}
			}

			if !be.liveout.Eq(newliveout) {
				change = true
				be.liveout.Copy(newliveout)
			}

			// A variable is live on input to this block
			// if it is used by this block, or live on output from this block and
			// not set by the code in this block.
			//
			// in[b] = uevar[b] \cup (out[b] \setminus varkill[b])
			newlivein.AndNot(be.liveout, be.varkill)
			be.livein.Or(newlivein, be.uevar)

	linesIn := strings.Split(f.Preamble, "\n")
	linesOut := make([]string, 0, len(linesIn))
	f.NoCallbacks = make(map[string]bool)
	f.NoEscapes = make(map[string]bool)
	for _, line := range linesIn {
		l := strings.TrimSpace(line)
		if len(l) < 5 || l[:4] != "#cgo" || !unicode.IsSpace(rune(l[4])) {
			linesOut = append(linesOut, line)
		} else {
			linesOut = append(linesOut, "")

			// #cgo (nocallback|noescape) <function name>