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372 lines
14 KiB
C++
372 lines
14 KiB
C++
//===- DominatorSet.cpp - Dominator Set Calculation --------------*- C++ -*--=//
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//
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// This file provides a simple class to calculate the dominator set of a method.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/SimplifyCFG.h" // To get cfg::UnifyAllExitNodes
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#include "llvm/CFG.h"
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#include "llvm/Tools/STLExtras.h"
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#include <algorithm>
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//===----------------------------------------------------------------------===//
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// Helper Template
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//===----------------------------------------------------------------------===//
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// set_intersect - Identical to set_intersection, except that it works on
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// set<>'s and is nicer to use. Functionally, this iterates through S1,
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// removing elements that are not contained in S2.
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//
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template <class Ty, class Ty2>
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void set_intersect(set<Ty> &S1, const set<Ty2> &S2) {
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for (typename set<Ty>::iterator I = S1.begin(); I != S1.end();) {
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const Ty &E = *I;
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++I;
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if (!S2.count(E)) S1.erase(E); // Erase element if not in S2
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}
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}
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//===----------------------------------------------------------------------===//
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// DominatorBase Implementation
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//===----------------------------------------------------------------------===//
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bool cfg::DominatorBase::isPostDominator() const {
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return Root != Root->getParent()->front();
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}
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//===----------------------------------------------------------------------===//
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// DominatorSet Implementation
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//===----------------------------------------------------------------------===//
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// DominatorSet ctor - Build either the dominator set or the post-dominator
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// set for a method...
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//
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cfg::DominatorSet::DominatorSet(const Method *M) : DominatorBase(M->front()) {
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calcForwardDominatorSet(M);
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}
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// calcForwardDominatorSet - This method calculates the forward dominator sets
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// for the specified method.
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//
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void cfg::DominatorSet::calcForwardDominatorSet(const Method *M) {
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assert(Root && M && "Can't build dominator set of null method!");
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bool Changed;
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do {
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Changed = false;
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DomSetType WorkingSet;
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df_const_iterator It = df_begin(M), End = df_end(M);
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for ( ; It != End; ++It) {
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const BasicBlock *BB = *It;
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pred_const_iterator PI = pred_begin(BB), PEnd = pred_end(BB);
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if (PI != PEnd) { // Is there SOME predecessor?
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// Loop until we get to a predecessor that has had it's dom set filled
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// in at least once. We are guaranteed to have this because we are
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// traversing the graph in DFO and have handled start nodes specially.
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//
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while (Doms[*PI].size() == 0) ++PI;
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WorkingSet = Doms[*PI];
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for (++PI; PI != PEnd; ++PI) { // Intersect all of the predecessor sets
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DomSetType &PredSet = Doms[*PI];
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if (PredSet.size())
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set_intersect(WorkingSet, PredSet);
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}
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}
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WorkingSet.insert(BB); // A block always dominates itself
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DomSetType &BBSet = Doms[BB];
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if (BBSet != WorkingSet) {
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BBSet.swap(WorkingSet); // Constant time operation!
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Changed = true; // The sets changed.
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}
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WorkingSet.clear(); // Clear out the set for next iteration
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}
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} while (Changed);
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}
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// Postdominator set constructor. This ctor converts the specified method to
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// only have a single exit node (return stmt), then calculates the post
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// dominance sets for the method.
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//
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cfg::DominatorSet::DominatorSet(Method *M, bool PostDomSet)
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: DominatorBase(M->front()) {
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if (!PostDomSet) { calcForwardDominatorSet(M); return; }
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Root = cfg::UnifyAllExitNodes(M);
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assert(Root && "TODO: Don't handle case where there are no exit nodes yet!");
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bool Changed;
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do {
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Changed = false;
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set<const BasicBlock*> Visited;
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DomSetType WorkingSet;
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idf_const_iterator It = idf_begin(Root), End = idf_end(Root);
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for ( ; It != End; ++It) {
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const BasicBlock *BB = *It;
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succ_const_iterator PI = succ_begin(BB), PEnd = succ_end(BB);
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if (PI != PEnd) { // Is there SOME predecessor?
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// Loop until we get to a successor that has had it's dom set filled
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// in at least once. We are guaranteed to have this because we are
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// traversing the graph in DFO and have handled start nodes specially.
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//
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while (Doms[*PI].size() == 0) ++PI;
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WorkingSet = Doms[*PI];
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for (++PI; PI != PEnd; ++PI) { // Intersect all of the successor sets
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DomSetType &PredSet = Doms[*PI];
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if (PredSet.size())
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set_intersect(WorkingSet, PredSet);
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}
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}
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WorkingSet.insert(BB); // A block always dominates itself
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DomSetType &BBSet = Doms[BB];
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if (BBSet != WorkingSet) {
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BBSet.swap(WorkingSet); // Constant time operation!
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Changed = true; // The sets changed.
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}
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WorkingSet.clear(); // Clear out the set for next iteration
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}
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} while (Changed);
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}
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//===----------------------------------------------------------------------===//
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// ImmediateDominators Implementation
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//===----------------------------------------------------------------------===//
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// calcIDoms - Calculate the immediate dominator mapping, given a set of
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// dominators for every basic block.
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void cfg::ImmediateDominators::calcIDoms(const DominatorSet &DS) {
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// Loop over all of the nodes that have dominators... figuring out the IDOM
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// for each node...
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//
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for (DominatorSet::const_iterator DI = DS.begin(), DEnd = DS.end();
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DI != DEnd; ++DI) {
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const BasicBlock *BB = DI->first;
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const DominatorSet::DomSetType &Dominators = DI->second;
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unsigned DomSetSize = Dominators.size();
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if (DomSetSize == 1) continue; // Root node... IDom = null
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// Loop over all dominators of this node. This corresponds to looping over
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// nodes in the dominator chain, looking for a node whose dominator set is
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// equal to the current nodes, except that the current node does not exist
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// in it. This means that it is one level higher in the dom chain than the
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// current node, and it is our idom!
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//
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DominatorSet::DomSetType::const_iterator I = Dominators.begin();
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DominatorSet::DomSetType::const_iterator End = Dominators.end();
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for (; I != End; ++I) { // Iterate over dominators...
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// All of our dominators should form a chain, where the number of elements
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// in the dominator set indicates what level the node is at in the chain.
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// We want the node immediately above us, so it will have an identical
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// dominator set, except that BB will not dominate it... therefore it's
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// dominator set size will be one less than BB's...
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//
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if (DS.getDominators(*I).size() == DomSetSize - 1) {
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IDoms[BB] = *I;
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break;
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}
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}
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}
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}
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//===----------------------------------------------------------------------===//
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// DominatorTree Implementation
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//===----------------------------------------------------------------------===//
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// DominatorTree dtor - Free all of the tree node memory.
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//
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cfg::DominatorTree::~DominatorTree() {
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for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
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delete I->second;
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}
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cfg::DominatorTree::DominatorTree(const ImmediateDominators &IDoms)
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: DominatorBase(IDoms.getRoot()) {
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const Method *M = Root->getParent();
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Nodes[Root] = new Node(Root, 0); // Add a node for the root...
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// Iterate over all nodes in depth first order...
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for (df_const_iterator I = df_begin(M), E = df_end(M); I != E; ++I) {
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const BasicBlock *BB = *I, *IDom = IDoms[*I];
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if (IDom != 0) { // Ignore the root node and other nasty nodes
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// We know that the immediate dominator should already have a node,
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// because we are traversing the CFG in depth first order!
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//
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assert(Nodes[IDom] && "No node for IDOM?");
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Node *IDomNode = Nodes[IDom];
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// Add a new tree node for this BasicBlock, and link it as a child of
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// IDomNode
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Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
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}
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}
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}
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void cfg::DominatorTree::calculate(const DominatorSet &DS) {
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Nodes[Root] = new Node(Root, 0); // Add a node for the root...
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if (!isPostDominator()) {
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// Iterate over all nodes in depth first order...
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for (df_const_iterator I = df_begin(Root), E = df_end(Root); I != E; ++I) {
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const BasicBlock *BB = *I;
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const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
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unsigned DomSetSize = Dominators.size();
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if (DomSetSize == 1) continue; // Root node... IDom = null
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// Loop over all dominators of this node. This corresponds to looping over
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// nodes in the dominator chain, looking for a node whose dominator set is
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// equal to the current nodes, except that the current node does not exist
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// in it. This means that it is one level higher in the dom chain than the
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// current node, and it is our idom! We know that we have already added
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// a DominatorTree node for our idom, because the idom must be a
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// predecessor in the depth first order that we are iterating through the
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// method.
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//
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DominatorSet::DomSetType::const_iterator I = Dominators.begin();
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DominatorSet::DomSetType::const_iterator End = Dominators.end();
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for (; I != End; ++I) { // Iterate over dominators...
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// All of our dominators should form a chain, where the number of elements
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// in the dominator set indicates what level the node is at in the chain.
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// We want the node immediately above us, so it will have an identical
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// dominator set, except that BB will not dominate it... therefore it's
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// dominator set size will be one less than BB's...
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//
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if (DS.getDominators(*I).size() == DomSetSize - 1) {
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// We know that the immediate dominator should already have a node,
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// because we are traversing the CFG in depth first order!
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//
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Node *IDomNode = Nodes[*I];
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assert(IDomNode && "No node for IDOM?");
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// Add a new tree node for this BasicBlock, and link it as a child of
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// IDomNode
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Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
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break;
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}
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}
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}
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} else {
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// Iterate over all nodes in depth first order...
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for (idf_const_iterator I = idf_begin(Root), E = idf_end(Root); I != E; ++I) {
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const BasicBlock *BB = *I;
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const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
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unsigned DomSetSize = Dominators.size();
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if (DomSetSize == 1) continue; // Root node... IDom = null
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// Loop over all dominators of this node. This corresponds to looping over
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// nodes in the dominator chain, looking for a node whose dominator set is
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// equal to the current nodes, except that the current node does not exist
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// in it. This means that it is one level higher in the dom chain than the
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// current node, and it is our idom! We know that we have already added
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// a DominatorTree node for our idom, because the idom must be a
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// predecessor in the depth first order that we are iterating through the
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// method.
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//
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DominatorSet::DomSetType::const_iterator I = Dominators.begin();
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DominatorSet::DomSetType::const_iterator End = Dominators.end();
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for (; I != End; ++I) { // Iterate over dominators...
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// All of our dominators should form a chain, where the number of elements
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// in the dominator set indicates what level the node is at in the chain.
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// We want the node immediately above us, so it will have an identical
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// dominator set, except that BB will not dominate it... therefore it's
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// dominator set size will be one less than BB's...
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//
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if (DS.getDominators(*I).size() == DomSetSize - 1) {
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// We know that the immediate dominator should already have a node,
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// because we are traversing the CFG in depth first order!
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//
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Node *IDomNode = Nodes[*I];
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assert(IDomNode && "No node for IDOM?");
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// Add a new tree node for this BasicBlock, and link it as a child of
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// IDomNode
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Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
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break;
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}
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}
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}
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}
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}
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//===----------------------------------------------------------------------===//
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// DominanceFrontier Implementation
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//===----------------------------------------------------------------------===//
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const cfg::DominanceFrontier::DomSetType &
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cfg::DominanceFrontier::calcDomFrontier(const DominatorTree &DT,
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const DominatorTree::Node *Node) {
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// Loop over CFG successors to calculate DFlocal[Node]
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const BasicBlock *BB = Node->getNode();
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DomSetType &S = Frontiers[BB]; // The new set to fill in...
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for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
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SI != SE; ++SI) {
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// Does Node immediately dominate this successor?
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if (DT[*SI]->getIDom() != Node)
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S.insert(*SI);
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}
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// At this point, S is DFlocal. Now we union in DFup's of our children...
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// Loop through and visit the nodes that Node immediately dominates (Node's
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// children in the IDomTree)
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//
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for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
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NI != NE; ++NI) {
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DominatorTree::Node *IDominee = *NI;
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const DomSetType &ChildDF = calcDomFrontier(DT, IDominee);
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DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
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for (; CDFI != CDFE; ++CDFI) {
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if (!Node->dominates(DT[*CDFI]))
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S.insert(*CDFI);
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}
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}
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return S;
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}
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const cfg::DominanceFrontier::DomSetType &
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cfg::DominanceFrontier::calcPostDomFrontier(const DominatorTree &DT,
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const DominatorTree::Node *Node) {
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// Loop over CFG successors to calculate DFlocal[Node]
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const BasicBlock *BB = Node->getNode();
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DomSetType &S = Frontiers[BB]; // The new set to fill in...
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for (pred_const_iterator SI = pred_begin(BB), SE = pred_end(BB);
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SI != SE; ++SI) {
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// Does Node immediately dominate this predeccessor?
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if (DT[*SI]->getIDom() != Node)
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S.insert(*SI);
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}
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// At this point, S is DFlocal. Now we union in DFup's of our children...
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// Loop through and visit the nodes that Node immediately dominates (Node's
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// children in the IDomTree)
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//
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for (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
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NI != NE; ++NI) {
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DominatorTree::Node *IDominee = *NI;
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const DomSetType &ChildDF = calcPostDomFrontier(DT, IDominee);
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DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
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for (; CDFI != CDFE; ++CDFI) {
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if (!Node->dominates(DT[*CDFI]))
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S.insert(*CDFI);
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}
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}
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return S;
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}
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