http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51446
--- Comment #12 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2011-12-08 20:37:11 UTC --- I think the soft-fp code tries to generate particular target-specific NaNs because it's also used in the Linux kernel emulation of floating-point instructions - which is a use case where doing the same as particular hardware is desirable. At the level of GCC compiling C code, the compiler provides the language semantics. It doesn't provide the semantics of any particular choice of instructions someone might expect to be used to implement the source code - and in particular doesn't guarantee any choice of NaN where the language (and IEEE 754 as applicable) don't determine the choice of NaN.
