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Split mantissa calculation loop and add branch prediction

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Siddhesh Poyarekar 2013-01-02 11:44:13 +05:30
parent 4d55b4e596
commit 44e0d4c20c
2 changed files with 44 additions and 22 deletions
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3
ChangeLog
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@ -1,5 +1,8 @@
2013-01-02 Siddhesh Poyarekar <siddhesh@redhat.com>
* sysdeps/ieee754/dbl-64/mpa.c (__mul): Split mantissa
calculation loop and add branch prediction.
* sysdeps/ieee754/dbl-64/mpexp.c (__mpexp): Add assert to
check access beyond bounds of m1np.

63
sysdeps/ieee754/dbl-64/mpa.c
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@ -447,33 +447,52 @@ void
SECTION
__mul(const mp_no *x, const mp_no *y, mp_no *z, int p) {
int i, i1, i2, j, k, k2;
int i, j, k, k2;
double u;
/* Is z=0? */
if (X[0]*Y[0]==ZERO)
{ Z[0]=ZERO; return; }
/* Is z=0? */
if (__glibc_unlikely (X[0] * Y[0] == ZERO))
{
Z[0]=ZERO;
return;
}
/* Multiply, add and carry */
k2 = (p<3) ? p+p : p+3;
Z[k2]=ZERO;
for (k=k2; k>1; ) {
if (k > p) {i1=k-p; i2=p+1; }
else {i1=1; i2=k; }
for (i=i1,j=i2-1; i<i2; i++,j--) Z[k] += X[i]*Y[j];
/* Multiply, add and carry */
k2 = (__glibc_unlikely (p < 3)) ? p + p : p + 3;
Z[k2] = ZERO;
u = (Z[k] + CUTTER)-CUTTER;
if (u > Z[k]) u -= RADIX;
Z[k] -= u;
Z[--k] = u*RADIXI;
}
for (k = k2; k > p; )
{
for (i = k - p, j = p; i < p + 1; i++, j--)
Z[k] += X[i] * Y[j];
/* Is there a carry beyond the most significant digit? */
if (Z[1] == ZERO) {
for (i=1; i<=p; i++) Z[i]=Z[i+1];
EZ = EX + EY - 1; }
else
EZ = EX + EY;
u = (Z[k] + CUTTER) - CUTTER;
if (u > Z[k])
u -= RADIX;
Z[k] -= u;
Z[--k] = u * RADIXI;
}
while (k > 1)
{
for (i = 1,j = k - 1; i < k; i++, j--)
Z[k] += X[i] * Y[j];
u = (Z[k] + CUTTER) - CUTTER;
if (u > Z[k])
u -= RADIX;
Z[k] -= u;
Z[--k] = u * RADIXI;
}
EZ = EX + EY;
/* Is there a carry beyond the most significant digit? */
if (__glibc_unlikely (Z[1] == ZERO))
{
for (i = 1; i <= p; i++)
Z[i] = Z[i+1];
EZ--;
}
Z[0] = X[0] * Y[0];
}