Fastftol.h

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// KB  8/21/2003  \Ken105\Include\Fastftol.h

#define __FASTFTOL_H

#ifndef _MAC
#define ASSEMBLER_OPTIMIZATIONS 1

#define FAST_ROUND(fx,x) \
   { \
      float __fx = (fx); \
      _asm fld __fx \
      _asm fistp x \
   } 
#else
#define FAST_ROUND(fx,x) {}
#endif

inline int fast_round( float d ) // this the fastest
{
#if ASSEMBLER_OPTIMIZATIONS
   int result;
   FAST_ROUND( d, result );
   return result;
#else
   if (d<0)
      return (int)(d-0.5f);
   else
      return (int)(d+0.5f);
#endif
}

inline int fast_ftol_unsigned( float d ) // extract the long from the IEEE float
{
// SXXX XXXX   XMMM MMMM   MMMM MMMM   MMMM MMMM
#ifdef _MAC  // KB: not needed for PowerPC
   return abs((int)d);
#else
   ULONG *ptr = (ULONG *)&d;
   int exp = ((*ptr & 0x7F800000) >> 23) - 127;
   int man =  (*ptr & 0x007FFFFF) | 0x00800000;
   exp = 23 - exp;
   if (exp > 0) {
      if (exp > 31)
         return 0;
      else
         return man >> exp;
   }
   else
      return man << -exp;
#endif
}

inline int fast_ftol_signed( float d ) // extract the long from the IEEE float
{
// SXXX XXXX   XMMM MMMM   MMMM MMMM   MMMM MMMM
#ifdef _MAC  // KB: not needed for PowerPC
   return (int)d;
#else
   ULONG *ptr = (ULONG *)&d;
   int exp = ((*ptr & 0x7F800000) >> 23) - 127;
   int man =  (*ptr & 0x007FFFFF) | 0x00800000;
   exp = 23 - exp;
   if (*ptr & 0x80000000) { // signed
      if (exp > 0) {
         if (exp > 31)
            return 0;
         else
            return -(man >> exp);
      }
      else
         return -(man << -exp);
   }
   else {
      if (exp > 0) {
         if (exp > 31)
            return 0;
         else
            return man >> exp;
      }
      else
         return man << -exp;
   }   
#endif
}

inline int fast_floor( float d ) // extract the long from the IEEE float
{
// SXXX XXXX   XMMM MMMM   MMMM MMMM   MMMM MMMM
   ULONG *ptr = (ULONG *)&d;
   int exp = ((*ptr & 0x7F800000) >> 23) - 127;
   int man =  (*ptr & 0x007FFFFF) | 0x00800000;
   exp = 23 - exp;
   if (*ptr & 0x80000000) { // signed
      if (exp > 0) {
         if (exp > 31)
            return -1;
         int i = man >> exp;
         if ((i << exp) == man)
            return -i;
         else
            return -(i+1);
      }
      else
         return -(man << -exp);
   }
   else {
      if (exp > 0) {
         if (exp > 31)
            return 0;
         else
            return man >> exp;
      }
      else
         return man << -exp;
   }   
}

#ifdef _MAC
#include <math.h>
inline float InverseSqrt(float a)
#else
inline __declspec(naked) float __fastcall InverseSqrt(float a)
#endif
{
#ifndef _MAC
   __asm {
         mov      eax, 0be6eb508h
         mov      DWORD PTR [esp-12],03fc00000h ;  1.5 on the stack
         sub      eax, DWORD PTR [esp+4]; a
         sub      DWORD PTR [esp+4], 800000h ; a/2 a=Y0
         shr      eax, 1     ; firs approx in eax=R0
         mov      DWORD PTR [esp-8], eax
         
         fld      DWORD PTR [esp-8] ;r
         fmul  st, st            ;r*r
         fld      DWORD PTR [esp-8] ;r
         fxch  st(1)
         fmul  DWORD PTR [esp+4];a ;r*r*y0
         fld      DWORD PTR [esp-12];load 1.5
         fld      st(0)
         fsub  st,st(2)          ;r1 = 1.5 - y1
         ;x1 = st(3)
         ;y1 = st(2)
         ;1.5 = st(1)
         ;r1 = st(0)
         
         fld      st(1)
         fxch  st(1)
         fmul  st(3),st       ; y2=y1*r1*...
         fmul  st(3),st       ; y2=y1*r1*r1
         fmulp st(4),st            ; x2=x1*r1
         fsub  st,st(2)               ; r2=1.5-y2
         ;x2=st(3)
         ;y2=st(2)
         ;1.5=st(1)
         ;r2 = st(0)
         
         fmul  st(2),st       ;y3=y2*r2*...
         fmul  st(3),st       ;x3=x2*r2
         fmulp st(2),st       ;y3=y2*r2*r2
         fxch  st(1)
         fsubp st(1),st       ;r3= 1.5 - y3
         ;x3 = st(1)
         ;r3 = st(0)
         fmulp st(1), st
         ret 4
   }
#else
   return 1.0f/(float)sqrt(a);
#endif //_MAC
}

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