src/libm/s_floor.c
author Sam Lantinga <slouken@libsdl.org>
Sat, 04 Nov 2017 15:53:19 -0700
changeset 11683 48bcba563d9c
parent 6044 35448a5ea044
child 11685 1788f503254d
permissions -rw-r--r--
Updated math code from the uClibc 0.9.33 release
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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/*
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 * floor(x)
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 * Return x rounded toward -inf to integral value
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 * Method:
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 *	Bit twiddling.
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 * Exception:
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 *	Inexact flag raised if x not equal to floor(x).
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 */
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/*#include <features.h>*/
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/* Prevent math.h from defining a colliding inline */
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#undef __USE_EXTERN_INLINES
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#include "math_libm.h"
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#include "math_private.h"
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static const double huge = 1.0e300;
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double floor(double x)
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{
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	int32_t i0,i1,j0;
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	u_int32_t i,j;
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	EXTRACT_WORDS(i0,i1,x);
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	j0 = ((i0>>20)&0x7ff)-0x3ff;
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	if(j0<20) {
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	    if(j0<0) { 	/* raise inexact if x != 0 */
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		if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
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		    if(i0>=0) {i0=i1=0;}
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		    else if(((i0&0x7fffffff)|i1)!=0)
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			{ i0=0xbff00000;i1=0;}
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		}
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	    } else {
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		i = (0x000fffff)>>j0;
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		if(((i0&i)|i1)==0) return x; /* x is integral */
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		if(huge+x>0.0) {	/* raise inexact flag */
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		    if(i0<0) i0 += (0x00100000)>>j0;
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		    i0 &= (~i); i1=0;
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		}
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	    }
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	} else if (j0>51) {
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	    if(j0==0x400) return x+x;	/* inf or NaN */
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	    else return x;		/* x is integral */
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	} else {
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	    i = ((u_int32_t)(0xffffffff))>>(j0-20);
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	    if((i1&i)==0) return x;	/* x is integral */
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	    if(huge+x>0.0) { 		/* raise inexact flag */
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		if(i0<0) {
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		    if(j0==20) i0+=1;
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		    else {
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			j = i1+(1<<(52-j0));
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			if(j<i1) i0 +=1 ; 	/* got a carry */
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			i1=j;
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		    }
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		}
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		i1 &= (~i);
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	    }
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	}
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	INSERT_WORDS(x,i0,i1);
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	return x;
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}
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libm_hidden_def(floor)