http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56788
--- Comment #7 from Marc Glisse <glisse at gcc dot gnu.org> --- Ah no, I was wrong, sorry about that: The VFRCZSS and VFRCZSD instructions extract the fractional portion of the single-/double-precision scalar floating-point value in an XMM register or 32- or 64-bit memory location and writes the result in the lower element of the destination register. The upper elements of the destination XMM register are unaffected by the operation, while the upper 128 bits of the corresponding YMM register are cleared to zeros http://support.amd.com/TechDocs/43479.pdf
