xor %rdx,%rdx # clear any descriptor registers
xor %rdi,%rdi # that we can't be sure we'll
xor %rsi,%rsi # initialise properly. XX do r8-r15 too?
xor %rdx,%rdx # clear any descriptor registers
xor %rdi,%rdi # that we can't be sure we'll
xor %rsi,%rsi # initialise properly. XX do r8-r15 too?