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GNU C Library master sources branch master updated. glibc-2.17-144-gcaa99d0
- From: siddhesh at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 18 Jan 2013 05:58:02 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.17-144-gcaa99d0
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http://sources.redhat.com/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=caa99d06e7f1403887294442af520b0f8c6f3de0
commit caa99d06e7f1403887294442af520b0f8c6f3de0
Author: Siddhesh Poyarekar <siddhesh@redhat.com>
Date: Fri Jan 18 11:18:13 2013 +0530
Simplify calculation of 2^-m in __mpexp
diff --git a/ChangeLog b/ChangeLog
index 1d17c4d..52a9542 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
2013-01-18 Siddhesh Poyarekar <siddhesh@redhat.com>
+ * sysdeps/ieee754/dbl-64/mpa.h (__pow_mp): New function to get an
+ mp_no from a power of two.
+ * sysdeps/ieee754/dbl-64/mpexp.c (__mpexp): Remove
+ __mpexp_twomm1. Use __pow_mp.
+
* sysdeps/ieee754/dbl-64/mpexp.c (__mpexp): Remove unnecessary
multiplication.
diff --git a/sysdeps/ieee754/dbl-64/mpa.h b/sysdeps/ieee754/dbl-64/mpa.h
index debb3b2..06343d4 100644
--- a/sysdeps/ieee754/dbl-64/mpa.h
+++ b/sysdeps/ieee754/dbl-64/mpa.h
@@ -123,3 +123,33 @@ extern void __mpsqrt (mp_no *, mp_no *, int);
extern void __mpexp (mp_no *, mp_no *, int);
extern void __c32 (mp_no *, mp_no *, mp_no *, int);
extern int __mpranred (double, mp_no *, int);
+
+/* Given a power POW, build a multiprecision number 2^POW. */
+static inline void
+__pow_mp (int pow, mp_no *y, int p)
+{
+ int i, rem;
+
+ /* The exponent is E such that E is a factor of 2^24. The remainder (of the
+ form 2^x) goes entirely into the first digit of the mantissa as it is
+ always less than 2^24. */
+ EY = pow / 24;
+ rem = pow - EY * 24;
+ EY++;
+
+ /* If the remainder is negative, it means that POW was negative since
+ |EY * 24| <= |pow|. Adjust so that REM is positive and still less than
+ 24 because of which, the mantissa digit is less than 2^24. */
+ if (rem < 0)
+ {
+ EY--;
+ rem += 24;
+ }
+ /* The sign of any 2^x is always positive. */
+ Y[0] = ONE;
+ Y[1] = 1 << rem;
+
+ /* Everything else is ZERO. */
+ for (i = 2; i <= p; i++)
+ Y[i] = ZERO;
+}
diff --git a/sysdeps/ieee754/dbl-64/mpexp.c b/sysdeps/ieee754/dbl-64/mpexp.c
index 811fb46..8d288ff 100644
--- a/sysdeps/ieee754/dbl-64/mpexp.c
+++ b/sysdeps/ieee754/dbl-64/mpexp.c
@@ -43,7 +43,7 @@ SECTION
__mpexp (mp_no *x, mp_no *y, int p)
{
int i, j, k, m, m1, m2, n;
- double a, b;
+ double b;
static const int np[33] =
{
0, 0, 0, 0, 3, 3, 4, 4, 5, 4, 4, 5, 5, 5, 6, 6, 6, 6, 6, 6,
@@ -61,19 +61,6 @@ __mpexp (mp_no *x, mp_no *y, int p)
70, 73, 76, 78,
81
};
- /* Stored values for 2^-m, where values of m are defined in M1P above. */
- static const double __mpexp_twomm1[33] =
- {
- 0x1.0p0, 0x1.0p0, 0x1.0p0, 0x1.0p0,
- 0x1.0p-17, 0x1.0p-23, 0x1.0p-23, 0x1.0p-28,
- 0x1.0p-27, 0x1.0p-38, 0x1.0p-42, 0x1.0p-39,
- 0x1.0p-43, 0x1.0p-47, 0x1.0p-43, 0x1.0p-47,
- 0x1.0p-50, 0x1.0p-54, 0x1.0p-57, 0x1.0p-60,
- 0x1.0p-64, 0x1.0p-67, 0x1.0p-71, 0x1.0p-74,
- 0x1.0p-68, 0x1.0p-71, 0x1.0p-74, 0x1.0p-77,
- 0x1.0p-70, 0x1.0p-73, 0x1.0p-76, 0x1.0p-78,
- 0x1.0p-81
- };
static const int m1np[7][18] =
{
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
@@ -98,18 +85,10 @@ __mpexp (mp_no *x, mp_no *y, int p)
/* Choose m,n and compute a=2**(-m). */
n = np[p];
m1 = m1p[p];
- a = __mpexp_twomm1[p];
- for (i = 0; i < EX; i++)
- a *= RADIXI;
- for (; i > EX; i--)
- a *= RADIX;
b = X[1];
m2 = 24 * EX;
for (; b < HALFRAD; m2--)
- {
- a *= TWO;
- b *= TWO;
- }
+ b *= TWO;
if (b == HALFRAD)
{
for (i = 2; i <= p; i++)
@@ -118,10 +97,7 @@ __mpexp (mp_no *x, mp_no *y, int p)
break;
}
if (i == p + 1)
- {
- m2--;
- a *= TWO;
- }
+ m2--;
}
m = m1 + m2;
@@ -134,14 +110,13 @@ __mpexp (mp_no *x, mp_no *y, int p)
than 2^-55. */
assert (p < 18);
m = 0;
- a = ONE;
for (i = n - 1; i > 0; i--, n--)
if (m1np[i][p] + m2 > 0)
break;
}
/* Compute s=x*2**(-m). Put result in mps. */
- __dbl_mp (a, &mpt1, p);
+ __pow_mp (-m, &mpt1, p);
__mul (x, &mpt1, &mps, p);
/* Evaluate the polynomial. Put result in mpt2. */
http://sources.redhat.com/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=d3b9ea614822b66f88ba6815a2d2c6cf63922cd7
commit d3b9ea614822b66f88ba6815a2d2c6cf63922cd7
Author: Siddhesh Poyarekar <siddhesh@redhat.com>
Date: Fri Jan 18 11:14:34 2013 +0530
Remove unnecessary multiplication with RADIXI
diff --git a/ChangeLog b/ChangeLog
index 6ca7a8b..1d17c4d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2013-01-18 Siddhesh Poyarekar <siddhesh@redhat.com>
+
+ * sysdeps/ieee754/dbl-64/mpexp.c (__mpexp): Remove unnecessary
+ multiplication.
+
2013-01-17 David S. Miller <davem@davemloft.net>
* sysdeps/sparc/fpu/libm-test-ulps: Update.
diff --git a/sysdeps/ieee754/dbl-64/mpexp.c b/sysdeps/ieee754/dbl-64/mpexp.c
index aca6bf6..811fb46 100644
--- a/sysdeps/ieee754/dbl-64/mpexp.c
+++ b/sysdeps/ieee754/dbl-64/mpexp.c
@@ -103,14 +103,14 @@ __mpexp (mp_no *x, mp_no *y, int p)
a *= RADIXI;
for (; i > EX; i--)
a *= RADIX;
- b = X[1] * RADIXI;
+ b = X[1];
m2 = 24 * EX;
- for (; b < HALF; m2--)
+ for (; b < HALFRAD; m2--)
{
a *= TWO;
b *= TWO;
}
- if (b == HALF)
+ if (b == HALFRAD)
{
for (i = 2; i <= p; i++)
{
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 10 ++++++++++
sysdeps/ieee754/dbl-64/mpa.h | 30 ++++++++++++++++++++++++++++++
sysdeps/ieee754/dbl-64/mpexp.c | 39 +++++++--------------------------------
3 files changed, 47 insertions(+), 32 deletions(-)
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