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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40564 91177308-0d34-0410-b5e6-96231b3b80d8
817 lines
26 KiB
C++
817 lines
26 KiB
C++
//===- Dominators.cpp - Dominator Calculation -----------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements simple dominator construction algorithms for finding
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// forward dominators. Postdominators are available in libanalysis, but are not
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// included in libvmcore, because it's not needed. Forward dominators are
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// needed to support the Verifier pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SetOperations.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/Instructions.h"
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#include "llvm/Support/Streams.h"
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#include <algorithm>
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using namespace llvm;
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namespace llvm {
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static std::ostream &operator<<(std::ostream &o,
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const std::set<BasicBlock*> &BBs) {
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for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
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I != E; ++I)
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if (*I)
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WriteAsOperand(o, *I, false);
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else
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o << " <<exit node>>";
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return o;
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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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//
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// DominatorTree construction - This pass constructs immediate dominator
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// information for a flow-graph based on the algorithm described in this
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// document:
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//
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// A Fast Algorithm for Finding Dominators in a Flowgraph
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// T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
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//
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// This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
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// LINK, but it turns out that the theoretically slower O(n*log(n))
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// implementation is actually faster than the "efficient" algorithm (even for
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// large CFGs) because the constant overheads are substantially smaller. The
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// lower-complexity version can be enabled with the following #define:
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//
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#define BALANCE_IDOM_TREE 0
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//
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//===----------------------------------------------------------------------===//
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char DominatorTree::ID = 0;
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static RegisterPass<DominatorTree>
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E("domtree", "Dominator Tree Construction", true);
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// NewBB is split and now it has one successor. Update dominator tree to
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// reflect this change.
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void DominatorTree::splitBlock(BasicBlock *NewBB) {
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assert(NewBB->getTerminator()->getNumSuccessors() == 1
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&& "NewBB should have a single successor!");
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BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
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std::vector<BasicBlock*> PredBlocks;
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for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
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PI != PE; ++PI)
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PredBlocks.push_back(*PI);
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assert(!PredBlocks.empty() && "No predblocks??");
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// The newly inserted basic block will dominate existing basic blocks iff the
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// PredBlocks dominate all of the non-pred blocks. If all predblocks dominate
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// the non-pred blocks, then they all must be the same block!
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//
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bool NewBBDominatesNewBBSucc = true;
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{
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BasicBlock *OnePred = PredBlocks[0];
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unsigned i = 1, e = PredBlocks.size();
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for (i = 1; !isReachableFromEntry(OnePred); ++i) {
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assert(i != e && "Didn't find reachable pred?");
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OnePred = PredBlocks[i];
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}
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for (; i != e; ++i)
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if (PredBlocks[i] != OnePred && isReachableFromEntry(OnePred)){
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NewBBDominatesNewBBSucc = false;
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break;
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}
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if (NewBBDominatesNewBBSucc)
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for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
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PI != E; ++PI)
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if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
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NewBBDominatesNewBBSucc = false;
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break;
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}
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}
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// The other scenario where the new block can dominate its successors are when
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// all predecessors of NewBBSucc that are not NewBB are dominated by NewBBSucc
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// already.
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if (!NewBBDominatesNewBBSucc) {
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NewBBDominatesNewBBSucc = true;
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for (pred_iterator PI = pred_begin(NewBBSucc), E = pred_end(NewBBSucc);
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PI != E; ++PI)
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if (*PI != NewBB && !dominates(NewBBSucc, *PI)) {
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NewBBDominatesNewBBSucc = false;
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break;
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}
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}
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// Find NewBB's immediate dominator and create new dominator tree node for NewBB.
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BasicBlock *NewBBIDom = 0;
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unsigned i = 0;
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for (i = 0; i < PredBlocks.size(); ++i)
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if (isReachableFromEntry(PredBlocks[i])) {
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NewBBIDom = PredBlocks[i];
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break;
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}
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assert(i != PredBlocks.size() && "No reachable preds?");
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for (i = i + 1; i < PredBlocks.size(); ++i) {
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if (isReachableFromEntry(PredBlocks[i]))
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NewBBIDom = findNearestCommonDominator(NewBBIDom, PredBlocks[i]);
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}
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assert(NewBBIDom && "No immediate dominator found??");
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// Create the new dominator tree node... and set the idom of NewBB.
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DomTreeNode *NewBBNode = addNewBlock(NewBB, NewBBIDom);
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// If NewBB strictly dominates other blocks, then it is now the immediate
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// dominator of NewBBSucc. Update the dominator tree as appropriate.
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if (NewBBDominatesNewBBSucc) {
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DomTreeNode *NewBBSuccNode = getNode(NewBBSucc);
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changeImmediateDominator(NewBBSuccNode, NewBBNode);
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}
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}
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unsigned DominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
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unsigned N) {
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// This is more understandable as a recursive algorithm, but we can't use the
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// recursive algorithm due to stack depth issues. Keep it here for
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// documentation purposes.
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#if 0
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VInfo.Semi = ++N;
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VInfo.Label = V;
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Vertex.push_back(V); // Vertex[n] = V;
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//Info[V].Ancestor = 0; // Ancestor[n] = 0
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//Info[V].Child = 0; // Child[v] = 0
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VInfo.Size = 1; // Size[v] = 1
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for (succ_iterator SI = succ_begin(V), E = succ_end(V); SI != E; ++SI) {
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InfoRec &SuccVInfo = Info[*SI];
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if (SuccVInfo.Semi == 0) {
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SuccVInfo.Parent = V;
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N = DFSPass(*SI, SuccVInfo, N);
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}
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}
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#else
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std::vector<std::pair<BasicBlock*, unsigned> > Worklist;
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Worklist.push_back(std::make_pair(V, 0U));
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while (!Worklist.empty()) {
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BasicBlock *BB = Worklist.back().first;
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unsigned NextSucc = Worklist.back().second;
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// First time we visited this BB?
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if (NextSucc == 0) {
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InfoRec &BBInfo = Info[BB];
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BBInfo.Semi = ++N;
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BBInfo.Label = BB;
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Vertex.push_back(BB); // Vertex[n] = V;
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//BBInfo[V].Ancestor = 0; // Ancestor[n] = 0
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//BBInfo[V].Child = 0; // Child[v] = 0
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BBInfo.Size = 1; // Size[v] = 1
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}
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// If we are done with this block, remove it from the worklist.
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if (NextSucc == BB->getTerminator()->getNumSuccessors()) {
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Worklist.pop_back();
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continue;
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}
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// Otherwise, increment the successor number for the next time we get to it.
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++Worklist.back().second;
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// Visit the successor next, if it isn't already visited.
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BasicBlock *Succ = BB->getTerminator()->getSuccessor(NextSucc);
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InfoRec &SuccVInfo = Info[Succ];
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if (SuccVInfo.Semi == 0) {
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SuccVInfo.Parent = BB;
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Worklist.push_back(std::make_pair(Succ, 0U));
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}
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}
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#endif
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return N;
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}
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void DominatorTree::Compress(BasicBlock *VIn) {
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std::vector<BasicBlock *> Work;
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std::set<BasicBlock *> Visited;
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InfoRec &VInInfo = Info[VIn];
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BasicBlock *VInAncestor = VInInfo.Ancestor;
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InfoRec &VInVAInfo = Info[VInAncestor];
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if (VInVAInfo.Ancestor != 0)
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Work.push_back(VIn);
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while (!Work.empty()) {
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BasicBlock *V = Work.back();
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InfoRec &VInfo = Info[V];
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BasicBlock *VAncestor = VInfo.Ancestor;
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InfoRec &VAInfo = Info[VAncestor];
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// Process Ancestor first
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if (Visited.count(VAncestor) == 0 && VAInfo.Ancestor != 0) {
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Work.push_back(VAncestor);
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Visited.insert(VAncestor);
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continue;
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}
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Work.pop_back();
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// Update VINfo based on Ancestor info
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if (VAInfo.Ancestor == 0)
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continue;
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BasicBlock *VAncestorLabel = VAInfo.Label;
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BasicBlock *VLabel = VInfo.Label;
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if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
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VInfo.Label = VAncestorLabel;
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VInfo.Ancestor = VAInfo.Ancestor;
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}
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}
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BasicBlock *DominatorTree::Eval(BasicBlock *V) {
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InfoRec &VInfo = Info[V];
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#if !BALANCE_IDOM_TREE
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// Higher-complexity but faster implementation
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if (VInfo.Ancestor == 0)
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return V;
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Compress(V);
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return VInfo.Label;
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#else
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// Lower-complexity but slower implementation
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if (VInfo.Ancestor == 0)
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return VInfo.Label;
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Compress(V);
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BasicBlock *VLabel = VInfo.Label;
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BasicBlock *VAncestorLabel = Info[VInfo.Ancestor].Label;
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if (Info[VAncestorLabel].Semi >= Info[VLabel].Semi)
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return VLabel;
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else
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return VAncestorLabel;
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#endif
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}
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void DominatorTree::Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo){
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#if !BALANCE_IDOM_TREE
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// Higher-complexity but faster implementation
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WInfo.Ancestor = V;
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#else
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// Lower-complexity but slower implementation
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BasicBlock *WLabel = WInfo.Label;
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unsigned WLabelSemi = Info[WLabel].Semi;
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BasicBlock *S = W;
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InfoRec *SInfo = &Info[S];
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BasicBlock *SChild = SInfo->Child;
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InfoRec *SChildInfo = &Info[SChild];
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while (WLabelSemi < Info[SChildInfo->Label].Semi) {
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BasicBlock *SChildChild = SChildInfo->Child;
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if (SInfo->Size+Info[SChildChild].Size >= 2*SChildInfo->Size) {
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SChildInfo->Ancestor = S;
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SInfo->Child = SChild = SChildChild;
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SChildInfo = &Info[SChild];
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} else {
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SChildInfo->Size = SInfo->Size;
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S = SInfo->Ancestor = SChild;
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SInfo = SChildInfo;
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SChild = SChildChild;
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SChildInfo = &Info[SChild];
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}
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}
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InfoRec &VInfo = Info[V];
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SInfo->Label = WLabel;
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assert(V != W && "The optimization here will not work in this case!");
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unsigned WSize = WInfo.Size;
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unsigned VSize = (VInfo.Size += WSize);
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if (VSize < 2*WSize)
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std::swap(S, VInfo.Child);
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while (S) {
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SInfo = &Info[S];
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SInfo->Ancestor = V;
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S = SInfo->Child;
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}
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#endif
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}
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void DominatorTree::calculate(Function& F) {
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BasicBlock* Root = Roots[0];
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// Add a node for the root...
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DomTreeNodes[Root] = RootNode = new DomTreeNode(Root, 0);
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Vertex.push_back(0);
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// Step #1: Number blocks in depth-first order and initialize variables used
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// in later stages of the algorithm.
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unsigned N = 0;
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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N = DFSPass(Roots[i], Info[Roots[i]], 0);
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for (unsigned i = N; i >= 2; --i) {
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BasicBlock *W = Vertex[i];
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InfoRec &WInfo = Info[W];
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// Step #2: Calculate the semidominators of all vertices
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for (pred_iterator PI = pred_begin(W), E = pred_end(W); PI != E; ++PI)
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if (Info.count(*PI)) { // Only if this predecessor is reachable!
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unsigned SemiU = Info[Eval(*PI)].Semi;
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if (SemiU < WInfo.Semi)
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WInfo.Semi = SemiU;
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}
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Info[Vertex[WInfo.Semi]].Bucket.push_back(W);
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BasicBlock *WParent = WInfo.Parent;
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Link(WParent, W, WInfo);
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// Step #3: Implicitly define the immediate dominator of vertices
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std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
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while (!WParentBucket.empty()) {
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BasicBlock *V = WParentBucket.back();
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WParentBucket.pop_back();
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BasicBlock *U = Eval(V);
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IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
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}
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}
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// Step #4: Explicitly define the immediate dominator of each vertex
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for (unsigned i = 2; i <= N; ++i) {
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BasicBlock *W = Vertex[i];
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BasicBlock *&WIDom = IDoms[W];
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if (WIDom != Vertex[Info[W].Semi])
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WIDom = IDoms[WIDom];
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}
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// Loop over all of the reachable blocks in the function...
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (BasicBlock *ImmDom = getIDom(I)) { // Reachable block.
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DomTreeNode *&BBNode = DomTreeNodes[I];
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if (!BBNode) { // Haven't calculated this node yet?
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// Get or calculate the node for the immediate dominator
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DomTreeNode *IDomNode = getNodeForBlock(ImmDom);
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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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DomTreeNode *C = new DomTreeNode(I, IDomNode);
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DomTreeNodes[I] = C;
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BBNode = IDomNode->addChild(C);
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}
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}
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// Free temporary memory used to construct idom's
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Info.clear();
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IDoms.clear();
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std::vector<BasicBlock*>().swap(Vertex);
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updateDFSNumbers();
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}
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void DominatorTreeBase::updateDFSNumbers()
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{
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int dfsnum = 0;
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// Iterate over all nodes in depth first order.
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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for (df_iterator<BasicBlock*> I = df_begin(Roots[i]),
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E = df_end(Roots[i]); I != E; ++I) {
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BasicBlock *BB = *I;
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DomTreeNode *BBNode = getNode(BB);
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if (BBNode) {
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if (!BBNode->getIDom())
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BBNode->assignDFSNumber(dfsnum);
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}
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}
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SlowQueries = 0;
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DFSInfoValid = true;
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}
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/// isReachableFromEntry - Return true if A is dominated by the entry
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/// block of the function containing it.
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const bool DominatorTreeBase::isReachableFromEntry(BasicBlock* A) {
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assert (!isPostDominator()
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&& "This is not implemented for post dominators");
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return dominates(&A->getParent()->getEntryBlock(), A);
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}
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// dominates - Return true if A dominates B. THis performs the
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// special checks necessary if A and B are in the same basic block.
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bool DominatorTreeBase::dominates(Instruction *A, Instruction *B) {
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BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
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if (BBA != BBB) return dominates(BBA, BBB);
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// It is not possible to determine dominance between two PHI nodes
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// based on their ordering.
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if (isa<PHINode>(A) && isa<PHINode>(B))
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return false;
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// Loop through the basic block until we find A or B.
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BasicBlock::iterator I = BBA->begin();
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for (; &*I != A && &*I != B; ++I) /*empty*/;
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if(!IsPostDominators) {
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// A dominates B if it is found first in the basic block.
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return &*I == A;
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} else {
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// A post-dominates B if B is found first in the basic block.
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return &*I == B;
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}
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}
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// DominatorTreeBase::reset - Free all of the tree node memory.
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//
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void DominatorTreeBase::reset() {
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for (DomTreeNodeMapType::iterator I = DomTreeNodes.begin(),
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E = DomTreeNodes.end(); I != E; ++I)
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delete I->second;
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DomTreeNodes.clear();
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IDoms.clear();
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Roots.clear();
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Vertex.clear();
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RootNode = 0;
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}
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/// findNearestCommonDominator - Find nearest common dominator basic block
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/// for basic block A and B. If there is no such block then return NULL.
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BasicBlock *DominatorTreeBase::findNearestCommonDominator(BasicBlock *A,
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BasicBlock *B) {
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assert (!isPostDominator()
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&& "This is not implemented for post dominators");
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assert (A->getParent() == B->getParent()
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&& "Two blocks are not in same function");
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// If either A or B is a entry block then it is nearest common dominator.
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BasicBlock &Entry = A->getParent()->getEntryBlock();
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if (A == &Entry || B == &Entry)
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return &Entry;
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// If B dominates A then B is nearest common dominator.
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if (dominates(B,A))
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return B;
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// If A dominates B then A is nearest common dominator.
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if (dominates(A,B))
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return A;
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DomTreeNode *NodeA = getNode(A);
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DomTreeNode *NodeB = getNode(B);
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// Collect NodeA dominators set.
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SmallPtrSet<DomTreeNode*, 16> NodeADoms;
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NodeADoms.insert(NodeA);
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DomTreeNode *IDomA = NodeA->getIDom();
|
|
while(IDomA) {
|
|
NodeADoms.insert(IDomA);
|
|
IDomA = IDomA->getIDom();
|
|
}
|
|
|
|
// Walk NodeB immediate dominators chain and find common dominator node.
|
|
DomTreeNode *IDomB = NodeB->getIDom();
|
|
while(IDomB) {
|
|
if (NodeADoms.count(IDomB) != 0)
|
|
return IDomB->getBlock();
|
|
|
|
IDomB = IDomB->getIDom();
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/// assignDFSNumber - Assign In and Out numbers while walking dominator tree
|
|
/// in dfs order.
|
|
void DomTreeNode::assignDFSNumber(int num) {
|
|
std::vector<DomTreeNode *> workStack;
|
|
std::set<DomTreeNode *> visitedNodes;
|
|
|
|
workStack.push_back(this);
|
|
visitedNodes.insert(this);
|
|
this->DFSNumIn = num++;
|
|
|
|
while (!workStack.empty()) {
|
|
DomTreeNode *Node = workStack.back();
|
|
|
|
bool visitChild = false;
|
|
for (std::vector<DomTreeNode*>::iterator DI = Node->begin(),
|
|
E = Node->end(); DI != E && !visitChild; ++DI) {
|
|
DomTreeNode *Child = *DI;
|
|
if (visitedNodes.count(Child) == 0) {
|
|
visitChild = true;
|
|
Child->DFSNumIn = num++;
|
|
workStack.push_back(Child);
|
|
visitedNodes.insert(Child);
|
|
}
|
|
}
|
|
if (!visitChild) {
|
|
// If we reach here means all children are visited
|
|
Node->DFSNumOut = num++;
|
|
workStack.pop_back();
|
|
}
|
|
}
|
|
}
|
|
|
|
void DomTreeNode::setIDom(DomTreeNode *NewIDom) {
|
|
assert(IDom && "No immediate dominator?");
|
|
if (IDom != NewIDom) {
|
|
std::vector<DomTreeNode*>::iterator I =
|
|
std::find(IDom->Children.begin(), IDom->Children.end(), this);
|
|
assert(I != IDom->Children.end() &&
|
|
"Not in immediate dominator children set!");
|
|
// I am no longer your child...
|
|
IDom->Children.erase(I);
|
|
|
|
// Switch to new dominator
|
|
IDom = NewIDom;
|
|
IDom->Children.push_back(this);
|
|
}
|
|
}
|
|
|
|
DomTreeNode *DominatorTree::getNodeForBlock(BasicBlock *BB) {
|
|
DomTreeNode *&BBNode = DomTreeNodes[BB];
|
|
if (BBNode) return BBNode;
|
|
|
|
// Haven't calculated this node yet? Get or calculate the node for the
|
|
// immediate dominator.
|
|
BasicBlock *IDom = getIDom(BB);
|
|
DomTreeNode *IDomNode = getNodeForBlock(IDom);
|
|
|
|
// Add a new tree node for this BasicBlock, and link it as a child of
|
|
// IDomNode
|
|
DomTreeNode *C = new DomTreeNode(BB, IDomNode);
|
|
DomTreeNodes[BB] = C;
|
|
return BBNode = IDomNode->addChild(C);
|
|
}
|
|
|
|
static std::ostream &operator<<(std::ostream &o,
|
|
const DomTreeNode *Node) {
|
|
if (Node->getBlock())
|
|
WriteAsOperand(o, Node->getBlock(), false);
|
|
else
|
|
o << " <<exit node>>";
|
|
return o << "\n";
|
|
}
|
|
|
|
static void PrintDomTree(const DomTreeNode *N, std::ostream &o,
|
|
unsigned Lev) {
|
|
o << std::string(2*Lev, ' ') << "[" << Lev << "] " << N;
|
|
for (DomTreeNode::const_iterator I = N->begin(), E = N->end();
|
|
I != E; ++I)
|
|
PrintDomTree(*I, o, Lev+1);
|
|
}
|
|
|
|
void DominatorTreeBase::print(std::ostream &o, const Module* ) const {
|
|
o << "=============================--------------------------------\n"
|
|
<< "Inorder Dominator Tree:\n";
|
|
PrintDomTree(getRootNode(), o, 1);
|
|
}
|
|
|
|
void DominatorTreeBase::dump() {
|
|
print (llvm::cerr);
|
|
}
|
|
|
|
bool DominatorTree::runOnFunction(Function &F) {
|
|
reset(); // Reset from the last time we were run...
|
|
Roots.push_back(&F.getEntryBlock());
|
|
calculate(F);
|
|
return false;
|
|
}
|
|
|
|
//===----------------------------------------------------------------------===//
|
|
// DominanceFrontier Implementation
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
char DominanceFrontier::ID = 0;
|
|
static RegisterPass<DominanceFrontier>
|
|
G("domfrontier", "Dominance Frontier Construction", true);
|
|
|
|
// NewBB is split and now it has one successor. Update dominace frontier to
|
|
// reflect this change.
|
|
void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
|
|
|
|
assert(NewBB->getTerminator()->getNumSuccessors() == 1
|
|
&& "NewBB should have a single successor!");
|
|
BasicBlock *NewBBSucc = NewBB->getTerminator()->getSuccessor(0);
|
|
|
|
std::vector<BasicBlock*> PredBlocks;
|
|
for (pred_iterator PI = pred_begin(NewBB), PE = pred_end(NewBB);
|
|
PI != PE; ++PI)
|
|
PredBlocks.push_back(*PI);
|
|
|
|
if (PredBlocks.empty())
|
|
// If NewBB does not have any predecessors then it is a entry block.
|
|
// In this case, NewBB and its successor NewBBSucc dominates all
|
|
// other blocks.
|
|
return;
|
|
|
|
DominatorTree &DT = getAnalysis<DominatorTree>();
|
|
bool NewBBDominatesNewBBSucc = true;
|
|
if (!DT.dominates(NewBB, NewBBSucc))
|
|
NewBBDominatesNewBBSucc = false;
|
|
|
|
// If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
|
|
// DF(PredBlocks[0]) without the stuff that the new block does not dominate
|
|
// a predecessor of.
|
|
if (NewBBDominatesNewBBSucc) {
|
|
DominanceFrontier::iterator DFI = find(PredBlocks[0]);
|
|
if (DFI != end()) {
|
|
DominanceFrontier::DomSetType Set = DFI->second;
|
|
// Filter out stuff in Set that we do not dominate a predecessor of.
|
|
for (DominanceFrontier::DomSetType::iterator SetI = Set.begin(),
|
|
E = Set.end(); SetI != E;) {
|
|
bool DominatesPred = false;
|
|
for (pred_iterator PI = pred_begin(*SetI), E = pred_end(*SetI);
|
|
PI != E; ++PI)
|
|
if (DT.dominates(NewBB, *PI))
|
|
DominatesPred = true;
|
|
if (!DominatesPred)
|
|
Set.erase(SetI++);
|
|
else
|
|
++SetI;
|
|
}
|
|
|
|
DominanceFrontier::iterator NewBBI = find(NewBB);
|
|
if (NewBBI != end()) {
|
|
DominanceFrontier::DomSetType NewBBSet = NewBBI->second;
|
|
NewBBSet.insert(Set.begin(), Set.end());
|
|
} else
|
|
addBasicBlock(NewBB, Set);
|
|
}
|
|
|
|
} else {
|
|
// DF(NewBB) is {NewBBSucc} because NewBB does not strictly dominate
|
|
// NewBBSucc, but it does dominate itself (and there is an edge (NewBB ->
|
|
// NewBBSucc)). NewBBSucc is the single successor of NewBB.
|
|
DominanceFrontier::DomSetType NewDFSet;
|
|
NewDFSet.insert(NewBBSucc);
|
|
addBasicBlock(NewBB, NewDFSet);
|
|
}
|
|
|
|
// Now we must loop over all of the dominance frontiers in the function,
|
|
// replacing occurrences of NewBBSucc with NewBB in some cases. All
|
|
// blocks that dominate a block in PredBlocks and contained NewBBSucc in
|
|
// their dominance frontier must be updated to contain NewBB instead.
|
|
//
|
|
for (Function::iterator FI = NewBB->getParent()->begin(),
|
|
FE = NewBB->getParent()->end(); FI != FE; ++FI) {
|
|
DominanceFrontier::iterator DFI = find(FI);
|
|
if (DFI == end()) continue; // unreachable block.
|
|
|
|
// Only consider dominators of NewBBSucc
|
|
if (!DFI->second.count(NewBBSucc)) continue;
|
|
|
|
bool BlockDominatesAny = false;
|
|
for (std::vector<BasicBlock*>::const_iterator BI = PredBlocks.begin(),
|
|
BE = PredBlocks.end(); BI != BE; ++BI) {
|
|
if (DT.dominates(FI, *BI)) {
|
|
BlockDominatesAny = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (BlockDominatesAny) {
|
|
// If NewBBSucc should not stay in our dominator frontier, remove it.
|
|
// We remove it unless there is a predecessor of NewBBSucc that we
|
|
// dominate, but we don't strictly dominate NewBBSucc.
|
|
bool ShouldRemove = true;
|
|
if ((BasicBlock*)FI == NewBBSucc
|
|
|| !DT.dominates(FI, NewBBSucc)) {
|
|
// Okay, we know that PredDom does not strictly dominate NewBBSucc.
|
|
// Check to see if it dominates any predecessors of NewBBSucc.
|
|
for (pred_iterator PI = pred_begin(NewBBSucc),
|
|
E = pred_end(NewBBSucc); PI != E; ++PI)
|
|
if (DT.dominates(FI, *PI)) {
|
|
ShouldRemove = false;
|
|
break;
|
|
}
|
|
|
|
if (ShouldRemove)
|
|
removeFromFrontier(DFI, NewBBSucc);
|
|
addToFrontier(DFI, NewBB);
|
|
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
namespace {
|
|
class DFCalculateWorkObject {
|
|
public:
|
|
DFCalculateWorkObject(BasicBlock *B, BasicBlock *P,
|
|
const DomTreeNode *N,
|
|
const DomTreeNode *PN)
|
|
: currentBB(B), parentBB(P), Node(N), parentNode(PN) {}
|
|
BasicBlock *currentBB;
|
|
BasicBlock *parentBB;
|
|
const DomTreeNode *Node;
|
|
const DomTreeNode *parentNode;
|
|
};
|
|
}
|
|
|
|
const DominanceFrontier::DomSetType &
|
|
DominanceFrontier::calculate(const DominatorTree &DT,
|
|
const DomTreeNode *Node) {
|
|
BasicBlock *BB = Node->getBlock();
|
|
DomSetType *Result = NULL;
|
|
|
|
std::vector<DFCalculateWorkObject> workList;
|
|
SmallPtrSet<BasicBlock *, 32> visited;
|
|
|
|
workList.push_back(DFCalculateWorkObject(BB, NULL, Node, NULL));
|
|
do {
|
|
DFCalculateWorkObject *currentW = &workList.back();
|
|
assert (currentW && "Missing work object.");
|
|
|
|
BasicBlock *currentBB = currentW->currentBB;
|
|
BasicBlock *parentBB = currentW->parentBB;
|
|
const DomTreeNode *currentNode = currentW->Node;
|
|
const DomTreeNode *parentNode = currentW->parentNode;
|
|
assert (currentBB && "Invalid work object. Missing current Basic Block");
|
|
assert (currentNode && "Invalid work object. Missing current Node");
|
|
DomSetType &S = Frontiers[currentBB];
|
|
|
|
// Visit each block only once.
|
|
if (visited.count(currentBB) == 0) {
|
|
visited.insert(currentBB);
|
|
|
|
// Loop over CFG successors to calculate DFlocal[currentNode]
|
|
for (succ_iterator SI = succ_begin(currentBB), SE = succ_end(currentBB);
|
|
SI != SE; ++SI) {
|
|
// Does Node immediately dominate this successor?
|
|
if (DT[*SI]->getIDom() != currentNode)
|
|
S.insert(*SI);
|
|
}
|
|
}
|
|
|
|
// At this point, S is DFlocal. Now we union in DFup's of our children...
|
|
// Loop through and visit the nodes that Node immediately dominates (Node's
|
|
// children in the IDomTree)
|
|
bool visitChild = false;
|
|
for (DomTreeNode::const_iterator NI = currentNode->begin(),
|
|
NE = currentNode->end(); NI != NE; ++NI) {
|
|
DomTreeNode *IDominee = *NI;
|
|
BasicBlock *childBB = IDominee->getBlock();
|
|
if (visited.count(childBB) == 0) {
|
|
workList.push_back(DFCalculateWorkObject(childBB, currentBB,
|
|
IDominee, currentNode));
|
|
visitChild = true;
|
|
}
|
|
}
|
|
|
|
// If all children are visited or there is any child then pop this block
|
|
// from the workList.
|
|
if (!visitChild) {
|
|
|
|
if (!parentBB) {
|
|
Result = &S;
|
|
break;
|
|
}
|
|
|
|
DomSetType::const_iterator CDFI = S.begin(), CDFE = S.end();
|
|
DomSetType &parentSet = Frontiers[parentBB];
|
|
for (; CDFI != CDFE; ++CDFI) {
|
|
if (!DT.properlyDominates(parentNode, DT[*CDFI]))
|
|
parentSet.insert(*CDFI);
|
|
}
|
|
workList.pop_back();
|
|
}
|
|
|
|
} while (!workList.empty());
|
|
|
|
return *Result;
|
|
}
|
|
|
|
void DominanceFrontierBase::print(std::ostream &o, const Module* ) const {
|
|
for (const_iterator I = begin(), E = end(); I != E; ++I) {
|
|
o << " DomFrontier for BB";
|
|
if (I->first)
|
|
WriteAsOperand(o, I->first, false);
|
|
else
|
|
o << " <<exit node>>";
|
|
o << " is:\t" << I->second << "\n";
|
|
}
|
|
}
|
|
|
|
void DominanceFrontierBase::dump() {
|
|
print (llvm::cerr);
|
|
}
|