http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52107
--- Comment #2 from Alan Modra <amodra at gmail dot com> 2012-02-03 23:17:36
UTC ---
.tc generates an 8-byte word in both cases, so no space saved in the toc. This
bit of code in rs6000_emit_move does the loads in DImode, then cse1 shows the
toc load being converted to a load immediate and it all goes downhill from
there.
/* 128-bit constant floating-point values on Darwin should really be
loaded as two parts. */
if (!TARGET_IEEEQUAD && TARGET_LONG_DOUBLE_128
&& mode == TFmode && GET_CODE (operands[1]) == CONST_DOUBLE)
{
/* DImode is used, not DFmode, because simplify_gen_subreg doesn't
know how to get a DFmode SUBREG of a TFmode. */
