i == 21,22,38..45

I've tried to shift/mask the values / tests to fit 16 bit ints while keeping
to the spirit of the tests and leaving the int >= 32 bit case unchanged,
but the various leading bits, 0000/ffff masking, and 16 bit value comparisons
are just to intertwined for this to make any sense.

I think we should simply restrict the test to target { ! int16 } .