This comment suggests that #DF is rarely used anyway https://lkml.org/lkml/2008/3/6/50 https://lkml.org/lkml/2008/3/6/50 > The conclusion is that DF=1 in x86_6

This comment suggests that #DF is rarely used anyway https://lkml.org/lkml/2008/3/6/50 https://lkml.org/lkml/2008/3/6/50 > The conclusion is that DF=1 in x86_64 64-bit code is extremely rare