ECE 422 day11

/*
 * ECE 422
 * Calling functions
 */


/*
 * Global variables placed in SRAMj
 */
volatile char a, b, c, d;
volatile int out;  // holds function return values



/*
 * The "__attribute__ ((noinline))" business is GCC-specific syntax
 * saying to NOT optimize by inlining the code at the point of use.
 * We *want* to see the rcall / ret happening!
 * 
 * https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
 */
char __attribute__ ((noinline)) fOne(char first) {
  return first + 1;
}


char __attribute__ ((noinline)) fTwo(char first, char second) {
  return first + second + 1;
}


char __attribute__ ((noinline)) fThree(char first, char second, char third) {
  return first + second + third + 1;
}


char __attribute__ ((noinline)) fFour(char first, char second, char third, char fourth) {
  return first + second + third + fourth + 1;
}




void setup() {
  pinMode(LED_BUILTIN, OUTPUT);

  a = 2;
  b = 4;
  c = 16;
  d = 64;
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second

  // call function with one 8b argument
  out = fOne(a);

  // call function with two 8b arguments
  out = fTwo(a, b);

  // call function with three 8b arguments
  out = fThree(a, b, c);

  // call function with four 8b arguments
  out = fFour(a, b, c, d);
}