Szabolcs Nagy
3fdf94ec51
- remove the HAVE_EFFICIENT_IRINT case: fn is an exact integer, so it can be converted to int32_t a bit more efficiently than with a cast (the rounding mode change can be avoided), but musl does not support this case on any arch. - __rem_pio2: use double_t where possible - __rem_pio2f: use less assignments to avoid stores on i386 - use unsigned int bit manipulation (and union instead of macros) - use hexfloat literals instead of named constants
69 lines
1.8 KiB
C
69 lines
1.8 KiB
C
/* origin: FreeBSD /usr/src/lib/msun/src/e_rem_pio2f.c */
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/*
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* Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected].
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* Debugged and optimized by Bruce D. Evans.
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*/
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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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/* __rem_pio2f(x,y)
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*
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* return the remainder of x rem pi/2 in *y
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* use double precision for everything except passing x
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* use __rem_pio2_large() for large x
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*/
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#include "libm.h"
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/*
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* invpio2: 53 bits of 2/pi
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* pio2_1: first 25 bits of pi/2
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* pio2_1t: pi/2 - pio2_1
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*/
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static const double
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invpio2 = 6.36619772367581382433e-01, /* 0x3FE45F30, 0x6DC9C883 */
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pio2_1 = 1.57079631090164184570e+00, /* 0x3FF921FB, 0x50000000 */
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pio2_1t = 1.58932547735281966916e-08; /* 0x3E5110b4, 0x611A6263 */
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int __rem_pio2f(float x, double *y)
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{
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union {float f; uint32_t i;} u = {x};
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double tx[1],ty[1],fn;
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uint32_t ix;
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int n, sign, e0;
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ix = u.i & 0x7fffffff;
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/* 25+53 bit pi is good enough for medium size */
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if (ix < 0x4dc90fdb) { /* |x| ~< 2^28*(pi/2), medium size */
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/* Use a specialized rint() to get fn. Assume round-to-nearest. */
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fn = x*invpio2 + 0x1.8p52;
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fn = fn - 0x1.8p52;
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n = (int32_t)fn;
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*y = x - fn*pio2_1 - fn*pio2_1t;
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return n;
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}
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if(ix>=0x7f800000) { /* x is inf or NaN */
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*y = x-x;
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return 0;
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}
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/* scale x into [2^23, 2^24-1] */
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sign = u.i>>31;
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e0 = (ix>>23) - (0x7f+23); /* e0 = ilogb(|x|)-23, positive */
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u.i = ix - (e0<<23);
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tx[0] = u.f;
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n = __rem_pio2_large(tx,ty,e0,1,0);
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if (sign) {
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*y = -ty[0];
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return -n;
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}
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*y = ty[0];
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return n;
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}
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