Some references: 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://drpaulcarter.com/pcasm/ Debugging assembly code with gdb: gdb ./inline-asm-SIMD-sum (gdb) break sum (gdb) run (gdb) display/i $pc (gdb) stepi (gdb) stepi