Method IsValid

cfa/if_return.go:108–152

IsValid reports whether the cond, body and exit node candidates of prim form a valid 1-way conditional with a body return statement in g. Control flow graph: cond ↓ ↘ ↓ body ↓ exit

(g graph.Directed, dom cfg.DominatorTree)

//    ↓
//    exit
func (prim IfReturn) IsValid(g graph.Directed, dom cfg.DominatorTree) bool {
	// Dominator sanity check.
	cond, body, exit := prim.Cond, prim.Body, prim.Exit
	if !dom.Dominates(cond, body) || !dom.Dominates(cond, exit) {
		return false
	}

	// Verify that cond has two successors (body and exit).
	condSuccs := g.From(cond)
	if len(condSuccs) != 2 || !g.HasEdgeFromTo(cond, body) || !g.HasEdgeFromTo(cond, exit) {
		return false
	}

	// Verify that body has one predecessor (cond) and zero successors.
	bodyPreds := g.To(body)
	bodySuccs := g.From(body)
	if len(bodyPreds) != 1 || len(bodySuccs) != 0 {
		return false
	}

	// Verify that exit has one predecessor (cond).
	exitPreds := g.To(exit)
	if len(exitPreds) != 1 {
		return false
	}

	// Verify that the entry node (cond) has no predecessors dominated by cond,
	// as that would indicate a loop construct.
	//
	//       cond
	//     ↗ ↓   ↘
	//    ↑  ↓    body
	//    ↑  ↓
	//    ↑  exit
	//     ↖ ↓
	//       A
	condPreds := g.To(cond)
	for _, pred := range condPreds {
		if dom.Dominates(cond, pred) {
			return false
		}
	}

	return true
}