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Minor tweak to mp multiplication

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Add a local variable to remove extra copies to/from memory in the Z
array.
This commit is contained in:
Siddhesh Poyarekar 2013-01-14 21:36:58 +05:30
parent 1066a53440
commit 2a91b5735a
2 changed files with 18 additions and 13 deletions
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3
ChangeLog
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@ -1,5 +1,8 @@
2013-01-14 Siddhesh Poyarekar <siddhesh@redhat.com>
* sysdeps/ieee754/dbl-64/mpa.c (__mul): Add a local variable
to optimize copies.
* sysdeps/ieee754/dbl-64/mpa.c: Fix formatting.
* sysdeps/powerpc/powerpc32/power4/fpu/mpa.c: Likewise.
* sysdeps/powerpc/powerpc64/power4/fpu/mpa.c: Likewise.

28
sysdeps/ieee754/dbl-64/mpa.c
View File

@ -606,7 +606,7 @@ SECTION
__mul (const mp_no *x, const mp_no *y, mp_no *z, int p)
{
int i, j, k, k2;
double u;
double u, zk;
/* Is z=0? */
if (__glibc_unlikely (X[0] * Y[0] == ZERO))
@ -617,31 +617,33 @@ __mul (const mp_no *x, const mp_no *y, mp_no *z, int p)
/* Multiply, add and carry. */
k2 = (__glibc_unlikely (p < 3)) ? p + p : p + 3;
Z[k2] = ZERO;
zk = Z[k2] = ZERO;
for (k = k2; k > p;)
for (k = k2; k > p; k--)
{
for (i = k - p, j = p; i < p + 1; i++, j--)
Z[k] += X[i] * Y[j];
zk += X[i] * Y[j];
u = (Z[k] + CUTTER) - CUTTER;
if (u > Z[k])
u = (zk + CUTTER) - CUTTER;
if (u > zk)
u -= RADIX;
Z[k] -= u;
Z[--k] = u * RADIXI;
Z[k] = zk - u;
zk = u * RADIXI;
}
while (k > 1)
{
for (i = 1, j = k - 1; i < k; i++, j--)
Z[k] += X[i] * Y[j];
zk += X[i] * Y[j];
u = (Z[k] + CUTTER) - CUTTER;
if (u > Z[k])
u = (zk + CUTTER) - CUTTER;
if (u > zk)
u -= RADIX;
Z[k] -= u;
Z[--k] = u * RADIXI;
Z[k] = zk - u;
zk = u * RADIXI;
k--;
}
Z[k] = zk;
EZ = EX + EY;
/* Is there a carry beyond the most significant digit? */