------- 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 ([EMAIL PROTECTED])
* 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.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35885
