http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51446
--- Comment #3 from lucier at math dot purdue.edu 2011-12-07 21:07:09 UTC --- I've looked through the code in real.c a bit (and perhaps the component of this bug report should be changed). It appears that do_divide, when given 0.0/0.0, calls get_canonical_qnan with sign=0 (line 816 in real.c), but divsd actually returns a qnan with sign bit = 1. Similarly, do_add when given Inf - Inf, calls get_canonical_qnan with sign bit = 0 (line 574 of real.c), while subsd returns a qnan with sign bit = 1. It seems that the sign bit in this situation should be target-dependent if you want the constants to match what the actual instructions will provide.
