150 lines
3.7 KiB
Go
150 lines
3.7 KiB
Go
//go:build !amd64
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package avx
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import "math/bits"
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// Pure Go fallback implementation for non-amd64 platforms
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// Add adds two Uint128 values, returning the result and carry.
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func (a Uint128) Add(b Uint128) (result Uint128, carry uint64) {
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result.Lo, carry = bits.Add64(a.Lo, b.Lo, 0)
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result.Hi, carry = bits.Add64(a.Hi, b.Hi, carry)
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return
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}
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// AddCarry adds two Uint128 values with an input carry.
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func (a Uint128) AddCarry(b Uint128, carryIn uint64) (result Uint128, carryOut uint64) {
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result.Lo, carryOut = bits.Add64(a.Lo, b.Lo, carryIn)
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result.Hi, carryOut = bits.Add64(a.Hi, b.Hi, carryOut)
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return
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}
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// Sub subtracts b from a, returning the result and borrow.
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func (a Uint128) Sub(b Uint128) (result Uint128, borrow uint64) {
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result.Lo, borrow = bits.Sub64(a.Lo, b.Lo, 0)
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result.Hi, borrow = bits.Sub64(a.Hi, b.Hi, borrow)
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return
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}
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// SubBorrow subtracts b from a with an input borrow.
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func (a Uint128) SubBorrow(b Uint128, borrowIn uint64) (result Uint128, borrowOut uint64) {
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result.Lo, borrowOut = bits.Sub64(a.Lo, b.Lo, borrowIn)
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result.Hi, borrowOut = bits.Sub64(a.Hi, b.Hi, borrowOut)
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return
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}
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// Mul64 multiplies two 64-bit values and returns a 128-bit result.
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func Mul64(a, b uint64) Uint128 {
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hi, lo := bits.Mul64(a, b)
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return Uint128{Lo: lo, Hi: hi}
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}
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// Mul multiplies two Uint128 values and returns a 256-bit result as [4]uint64.
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// Result is [lo0, lo1, hi0, hi1] where value = lo0 + lo1<<64 + hi0<<128 + hi1<<192
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func (a Uint128) Mul(b Uint128) [4]uint64 {
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// (a.Hi*2^64 + a.Lo) * (b.Hi*2^64 + b.Lo)
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// = a.Hi*b.Hi*2^128 + (a.Hi*b.Lo + a.Lo*b.Hi)*2^64 + a.Lo*b.Lo
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// a.Lo * b.Lo -> r[0:1]
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r0Hi, r0Lo := bits.Mul64(a.Lo, b.Lo)
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// a.Lo * b.Hi -> r[1:2]
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r1Hi, r1Lo := bits.Mul64(a.Lo, b.Hi)
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// a.Hi * b.Lo -> r[1:2]
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r2Hi, r2Lo := bits.Mul64(a.Hi, b.Lo)
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// a.Hi * b.Hi -> r[2:3]
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r3Hi, r3Lo := bits.Mul64(a.Hi, b.Hi)
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var result [4]uint64
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var carry uint64
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result[0] = r0Lo
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// result[1] = r0Hi + r1Lo + r2Lo
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result[1], carry = bits.Add64(r0Hi, r1Lo, 0)
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result[1], carry = bits.Add64(result[1], r2Lo, carry)
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// result[2] = r1Hi + r2Hi + r3Lo + carry
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result[2], carry = bits.Add64(r1Hi, r2Hi, carry)
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result[2], carry = bits.Add64(result[2], r3Lo, carry)
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// result[3] = r3Hi + carry
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result[3] = r3Hi + carry
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return result
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}
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// IsZero returns true if the Uint128 is zero.
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func (a Uint128) IsZero() bool {
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return a.Lo == 0 && a.Hi == 0
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}
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// Cmp compares two Uint128 values.
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// Returns -1 if a < b, 0 if a == b, 1 if a > b.
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func (a Uint128) Cmp(b Uint128) int {
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if a.Hi < b.Hi {
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return -1
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}
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if a.Hi > b.Hi {
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return 1
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}
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if a.Lo < b.Lo {
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return -1
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}
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if a.Lo > b.Lo {
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return 1
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}
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return 0
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}
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// Lsh shifts a Uint128 left by n bits (n < 128).
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func (a Uint128) Lsh(n uint) Uint128 {
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if n >= 64 {
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return Uint128{Lo: 0, Hi: a.Lo << (n - 64)}
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}
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if n == 0 {
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return a
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}
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return Uint128{
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Lo: a.Lo << n,
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Hi: (a.Hi << n) | (a.Lo >> (64 - n)),
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}
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}
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// Rsh shifts a Uint128 right by n bits (n < 128).
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func (a Uint128) Rsh(n uint) Uint128 {
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if n >= 64 {
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return Uint128{Lo: a.Hi >> (n - 64), Hi: 0}
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}
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if n == 0 {
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return a
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}
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return Uint128{
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Lo: (a.Lo >> n) | (a.Hi << (64 - n)),
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Hi: a.Hi >> n,
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}
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}
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// Or returns the bitwise OR of two Uint128 values.
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func (a Uint128) Or(b Uint128) Uint128 {
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return Uint128{Lo: a.Lo | b.Lo, Hi: a.Hi | b.Hi}
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}
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// And returns the bitwise AND of two Uint128 values.
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func (a Uint128) And(b Uint128) Uint128 {
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return Uint128{Lo: a.Lo & b.Lo, Hi: a.Hi & b.Hi}
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}
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// Xor returns the bitwise XOR of two Uint128 values.
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func (a Uint128) Xor(b Uint128) Uint128 {
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return Uint128{Lo: a.Lo ^ b.Lo, Hi: a.Hi ^ b.Hi}
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}
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// Not returns the bitwise NOT of a Uint128.
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func (a Uint128) Not() Uint128 {
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return Uint128{Lo: ^a.Lo, Hi: ^a.Hi}
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}
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