diff options
Diffstat (limited to 'src/pkg/big/arith.go')
| -rw-r--r-- | src/pkg/big/arith.go | 28 |
1 files changed, 20 insertions, 8 deletions
diff --git a/src/pkg/big/arith.go b/src/pkg/big/arith.go index d5060bb88..a0c7aa31a 100644 --- a/src/pkg/big/arith.go +++ b/src/pkg/big/arith.go @@ -325,10 +325,16 @@ func subVW_g(z, x *Word, y Word, n int) (c Word) { func shlVW(z, x *Word, s Word, n int) (c Word) func shlVW_g(z, x *Word, s Word, n int) (c Word) { - ŝ := _W - s - for i := 0; i < n; i++ { - w := *x.at(i) - c, *z.at(i) = w>>ŝ, w<<s|c + if n > 0 { + ŝ := _W - s + w1 := *x.at(n - 1) + c = w1 >> ŝ + for i := n - 1; i > 0; i-- { + w := w1 + w1 = *x.at(i - 1) + *z.at(i) = w<<s | w1>>ŝ + } + *z.at(0) = w1 << s } return } @@ -336,10 +342,16 @@ func shlVW_g(z, x *Word, s Word, n int) (c Word) { func shrVW(z, x *Word, s Word, n int) (c Word) func shrVW_g(z, x *Word, s Word, n int) (c Word) { - ŝ := _W - s - for i := n - 1; i >= 0; i-- { - w := *x.at(i) - c, *z.at(i) = w<<ŝ, w>>s|c + if n > 0 { + ŝ := _W - s + w1 := *x.at(0) + c = w1 << ŝ + for i := 0; i < n-1; i++ { + w := w1 + w1 = *x.at(i + 1) + *z.at(i) = w>>s | w1<<ŝ + } + *z.at(n - 1) = w1 >> s } return } |