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use scalbn or *2.0 instead of ldexp, fix fmal

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Some code assumed ldexp(x, 1) is faster than 2.0*x,
but ldexp is a wrapper around scalbn which uses
multiplications inside, so this optimization is
wrong.

This commit also fixes fmal which accidentally
used ldexp instead of ldexpl loosing precision.

There are various additional changes from the
work-in-progress const cleanups.
This commit is contained in:
nsz 2012-03-19 22:57:58 +01:00
commit 2786c7d216
8 changed files with 102 additions and 101 deletions
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8
src/math/expl.c
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@ -102,13 +102,13 @@ long double expl(long double x)
if (x > MAXLOGL)
return INFINITY;
if (x < MINLOGL)
return 0.0L;
return 0.0;
/* Express e**x = e**g 2**n
* = e**g e**(n loge(2))
* = e**(g + n loge(2))
*/
px = floorl(LOG2EL * x + 0.5L); /* floor() truncates toward -infinity. */
px = floorl(LOG2EL * x + 0.5); /* floor() truncates toward -infinity. */
n = px;
x -= px * C1;
x -= px * C2;
@ -120,8 +120,8 @@ long double expl(long double x)
xx = x * x;
px = x * __polevll(xx, P, 2);
x = px/(__polevll(xx, Q, 3) - px);
x = 1.0L + ldexpl(x, 1);
x = ldexpl(x, n);
x = 1.0 + 2.0 * x;
x = scalbnl(x, n);
return x;
}
#endif