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110 lines
3.7 KiB
C++
110 lines
3.7 KiB
C++
//===- IteratedDominanceFrontier.cpp - Compute IDF ------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// 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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namespace llvm {
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template <class NodeTy, bool IsPostDom>
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void IDFCalculator<NodeTy, IsPostDom>::calculate(
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SmallVectorImpl<BasicBlock *> &PHIBlocks) {
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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. We also augment
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// the level with a DFS number to ensure that the blocks are ordered in a
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// deterministic way.
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typedef std::pair<DomTreeNode *, std::pair<unsigned, unsigned>>
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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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DT.updateDFSNumbers();
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for (BasicBlock *BB : *DefBlocks) {
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if (DomTreeNode *Node = DT.getNode(BB))
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PQ.push({Node, std::make_pair(Node->getLevel(), Node->getDFSNumIn())});
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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.first;
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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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// Succ is the successor in the direction we are calculating IDF, so it is
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// successor for IDF, and predecessor for Reverse IDF.
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auto DoWork = [&](BasicBlock *Succ) {
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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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return;
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const unsigned SuccLevel = SuccNode->getLevel();
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if (SuccLevel > RootLevel)
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return;
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if (!VisitedPQ.insert(SuccNode).second)
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return;
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BasicBlock *SuccBB = SuccNode->getBlock();
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if (useLiveIn && !LiveInBlocks->count(SuccBB))
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return;
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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(
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SuccNode, std::make_pair(SuccLevel, SuccNode->getDFSNumIn())));
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};
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if (GD) {
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for (auto Pair : children<
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std::pair<const GraphDiff<BasicBlock *, IsPostDom> *, NodeTy>>(
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{GD, BB}))
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DoWork(Pair.second);
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} else {
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for (auto *Succ : children<NodeTy>(BB))
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DoWork(Succ);
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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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template class IDFCalculator<BasicBlock *, false>;
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template class IDFCalculator<Inverse<BasicBlock *>, true>;
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}
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