Update float_twice

LAB2-datalab/datalab-handout/bits.c

@@ -368,63 +368,28 @@ unsigned float_i2f(int x)
  *   Max ops: 30
  *   Rating: 4
  */
-// unsigned float_twice(unsigned uf)
-// {
-//   // INF and NaN judge
-//   int expMask, exp, sign, signMask, frac, fracMask, uf_nosign;
-//   expMask = 0x7f800000; // get exponent bits
-//   exp = (uf & expMask);
-//   if (exp == expMask)
-//   {
-//     return uf;
-//   }
-//   // Special numbers
-//   signMask = 0x80000000; // get sign bit
-//   sign = (uf & signMask) >> 31;
-//   fracMask = 0x007fffff; // get fraction bits
-//   frac = uf & fracMask;
-//   if (sign == 0 && frac == 0) // Zero, just return 0
-//   {
-//     return 0;
-//   }
-//   // Denormalizd numbers
-//   uf_nosign = uf & 0x7fffffff; // remove sign bit
-//   if ((uf_nosign >> 23) == 0)
-//   {
-//     uf_nosign = uf_nosign << 1 | sign;
-//     return uf_nosign;
-//   }
-//   // Normalized numbers
-//   if (uf_nosign >> 23 == 0xff) //？？
-//   {
-//     return uf;
-//   }
-//   if ((exp >> 23) + 1 == 0xff)
-//   {
-//     return sign | 0x7f800000;
-//   }
-//   return sign | ((exp >> 23) + 1) << 23 | frac << 1;
-// }
 
 unsigned float_twice(unsigned uf)
 {
   int uf_nosign;
-  int sign = uf & 0x80000000;         // sign bit
-  int exp = uf & 0x7f800000;          // exponent bits
-  int fraction = uf & 0x7fffff;       // fraction bits
-  uf_nosign = uf & 0x7fffffff; // remove sign
-  if ((uf_nosign >> 23) == 0x0)
+  int sign = uf & 0x80000000;   // sign bit
+  int exp = uf & 0x7f800000;    // exponent bits
+  int fraction = uf & 0x7fffff; // fraction bits
+  uf_nosign = uf & 0x7fffffff;  // remove sign
+  if ((uf_nosign >> 23) == 0x0) // denormalized condition
   {
     uf_nosign = uf_nosign << 1 | sign;
     return uf_nosign;
   }
-  if ((uf_nosign >> 23) == 0xff)
+  if ((uf_nosign >> 23) == 0xff) // special numbers (NaN and infty)
   {
     return uf;
   }
-  if ((exp >> 23) + 1 == 0xff)
+  // if ((exp >> 23) + 1 == 0xff) // exponent overflow
+  if (exp == 0x7f000000) // exponent overflow
   {
     return sign | 0x7f800000;
   }
-  return sign | (((exp >> 23) + 1) << 23) | fraction;
+  // return sign | (((exp >> 23) + 1) << 23) | fraction;
+  return sign | (exp + 0x800000) | fraction;
 }