place where p was used was as an argument to printf and some_function and therefore it just moved it to rsi optimized away rcx register usage completely.
But then, if I assume that p was in rcx all along and try to use it (mov %rdx, %rcx), it gets garbage (4/n)
But then, if I assume that p was in rcx all along and try to use it (mov %rdx, %rcx), it gets garbage (4/n)
Comments
But, if you use a call-clobbered register such as rdi etc., you _will_ lose the variable value on a function call. https://godbolt.org/z/oq5cjPd34
GCC very kindly provides a warning here (5/n)