diff options
Diffstat (limited to 'libgo/go/math/big/arith.go')
| -rw-r--r-- | libgo/go/math/big/arith.go | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/libgo/go/math/big/arith.go b/libgo/go/math/big/arith.go index 242bd1e..41de17b 100644 --- a/libgo/go/math/big/arith.go +++ b/libgo/go/math/big/arith.go @@ -54,6 +54,7 @@ func subWW_g(x, y, c Word) (z1, z0 Word) { // z1<<_W + z0 = x*y func mulWW(x, y Word) (z1, z0 Word) { return mulWW_g(x, y) } + // Adapted from Warren, Hacker's Delight, p. 132. func mulWW_g(x, y Word) (z1, z0 Word) { x0 := x & _M2 @@ -80,11 +81,24 @@ func mulAddWWW_g(x, y, c Word) (z1, z0 Word) { } // Length of x in bits. -func bitLen(x Word) (n int) { - for ; x >= 0x100; x >>= 8 { +func bitLen(x Word) (n int) { return bitLen_g(x) } +func bitLen_g(x Word) (n int) { + for ; x >= 0x8000; x >>= 16 { + n += 16 + } + if x >= 0x80 { + x >>= 8 n += 8 } - for ; x > 0; x >>= 1 { + if x >= 0x8 { + x >>= 4 + n += 4 + } + if x >= 0x2 { + x >>= 2 + n += 2 + } + if x >= 0x1 { n++ } return @@ -104,6 +118,7 @@ func leadingZeros(x Word) uint { // q = (u1<<_W + u0 - r)/y func divWW(x1, x0, y Word) (q, r Word) { return divWW_g(x1, x0, y) } + // Adapted from Warren, Hacker's Delight, p. 152. func divWW_g(u1, u0, v Word) (q, r Word) { if u1 >= v { |