96 lines
3.1 KiB
C++
96 lines
3.1 KiB
C++
//===- IteratedDominanceFrontier.cpp - Compute IDF ------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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/// \brief Compute iterated dominance frontiers using a linear time algorithm.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/IteratedDominanceFrontier.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Dominators.h"
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#include <queue>
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using namespace llvm;
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void IDFCalculator::calculate(SmallVectorImpl<BasicBlock *> &PHIBlocks) {
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// If we haven't computed dominator tree levels, do so now.
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if (DomLevels.empty()) {
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for (auto DFI = df_begin(DT.getRootNode()), DFE = df_end(DT.getRootNode());
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DFI != DFE; ++DFI) {
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DomLevels[*DFI] = DFI.getPathLength() - 1;
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}
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}
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// Use a priority queue keyed on dominator tree level so that inserted nodes
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// are handled from the bottom of the dominator tree upwards.
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typedef std::pair<DomTreeNode *, unsigned> DomTreeNodePair;
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typedef std::priority_queue<DomTreeNodePair, SmallVector<DomTreeNodePair, 32>,
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less_second> IDFPriorityQueue;
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IDFPriorityQueue PQ;
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for (BasicBlock *BB : *DefBlocks) {
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if (DomTreeNode *Node = DT.getNode(BB))
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PQ.push(std::make_pair(Node, DomLevels.lookup(Node)));
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}
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SmallVector<DomTreeNode *, 32> Worklist;
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SmallPtrSet<DomTreeNode *, 32> VisitedPQ;
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SmallPtrSet<DomTreeNode *, 32> VisitedWorklist;
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while (!PQ.empty()) {
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DomTreeNodePair RootPair = PQ.top();
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PQ.pop();
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DomTreeNode *Root = RootPair.first;
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unsigned RootLevel = RootPair.second;
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// Walk all dominator tree children of Root, inspecting their CFG edges with
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// targets elsewhere on the dominator tree. Only targets whose level is at
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// most Root's level are added to the iterated dominance frontier of the
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// definition set.
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Worklist.clear();
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Worklist.push_back(Root);
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VisitedWorklist.insert(Root);
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while (!Worklist.empty()) {
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DomTreeNode *Node = Worklist.pop_back_val();
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BasicBlock *BB = Node->getBlock();
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for (auto Succ : successors(BB)) {
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DomTreeNode *SuccNode = DT.getNode(Succ);
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// Quickly skip all CFG edges that are also dominator tree edges instead
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// of catching them below.
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if (SuccNode->getIDom() == Node)
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continue;
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unsigned SuccLevel = DomLevels.lookup(SuccNode);
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if (SuccLevel > RootLevel)
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continue;
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if (!VisitedPQ.insert(SuccNode).second)
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continue;
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BasicBlock *SuccBB = SuccNode->getBlock();
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if (useLiveIn && !LiveInBlocks->count(SuccBB))
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continue;
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PHIBlocks.emplace_back(SuccBB);
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if (!DefBlocks->count(SuccBB))
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PQ.push(std::make_pair(SuccNode, SuccLevel));
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}
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for (auto DomChild : *Node) {
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if (VisitedWorklist.insert(DomChild).second)
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Worklist.push_back(DomChild);
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}
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}
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}
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}
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