beetle-psx-libretro/mednafen/math_ops.h

#ifndef __MDFN_MATH_OPS_H
#define __MDFN_MATH_OPS_H

#ifdef _MSC_VER
#include <intrin.h>
#endif

//
// Result is defined for all possible inputs(including 0).
//
static INLINE unsigned MDFN_lzcount32(uint32 v)
{
 #if defined(__GNUC__) || defined(__clang__) || defined(__ICC) || defined(__INTEL_COMPILER)
 return v ? __builtin_clz(v) : 32;
 #elif defined(_MSC_VER)
 unsigned long idx;

 if(!v)
  return 32;

 _BitScanReverse(&idx, v);

 return 31 - idx;
 #else
 unsigned ret = 0;

 if(!v)
  return(32);

 if(!(v & 0xFFFF0000))
 {
  v <<= 16;
  ret += 16;
 }

 if(!(v & 0xFF000000))
 {
  v <<= 8;
  ret += 8;
 }

 if(!(v & 0xF0000000))
 {
  v <<= 4;
  ret += 4;
 }

 if(!(v & 0xC0000000))
 {
  v <<= 2;
  ret += 2;
 }

 if(!(v & 0x80000000))
 {
  v <<= 1;
  ret += 1;
 }

 return(ret);
 #endif
}

// Source: http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
// Rounds up to the nearest power of 2.
static INLINE uint32 round_up_pow2(uint32 v)
{
 v--;
 v |= v >> 1;
 v |= v >> 2;
 v |= v >> 4;
 v |= v >> 8;
 v |= v >> 16;
 v++;

 v += (v == 0);

 return(v);
}

// Some compilers' optimizers and some platforms might fubar the generated code from these macros,
// so some tests are run in...tests.cpp
#define sign_8_to_s16(_value) ((int16)(int8)(_value))
#define sign_9_to_s16(_value)  (((int16)((unsigned int)(_value) << 7)) >> 7)
#define sign_10_to_s16(_value)  (((int16)((uint32)(_value) << 6)) >> 6)
#define sign_11_to_s16(_value)  (((int16)((uint32)(_value) << 5)) >> 5)
#define sign_12_to_s16(_value)  (((int16)((uint32)(_value) << 4)) >> 4)
#define sign_13_to_s16(_value)  (((int16)((uint32)(_value) << 3)) >> 3)
#define sign_14_to_s16(_value)  (((int16)((uint32)(_value) << 2)) >> 2)
#define sign_15_to_s16(_value)  (((int16)((uint32)(_value) << 1)) >> 1)

// This obviously won't convert higher-than-32 bit numbers to signed 32-bit ;)
// Also, this shouldn't be used for 8-bit and 16-bit signed numbers, since you can
// convert those faster with typecasts...
#define sign_x_to_s32(_bits, _value) (((int32)((uint32)(_value) << (32 - _bits))) >> (32 - _bits))

#endif