Add floats (non negative)

floatadd.c

// DOES NOT WORK ON NEGATIVE VALUES !! :P

#include <stdio.h>

union MyFloat {
  float fv;
  struct {
    unsigned mantissa: 23;
    unsigned exponent: 8;
    unsigned sign: 1;
  } bv;
}
typedef MyFloat;

#define IMPLICIT_ONE (1u << 23u)

void dump(MyFloat f, const char *name) {
  int x = ((int)f.bv.exponent - 127 - 23);
  if (x < 0) { 
      x *= -1;
      x = (f.bv.mantissa + IMPLICIT_ONE) >> x;
  } else {
      x = (f.bv.mantissa + IMPLICIT_ONE) << x;
  }

  printf("%s: %b %08b %d%023b %d\n", name, f.bv.sign, f.bv.exponent, f.bv.exponent > 0, f.bv.mantissa, x);
}

MyFloat fadd(MyFloat a, MyFloat b) {
  if (a.bv.exponent <= b.bv.exponent) {
    MyFloat tmp = a;
    a = b;
    b = tmp;
  }

  unsigned am = ((a.bv.exponent == 0) ? (a.bv.mantissa) : (a.bv.mantissa + IMPLICIT_ONE));
  unsigned bm = ((b.bv.exponent == 0) ? (b.bv.mantissa) : (b.bv.mantissa + IMPLICIT_ONE));

  unsigned diff = a.bv.exponent-b.bv.exponent;
  
  unsigned new_mantissa = am + (bm >> diff);

  if (new_mantissa >= (IMPLICIT_ONE << 1)) {
    a.bv.exponent += 1;
    new_mantissa &= ~IMPLICIT_ONE;
    new_mantissa >>= 1;
  }

  return (MyFloat){.bv = {new_mantissa, a.bv.exponent, (a.bv.sign|b.bv.sign)}};
}

int main() {
  MyFloat a = {9.234234};
  MyFloat b = {2.934234};

  dump(a, "a");
  printf("%f + %f = %f\n", a.fv, b.fv, fadd(a, b).fv);
}