irrlicht/source/Irrlicht/irrMathFastCompat.h

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// This file is part of the "Irrlicht Engine".
// For conditions of distribution and use, see copyright notice in irrlicht.h
#ifndef __IRR_FAST_MATH_COMPAT_H_INCLUDED__
#define __IRR_FAST_MATH_COMPAT_H_INCLUDED__
#include "irrMath.h"
namespace irr
{
namespace core
{
// IRRLICHT_FAST_MATH functions which I wanted to kick out because they return
// wrong results. But last time I proposed that I've been asked to keep them for
// Burnings software renderer. So to avoid changing that accidentally or messing up
// it's speed I'll keep them around, but only as internal header.
// They should not be used otherwise any longer.
// Some examples for unexpected results when using this with IRRLICHT_FAST_MATH:
// Input 1, expected 1, got 0
// Input 3, expected 3, got 2
// Input -1.40129846e-45, expected -1, got 0
REALINLINE s32 floor32_fast(f32 x)
{
#ifdef IRRLICHT_FAST_MATH
const f32 h = 0.5f;
s32 t;
#if defined(_MSC_VER) && !defined(_WIN64)
__asm
{
fld x
fsub h
fistp t
}
#elif defined(__GNUC__)
__asm__ __volatile__ (
"fsub %2 \n\t"
"fistpl %0"
: "=m" (t)
: "t" (x), "f" (h)
: "st"
);
#else
return (s32) floorf ( x );
#endif
return t;
#else // no fast math
return (s32) floorf ( x );
#endif
}
// Some examples for unexpected results when using this with IRRLICHT_FAST_MATH:
// Input 1.40129846e-45, expected 1, got 0
// Input -1, expected -1, got 0
// Input -3, expected -3, got -2
REALINLINE s32 ceil32_fast ( f32 x )
{
#ifdef IRRLICHT_FAST_MATH
const f32 h = 0.5f;
s32 t;
#if defined(_MSC_VER) && !defined(_WIN64)
__asm
{
fld x
fadd h
fistp t
}
#elif defined(__GNUC__)
__asm__ __volatile__ (
"fadd %2 \n\t"
"fistpl %0 \n\t"
: "=m"(t)
: "t"(x), "f"(h)
: "st"
);
#else
return (s32) ceilf ( x );
#endif
return t;
#else // not fast math
return (s32) ceilf ( x );
#endif
}
// Some examples for unexpected results when using this with IRRLICHT_FAST_MATH:
// Input 0.5, expected 1, got 0
// Input 2.5, expected 3, got 2
// Input -1.40129846e-45, expected -nan(ind), got -inf
// Input -2.80259693e-45, expected -nan(ind), got -inf
REALINLINE s32 round32_fast(f32 x)
{
#if defined(IRRLICHT_FAST_MATH)
s32 t;
#if defined(_MSC_VER) && !defined(_WIN64)
__asm
{
fld x
fistp t
}
#elif defined(__GNUC__)
__asm__ __volatile__ (
"fistpl %0 \n\t"
: "=m"(t)
: "t"(x)
: "st"
);
#else
return (s32) round_(x);
#endif
return t;
#else // no fast math
return (s32) round_(x);
#endif
}
} // end namespace core
} // end namespace irr
#endif // __IRR_FAST_MATH_COMPAT_H_INCLUDED__