pointers in c translated to assembly

Question

the code below as I understand it says store the pointer in %rsi in %eax if thats correct then the second line says add the pointer in %eax to the pointer in %rdi ?

very confused. I know assembly doesn't have pointers I am just speaking as translating assembly to c. I must write the assembly code into c code, and these two lines are killing me. Can I have clarification?

movl    (%rsi), %eax
addl    %eax, (%rdi)

Answer 1

Since you seem to be using using AT&T syntax, the parentheses dereference the value in %rsi . The C equivalent for these expressions would be:

/* Expression 1 */
unsigned int* p = some_address;
unsigned int i = *p; /* *p dereferences the address in p */


/* Expression 2 */
unsigned int* p = some_address;
unsigned int i = 8;
i += *p /* Increase i by the value pointed to by p */