float_cast.h

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/*
** Copyright (C) 2001 Erik de Castro Lopo <erikd AT mega-nerd DOT com>
**
** Permission to use, copy, modify, distribute, and sell this file for any
** purpose is hereby granted without fee, provided that the above copyright
** and this permission notice appear in all copies.  No representations are
** made about the suitability of this software for any purpose.  It is
** provided "as is" without express or implied warranty.
*/

/* Version 1.1 */


/*============================================================================
**	On Intel Pentium processors (especially PIII and probably P4), converting
**	from float to int is very slow. To meet the C specs, the code produced by
**	most C compilers targeting Pentium needs to change the FPU rounding mode
**	before the float to int conversion is performed.
**
**	Changing the FPU rounding mode causes the FPU pipeline to be flushed. It
**	is this flushing of the pipeline which is so slow.
**
**	Fortunately the ISO C99 specifications define the functions lrint, lrintf,
**	llrint and llrintf which fix this problem as a side effect.
**
**	On Unix-like systems, the configure process should have detected the
**	presence of these functions. If they weren't found we have to replace them
**	here with a standard C cast.
*/

/*
**	The C99 prototypes for lrint and lrintf are as follows:
**
**		long int lrintf (float x) ;
**		long int lrint  (double x) ;
*/

/*	The presence of the required functions are detected during the configure
**	process and the values HAVE_LRINT and HAVE_LRINTF are set accordingly in
**	the config.h file.
*/

#if (HAVE_LRINT && HAVE_LRINTF)

	/*	These defines enable functionality introduced with the 1999 ISO C
	**	standard. They must be defined before the inclusion of math.h to
	**	engage them. If optimisation is enabled, these functions will be
	**	inlined. With optimisation switched off, you have to link in the
	**	maths library using -lm.
	*/

	#define	_ISOC9X_SOURCE	1
	#define _ISOC99_SOURCE	1

	#define	__USE_ISOC9X	1
	#define	__USE_ISOC99	1

	#include	<math.h>

#elif (defined (WIN32) || defined (_WIN32))

	#include	<math.h>

	/*	Win32 doesn't seem to have these functions.
	**	Therefore implement inline versions of these functions here.
	*/

	__inline long int
	lrint (double flt)
	{	int intgr;

		_asm
		{	fld flt
			fistp intgr
			};

		return intgr;
	}

	__inline long int
	lrintf (float flt)
	{	int intgr;

		_asm
		{	fld flt
			fistp intgr
		};

		return intgr;
	}

#else

	#warning "Don't have the functions lrint() and lrintf ()."
	#warning "Replacing these functions with a standard C cast."

	#include	<math.h>

	#define	lrint(dbl)		((int)(dbl))
	#define	lrintf(flt)		((int)(flt))

#endif