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)
24 lines
513 B
C
24 lines
513 B
C
#include "libm.h"
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double floor(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 || x == 0)
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return x;
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/* y = int(x) - x, where int(x) is an integer neighbor of x */
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if (u.i >> 63)
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y = (double)(x - 0x1p52) + 0x1p52 - x;
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else
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y = (double)(x + 0x1p52) - 0x1p52 - x;
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/* special case because of non-nearest rounding modes */
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if (e <= 0x3ff-1) {
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FORCE_EVAL(y);
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return u.i >> 63 ? -1 : 0;
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}
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if (y > 0)
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return x + y - 1;
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return x + y;
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}
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