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//go:build amd64 && !purego
// +build amd64,!purego
package csidh
import (
"math/bits"
"golang.org/x/sys/cpu"
)
var (
// Signals support for BMI2 (MULX)
hasBMI2 = cpu.X86.HasBMI2
// Signals support for ADX and BMI2
hasADXandBMI2 = cpu.X86.HasBMI2 && cpu.X86.HasADX
)
var _ = hasBMI2
func mul512(r, m1 *fp, m2 uint64) { mul512Amd64(r, m1, m2) }
func cswap512(x, y *fp, choice uint8) { cswap512Amd64(x, y, choice) }
func mulRdc(r, x, y *fp) { mulRdcAmd64(r, x, y) }
//go:noescape
func mul512Amd64(a, b *fp, c uint64)
//go:noescape
func cswap512Amd64(x, y *fp, choice uint8)
//go:noescape
func mulBmiAsm(res, x, y *fp)
// mulRdc performs montgomery multiplication r = x * y mod P.
// Returned result r is already reduced and in Montgomery domain.
func mulRdcAmd64(r, x, y *fp) {
var t fp
var c uint64
if hasADXandBMI2 {
mulBmiAsm(r, x, y)
} else {
mulGeneric(r, x, y)
}
// if p <= r < 2p then r = r-p
t[0], c = bits.Sub64(r[0], p[0], 0)
t[1], c = bits.Sub64(r[1], p[1], c)
t[2], c = bits.Sub64(r[2], p[2], c)
t[3], c = bits.Sub64(r[3], p[3], c)
t[4], c = bits.Sub64(r[4], p[4], c)
t[5], c = bits.Sub64(r[5], p[5], c)
t[6], c = bits.Sub64(r[6], p[6], c)
t[7], c = bits.Sub64(r[7], p[7], c)
w := 0 - c
r[0] = ctPick64(w, r[0], t[0])
r[1] = ctPick64(w, r[1], t[1])
r[2] = ctPick64(w, r[2], t[2])
r[3] = ctPick64(w, r[3], t[3])
r[4] = ctPick64(w, r[4], t[4])
r[5] = ctPick64(w, r[5], t[5])
r[6] = ctPick64(w, r[6], t[6])
r[7] = ctPick64(w, r[7], t[7])
}
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