OpenDX/src/util/util_bit.h

#pragma once

#ifndef _MSC_VER
#include <x86intrin.h>
#else
#include <intrin.h>
#endif

namespace dxvk::bit {
  
  template<typename T>
  T extract(T value, uint32_t fst, uint32_t lst) {
    return (value >> fst) & ~(~T(0) << (lst - fst + 1));
  }
  
  template<typename T>
  T popcnt(T value) {
    return value != 0
      ? (value & 1) + popcnt(value >> 1)
      : 0;
  }
  
  inline uint32_t tzcnt(uint32_t n) {
    #if defined(_MSC_VER)
    return _tzcnt_u32(n);
    #elif defined(__BMI__)
    return __tzcnt_u32(n);
    #elif defined(__GNUC__)
    uint32_t res;
    uint32_t tmp;
    asm (
      "mov  $32, %1;"
      "bsf   %2, %0;"
      "cmovz %1, %0;"
      : "=&r" (res), "=&r" (tmp)
      : "r" (n));
    return res;
    #else
    uint32_t r = 31;
    n &= -n;
    r -= (n & 0x0000FFFF) ? 16 : 0;
    r -= (n & 0x00FF00FF) ?  8 : 0;
    r -= (n & 0x0F0F0F0F) ?  4 : 0;
    r -= (n & 0x33333333) ?  2 : 0;
    r -= (n & 0x55555555) ?  1 : 0;
    return n != 0 ? r : 32;
    #endif
  }
  
}