http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49257
--- Comment #13 from Richard Henderson <rth at gcc dot gnu.org> 2011-06-07
18:40:48 UTC ---
I apologize. The error you're seeing here is the sort that's
handled by the second #if section in libgcc's __floatdisf.
In particular,
/* Protect against double-rounding error.
Represent any low-order bits, that might be truncated by a bit that
won't be lost. The bit can go in anywhere below the rounding position
of the FSTYPE. A fixed mask and bit position handles all usual
configurations. */
if (! (- ((DWtype) 1 << FSIZE) < u
&& u < ((DWtype) 1 << FSIZE)))
This is because, while DF > 2*SF bits, DF < DI bits, so we've
already lost a bit while converting to DFmode.
This doesn't appear to be supportable inline without excessive code bloat.
