Szabolcs Nagy
1d5ba3bb5a
* use unsigned arithmetics on the representation * store arg reduction quotient in unsigned (so n%2 would work like n&1) * use different convention to pass the arg reduction bit to __tan (this argument used to be 1 for even and -1 for odd reduction which meant obscure bithacks, the new n&1 is cleaner) * raise inexact and underflow flags correctly for small x (tanl(x) may still raise spurious underflow for small but normal x) (this exception raising code increases codesize a bit, similar fixes are needed in many other places, it may worth investigating at some point if the inexact and underflow flags are worth raising correctly as this is not strictly required by the standard) * tanf manual reduction optimization is kept for now * tanl code path is cleaned up to follow similar logic to tan and tanf
65 lines
1.7 KiB
C
65 lines
1.7 KiB
C
/* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */
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/*
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* Conversion to float by Ian Lance Taylor, Cygnus Support, [email protected].
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* 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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#include "libm.h"
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/* Small multiples of pi/2 rounded to double precision. */
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static const double
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t1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
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t2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
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t3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
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t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
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float tanf(float x)
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{
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double y;
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uint32_t ix;
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unsigned n, sign;
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GET_FLOAT_WORD(ix, x);
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sign = ix >> 31;
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ix &= 0x7fffffff;
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if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */
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if (ix < 0x39800000) { /* |x| < 2**-12 */
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/* raise inexact if x!=0 and underflow if subnormal */
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FORCE_EVAL(ix < 0x00800000 ? x/0x1p120f : x+0x1p120f);
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return x;
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}
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return __tandf(x, 0);
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}
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if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */
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if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */
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return __tandf((sign ? x+t1pio2 : x-t1pio2), 1);
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else
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return __tandf((sign ? x+t2pio2 : x-t2pio2), 0);
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}
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if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */
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if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */
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return __tandf((sign ? x+t3pio2 : x-t3pio2), 1);
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else
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return __tandf((sign ? x+t4pio2 : x-t4pio2), 0);
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}
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/* tan(Inf or NaN) is NaN */
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if (ix >= 0x7f800000)
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return x - x;
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/* argument reduction */
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n = __rem_pio2f(x, &y);
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return __tandf(y, n&1);
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}
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