OGE:               ">=",
	OGOTO:             "goto",
	OGT:               ">",
	OIF:               "if",
	OIMAG:             "imag",
	OINLMARK:          "inlmark",
	ODEREF:            "*",
	OLEN:              "len",
	OLE:               "<=",
	OLSH:              "<<",
	OLT:               "<",
	OMAKE:             "make",
	ONEG:              "-",
	OMAX:              "max",
	OMIN:              "min",

// and then returns tmp.
func (o *orderState) cheapExpr(n ir.Node) ir.Node {
	if n == nil {
		return nil
	}

	switch n.Op() {
	case ir.ONAME, ir.OLITERAL, ir.ONIL:
		return n
	case ir.OLEN, ir.OCAP:
		n := n.(*ir.UnaryExpr)
		l := o.cheapExpr(n.X)
		if l == n.X {
			return n
		}
		a := ir.Copy(n).(*ir.UnaryExpr)
		a.X = l
		return typecheck.Expr(a)
	}

	return o.copyExpr(n)

	l := n.Fun

	if l.Op() == ir.ONAME && l.(*ir.Name).BuiltinOp != 0 {
		l := l.(*ir.Name)
		if n.IsDDD && l.BuiltinOp != ir.OAPPEND {
			base.Errorf("invalid use of ... with builtin %v", l)
		}

		// builtin: OLEN, OCAP, etc.
		switch l.BuiltinOp {
		default:
			base.Fatalf("unknown builtin %v", l)

		case ir.OAPPEND, ir.ODELETE, ir.OMAKE, ir.OMAX, ir.OMIN, ir.OPRINT, ir.OPRINTLN, ir.ORECOVER:
			n.SetOp(l.BuiltinOp)

	case ir.OAPPEND,
		ir.OCALL,
		ir.OCALLFUNC,
		ir.OCALLINTER,
		ir.OCALLMETH,
		ir.OCAP,
		ir.OCLEAR,
		ir.OCLOSE,
		ir.OCOMPLEX,
		ir.OCOPY,
		ir.ODELETE,
		ir.OIMAG,
		ir.OLEN,
		ir.OMAKE,
		ir.OMAX,
		ir.OMIN,
		ir.ONEW,
		ir.OPANIC,
		ir.OPRINT,
		ir.OPRINTLN,
		ir.OREAL,
		ir.ORECOVER,
		ir.ORECOVERFP,
		ir.ORECV,
		ir.OUNSAFEADD,
		ir.OUNSAFESLICE,

		n.Assigned = false
	}
	return n
}

// tcLenCap typechecks an OLEN or OCAP node.
func tcLenCap(n *ir.UnaryExpr) ir.Node {
	n.X = Expr(n.X)
	n.X = DefaultLit(n.X, nil)
	n.X = implicitstar(n.X)
	l := n.X
	t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}

	var ok bool
	if n.Op() == ir.OLEN {
		ok = okforlen[t.Kind()]
	} else {
		ok = okforcap[t.Kind()]
	}

		n := n.(*ir.TypeAssertExpr)
		return walkDotType(n, init)

	case ir.ODYNAMICDOTTYPE, ir.ODYNAMICDOTTYPE2:
		n := n.(*ir.DynamicTypeAssertExpr)
		return walkDynamicDotType(n, init)

	case ir.OLEN, ir.OCAP:
		n := n.(*ir.UnaryExpr)
		return walkLenCap(n, init)

	case ir.OCOMPLEX:
		n := n.(*ir.BinaryExpr)
		n.X = walkExpr(n.X, init)
		n.Y = walkExpr(n.Y, init)
		return n

			maxRewriteLen = 0
		}
		if s := ir.StringVal(cs); len(s) <= maxRewriteLen {
			if len(s) > 0 {
				ncs = safeExpr(ncs, init)
			}
			r := ir.Node(ir.NewBinaryExpr(base.Pos, cmp, ir.NewUnaryExpr(base.Pos, ir.OLEN, ncs), ir.NewInt(base.Pos, int64(len(s)))))
			remains := len(s)
			for i := 0; remains > 0; {
				if remains == 1 || !canCombineLoads {
					cb := ir.NewInt(base.Pos, int64(s[i]))

		// Jump around all the individual switches for each length.
		s.done.Append(ir.NewBranchStmt(s.pos, ir.OGOTO, outerLabel))

		var outer exprSwitch
		outer.exprname = ir.NewUnaryExpr(s.pos, ir.OLEN, s.exprname)
		outer.exprname.SetType(types.Types[types.TINT])

		for _, run := range runs {
			// Target label to jump to when we match this length.
			label := typecheck.AutoLabel(".s")

		ir.OSLICELIT,
		ir.OPTRLIT,
		ir.OCONV,
		ir.OCONVIFACE,
		ir.OCONVNOP,
		ir.ODOT,
		ir.OEQ,
		ir.ONE,
		ir.OLT,
		ir.OLE,
		ir.OGT,
		ir.OGE,
		ir.OKEY,
		ir.OSTRUCTKEY,
		ir.OLEN,
		ir.OMUL,
		ir.OLSH,
		ir.ORSH,
		ir.OAND,
		ir.OANDNOT,
		ir.ONEW,
		ir.ONOT,
		ir.OBITNOT,
		ir.OPLUS,
		ir.ONEG,
		ir.OOROR,
		ir.OPAREN,
		ir.ORUNESTR,
		ir.OREAL,

	case ir.OSLICE, ir.OSLICE3:
		n := n.(*ir.SliceExpr)
		return tcSlice(n)

	// call and call like
	case ir.OCALL:
		n := n.(*ir.CallExpr)
		return tcCall(n, top)

	case ir.OCAP, ir.OLEN:
		n := n.(*ir.UnaryExpr)
		return tcLenCap(n)

	case ir.OMIN, ir.OMAX:
		n := n.(*ir.CallExpr)
		return tcMinMax(n)

	case ir.OREAL, ir.OIMAG:
		n := n.(*ir.UnaryExpr)
		return tcRealImag(n)