md5x16

md5x16

AVX-512 accelerated 16-lane MD5 in avo.

Inspired by minio/md5-simd and igneous-systems/md5vec.

Note that the focus of this example is the core assembly block function. The Sum function can only handle parallel hashes of exactly the same length. In practice you'd likely need hash server functionality provided by md5-simd to multiplex independent hashes of different lengths into the 16 SIMD lanes.

func main() {
	// Define round constants data section.
	//
	// These may be computed as the integer part of abs(sin(i+1))*2^32.
	T := GLOBL("consts", RODATA|NOPTR)
	for i := 0; i < 64; i++ {
		k := uint32(math.Floor(math.Ldexp(math.Abs(math.Sin(float64(i+1))), 32)))
		DATA(4*i, U32(k))
	}

	// MD5 16-lane block function.
	TEXT("block", 0, "func(h *[4][16]uint32, base uintptr, offsets *[16]uint32, mask uint16)")
	Doc(
		"block MD5 hashes 16 messages into the running hash states h. Messages are",
		"at the given offsets from the base pointer. The 16-bit mask specifies",
		"which lanes are active: when bit i is not set loads will be disabled and",
		"the value of the resulting hash is undefined.",
	)
	h := Mem{Base: Load(Param("h"), GP64())}
	base := Mem{Base: Load(Param("base"), GP64())}
	offsetsptr := Mem{Base: Load(Param("offsets"), GP64())}
	mask := Load(Param("mask"), K())

	Comment("Load offsets.")
	offsets := ZMM()
	VMOVUPD(offsetsptr, offsets)

	Comment("Load initial hash.")
	hash := [4]Register{ZMM(), ZMM(), ZMM(), ZMM()}
	for i, r := range hash {
		VMOVUPD(h.Offset(64*i), r)
	}

	Comment("Initialize registers.")
	a, b, c, d := ZMM(), ZMM(), ZMM(), ZMM()
	for i, r := range []Register{a, b, c, d} {
		VMOVUPD(hash[i], r)
	}

	// Allocate message registers.
	m := make([]Register, 16)
	for i := range m {
		m[i] = ZMM()
	}

	// Generate round updates.
	//
	// Each 16-round block is parameterized based on the btiwise function,
	// message indexes and shift amounts. Constants B, C, D are helpers in
	// computing the logic table required by VPTERNLOGD.
	const (
		B = uint8(0b10101010)
		C = uint8(0b11001100)
		D = uint8(0b11110000)
	)
	quarter := []struct {
		F uint8         // ternary logic table
		i func(int) int // message index at round r
		s []int         // shift amounts
	}{
		{
			F: (B & C) | (^B & D),
			i: func(r int) int { return r % 16 },
			s: []int{7, 12, 17, 22},
		},
		{
			F: (D & B) | (^D & C),
			i: func(r int) int { return (5*r + 1) % 16 },
			s: []int{5, 9, 14, 20},
		},
		{
			F: B ^ C ^ D,
			i: func(r int) int { return (3*r + 5) % 16 },
			s: []int{4, 11, 16, 23},
		},
		{
			F: C ^ (B | ^D),
			i: func(r int) int { return (7 * r) % 16 },
			s: []int{6, 10, 15, 21},
		},
	}

	for r := 0; r < 64; r++ {
		Commentf("Round %d.", r)
		q := quarter[r/16]

		// Load message words.
		if r < 16 {
			k := K()
			KMOVW(mask, k)
			VPGATHERDD(base.Offset(4*r).Idx(offsets, 1), k, m[r])
		}

		VPADDD(m[q.i(r)], a, a)
		VPADDD_BCST(T.Offset(4*r), a, a)
		f := ZMM()
		VMOVUPD(d, f)
		VPTERNLOGD(U8(q.F), b, c, f)
		VPADDD(f, a, a)
		VPROLD(U8(q.s[r%4]), a, a)
		VPADDD(b, a, a)
		a, b, c, d = d, a, b, c
	}

	Comment("Final add.")
	for i, r := range []Register{a, b, c, d} {
		VPADDD(r, hash[i], hash[i])
	}

	Comment("Store results back.")
	for i, r := range hash {
		VMOVUPD(r, h.Offset(64*i))
	}

	VZEROUPPER()
	RET()

	Generate()
}