Function Calls

For external functions, it is necessary to:

1. Set up the arguments for the function call.

2. Call the function.

3. Retrieve the result and do any necessary final actions.

A function call involves the following:

1. Load arguments into registers:
   • For string literals, address in %edi:

     
        movl  $.LC12,%edi # addr of literal .LC12
     

   • For floating arguments, %xmm0

2. Execute a call instruction:

   
      call   sin
   

3. Floating results are returned in %xmm0. Integer results are returned in %eax or %rax.