Do some datalab

LAB2-datalab/datalab-handout/bits.c

@@ -284,7 +284,7 @@ int isPositive(int x)
  */
 int isLessOrEqual(int x, int y)
 {
-  int val = ((x + ~y) >> 31)&1;
+  int val = ((x + ~y) >> 31) & 1;
   x = x >> 31;
   y = y >> 31;
   return ((x & 1) | !y) & (((x & 1) & !y) | (val));
@@ -368,7 +368,63 @@ 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)
 {
-  return 2;
-}
+  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)
+  {
+    uf_nosign = uf_nosign << 1 | sign;
+    return uf_nosign;
+  }
+  if ((uf_nosign >> 23) == 0xff)
+  {
+    return uf;
+  }
+  if ((exp >> 23) + 1 == 0xff)
+  {
+    return sign | 0x7f800000;
+  }
+  return sign | (((exp >> 23) + 1) << 23) | fraction;
+}