------- Comment #2 from pinskia at gcc dot gnu dot org 2010-08-21 03:58 ------- How are they are not commutative with respect of the NaNs? Is it only when both are operands are NaNs, it causes an issue?
If I read your testcase correctly, x87 and SSE both don't do IEEE FP correctly with respect of NaNs. For multiply and add if either operand is a NaN, the result is also a NaN IIRC. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45365
