[PATCH] [COMPILER-RT] Implement long double comparison functions

[Joerg Sonnenberger]

  Can you add a define similar to CRT_HAS_128BIT to flag whether a platform should use this code? x86_64 uses 80bit long double, so it doesn't match. Checking __LDBL_MANT_DIG__ == 113 or so would be a good first approximiation.

http://llvm-reviews.chandlerc.com/D2797