1 //===- PostOrderCFGView.cpp - Post order view of CFG blocks -------*- C++ --*-//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements post order views of the blocks in a CFG.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/Analysis/Analyses/PostOrderCFGView.h"
15 
16 using namespace clang;
17 
18 void PostOrderCFGView::anchor() { }
19 
20 ReversePostOrderCFGView::ReversePostOrderCFGView(const CFG *cfg) {
21   Blocks.reserve(cfg->getNumBlockIDs());
22   CFGBlockSet BSet(cfg);
23 
24   typedef llvm::po_iterator<const CFG*, CFGBlockSet, true> po_iterator;
25 
26   for (po_iterator I = po_iterator::begin(cfg, BSet),
27                    E = po_iterator::end(cfg, BSet); I != E; ++I) {
28     Blocks.push_back(*I);
29     BlockOrder[*I] = Blocks.size();
30   }
31 }
32 
33 PostOrderCFGView *PostOrderCFGView::create(AnalysisDeclContext &ctx) {
34   const CFG *cfg = ctx.getCFG();
35   if (!cfg)
36     return nullptr;
37   return new PostOrderCFGView(cfg);
38 }
39 
40 const void *PostOrderCFGView::getTag() { static int x; return &x; }
41 
42 bool PostOrderCFGView::BlockOrderCompare::operator()(const CFGBlock *b1,
43                                                      const CFGBlock *b2) const {
44   PostOrderCFGView::BlockOrderTy::const_iterator b1It = POV.BlockOrder.find(b1);
45   PostOrderCFGView::BlockOrderTy::const_iterator b2It = POV.BlockOrder.find(b2);
46 
47   unsigned b1V = (b1It == POV.BlockOrder.end()) ? 0 : b1It->second;
48   unsigned b2V = (b2It == POV.BlockOrder.end()) ? 0 : b2It->second;
49   return b1V > b2V;
50 }
51 
52 PostOrderCFGView::PostOrderCFGView(const CFG *cfg) {
53   unsigned size = cfg->getNumBlockIDs();
54   Blocks.reserve(size);
55   CFGBlockSet BSet(cfg);
56 
57   typedef llvm::po_iterator<const CFG*, CFGBlockSet, true,
58                             llvm::GraphTraits<llvm::Inverse<const CFG*> >
59                            > po_iterator;
60 
61   for (po_iterator I = po_iterator::begin(cfg, BSet),
62                    E = po_iterator::end(cfg, BSet); I != E; ++I) {
63     Blocks.push_back(*I);
64     BlockOrder[*I] = Blocks.size();
65   }
66 
67   // It may be that some blocks are inaccessible going from the CFG exit upwards
68   // (e.g. infinite loops); we still need to add them.
69   for (CFG::const_iterator I = cfg->begin(), E = cfg->end();
70        (Blocks.size() < size) && (I != E); ++I) {
71     const CFGBlock* block = *I;
72     // Add a chain going upwards.
73     while (!BlockOrder.count(block)) {
74       Blocks.push_back(block);
75       BlockOrder[block] = Blocks.size();
76       CFGBlock::const_pred_iterator PI = block->pred_begin(),
77                                     PE = block->pred_end();
78       for (; PI != PE; ++PI) {
79         const CFGBlock* pred = *PI;
80         if (pred && !BlockOrder.count(pred)) {
81           block = pred;
82           break;
83         }
84       }
85       // Chain ends when we couldn't find an unmapped pred.
86       if (PI == PE) break;
87     }
88   }
89 }
90 
91 ReversePostOrderCFGView *
92 ReversePostOrderCFGView::create(AnalysisDeclContext &ctx) {
93   const CFG *cfg = ctx.getCFG();
94   if (!cfg)
95     return nullptr;
96   return new ReversePostOrderCFGView(cfg);
97 }
98