t.addUses(val)
		}
	}()

	switch val.Op {
	// they are constant values, aren't they?
	case OpConst64, OpConst32, OpConst16, OpConst8,
		OpConstBool, OpConst32F, OpConst64F: //TODO: support ConstNil ConstString etc
		t.latticeCells[val] = lattice{constant, val}
	// lattice value of copy(x) actually means lattice value of (x)
	case OpCopy:
		t.latticeCells[val] = t.getLatticeCell(val.Args[0])

(StringLen (StringMake _ (Const64 <t> [c]))) => (Const64 <t> [c])
(ConstString {str}) && config.PtrSize == 4 && str == "" =>
  (StringMake (ConstNil) (Const32 <typ.Int> [0]))
(ConstString {str}) && config.PtrSize == 8 && str == "" =>
  (StringMake (ConstNil) (Const64 <typ.Int> [0]))
(ConstString {str}) && config.PtrSize == 4 && str != "" =>
  (StringMake
    (Addr <typ.BytePtr> {fe.StringData(str)}

	// constants. Constant values are stored in the aux or
	// auxint fields.
	{name: "ConstBool", aux: "Bool"},     // auxint is 0 for false and 1 for true
	{name: "ConstString", aux: "String"}, // value is aux.(string)
	{name: "ConstNil", typ: "BytePtr"},   // nil pointer
	{name: "Const8", aux: "Int8"},        // auxint is sign-extended 8 bits

		return true
	}
	return false
}
func rewriteValuegeneric_OpConstString(v *Value) bool {
	b := v.Block
	config := b.Func.Config
	fe := b.Func.fe
	typ := &b.Func.Config.Types
	// match: (ConstString {str})
	// cond: config.PtrSize == 4 && str == ""
	// result: (StringMake (ConstNil) (Const32 <typ.Int> [0]))
	for {
		str := auxToString(v.Aux)
		if !(config.PtrSize == 4 && str == "") {
			break
		}

		resultInArg0: true,
		zeroWidth:    true,
		generic:      true,
	},
	{
		name:    "ConstBool",
		auxType: auxBool,
		argLen:  0,
		generic: true,
	},
	{
		name:    "ConstString",
		auxType: auxString,
		argLen:  0,
		generic: true,
	},
	{
		name:    "ConstNil",
		argLen:  0,
		generic: true,
	},
	{
		name:    "Const8",