Signed number grief.

Projects Programming
20

I put this to some exercise:

#define FLP(pin)  {PORTD |= 1<<1; PORTD &=~1<<1;}

void setup(void) {
  PORTD &=~(1<<1);
  DDRD |= (1<<1);
}

const long deviceBits = 10;
const long deviceWordLength = 16;
const long deviceMask = -(1l << (deviceWordLength - 1));
const float deviceScaleFactor = 0.25;
int x=511;
float someFloatVariable;

void loop(void) {

  FLP(OUT_PIN); FLP(OUT_PIN);  FLP(OUT_PIN); //flip out pin
  if (x & deviceMask) {
    x |= deviceMask;
  }
  someFloatVariable = x * (deviceScaleFactor * (1.0/(1 << (deviceWordLength-deviceBits))));
  FLP(OUT_PIN); FLP(OUT_PIN); //flip out pin
  someFloatVariable = (signed short) ((x & 0x0200)?(x|(-1<<10)):x);
  FLP(OUT_PIN);
  delay(10);
}

Question: how much time does the floating point approach take than the integer shift approach?
1: less time;
2: the same;
3: 8x;
4: all the above.