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[PATCH] Remove more redundant computations in s_sin.c
- From: Siddhesh Poyarekar <siddhesh at redhat dot com>
- To: libc-alpha at sourceware dot org
- Date: Wed, 18 Dec 2013 17:47:05 +0530
- Subject: [PATCH] Remove more redundant computations in s_sin.c
- Authentication-results: sourceware.org; auth=none
Hi,
I've removed more redundant computations in the slow paths of the sin
and cos functions. The notable change is the passing of the most
significant bits of X to the slow functions to check if X is positive
so that just the absolute value of x can be passed and the repeated
ABS() operation is avoided.
Tested to verify that it does not break any tests on x86_64. OK to
commit?
Siddhesh
* sysdeps/ieee754/dbl-64/s_sin.c (sloww1): Add new argument M.
Use M to change sign of result instead of X. Assume X is
positive.
(csloww1): Likewise.
(__sin): Adjust.
(__cos): Adjust.
diff --git a/sysdeps/ieee754/dbl-64/s_sin.c b/sysdeps/ieee754/dbl-64/s_sin.c
index 48a26f5..0033f94 100644
--- a/sysdeps/ieee754/dbl-64/s_sin.c
+++ b/sysdeps/ieee754/dbl-64/s_sin.c
@@ -134,7 +134,7 @@ static double slow (double x);
static double slow1 (double x);
static double slow2 (double x);
static double sloww (double x, double dx, double orig);
-static double sloww1 (double x, double dx, double orig);
+static double sloww1 (double x, double dx, double orig, int m);
static double sloww2 (double x, double dx, double orig, int n);
static double bsloww (double x, double dx, double orig, int n);
static double bsloww1 (double x, double dx, double orig, int n);
@@ -142,7 +142,7 @@ static double bsloww2 (double x, double dx, double orig, int n);
int __branred (double x, double *a, double *aa);
static double cslow2 (double x);
static double csloww (double x, double dx, double orig);
-static double csloww1 (double x, double dx, double orig);
+static double csloww1 (double x, double dx, double orig, int m);
static double csloww2 (double x, double dx, double orig, int n);
/* Reduce range of X and compute sin of a + da. K is the amount by which to
@@ -287,18 +287,15 @@ __sin (double x)
else
{
if (a > 0)
- {
- m = 1;
- t = a;
- }
+ m = 1;
else
{
m = 0;
- t = -a;
+ a = -a;
da = -da;
}
- u.x = big + t;
- y = t - (u.x - big);
+ u.x = big + a;
+ y = a - (u.x - big);
xx = y * y;
s = y + (da + y * xx * (sn3 + xx * sn5));
c = y * da + xx * (cs2 + xx * (cs4 + xx * cs6));
@@ -308,7 +305,7 @@ __sin (double x)
cor = (sn - res) + cor;
cor = (cor > 0) ? 1.035 * cor + eps : 1.035 * cor - eps;
retval = ((res == res + cor) ? ((m) ? res : -res)
- : sloww1 (a, da, x));
+ : sloww1 (a, da, x, m));
}
break;
@@ -375,17 +372,16 @@ __sin (double x)
if (a > 0)
{
m = 1;
- t = a;
db = da;
}
else
{
m = 0;
- t = -a;
+ a = -a;
db = -da;
}
- u.x = big + t;
- y = t - (u.x - big);
+ u.x = big + a;
+ y = a - (u.x - big);
xx = y * y;
s = y + (db + y * xx * (sn3 + xx * sn5));
c = y * db + xx * (cs2 + xx * (cs4 + xx * cs6));
@@ -496,16 +492,15 @@ __cos (double x)
if (a > 0)
{
m = 1;
- t = a;
}
else
{
m = 0;
- t = -a;
+ a = -a;
da = -da;
}
- u.x = big + t;
- y = t - (u.x - big);
+ u.x = big + a;
+ y = a - (u.x - big);
xx = y * y;
s = y + (da + y * xx * (sn3 + xx * sn5));
c = y * da + xx * (cs2 + xx * (cs4 + xx * cs6));
@@ -515,7 +510,7 @@ __cos (double x)
cor = (sn - res) + cor;
cor = (cor > 0) ? 1.035 * cor + 1.0e-31 : 1.035 * cor - 1.0e-31;
retval = ((res == res + cor) ? ((m) ? res : -res)
- : csloww1 (a, da, x));
+ : csloww1 (a, da, x, m));
}
} /* else if (k < 0x400368fd) */
@@ -554,16 +549,15 @@ __cos (double x)
if (a > 0)
{
m = 1;
- t = a;
}
else
{
m = 0;
- t = -a;
+ a = -a;
da = -da;
}
- u.x = big + t;
- y = t - (u.x - big);
+ u.x = big + a;
+ y = a - (u.x - big);
xx = y * y;
s = y + (da + y * xx * (sn3 + xx * sn5));
c = y * da + xx * (cs2 + xx * (cs4 + xx * cs6));
@@ -573,7 +567,7 @@ __cos (double x)
cor = (sn - res) + cor;
cor = (cor > 0) ? 1.035 * cor + eps : 1.035 * cor - eps;
retval = ((res == res + cor) ? ((m) ? res : -res)
- : csloww1 (a, da, x));
+ : csloww1 (a, da, x, m));
}
break;
@@ -638,17 +632,16 @@ __cos (double x)
if (a > 0)
{
m = 1;
- t = a;
db = da;
}
else
{
m = 0;
- t = -a;
+ a = -a;
db = -da;
}
- u.x = big + t;
- y = t - (u.x - big);
+ u.x = big + a;
+ y = a - (u.x - big);
xx = y * y;
s = y + (db + y * xx * (sn3 + xx * sn5));
c = y * db + xx * (cs2 + xx * (cs4 + xx * cs6));
@@ -888,14 +881,13 @@ sloww (double x, double dx, double orig)
static double
SECTION
-sloww1 (double x, double dx, double orig)
+sloww1 (double x, double dx, double orig, int m)
{
mynumber u;
double sn, ssn, cs, ccs, s, c, w[2], y, y1, y2, c1, c2, xx, cor, res;
- y = ABS (x);
- u.x = big + y;
- y = y - (u.x - big);
+ u.x = big + x;
+ y = x - (u.x - big);
xx = y * y;
s = y * xx * (sn3 + xx * sn5);
c = xx * (cs2 + xx * (cs4 + xx * cs6));
@@ -916,10 +908,10 @@ sloww1 (double x, double dx, double orig)
cor = 1.0005 * cor - 3.1e-30 * ABS (orig);
if (res == res + cor)
- return (x > 0) ? res : -res;
+ return (m > 0) ? res : -res;
else
{
- __dubsin (ABS (x), dx, w);
+ __dubsin (x, dx, w);
if (w[1] > 0)
cor = 1.000000005 * w[1] + 1.1e-30 * ABS (orig);
@@ -927,7 +919,7 @@ sloww1 (double x, double dx, double orig)
cor = 1.000000005 * w[1] - 1.1e-30 * ABS (orig);
if (w[0] == w[0] + cor)
- return (x > 0) ? w[0] : -w[0];
+ return (m > 0) ? w[0] : -w[0];
else
return __mpsin (orig, 0, true);
}
@@ -1240,14 +1232,13 @@ csloww (double x, double dx, double orig)
static double
SECTION
-csloww1 (double x, double dx, double orig)
+csloww1 (double x, double dx, double orig, int m)
{
mynumber u;
double sn, ssn, cs, ccs, s, c, w[2], y, y1, y2, c1, c2, xx, cor, res;
- y = ABS (x);
- u.x = big + y;
- y = y - (u.x - big);
+ u.x = big + x;
+ y = x - (u.x - big);
xx = y * y;
s = y * xx * (sn3 + xx * sn5);
c = xx * (cs2 + xx * (cs4 + xx * cs6));
@@ -1268,16 +1259,16 @@ csloww1 (double x, double dx, double orig)
cor = 1.0005 * cor - 3.1e-30 * ABS (orig);
if (res == res + cor)
- return (x > 0) ? res : -res;
+ return (m > 0) ? res : -res;
else
{
- __dubsin (ABS (x), dx, w);
+ __dubsin (x, dx, w);
if (w[1] > 0)
cor = 1.000000005 * w[1] + 1.1e-30 * ABS (orig);
else
cor = 1.000000005 * w[1] - 1.1e-30 * ABS (orig);
if (w[0] == w[0] + cor)
- return (x > 0) ? w[0] : -w[0];
+ return (m > 0) ? w[0] : -w[0];
else
return __mpcos (orig, 0, true);
}