47 lines
1.1 KiB
C
47 lines
1.1 KiB
C
#include <limits.h>
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#include <fenv.h>
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#include "libm.h"
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/*
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If the result cannot be represented (overflow, nan), then
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lrint raises the invalid exception.
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Otherwise if the input was not an integer then the inexact
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exception is raised.
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C99 is a bit vague about whether inexact exception is
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allowed to be raised when invalid is raised.
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(F.9 explicitly allows spurious inexact exceptions, F.9.6.5
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does not make it clear if that rule applies to lrint, but
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IEEE 754r 7.8 seems to forbid spurious inexact exception in
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the ineger conversion functions)
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So we try to make sure that no spurious inexact exception is
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raised in case of an overflow.
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If the bit size of long > precision of double, then there
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cannot be inexact rounding in case the result overflows,
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otherwise LONG_MAX and LONG_MIN can be represented exactly
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as a double.
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*/
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#if LONG_MAX < 1U<<53 && defined(FE_INEXACT)
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long lrint(double x)
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{
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#pragma STDC FENV_ACCESS ON
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int e;
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e = fetestexcept(FE_INEXACT);
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x = rint(x);
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if (!e && (x > LONG_MAX || x < LONG_MIN))
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feclearexcept(FE_INEXACT);
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/* conversion */
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return x;
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}
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#else
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long lrint(double x)
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{
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return rint(x);
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}
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#endif
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