Comment # 8 on bug 1202727 from Petr Tesa������������k

Let me think...

One difference between the inline function and a global register value is that
the function contained an "asm volatile", so the compiler was not allowed to
re-order execution. Is KLP using the value of "current_stack_pointer" in a
context that might change %r15 by any chance?

If that's the case, you may have to save the stack pointer into another
variable like this:

    const unsigned long current_sp = current_stack_pointer

The "const" qualifier may be needed to tell the compiler that the value is
initialized once and never changed.