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Jul 26th, 2014
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C++ 0.39 KB | None | 0 0
  1. int __clzsi2(unsigned x)
  2. {
  3.   // This uses a binary search (counting down) algorithm from Hacker's Delight.
  4.    unsigned y;
  5.    int n = 32;
  6.    y = x >>16;  if (y != 0) {n = n -16;  x = y;}
  7.    y = x >> 8;  if (y != 0) {n = n - 8;  x = y;}
  8.    y = x >> 4;  if (y != 0) {n = n - 4;  x = y;}
  9.    y = x >> 2;  if (y != 0) {n = n - 2;  x = y;}
  10.    y = x >> 1;  if (y != 0) return n - 2;
  11.    return n - x;
  12. }
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