Kip Macy wrote: My first guess would be that that is a binutils issue. In other words, the assembler might not be up to date with the compiler. Hm... no, this sounds like a compiler and/or code issue to me. %sil is apparently an AMD-64 register; it doesn't exist on any of the IA-32 or variants. Related GCC bug: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=10153 Dave