[PATCH 8/8] math: Use binary search on tgammaf slow path

[Wilco Dijkstra]

Hi Adhemerval,

> Hum, I am having some trouble to implement this approach.

This has multiple bugs in it...

>> +      while (a <= b)
>> +	{ /* Binary search.  */
>> +	  uint32_t tbi = asuint (tb[m].x);
>> +	  if (t == tbi)
>> +	    return tb[m].f + tb[m].df;
>> +	  else if (t > tbi)
>> +	    a = m + 1;         // this can read beyond the array in next iteration
>> +	  else
>> +	    b = m - 1;          // this skips m-1 due to b being 1 beyond the end
>> +	  m = (a + b) / 2;

Something like this should work (assumes array is not empty like above):
 
int a = 0, b = array_length (tb) - 1;
while (a < b)
 {
    m = (a + b) >> 1;
    tbi = asuint (tb[m].x);
    if (t > tbi)
      a = m + 1;
    else
      b = m;
 }
 if (t == asuint (tb[a].x))
   // found


Cheers,
Wilco