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[PATCH 6/7] sin/cos slow paths: refactor duplicated code into dosin

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Refactor duplicated code into do_sin.  Since all calls to do_sin use copysign to
set the sign of the result, move it inside do_sin.  Small inputs use a separate
polynomial, so move this into do_sin as well (the check is based on the more
conservative case when doing large range reduction, but could be relaxed).

	* sysdeps/ieee754/dbl-64/s_sin.c (do_sin): Use TAYLOR_SIN for small
	inputs.  Return correct sign.
	(do_sincos): Remove small input check before do_sin, let do_sin set
	the sign.
	(__sin): Likewise.
	(__cos): Likewise.
This commit is contained in:
Wilco Dijkstra 2018-04-03 16:46:10 +01:00
parent 72f6e9a3e3
commit aef3e2558a
2 changed files with 22 additions and 27 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2018-04-03 Wilco Dijkstra <wdijkstr@arm.com>
* sysdeps/ieee754/dbl-64/s_sin.c (do_sin): Use TAYLOR_SIN for small
inputs. Return correct sign.
(do_sincos): Remove small input check before do_sin, let do_sin set
the sign.
(__sin): Likewise.
(__cos): Likewise.
2018-04-03 Wilco Dijkstra <wdijkstr@arm.com>
* sysdeps/ieee754/dbl-64/s_sin.c (TAYLOR_SLOW): Remove.

40
sysdeps/ieee754/dbl-64/s_sin.c
View File

@ -124,6 +124,11 @@ static inline double
__always_inline
do_sin (double x, double dx)
{
double xold = x;
/* Max ULP is 0.501 if |x| < 0.126, otherwise ULP is 0.518. */
if (fabs (x) < 0.126)
return TAYLOR_SIN (x * x, x, dx);
mynumber u;
if (x <= 0)
@ -137,7 +142,7 @@ do_sin (double x, double dx)
c = x * dx + xx * (cs2 + xx * (cs4 + xx * cs6));
SINCOS_TABLE_LOOKUP (u, sn, ssn, cs, ccs);
cor = (ssn + s * ccs - sn * c) + cs * s;
return sn + cor;
return __copysign (sn + cor, xold);
}
/* Reduce range of x to within PI/2 with abs (x) < 105414350. The high part
@ -181,14 +186,8 @@ do_sincos (double a, double da, int4 n)
/* Max ULP is 0.513. */
retval = do_cos (a, da);
else
{
double xx = a * a;
/* Max ULP is 0.501 if xx < 0.01588, otherwise ULP is 0.518. */
if (xx < 0.01588)
retval = TAYLOR_SIN (xx, a, da);
else
retval = __copysign (do_sin (a, da), a);
}
/* Max ULP is 0.501 if xx < 0.01588, otherwise ULP is 0.518. */
retval = do_sin (a, da);
return (n & 2) ? -retval : retval;
}
@ -207,7 +206,7 @@ SECTION
__sin (double x)
{
#ifndef IN_SINCOS
double xx, t, a, da;
double t, a, da;
mynumber u;
int4 k, m, n;
double retval = 0;
@ -228,20 +227,11 @@ __sin (double x)
math_check_force_underflow (x);
retval = x;
}
/*---------------------------- 2^-26 < |x|< 0.25 ----------------------*/
else if (k < 0x3fd00000)
{
xx = x * x;
/* Taylor series. */
t = POLYNOMIAL (xx) * (xx * x);
/* Max ULP of x + t is 0.535. */
retval = x + t;
} /* else if (k < 0x3fd00000) */
/*---------------------------- 0.25<|x|< 0.855469---------------------- */
/*--------------------------- 2^-26<|x|< 0.855469---------------------- */
else if (k < 0x3feb6000)
{
/* Max ULP is 0.548. */
retval = __copysign (do_sin (x, 0), x);
retval = do_sin (x, 0);
} /* else if (k < 0x3feb6000) */
/*----------------------- 0.855469 <|x|<2.426265 ----------------------*/
@ -292,7 +282,7 @@ SECTION
#endif
__cos (double x)
{
double y, xx, a, da;
double y, a, da;
mynumber u;
#ifndef IN_SINCOS
int4 k, m, n;
@ -325,13 +315,9 @@ __cos (double x)
y = hp0 - fabs (x);
a = y + hp1;
da = (y - a) + hp1;
xx = a * a;
/* Max ULP is 0.501 if xx < 0.01588 or 0.518 otherwise.
Range reduction uses 106 bits here which is sufficient. */
if (xx < 0.01588)
retval = TAYLOR_SIN (xx, a, da);
else
retval = __copysign (do_sin (a, da), a);
retval = do_sin (a, da);
} /* else if (k < 0x400368fd) */