For a C function having the general structure

A. What value does rfun store in the callee-saved register %rbx?

B. Fill in the missing expressions in the C code shown above.

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long rfun (unsigned long x) { if ( ) } return 1 2 3 4 5 6 7 8 9 10 11 12 unsigned long nx = long rv = rfun (nx); return ; GCC generates the following assembly code: long rfun (unsigned long x) x in %rdi rfun: pushq movq movl testq je shrq call addq .L2: popq ret %rbx %rdi, %rbx $0, %eax %rdi, %rdi .L2 $2, %rdi rfun rbx, rax %rbx