if z == 0 {
		return 77
	}
	// use z by returning it
	return z
}

// Verify (OR x (NOT y)) rewrites to (ORN x y) where supported
func ornot(x, y int) int {
	// ppc64x:"ORN"
	z := x | ^y
	return z
}

// Verify that (OR (NOT x) (NOT y)) rewrites to (NOT (AND x y))
func orDemorgans(x, y int) int {
	// amd64:"AND",-"OR"
	z := ^x | ^y
	return z

			// and
			//   if a { x = false } else { x = true } with x = !a
			if v.Args[0].Op == OpConstBool && v.Args[1].Op == OpConstBool {
				if v.Args[reverse].AuxInt != v.Args[1-reverse].AuxInt {
					ops := [2]Op{OpNot, OpCopy}
					v.reset(ops[v.Args[reverse].AuxInt])
					v.AddArg(b0.Controls[0])
					if f.pass.debug > 0 {
						f.Warnl(b.Pos, "converted OpPhi to %v", v.Op)
					}
					continue
				}
			}

	for i := len(f.Blocks) - 1; i >= 0; i-- {
		b := f.Blocks[i]
		if b.Kind != BlockIf {
			continue
		}
		// b is either empty or only contains the control value.
		// TODO: if b contains only OpCopy or OpNot related to b.Controls,
		// such as Copy(Not(Copy(Less64(v1, v2)))), perhaps it can be optimized.
		bCtl := b.Controls[0]
		if bCtl.Block != b && len(b.Values) != 0 || (len(b.Values) != 1 || bCtl.Uses != 1) && bCtl.Block == b {

			Valu("t20", OpCtz64, c.config.Types.Int64, 0, nil, "v2"),
			Valu("t21", OpSlicemask, c.config.Types.Int64, 0, nil, "t20"),
			Valu("t22", OpIsNonNil, c.config.Types.Int64, 0, nil, "v2"),
			Valu("t23", OpNot, c.config.Types.Bool, 0, nil, "v4"),
			Valu("t24", OpEq64, c.config.Types.Bool, 0, nil, "v1", "v2"),
			Valu("t25", OpLess64, c.config.Types.Bool, 0, nil, "v1", "v2"),
			Valu("t26", OpLeq64, c.config.Types.Bool, 0, nil, "v1", "v2"),

		call.Args.Append(typecheck.NodAddr(cmpr))
		if needsLength {
			call.Args.Append(ir.NewInt(base.Pos, t.Size()))
		}
		res := ir.Node(call)
		if n.Op() != ir.OEQ {
			res = ir.NewUnaryExpr(base.Pos, ir.ONOT, res)
		}
		return finishCompare(n, res, init)
	}

	// inline: build boolean expression comparing element by element
	andor := ir.OANDAND
	if n.Op() == ir.ONE {
		andor = ir.OOROR
	}

	okfor[ir.OSUB] = okforarith[:]
	okfor[ir.OXOR] = okforand[:]
	okfor[ir.OLSH] = okforand[:]
	okfor[ir.ORSH] = okforand[:]

	// unary
	okfor[ir.OBITNOT] = okforand[:]
	okfor[ir.ONEG] = okforarith[:]
	okfor[ir.ONOT] = okforbool[:]
	okfor[ir.OPLUS] = okforarith[:]

	// special
	okfor[ir.OCAP] = okforcap[:]
	okfor[ir.OLEN] = okforlen[:]

		OpSignExt8to64, OpSignExt16to32, OpSignExt16to64, OpSignExt32to64,
		// bit
		OpCtz8, OpCtz16, OpCtz32, OpCtz64,
		// mask
		OpSlicemask,
		// safety check
		OpIsNonNil,
		// not
		OpNot:
		return true
	case
		// add
		OpAdd64, OpAdd32, OpAdd16, OpAdd8,
		OpAdd32F, OpAdd64F,
		// sub
		OpSub64, OpSub32, OpSub16, OpSub8,
		OpSub32F, OpSub64F,
		// mul

	// Track the negations so that we can swap successors as needed later.
	ctl := b.Controls[0]
	nval := 1 // the control value
	var swap int64
	for ctl.Uses == 1 && ctl.Block == b && (ctl.Op == OpCopy || ctl.Op == OpNot) {
		if ctl.Op == OpNot {
			swap = 1 ^ swap
		}
		ctl = ctl.Args[0]
		nval++ // wrapper around control value
	}
	if ctl.Op != OpPhi || ctl.Block != b || ctl.Uses != 1 {
		return false
	}
	nOtherPhi := 0

	OMAKE:             "make",
	ONEG:              "-",
	OMAX:              "max",
	OMIN:              "min",
	OMOD:              "%",
	OMUL:              "*",
	ONEW:              "new",
	ONE:               "!=",
	ONOT:              "!",
	OOROR:             "||",
	OOR:               "|",
	OPANIC:            "panic",
	OPLUS:             "+",
	OPRINTLN:          "println",
	OPRINT:            "print",
	ORANGE:            "range",

	opRot        = 0x17
	opXderef     = 0x18
	opAbs        = 0x19
	opAnd        = 0x1A
	opDiv        = 0x1B
	opMinus      = 0x1C
	opMod        = 0x1D
	opMul        = 0x1E
	opNeg        = 0x1F
	opNot        = 0x20
	opOr         = 0x21
	opPlus       = 0x22
	opPlusUconst = 0x23 /* 1 op, ULEB128 addend */
	opShl        = 0x24
	opShr        = 0x25
	opShra       = 0x26
	opXor        = 0x27