diff options
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | sysdeps/ieee754/dbl-64/mpa.c | 112 |
2 files changed, 66 insertions, 52 deletions
diff --git a/ChangeLog b/ChangeLog index b46fb855d7..9b224a41c5 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2013-02-13 Siddhesh Poyarekar <siddhesh@redhat.com> + + * sysdeps/ieee754/dbl-64/mpa.c (add_magnitudes): Use ZK to + minimize writes to Z. + (sub_magnitudes): Simplify code a bit. + 2013-02-12 Roland McGrath <roland@hack.frob.com> * include/libc-symbols.h (stub_warning): Remove "warning: " prefix diff --git a/sysdeps/ieee754/dbl-64/mpa.c b/sysdeps/ieee754/dbl-64/mpa.c index ede8ed1986..005aa0c2c1 100644 --- a/sysdeps/ieee754/dbl-64/mpa.c +++ b/sysdeps/ieee754/dbl-64/mpa.c @@ -370,6 +370,7 @@ SECTION add_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p) { int i, j, k; + double zk; EZ = EX; @@ -377,45 +378,54 @@ add_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p) j = p + EY - EX; k = p + 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 <= p; 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. @@ -427,65 +437,63 @@ SECTION sub_magnitudes (const mp_no *x, const mp_no *y, mp_no *z, int p) { int i, j, k; + double zk; EZ = EX; + i = p; + j = p + EY - EX; + k = p; - if (EX == EY) + /* Y is too small compared to X, copy X over to the result. */ + if (__glibc_unlikely (j < 1)) { - i = j = k = p; - 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 < p && Y[j + 1] > ZERO) { - j = EX - EY; - if (j > p) - { - __cpy (x, z, p); - return; - } - else - { - i = p; - j = p + 1 - j; - k = p; - 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 <= p + 1;) |