d1a2ead878
* faster, smaller, cleaner implementation than the bit hacks of fdlibm * use arithmetics like y=(double)(x+0x1p52)-0x1p52, which is an integer neighbor of x in all rounding modes (0<=x<0x1p52) and only use bithacks when that's faster and smaller (for float it usually is) * the code assumes standard excess precision handling for casts * long double code supports both ld80 and ld128 * nearbyint is not changed (it is a wrapper around rint)
28 lines
446 B
C
28 lines
446 B
C
#include "libm.h"
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double round(double x)
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{
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union {double f; uint64_t i;} u = {x};
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int e = u.i >> 52 & 0x7ff;
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double_t y;
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if (e >= 0x3ff+52)
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return x;
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if (u.i >> 63)
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x = -x;
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if (e < 0x3ff-1) {
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/* raise inexact if x!=0 */
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FORCE_EVAL(x + 0x1p52);
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return 0*u.f;
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}
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y = (double)(x + 0x1p52) - 0x1p52 - 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 >> 63)
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y = -y;
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return y;
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}
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