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[PATCH] sync up add_magnitudes and sub_magnitudes in ppc mpa.c
- From: Siddhesh Poyarekar <siddhesh at redhat dot com>
- To: libc-alpha at sourceware dot org
- Date: Thu, 14 Feb 2013 14:57:26 +0530
- Subject: [PATCH] sync up add_magnitudes and sub_magnitudes in ppc mpa.c
Hi,
The patch below syncs up the logic in add_magnitudes and
sub_magnitudes in powerpc code, which makes the code run a *tiny* bit
faster. Built and tested on ppc64 and ppc on Power7. OK to commit?
Siddhesh
* sysdeps/powerpc/powerpc32/power4/fpu/mpa.c (add_magnitudes):
Use ZK to minimize writes to Z.
(sub_magnitudes): Simplify code a bit.
* sysdeps/powerpc/powerpc64/power4/fpu/mpa.c (add_magnitudes):
Use ZK to minimize writes to Z.
(sub_magnitudes): Simplify code a bit.
diff --git a/sysdeps/powerpc/powerpc32/power4/fpu/mpa.c b/sysdeps/powerpc/powerpc32/power4/fpu/mpa.c
index 7ebf50b..f948293 100644
--- a/sysdeps/powerpc/powerpc32/power4/fpu/mpa.c
+++ b/sysdeps/powerpc/powerpc32/power4/fpu/mpa.c
@@ -371,6 +371,7 @@ add_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p)
{
long i, j, k;
long p2 = p;
+ double zk;
EZ = EX;
@@ -378,45 +379,54 @@ add_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p)
j = p2 + EY - EX;
k = p2 + 1;
- if (j < 1)
+ if (__glibc_unlikely (j < 1))
{
__cpy (x, z, p);
return;
}
- else
- Z[k] = ZERO;
+
+ zk = ZERO;
for (; j > 0; i--, j--)
{
- Z[k] += X[i] + Y[j];
- if (Z[k] >= RADIX)
+ zk += X[i] + Y[j];
+ if (zk >= RADIX)
{
- Z[k] -= RADIX;
- Z[--k] = ONE;
+ Z[k--] = zk - RADIX;
+ zk = ONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
for (; i > 0; i--)
{
- Z[k] += X[i];
- if (Z[k] >= RADIX)
+ zk += X[i];
+ if (zk >= RADIX)
{
- Z[k] -= RADIX;
- Z[--k] = ONE;
+ Z[k--] = zk - RADIX;
+ zk = ONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
- if (Z[1] == ZERO)
+ if (zk == ZERO)
{
for (i = 1; i <= p2; i++)
Z[i] = Z[i + 1];
}
else
- EZ += ONE;
+ {
+ Z[1] = zk;
+ EZ += ONE;
+ }
}
/* Subtract the magnitudes of *X and *Y assuming that abs (*x) > abs (*y) > 0.
@@ -428,65 +438,63 @@ sub_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p)
{
long i, j, k;
long p2 = p;
+ double zk;
EZ = EX;
+ i = p2;
+ j = p2 + EY - EX;
+ k = p2;
- if (EX == EY)
+ /* Y is too small compared to X, copy X over to the result. */
+ if (__glibc_unlikely (j < 1))
{
- i = j = k = p2;
- Z[k] = Z[k + 1] = ZERO;
+ __cpy (x, z, p);
+ return;
}
- else
+
+ /* The relevant least significant digit in Y is non-zero, so we factor it in
+ to enhance accuracy. */
+ if (j < p2 && Y[j + 1] > ZERO)
{
- j = EX - EY;
- if (j > p2)
- {
- __cpy (x, z, p);
- return;
- }
- else
- {
- i = p2;
- j = p2 + 1 - j;
- k = p2;
- if (Y[j] > ZERO)
- {
- Z[k + 1] = RADIX - Y[j--];
- Z[k] = MONE;
- }
- else
- {
- Z[k + 1] = ZERO;
- Z[k] = ZERO;
- j--;
- }
- }
+ Z[k + 1] = RADIX - Y[j + 1];
+ zk = MONE;
}
+ else
+ zk = Z[k + 1] = ZERO;
+ /* Subtract and borrow. */
for (; j > 0; i--, j--)
{
- Z[k] += (X[i] - Y[j]);
- if (Z[k] < ZERO)
+ zk += (X[i] - Y[j]);
+ if (zk < ZERO)
{
- Z[k] += RADIX;
- Z[--k] = MONE;
+ Z[k--] = zk + RADIX;
+ zk = MONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
+ /* We're done with digits from Y, so it's just digits in X. */
for (; i > 0; i--)
{
- Z[k] += X[i];
- if (Z[k] < ZERO)
+ zk += X[i];
+ if (zk < ZERO)
{
- Z[k] += RADIX;
- Z[--k] = MONE;
+ Z[k--] = zk + RADIX;
+ zk = MONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
+ /* Normalize. */
for (i = 1; Z[i] == ZERO; i++);
EZ = EZ - i + 1;
for (k = 1; i <= p2 + 1;)
diff --git a/sysdeps/powerpc/powerpc64/power4/fpu/mpa.c b/sysdeps/powerpc/powerpc64/power4/fpu/mpa.c
index 7ebf50b..f948293 100644
--- a/sysdeps/powerpc/powerpc64/power4/fpu/mpa.c
+++ b/sysdeps/powerpc/powerpc64/power4/fpu/mpa.c
@@ -371,6 +371,7 @@ add_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p)
{
long i, j, k;
long p2 = p;
+ double zk;
EZ = EX;
@@ -378,45 +379,54 @@ add_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p)
j = p2 + EY - EX;
k = p2 + 1;
- if (j < 1)
+ if (__glibc_unlikely (j < 1))
{
__cpy (x, z, p);
return;
}
- else
- Z[k] = ZERO;
+
+ zk = ZERO;
for (; j > 0; i--, j--)
{
- Z[k] += X[i] + Y[j];
- if (Z[k] >= RADIX)
+ zk += X[i] + Y[j];
+ if (zk >= RADIX)
{
- Z[k] -= RADIX;
- Z[--k] = ONE;
+ Z[k--] = zk - RADIX;
+ zk = ONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
for (; i > 0; i--)
{
- Z[k] += X[i];
- if (Z[k] >= RADIX)
+ zk += X[i];
+ if (zk >= RADIX)
{
- Z[k] -= RADIX;
- Z[--k] = ONE;
+ Z[k--] = zk - RADIX;
+ zk = ONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
- if (Z[1] == ZERO)
+ if (zk == ZERO)
{
for (i = 1; i <= p2; i++)
Z[i] = Z[i + 1];
}
else
- EZ += ONE;
+ {
+ Z[1] = zk;
+ EZ += ONE;
+ }
}
/* Subtract the magnitudes of *X and *Y assuming that abs (*x) > abs (*y) > 0.
@@ -428,65 +438,63 @@ sub_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p)
{
long i, j, k;
long p2 = p;
+ double zk;
EZ = EX;
+ i = p2;
+ j = p2 + EY - EX;
+ k = p2;
- if (EX == EY)
+ /* Y is too small compared to X, copy X over to the result. */
+ if (__glibc_unlikely (j < 1))
{
- i = j = k = p2;
- Z[k] = Z[k + 1] = ZERO;
+ __cpy (x, z, p);
+ return;
}
- else
+
+ /* The relevant least significant digit in Y is non-zero, so we factor it in
+ to enhance accuracy. */
+ if (j < p2 && Y[j + 1] > ZERO)
{
- j = EX - EY;
- if (j > p2)
- {
- __cpy (x, z, p);
- return;
- }
- else
- {
- i = p2;
- j = p2 + 1 - j;
- k = p2;
- if (Y[j] > ZERO)
- {
- Z[k + 1] = RADIX - Y[j--];
- Z[k] = MONE;
- }
- else
- {
- Z[k + 1] = ZERO;
- Z[k] = ZERO;
- j--;
- }
- }
+ Z[k + 1] = RADIX - Y[j + 1];
+ zk = MONE;
}
+ else
+ zk = Z[k + 1] = ZERO;
+ /* Subtract and borrow. */
for (; j > 0; i--, j--)
{
- Z[k] += (X[i] - Y[j]);
- if (Z[k] < ZERO)
+ zk += (X[i] - Y[j]);
+ if (zk < ZERO)
{
- Z[k] += RADIX;
- Z[--k] = MONE;
+ Z[k--] = zk + RADIX;
+ zk = MONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
+ /* We're done with digits from Y, so it's just digits in X. */
for (; i > 0; i--)
{
- Z[k] += X[i];
- if (Z[k] < ZERO)
+ zk += X[i];
+ if (zk < ZERO)
{
- Z[k] += RADIX;
- Z[--k] = MONE;
+ Z[k--] = zk + RADIX;
+ zk = MONE;
}
else
- Z[--k] = ZERO;
+ {
+ Z[k--] = zk;
+ zk = ZERO;
+ }
}
+ /* Normalize. */
for (i = 1; Z[i] == ZERO; i++);
EZ = EZ - i + 1;
for (k = 1; i <= p2 + 1;)