(Com32 <typ.UInt32> (Int64Hi x))
		(Com32 <typ.UInt32> (Int64Lo x)))

// Sadly, just because we know that x is non-zero,
// we don't know whether either component is,
// so just treat Ctz64NonZero the same as Ctz64.
(Ctz64NonZero ...) => (Ctz64 ...)

(Ctz64 x) =>
	(Add32 <typ.UInt32>
		(Ctz32 <typ.UInt32> (Int64Lo x))
		(And32 <typ.UInt32>
			(Com32 <typ.UInt32> (Zeromask (Int64Lo x)))

	{name: "Ctz16NonZero", argLength: 1}, // same as above, but arg[0] known to be non-zero, returns 0-15
	{name: "Ctz32NonZero", argLength: 1}, // same as above, but arg[0] known to be non-zero, returns 0-31
	{name: "Ctz64NonZero", argLength: 1}, // same as above, but arg[0] known to be non-zero, returns 0-63
	{name: "BitLen8", argLength: 1},      // Number of bits in arg[0] (returns 0-8)

(Ctz16 x) => (BSFL (ORLconst <typ.UInt32> [1<<16] x))
(Ctz8  x) => (BSFL (ORLconst <typ.UInt32> [1<<8 ] x))

(Ctz64NonZero x) && buildcfg.GOAMD64 >= 3 => (TZCNTQ x)
(Ctz32NonZero x) && buildcfg.GOAMD64 >= 3 => (TZCNTL x)
(Ctz16NonZero x) && buildcfg.GOAMD64 >= 3 => (TZCNTL x)
(Ctz8NonZero  x) && buildcfg.GOAMD64 >= 3 => (TZCNTL x)
(Ctz64NonZero x) && buildcfg.GOAMD64 <  3 => (Select0 (BSFQ x))
(Ctz32NonZero x) && buildcfg.GOAMD64 <  3 => (BSFL x)

(MOVDaddr {sym} [n] ptr) && sym == nil && n == 0 && (ptr.Op == OpArgIntReg || ptr.Op == OpPhi) => ptr

// TODO: optimize these cases?
(Ctz32NonZero ...) => (Ctz32 ...)
(Ctz64NonZero ...) => (Ctz64 ...)

(Ctz64 x) && buildcfg.GOPPC64<=8 => (POPCNTD (ANDN <typ.Int64> (ADDconst <typ.Int64> [-1] x) x))
(Ctz64 x) => (CNTTZD x)

(OffPtr [off] ptr:(SP)) => (MOVDaddr [int32(off)] ptr)
(OffPtr [off] ptr) && is32Bit(off) => (ADDconst [int32(off)] ptr)
(OffPtr [off] ptr) => (ADD (MOVDconst [off]) ptr)

// TODO: optimize these cases?
(Ctz64NonZero ...) => (Ctz64 ...)
(Ctz32NonZero ...) => (Ctz32 ...)

// Ctz(x) = 64 - findLeftmostOne((x-1)&^x)
(Ctz64 <t> x) => (SUB (MOVDconst [64]) (FLOGR (AND <t> (SUBconst <t> [1] x) (NOT <t> x))))

	v_0 := v.Args[0]
	b := v.Block
	typ := &b.Func.Config.Types
	// match: (Ctz64NonZero x)
	// cond: buildcfg.GOAMD64 >= 3
	// result: (TZCNTQ x)
	for {
		x := v_0
		if !(buildcfg.GOAMD64 >= 3) {
			break
		}
		v.reset(OpAMD64TZCNTQ)
		v.AddArg(x)
		return true
	}
	// match: (Ctz64NonZero x)
	// cond: buildcfg.GOAMD64 < 3
	// result: (Select0 (BSFQ x))
	for {

	},
	{
		name:    "Ctz16NonZero",
		argLen:  1,
		generic: true,
	},
	{
		name:    "Ctz32NonZero",
		argLen:  1,
		generic: true,
	},
	{
		name:    "Ctz64NonZero",
		argLen:  1,
		generic: true,
	},
	{
		name:    "BitLen8",
		argLen:  1,
		generic: true,
	},
	{
		name:    "BitLen16",
		argLen:  1,
		generic: true,