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      1 /* e_rem_pio2f.c -- float version of e_rem_pio2.c
      2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian (at) cygnus.com.
      3  * Debugged and optimized by Bruce D. Evans.
      4  */
      5 
      6 /*
      7  * ====================================================
      8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      9  *
     10  * Developed at SunPro, a Sun Microsystems, Inc. business.
     11  * Permission to use, copy, modify, and distribute this
     12  * software is freely granted, provided that this notice
     13  * is preserved.
     14  * ====================================================
     15  */
     16 
     17 #include <sys/cdefs.h>
     18 #if 0
     19 __FBSDID("$FreeBSD: head/lib/msun/src/e_rem_pio2f.c 336545 2018-07-20 12:42:24Z bde $");
     20 #endif
     21 
     22 /* __ieee754_rem_pio2fd(x,y)
     23  *
     24  * return the remainder of x rem pi/2 in *y
     25  * use double precision for everything except passing x
     26  * use __kernel_rem_pio2() for large x
     27  */
     28 
     29 #include <float.h>
     30 
     31 #include "math.h"
     32 #include "math_private.h"
     33 
     34 /*
     35  * invpio2:  53 bits of 2/pi
     36  * pio2_1:   first 25 bits of pi/2
     37  * pio2_1t:  pi/2 - pio2_1
     38  */
     39 
     40 static const double
     41 invpio2 =  6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
     42 pio2_1  =  1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
     43 pio2_1t =  1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
     44 
     45 #ifdef INLINE_REM_PIO2F
     46 static __inline __always_inline
     47 #endif
     48 int
     49 __ieee754_rem_pio2fd(float x, double *y)
     50 {
     51 	double w,r,fn;
     52 	double tx[1],ty[1];
     53 	float z;
     54 	int32_t e0,n,ix,hx;
     55 
     56 	GET_FLOAT_WORD(hx,x);
     57 	ix = hx&0x7fffffff;
     58     /* 33+53 bit pi is good enough for medium size */
     59 	if(ix<0x4dc90fdb) {		/* |x| ~< 2^28*(pi/2), medium size */
     60 	    fn = rnint((float_t)x*invpio2);
     61 	    n  = irint(fn);
     62 	    r  = x-fn*pio2_1;
     63 	    w  = fn*pio2_1t;
     64 	    *y = r-w;
     65 	    return n;
     66 	}
     67     /*
     68      * all other (large) arguments
     69      */
     70 	if(ix>=0x7f800000) {		/* x is inf or NaN */
     71 	    *y=x-x; return 0;
     72 	}
     73     /* set z = scalbn(|x|,ilogb(|x|)-23) */
     74 	e0 = (ix>>23)-150;		/* e0 = ilogb(|x|)-23; */
     75 	SET_FLOAT_WORD(z, ix - ((int32_t)(e0<<23)));
     76 	tx[0] = z;
     77 	n  =  __kernel_rem_pio2(tx,ty,e0,1,0);
     78 	if(hx<0) {*y = -ty[0]; return -n;}
     79 	*y = ty[0]; return n;
     80 }
     81