[Bug middle-end/35885] unsigned long long and while loop evaluation regression?

["wilson at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #5 from wilson at gcc dot gnu dot org  2008-04-15 00:25 -------
Gcc-2.5.8 uses the code I suggested was correct.  gcc-2.6.3 does not.  The
ChangeLog entry is

Fri Aug  5 12:29:42 1994  Jim Wilson  (wilson@cygnus.com)

        * expmed.c (expand_mult): Accept DImode for synth_mult only if
        CONST_DOUBLE_HIGH is zero.  Reject negative values for synth_mult
        if the mode is larger than HOST_BITS_PER_INT.  Don't do the
        negate_variant if the mode is larger than HOST_BITS_PER_INT.

So it seems that we used to allow any constant that would fit in a signed HWI,
then I found a bug with negative values so I changed it to any constant that
would fit in an unsigned HWI.  Now we found another bug with a constant that
doesn't fit in a signed HWI but does fit in an unsigned HWI.

So now the apparent solution is to only accept positive values that fit in a
signed HWI.  But of course such values should never be found in a CONST_DOUBLE
anyways.  If they fit in a signed HWI they would have been emitted as a
CONST_INT in the first place.  I think we should just drop all of this
CONST_DOUBLE nonsense.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35885