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package irutil
import "honnef.co/go/tools/go/ir"
type Loop struct{ *ir.BlockSet }
func FindLoops(fn *ir.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 {
set := Loop{ir.NewBlockSet(len(fn.Blocks))}
set.Add(n)
sets = append(sets, set)
continue
}
set := Loop{ir.NewBlockSet(len(fn.Blocks))}
set.Add(h)
set.Add(n)
for _, b := range allPredsBut(n, h, nil) {
set.Add(b)
}
sets = append(sets, set)
}
}
return sets
}
func allPredsBut(b, but *ir.BasicBlock, list []*ir.BasicBlock) []*ir.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
}
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