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annotate lib/Analysis/IteratedDominanceFrontier.cpp @ 95:afa8332a0e37

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LLVM 3.8
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Tue, 13 Oct 2015 17:48:58 +0900
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children 1172e4bd9c6f
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95
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1 //===- IteratedDominanceFrontier.cpp - Compute IDF ------------------------===//
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2 //
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3 // The LLVM Compiler Infrastructure
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4 //
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5 // This file is distributed under the University of Illinois Open Source
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6 // License. See LICENSE.TXT for details.
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7 //
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8 //===----------------------------------------------------------------------===//
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9 //
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10 /// \brief Compute iterated dominance frontiers using a linear time algorithm.
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11 //
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12 //===----------------------------------------------------------------------===//
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13
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14 #include "llvm/Analysis/IteratedDominanceFrontier.h"
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15 #include "llvm/IR/CFG.h"
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16 #include "llvm/IR/Dominators.h"
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17 #include <queue>
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18
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19 using namespace llvm;
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20
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21 void IDFCalculator::calculate(SmallVectorImpl<BasicBlock *> &PHIBlocks) {
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22 // If we haven't computed dominator tree levels, do so now.
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23 if (DomLevels.empty()) {
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24 for (auto DFI = df_begin(DT.getRootNode()), DFE = df_end(DT.getRootNode());
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25 DFI != DFE; ++DFI) {
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26 DomLevels[*DFI] = DFI.getPathLength() - 1;
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27 }
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28 }
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29
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30 // Use a priority queue keyed on dominator tree level so that inserted nodes
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31 // are handled from the bottom of the dominator tree upwards.
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32 typedef std::pair<DomTreeNode *, unsigned> DomTreeNodePair;
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33 typedef std::priority_queue<DomTreeNodePair, SmallVector<DomTreeNodePair, 32>,
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34 less_second> IDFPriorityQueue;
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35 IDFPriorityQueue PQ;
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36
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37 for (BasicBlock *BB : *DefBlocks) {
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38 if (DomTreeNode *Node = DT.getNode(BB))
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39 PQ.push(std::make_pair(Node, DomLevels.lookup(Node)));
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40 }
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41
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42 SmallVector<DomTreeNode *, 32> Worklist;
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43 SmallPtrSet<DomTreeNode *, 32> VisitedPQ;
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44 SmallPtrSet<DomTreeNode *, 32> VisitedWorklist;
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45
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46 while (!PQ.empty()) {
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47 DomTreeNodePair RootPair = PQ.top();
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48 PQ.pop();
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49 DomTreeNode *Root = RootPair.first;
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50 unsigned RootLevel = RootPair.second;
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51
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52 // Walk all dominator tree children of Root, inspecting their CFG edges with
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53 // targets elsewhere on the dominator tree. Only targets whose level is at
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54 // most Root's level are added to the iterated dominance frontier of the
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55 // definition set.
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56
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57 Worklist.clear();
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58 Worklist.push_back(Root);
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59 VisitedWorklist.insert(Root);
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60
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61 while (!Worklist.empty()) {
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62 DomTreeNode *Node = Worklist.pop_back_val();
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63 BasicBlock *BB = Node->getBlock();
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64
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65 for (auto Succ : successors(BB)) {
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66 DomTreeNode *SuccNode = DT.getNode(Succ);
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67
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68 // Quickly skip all CFG edges that are also dominator tree edges instead
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69 // of catching them below.
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70 if (SuccNode->getIDom() == Node)
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71 continue;
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72
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73 unsigned SuccLevel = DomLevels.lookup(SuccNode);
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74 if (SuccLevel > RootLevel)
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75 continue;
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76
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77 if (!VisitedPQ.insert(SuccNode).second)
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78 continue;
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79
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80 BasicBlock *SuccBB = SuccNode->getBlock();
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81 if (useLiveIn && !LiveInBlocks->count(SuccBB))
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82 continue;
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83
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84 PHIBlocks.emplace_back(SuccBB);
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85 if (!DefBlocks->count(SuccBB))
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86 PQ.push(std::make_pair(SuccNode, SuccLevel));
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87 }
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88
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89 for (auto DomChild : *Node) {
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90 if (VisitedWorklist.insert(DomChild).second)
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91 Worklist.push_back(DomChild);
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92 }
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93 }
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94 }
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95 }