152 lines
4.0 KiB
C
152 lines
4.0 KiB
C
/*
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** Copyright (C) 2001 Erik de Castro Lopo <erikd AT mega-nerd DOT com>
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**
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** Permission to use, copy, modify, distribute, and sell this file for any
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** purpose is hereby granted without fee, provided that the above copyright
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** and this permission notice appear in all copies. No representations are
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** made about the suitability of this software for any purpose. It is
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** provided "as is" without express or implied warranty.
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*/
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/* Version 1.1 */
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/*============================================================================
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** On Intel Pentium processors (especially PIII and probably P4), converting
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** from float to int is very slow. To meet the C specs, the code produced by
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** most C compilers targeting Pentium needs to change the FPU rounding mode
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** before the float to int conversion is performed.
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**
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** Changing the FPU rounding mode causes the FPU pipeline to be flushed. It
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** is this flushing of the pipeline which is so slow.
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**
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** Fortunately the ISO C99 specifications define the functions lrint, lrintf,
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** llrint and llrintf which fix this problem as a side effect.
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**
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** On Unix-like systems, the configure process should have detected the
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** presence of these functions. If they weren't found we have to replace them
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** here with a standard C cast.
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*/
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/*
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** The C99 prototypes for lrint and lrintf are as follows:
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**
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** long int lrintf (float x) ;
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** long int lrint (double x) ;
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*/
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/* The presence of the required functions are detected during the configure
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** process and the values HAVE_LRINT and HAVE_LRINTF are set accordingly in
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** the config.h file.
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*/
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#if (defined (WIN32) || defined (_WIN32)) && defined(_MSC_VER) && defined(_M_IX86)
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// As of Visual Studio 2019 16.9, these functions have been made intrinsic and the build
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// will fail. Unfortunately, the intrinsic versions run a LOT slower than the ones
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// below, so force the compiler to use ours instead.
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#pragma function( lrint, lrintf )
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// Including math.h allows us to use the inline assembler versions without
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// producing errors in newer Visual Studio versions.
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// Without the include, we get different linkage error messages.
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// Without the inline assembler versions, these functions are VERY slow.
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// I also see that the include was part of the original source for this file:
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// http://www.mega-nerd.com/FPcast/
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#include <math.h>
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/* Win32 doesn't seem to have these functions.
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** Therefore implement inline versions of these functions here.
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*/
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__inline long int
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lrint (double flt)
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{ int intgr;
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_asm
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{ fld flt
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fistp intgr
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} ;
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return intgr ;
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}
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__inline long int
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lrintf (float flt)
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{ int intgr;
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_asm
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{ fld flt
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fistp intgr
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} ;
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return intgr ;
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}
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__inline long long int
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llrint (double flt)
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{ long long int intgr;
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_asm
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{ fld flt
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fistp intgr
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} ;
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return intgr ;
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}
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__inline long long int
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llrintf (float flt)
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{ long long int intgr;
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_asm
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{ fld flt
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fistp intgr
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} ;
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return intgr ;
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}
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#elif (defined (WIN32) || defined (_WIN32)) && defined(_M_3X64)
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#include <math.h>
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#include <immintrin.h>
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__inline long int
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lrintf (float flt)
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{
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return _mm_cvt_ss2si(_mm_set_ss(flt));
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}
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#elif (HAVE_LRINT && HAVE_LRINTF)
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/* These defines enable functionality introduced with the 1999 ISO C
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** standard. They must be defined before the inclusion of math.h to
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** engage them. If optimisation is enabled, these functions will be
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** inlined. With optimisation switched off, you have to link in the
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** maths library using -lm.
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*/
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#define _ISOC9X_SOURCE 1
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#define _ISOC99_SOURCE 1
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#define __USE_ISOC9X 1
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#define __USE_ISOC99 1
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#include <math.h>
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#else
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/* dmazzoni: modified these to do a proper rounding, even though
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* it's slower. Correctness and consistency is more important
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* than speed, especially since lrint/lrintf are certainly not
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* available everywhere.
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*
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* MM: Now uses internal math.h rint() function
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*/
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#include <math.h>
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#define lrint(dbl) ((int)rint(dbl))
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#define lrintf(flt) ((int)rint(flt))
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#endif
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