Annotation of src/lib/libm/src/s_floor.c, Revision 1.13.6.1
1.1 jtc 1: /* @(#)s_floor.c 5.1 93/09/24 */
2: /*
3: * ====================================================
4: * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5: *
6: * Developed at SunPro, a Sun Microsystems, Inc. business.
7: * Permission to use, copy, modify, and distribute this
1.10 simonb 8: * software is freely granted, provided that this notice
1.1 jtc 9: * is preserved.
10: * ====================================================
11: */
1.3 jtc 12:
1.9 lukem 13: #include <sys/cdefs.h>
1.7 jtc 14: #if defined(LIBM_SCCS) && !defined(lint)
1.13.6.1! yamt 15: __RCSID("$NetBSD: s_floor.c,v 1.13 2009/02/16 01:27:36 lukem Exp $");
1.3 jtc 16: #endif
1.1 jtc 17:
18: /*
19: * floor(x)
20: * Return x rounded toward -inf to integral value
21: * Method:
22: * Bit twiddling.
23: * Exception:
24: * Inexact flag raised if x not equal to floor(x).
25: */
26:
1.5 jtc 27: #include "math.h"
28: #include "math_private.h"
1.1 jtc 29:
1.13.6.1! yamt 30: #ifndef __HAVE_LONG_DOUBLE
! 31: __strong_alias(_floorl, floor)
! 32: __weak_alias(floorl, floor)
! 33: #endif
! 34:
1.4 jtc 35: static const double huge = 1.0e300;
1.1 jtc 36:
1.11 wiz 37: double
38: floor(double x)
1.1 jtc 39: {
1.12 christos 40: int32_t i0,i1,jj0;
1.6 jtc 41: u_int32_t i,j;
1.5 jtc 42: EXTRACT_WORDS(i0,i1,x);
1.12 christos 43: jj0 = ((i0>>20)&0x7ff)-0x3ff;
44: if(jj0<20) {
45: if(jj0<0) { /* raise inexact if x != 0 */
1.1 jtc 46: if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
1.10 simonb 47: if(i0>=0) {i0=i1=0;}
1.1 jtc 48: else if(((i0&0x7fffffff)|i1)!=0)
49: { i0=0xbff00000;i1=0;}
50: }
51: } else {
1.12 christos 52: i = (0x000fffff)>>jj0;
1.1 jtc 53: if(((i0&i)|i1)==0) return x; /* x is integral */
54: if(huge+x>0.0) { /* raise inexact flag */
1.12 christos 55: if(i0<0) i0 += (0x00100000)>>jj0;
1.1 jtc 56: i0 &= (~i); i1=0;
57: }
58: }
1.12 christos 59: } else if (jj0>51) {
60: if(jj0==0x400) return x+x; /* inf or NaN */
1.1 jtc 61: else return x; /* x is integral */
62: } else {
1.12 christos 63: i = ((u_int32_t)(0xffffffff))>>(jj0-20);
1.1 jtc 64: if((i1&i)==0) return x; /* x is integral */
65: if(huge+x>0.0) { /* raise inexact flag */
66: if(i0<0) {
1.12 christos 67: if(jj0==20) i0+=1;
1.1 jtc 68: else {
1.12 christos 69: j = i1+(1<<(52-jj0));
1.13 lukem 70: if(j<(u_int32_t)i1) i0 +=1 ; /* got a carry */
1.1 jtc 71: i1=j;
72: }
73: }
74: i1 &= (~i);
75: }
76: }
1.5 jtc 77: INSERT_WORDS(x,i0,i1);
1.1 jtc 78: return x;
79: }
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