}

		// Copy the control values - we need this so we can reduce the
		// uses property of these values later.
		controls := append(make([]*Value, 0, 2), b.ControlValues()...)

		// Load control values into registers.
		for i, v := range b.ControlValues() {
			if !s.values[v.ID].needReg {
				continue
			}
			if s.f.pass.debug > regDebug {
				fmt.Printf("  processing control %s\n", v.LongString())
			}

		for _, b := range f.Blocks {
			var b0 *Block
			if debug > 1 {
				b0 = new(Block)
				*b0 = *b
				b0.Succs = append([]Edge{}, b.Succs...) // make a new copy, not aliasing
			}
			for i, c := range b.ControlValues() {
				for c.Op == OpCopy {
					c = c.Args[0]
					b.ReplaceControl(i, c)
				}
			}
			if rb(b) {
				change = true
				if debug > 1 {