diff options
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | sysdeps/ieee754/dbl-64/mpa.c | 19 |
2 files changed, 20 insertions, 5 deletions
@@ -1,4 +1,8 @@ -2013-02-15 Siddhesh Poyarekar <siddhesh@redhat.com> +2013-02-16 Siddhesh Poyarekar <siddhesh@redhat.com> + + * sysdeps/ieee754/dbl-64/mpa.c (__mul): Use intermediate + variable to calculate EZ. + (__sqr): Likewise. * sysdeps/ieee754/dbl-64/mpa.c (__mul): Fix determination of the lower precision input. diff --git a/sysdeps/ieee754/dbl-64/mpa.c b/sysdeps/ieee754/dbl-64/mpa.c index 25f52f65c6..9da4257263 100644 --- a/sysdeps/ieee754/dbl-64/mpa.c +++ b/sysdeps/ieee754/dbl-64/mpa.c @@ -693,15 +693,20 @@ __mul (const mp_no *x, const mp_no *y, mp_no *z, int p) } Z[k] = zk; - EZ = EX + EY; + /* Get the exponent sum into an intermediate variable. This is a subtle + optimization, where given enough registers, all operations on the exponent + happen in registers and the result is written out only once into EZ. */ + int e = 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--; + e--; } + EZ = e; Z[0] = X[0] * Y[0]; } @@ -786,14 +791,20 @@ __sqr (const mp_no *x, mp_no *y, int p) /* Squares are always positive. */ Y[0] = 1.0; - EY = 2 * EX; + /* Get the exponent sum into an intermediate variable. This is a subtle + optimization, where given enough registers, all operations on the exponent + happen in registers and the result is written out only once into EZ. */ + int e = EX * 2; + /* Is there a carry beyond the most significant digit? */ if (__glibc_unlikely (Y[1] == ZERO)) { for (i = 1; i <= p; i++) Y[i] = Y[i + 1]; - EY--; + e--; } + + EY = e; } /* Invert *X and store in *Y. Relative error bound: |