Add labels to tasks (#45)

vendor/honnef.co/go/tools/functions/loops.go

@@ -0,0 +1,50 @@
+package functions
+
+import "honnef.co/go/tools/ssa"
+
+type Loop map[*ssa.BasicBlock]bool
+
+func findLoops(fn *ssa.Function) []Loop {
+	if fn.Blocks == nil {
+		return nil
+	}
+	tree := fn.DomPreorder()
+	var sets []Loop
+	for _, h := range tree {
+		for _, n := range h.Preds {
+			if !h.Dominates(n) {
+				continue
+			}
+			// n is a back-edge to h
+			// h is the loop header
+			if n == h {
+				sets = append(sets, Loop{n: true})
+				continue
+			}
+			set := Loop{h: true, n: true}
+			for _, b := range allPredsBut(n, h, nil) {
+				set[b] = true
+			}
+			sets = append(sets, set)
+		}
+	}
+	return sets
+}
+
+func allPredsBut(b, but *ssa.BasicBlock, list []*ssa.BasicBlock) []*ssa.BasicBlock {
+outer:
+	for _, pred := range b.Preds {
+		if pred == but {
+			continue
+		}
+		for _, p := range list {
+			// TODO improve big-o complexity of this function
+			if pred == p {
+				continue outer
+			}
+		}
+		list = append(list, pred)
+		list = allPredsBut(pred, but, list)
+	}
+	return list
+}