The %rip register on x86-64 is a special-purpose register that always holds the memory address of the next instruction to execute in the program's code segment.

• %rax: return value• %rsp: stack pointer• %rdi: 1st argument• %rsi: 2nd argument• %rdx: 3rd argument• %rcx: 4th argument• %r8: 5th argument• %r9: 6th argument

If one of those two expressions couldpossibly generate an error condition or a side effect, this could lead to invalidbehavior. Such is the case for our earlier example

The destination operand must be a register.

The ability of the leaq instruction to perform addition and limited forms ofmultiplication proves useful when compiling simple arithmetic expressions suchas this example.

local variables such as x are often kept in registers rather thanstored in memory locations. Register access is much faster than memory access.

we see that whatwe call “pointers” in C are simply addresses. Dereferencing a pointer involvescopying that pointer into a register, and then using this register in a memoryreference.