http://ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html
http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/Extended-Asm.html
http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/Constraints.html
http://ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html
http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/Extended-Asm.html
http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/Constraints.html