go-tools/functions/loops.go at 2019.2.2 · dominikh/go-tools

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package functions

import "honnef.co/go/tools/ssa"

type Loop struct{ ssa.BlockSet }

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 {

set := Loop{}

set.Add(n)

sets = append(sets, set)

continue

}

set := Loop{}

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 *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

}

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