Szabolcs NagyandRich Felker
0ce946cf80
the idiomatic rounding of x is n = x + toint - toint; where toint is either 1/EPSILON (x is non-negative) or 1.5/EPSILON (x may be negative and nearest rounding mode is assumed) and EPSILON is according to the evaluation precision (the type of toint is not very important, because single precision float can represent the 1/EPSILON of ieee binary128). in case of FLT_EVAL_METHOD!=0 this avoids a useless store to double or float precision, and the long double code became cleaner with 1/LDBL_EPSILON instead of ifdefs for toint. __rem_pio2f and __rem_pio2 functions slightly changed semantics: on i386 a double-rounding is avoided so close to half-way cases may get evaluated differently eg. as sin(pi/4-eps) instead of cos(pi/4+eps)
38 lines
659 B
C
38 lines
659 B
C
#include "libm.h"
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#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
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long double roundl(long double x)
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{
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return round(x);
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}
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#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
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static const long double toint = 1/LDBL_EPSILON;
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long double roundl(long double x)
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{
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union ldshape u = {x};
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int e = u.i.se & 0x7fff;
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long double y;
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if (e >= 0x3fff+LDBL_MANT_DIG-1)
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return x;
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if (u.i.se >> 15)
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x = -x;
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if (e < 0x3fff-1) {
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FORCE_EVAL(x + toint);
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return 0*u.f;
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}
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y = x + toint - toint - x;
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if (y > 0.5)
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y = y + x - 1;
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else if (y <= -0.5)
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y = y + x + 1;
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else
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y = y + x;
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if (u.i.se >> 15)
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y = -y;
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return y;
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}
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#endif
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