| 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 pointer |
| 6 | |
| 7 | // This file implements renumbering, a pre-solver optimization to |
| 8 | // improve the efficiency of the solver's points-to set representation. |
| 9 | // |
| 10 | // TODO(adonovan): rename file "renumber.go" |
| 11 | |
| 12 | import "fmt" |
| 13 | |
| 14 | // renumber permutes a.nodes so that all nodes within an addressable |
| 15 | // object appear before all non-addressable nodes, maintaining the |
| 16 | // order of nodes within the same object (as required by offsetAddr). |
| 17 | // |
| 18 | // renumber must update every nodeid in the analysis (constraints, |
| 19 | // Pointers, callgraph, etc) to reflect the new ordering. |
| 20 | // |
| 21 | // This is an optimisation to increase the locality and efficiency of |
| 22 | // sparse representations of points-to sets. (Typically only about |
| 23 | // 20% of nodes are within an object.) |
| 24 | // |
| 25 | // NB: nodes added during solving (e.g. for reflection, SetFinalizer) |
| 26 | // will be appended to the end. |
| 27 | // |
| 28 | // Renumbering makes the PTA log inscrutable. To aid debugging, later |
| 29 | // phases (e.g. HVN) must not rely on it having occurred. |
| 30 | func (a *analysis) renumber() { |
| 31 | if a.log != nil { |
| 32 | fmt.Fprintf(a.log, "\n\n==== Renumbering\n\n") |
| 33 | } |
| 34 | |
| 35 | N := nodeid(len(a.nodes)) |
| 36 | newNodes := make([]*node, N) |
| 37 | renumbering := make([]nodeid, N) // maps old to new |
| 38 | |
| 39 | var i, j nodeid |
| 40 | |
| 41 | // The zero node is special. |
| 42 | newNodes[j] = a.nodes[i] |
| 43 | renumbering[i] = j |
| 44 | i++ |
| 45 | j++ |
| 46 | |
| 47 | // Pass 1: object nodes. |
| 48 | for i < N { |
| 49 | obj := a.nodes[i].obj |
| 50 | if obj == nil { |
| 51 | i++ |
| 52 | continue |
| 53 | } |
| 54 | |
| 55 | end := i + nodeid(obj.size) |
| 56 | for i < end { |
| 57 | newNodes[j] = a.nodes[i] |
| 58 | renumbering[i] = j |
| 59 | i++ |
| 60 | j++ |
| 61 | } |
| 62 | } |
| 63 | nobj := j |
| 64 | |
| 65 | // Pass 2: non-object nodes. |
| 66 | for i = 1; i < N; { |
| 67 | obj := a.nodes[i].obj |
| 68 | if obj != nil { |
| 69 | i += nodeid(obj.size) |
| 70 | continue |
| 71 | } |
| 72 | |
| 73 | newNodes[j] = a.nodes[i] |
| 74 | renumbering[i] = j |
| 75 | i++ |
| 76 | j++ |
| 77 | } |
| 78 | |
| 79 | if j != N { |
| 80 | panic(fmt.Sprintf("internal error: j=%d, N=%d", j, N)) |
| 81 | } |
| 82 | |
| 83 | // Log the remapping table. |
| 84 | if a.log != nil { |
| 85 | fmt.Fprintf(a.log, "Renumbering nodes to improve density:\n") |
| 86 | fmt.Fprintf(a.log, "(%d object nodes of %d total)\n", nobj, N) |
| 87 | for old, new := range renumbering { |
| 88 | fmt.Fprintf(a.log, "\tn%d -> n%d\n", old, new) |
| 89 | } |
| 90 | } |
| 91 | |
| 92 | // Now renumber all existing nodeids to use the new node permutation. |
| 93 | // It is critical that all reachable nodeids are accounted for! |
| 94 | |
| 95 | // Renumber nodeids in queried Pointers. |
| 96 | for v, ptr := range a.result.Queries { |
| 97 | ptr.n = renumbering[ptr.n] |
| 98 | a.result.Queries[v] = ptr |
| 99 | } |
| 100 | for v, ptr := range a.result.IndirectQueries { |
| 101 | ptr.n = renumbering[ptr.n] |
| 102 | a.result.IndirectQueries[v] = ptr |
| 103 | } |
| 104 | for _, queries := range a.config.extendedQueries { |
| 105 | for _, query := range queries { |
| 106 | if query.ptr != nil { |
| 107 | query.ptr.n = renumbering[query.ptr.n] |
| 108 | } |
| 109 | } |
| 110 | } |
| 111 | |
| 112 | // Renumber nodeids in global objects. |
| 113 | for v, id := range a.globalobj { |
| 114 | a.globalobj[v] = renumbering[id] |
| 115 | } |
| 116 | |
| 117 | // Renumber nodeids in constraints. |
| 118 | for _, c := range a.constraints { |
| 119 | c.renumber(renumbering) |
| 120 | } |
| 121 | |
| 122 | // Renumber nodeids in the call graph. |
| 123 | for _, cgn := range a.cgnodes { |
| 124 | cgn.obj = renumbering[cgn.obj] |
| 125 | for _, site := range cgn.sites { |
| 126 | site.targets = renumbering[site.targets] |
| 127 | } |
| 128 | } |
| 129 | |
| 130 | a.nodes = newNodes |
| 131 | } |
| 132 |
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