(Ctz64NonZero ...) => (Ctz64 ...)

(Ctz64 x) && buildcfg.GOPPC64<=8 => (POPCNTD (ANDN <typ.Int64> (ADDconst <typ.Int64> [-1] x) x))
(Ctz64 x) => (CNTTZD x)
(Ctz32 x) && buildcfg.GOPPC64<=8 => (POPCNTW (MOVWZreg (ANDN <typ.Int> (ADDconst <typ.Int> [-1] x) x)))
(Ctz32 x) => (CNTTZW (MOVWZreg x))
(Ctz16 x) => (POPCNTW (MOVHZreg (ANDN <typ.Int16> (ADDconst <typ.Int16> [-1] x) x)))
(Ctz8 x)  => (POPCNTB (MOVBZreg (ANDN <typ.UInt8> (ADDconst <typ.UInt8> [-1] x) x)))

		v.AddArg2(y, x)
		return true
	}
}
func rewriteValuePPC64_OpCtz16(v *Value) bool {
	v_0 := v.Args[0]
	b := v.Block
	typ := &b.Func.Config.Types
	// match: (Ctz16 x)
	// result: (POPCNTW (MOVHZreg (ANDN <typ.Int16> (ADDconst <typ.Int16> [-1] x) x)))
	for {
		x := v_0
		v.reset(OpPPC64POPCNTW)
		v0 := b.NewValue0(v.Pos, OpPPC64MOVHZreg, typ.Int64)
		v1 := b.NewValue0(v.Pos, OpPPC64ANDN, typ.Int16)

			bFalse := s.f.NewBlock(ssa.BlockPlain)
			bEnd := s.f.NewBlock(ssa.BlockPlain)
			b.AddEdgeTo(bTrue)
			b.AddEdgeTo(bFalse)
			b.Likely = ssa.BranchLikely // most machines have popcnt nowadays

			// We have the intrinsic - use it directly.
			s.startBlock(bTrue)
			s.vars[n] = s.newValue1(op, types.Types[types.TINT], args[0])
			s.endBlock().AddEdgeTo(bEnd)