| 1 | // Copyright 2013 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package callgraph |
| 6 | |
| 7 | import "golang.org/x/tools/go/ssa" |
| 8 | |
| 9 | // This file provides various utilities over call graphs, such as |
| 10 | // visitation and path search. |
| 11 | |
| 12 | // CalleesOf returns a new set containing all direct callees of the |
| 13 | // caller node. |
| 14 | func CalleesOf(caller *Node) map[*Node]bool { |
| 15 | callees := make(map[*Node]bool) |
| 16 | for _, e := range caller.Out { |
| 17 | callees[e.Callee] = true |
| 18 | } |
| 19 | return callees |
| 20 | } |
| 21 | |
| 22 | // GraphVisitEdges visits all the edges in graph g in depth-first order. |
| 23 | // The edge function is called for each edge in postorder. If it |
| 24 | // returns non-nil, visitation stops and GraphVisitEdges returns that |
| 25 | // value. |
| 26 | func GraphVisitEdges(g *Graph, edge func(*Edge) error) error { |
| 27 | seen := make(map[*Node]bool) |
| 28 | var visit func(n *Node) error |
| 29 | visit = func(n *Node) error { |
| 30 | if !seen[n] { |
| 31 | seen[n] = true |
| 32 | for _, e := range n.Out { |
| 33 | if err := visit(e.Callee); err != nil { |
| 34 | return err |
| 35 | } |
| 36 | if err := edge(e); err != nil { |
| 37 | return err |
| 38 | } |
| 39 | } |
| 40 | } |
| 41 | return nil |
| 42 | } |
| 43 | for _, n := range g.Nodes { |
| 44 | if err := visit(n); err != nil { |
| 45 | return err |
| 46 | } |
| 47 | } |
| 48 | return nil |
| 49 | } |
| 50 | |
| 51 | // PathSearch finds an arbitrary path starting at node start and |
| 52 | // ending at some node for which isEnd() returns true. On success, |
| 53 | // PathSearch returns the path as an ordered list of edges; on |
| 54 | // failure, it returns nil. |
| 55 | func PathSearch(start *Node, isEnd func(*Node) bool) []*Edge { |
| 56 | stack := make([]*Edge, 0, 32) |
| 57 | seen := make(map[*Node]bool) |
| 58 | var search func(n *Node) []*Edge |
| 59 | search = func(n *Node) []*Edge { |
| 60 | if !seen[n] { |
| 61 | seen[n] = true |
| 62 | if isEnd(n) { |
| 63 | return stack |
| 64 | } |
| 65 | for _, e := range n.Out { |
| 66 | stack = append(stack, e) // push |
| 67 | if found := search(e.Callee); found != nil { |
| 68 | return found |
| 69 | } |
| 70 | stack = stack[:len(stack)-1] // pop |
| 71 | } |
| 72 | } |
| 73 | return nil |
| 74 | } |
| 75 | return search(start) |
| 76 | } |
| 77 | |
| 78 | // DeleteSyntheticNodes removes from call graph g all nodes for |
| 79 | // synthetic functions (except g.Root and package initializers), |
| 80 | // preserving the topology. In effect, calls to synthetic wrappers |
| 81 | // are "inlined". |
| 82 | func (g *Graph) DeleteSyntheticNodes() { |
| 83 | // Measurements on the standard library and go.tools show that |
| 84 | // resulting graph has ~15% fewer nodes and 4-8% fewer edges |
| 85 | // than the input. |
| 86 | // |
| 87 | // Inlining a wrapper of in-degree m, out-degree n adds m*n |
| 88 | // and removes m+n edges. Since most wrappers are monomorphic |
| 89 | // (n=1) this results in a slight reduction. Polymorphic |
| 90 | // wrappers (n>1), e.g. from embedding an interface value |
| 91 | // inside a struct to satisfy some interface, cause an |
| 92 | // increase in the graph, but they seem to be uncommon. |
| 93 | |
| 94 | // Hash all existing edges to avoid creating duplicates. |
| 95 | edges := make(map[Edge]bool) |
| 96 | for _, cgn := range g.Nodes { |
| 97 | for _, e := range cgn.Out { |
| 98 | edges[*e] = true |
| 99 | } |
| 100 | } |
| 101 | for fn, cgn := range g.Nodes { |
| 102 | if cgn == g.Root || fn.Synthetic == "" || isInit(cgn.Func) { |
| 103 | continue // keep |
| 104 | } |
| 105 | for _, eIn := range cgn.In { |
| 106 | for _, eOut := range cgn.Out { |
| 107 | newEdge := Edge{eIn.Caller, eIn.Site, eOut.Callee} |
| 108 | if edges[newEdge] { |
| 109 | continue // don't add duplicate |
| 110 | } |
| 111 | AddEdge(eIn.Caller, eIn.Site, eOut.Callee) |
| 112 | edges[newEdge] = true |
| 113 | } |
| 114 | } |
| 115 | g.DeleteNode(cgn) |
| 116 | } |
| 117 | } |
| 118 | |
| 119 | func isInit(fn *ssa.Function) bool { |
| 120 | return fn.Pkg != nil && fn.Pkg.Func("init") == fn |
| 121 | } |
| 122 | |
| 123 | // DeleteNode removes node n and its edges from the graph g. |
| 124 | // (NB: not efficient for batch deletion.) |
| 125 | func (g *Graph) DeleteNode(n *Node) { |
| 126 | n.deleteIns() |
| 127 | n.deleteOuts() |
| 128 | delete(g.Nodes, n.Func) |
| 129 | } |
| 130 | |
| 131 | // deleteIns deletes all incoming edges to n. |
| 132 | func (n *Node) deleteIns() { |
| 133 | for _, e := range n.In { |
| 134 | removeOutEdge(e) |
| 135 | } |
| 136 | n.In = nil |
| 137 | } |
| 138 | |
| 139 | // deleteOuts deletes all outgoing edges from n. |
| 140 | func (n *Node) deleteOuts() { |
| 141 | for _, e := range n.Out { |
| 142 | removeInEdge(e) |
| 143 | } |
| 144 | n.Out = nil |
| 145 | } |
| 146 | |
| 147 | // removeOutEdge removes edge.Caller's outgoing edge 'edge'. |
| 148 | func removeOutEdge(edge *Edge) { |
| 149 | caller := edge.Caller |
| 150 | n := len(caller.Out) |
| 151 | for i, e := range caller.Out { |
| 152 | if e == edge { |
| 153 | // Replace it with the final element and shrink the slice. |
| 154 | caller.Out[i] = caller.Out[n-1] |
| 155 | caller.Out[n-1] = nil // aid GC |
| 156 | caller.Out = caller.Out[:n-1] |
| 157 | return |
| 158 | } |
| 159 | } |
| 160 | panic("edge not found: " + edge.String()) |
| 161 | } |
| 162 | |
| 163 | // removeInEdge removes edge.Callee's incoming edge 'edge'. |
| 164 | func removeInEdge(edge *Edge) { |
| 165 | caller := edge.Callee |
| 166 | n := len(caller.In) |
| 167 | for i, e := range caller.In { |
| 168 | if e == edge { |
| 169 | // Replace it with the final element and shrink the slice. |
| 170 | caller.In[i] = caller.In[n-1] |
| 171 | caller.In[n-1] = nil // aid GC |
| 172 | caller.In = caller.In[:n-1] |
| 173 | return |
| 174 | } |
| 175 | } |
| 176 | panic("edge not found: " + edge.String()) |
| 177 | } |
| 178 |
Members