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"),

	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[:]