mirror of git://gcc.gnu.org/git/gcc.git
64 lines
1.1 KiB
C
64 lines
1.1 KiB
C
#include "quadmath-imp.h"
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#include <math.h>
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#include <float.h>
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__float128
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sqrtq (const __float128 x)
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{
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__float128 y;
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int exp;
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if (isnanq (x) || (isinfq (x) && x > 0))
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return x;
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if (x == 0)
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return x;
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if (x < 0)
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{
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/* Return NaN with invalid signal. */
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return (x - x) / (x - x);
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}
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if (x <= DBL_MAX && x >= DBL_MIN)
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{
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/* Use double result as starting point. */
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y = sqrt ((double) x);
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/* Two Newton iterations. */
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y -= 0.5q * (y - x / y);
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y -= 0.5q * (y - x / y);
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return y;
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}
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#ifdef HAVE_SQRTL
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{
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long double xl = (long double) x;
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if (xl <= LDBL_MAX && xl >= LDBL_MIN)
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{
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/* Use long double result as starting point. */
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y = (__float128) sqrtl (xl);
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/* One Newton iteration. */
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y -= 0.5q * (y - x / y);
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return y;
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}
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}
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#endif
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/* If we're outside of the range of C types, we have to compute
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the initial guess the hard way. */
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y = frexpq (x, &exp);
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if (exp % 2)
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y *= 2, exp--;
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y = sqrt (y);
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y = scalbnq (y, exp / 2);
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/* Two Newton iterations. */
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y -= 0.5q * (y - x / y);
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y -= 0.5q * (y - x / y);
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return y;
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}
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