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//===- IteratedDominanceFrontier.cpp - Compute IDF ------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Compute iterated dominance frontiers using a linear time algorithm.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/IteratedDominanceFrontier.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Dominators.h"
#include <queue>
namespace llvm {
template <class NodeTy, bool IsPostDom>
void IDFCalculator<NodeTy, IsPostDom>::calculate(
SmallVectorImpl<BasicBlock *> &PHIBlocks) {
// Use a priority queue keyed on dominator tree level so that inserted nodes
// are handled from the bottom of the dominator tree upwards. We also augment
// the level with a DFS number to ensure that the blocks are ordered in a
// deterministic way.
typedef std::pair<DomTreeNode *, std::pair<unsigned, unsigned>>
DomTreeNodePair;
typedef std::priority_queue<DomTreeNodePair, SmallVector<DomTreeNodePair, 32>,
less_second> IDFPriorityQueue;
IDFPriorityQueue PQ;
DT.updateDFSNumbers();
for (BasicBlock *BB : *DefBlocks) {
if (DomTreeNode *Node = DT.getNode(BB))
PQ.push({Node, std::make_pair(Node->getLevel(), Node->getDFSNumIn())});
}
SmallVector<DomTreeNode *, 32> Worklist;
SmallPtrSet<DomTreeNode *, 32> VisitedPQ;
SmallPtrSet<DomTreeNode *, 32> VisitedWorklist;
while (!PQ.empty()) {
DomTreeNodePair RootPair = PQ.top();
PQ.pop();
DomTreeNode *Root = RootPair.first;
unsigned RootLevel = RootPair.second.first;
// Walk all dominator tree children of Root, inspecting their CFG edges with
// targets elsewhere on the dominator tree. Only targets whose level is at
// most Root's level are added to the iterated dominance frontier of the
// definition set.
Worklist.clear();
Worklist.push_back(Root);
VisitedWorklist.insert(Root);
while (!Worklist.empty()) {
DomTreeNode *Node = Worklist.pop_back_val();
BasicBlock *BB = Node->getBlock();
// Succ is the successor in the direction we are calculating IDF, so it is
// successor for IDF, and predecessor for Reverse IDF.
for (auto *Succ : children<NodeTy>(BB)) {
DomTreeNode *SuccNode = DT.getNode(Succ);
// Quickly skip all CFG edges that are also dominator tree edges instead
// of catching them below.
if (SuccNode->getIDom() == Node)
continue;
const unsigned SuccLevel = SuccNode->getLevel();
if (SuccLevel > RootLevel)
continue;
if (!VisitedPQ.insert(SuccNode).second)
continue;
BasicBlock *SuccBB = SuccNode->getBlock();
if (useLiveIn && !LiveInBlocks->count(SuccBB))
continue;
PHIBlocks.emplace_back(SuccBB);
if (!DefBlocks->count(SuccBB))
PQ.push(std::make_pair(
SuccNode, std::make_pair(SuccLevel, SuccNode->getDFSNumIn())));
}
for (auto DomChild : *Node) {
if (VisitedWorklist.insert(DomChild).second)
Worklist.push_back(DomChild);
}
}
}
}
template class IDFCalculator<BasicBlock *, false>;
template class IDFCalculator<Inverse<BasicBlock *>, true>;
}