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081c34b725
must be called in the pass's constructor. This function uses static dependency declarations to recursively initialize the pass's dependencies. Clients that only create passes through the createFooPass() APIs will require no changes. Clients that want to use the CommandLine options for passes will need to manually call the appropriate initialization functions in PassInitialization.h before parsing commandline arguments. I have tested this with all standard configurations of clang and llvm-gcc on Darwin. It is possible that there are problems with the static dependencies that will only be visible with non-standard options. If you encounter any crash in pass registration/creation, please send the testcase to me directly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116820 91177308-0d34-0410-b5e6-96231b3b80d8
211 lines
7.1 KiB
C++
211 lines
7.1 KiB
C++
//===-- UnreachableBlockElim.cpp - Remove unreachable blocks for codegen --===//
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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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// This pass is an extremely simple version of the SimplifyCFG pass. Its sole
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// job is to delete LLVM basic blocks that are not reachable from the entry
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// node. To do this, it performs a simple depth first traversal of the CFG,
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// then deletes any unvisited nodes.
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//
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// Note that this pass is really a hack. In particular, the instruction
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// selectors for various targets should just not generate code for unreachable
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// blocks. Until LLVM has a more systematic way of defining instruction
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// selectors, however, we cannot really expect them to handle additional
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// complexity.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Constant.h"
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#include "llvm/Instructions.h"
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#include "llvm/Function.h"
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#include "llvm/Pass.h"
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#include "llvm/Type.h"
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#include "llvm/Analysis/ProfileInfo.h"
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#include "llvm/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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using namespace llvm;
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namespace {
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class UnreachableBlockElim : public FunctionPass {
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virtual bool runOnFunction(Function &F);
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public:
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static char ID; // Pass identification, replacement for typeid
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UnreachableBlockElim() : FunctionPass(ID) {
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initializeUnreachableBlockElimPass(*PassRegistry::getPassRegistry());
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addPreserved<ProfileInfo>();
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}
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};
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}
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char UnreachableBlockElim::ID = 0;
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INITIALIZE_PASS(UnreachableBlockElim, "unreachableblockelim",
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"Remove unreachable blocks from the CFG", false, false)
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FunctionPass *llvm::createUnreachableBlockEliminationPass() {
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return new UnreachableBlockElim();
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}
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bool UnreachableBlockElim::runOnFunction(Function &F) {
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SmallPtrSet<BasicBlock*, 8> Reachable;
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// Mark all reachable blocks.
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for (df_ext_iterator<Function*, SmallPtrSet<BasicBlock*, 8> > I =
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df_ext_begin(&F, Reachable), E = df_ext_end(&F, Reachable); I != E; ++I)
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/* Mark all reachable blocks */;
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// Loop over all dead blocks, remembering them and deleting all instructions
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// in them.
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std::vector<BasicBlock*> DeadBlocks;
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (!Reachable.count(I)) {
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BasicBlock *BB = I;
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DeadBlocks.push_back(BB);
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while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
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PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
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BB->getInstList().pop_front();
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}
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for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
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(*SI)->removePredecessor(BB);
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BB->dropAllReferences();
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}
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// Actually remove the blocks now.
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ProfileInfo *PI = getAnalysisIfAvailable<ProfileInfo>();
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for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i) {
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if (PI) PI->removeBlock(DeadBlocks[i]);
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DeadBlocks[i]->eraseFromParent();
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}
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return DeadBlocks.size();
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}
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namespace {
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class UnreachableMachineBlockElim : public MachineFunctionPass {
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virtual bool runOnMachineFunction(MachineFunction &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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MachineModuleInfo *MMI;
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public:
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static char ID; // Pass identification, replacement for typeid
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UnreachableMachineBlockElim() : MachineFunctionPass(ID) {}
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};
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}
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char UnreachableMachineBlockElim::ID = 0;
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INITIALIZE_PASS(UnreachableMachineBlockElim, "unreachable-mbb-elimination",
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"Remove unreachable machine basic blocks", false, false)
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char &llvm::UnreachableMachineBlockElimID = UnreachableMachineBlockElim::ID;
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void UnreachableMachineBlockElim::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addPreserved<MachineLoopInfo>();
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AU.addPreserved<MachineDominatorTree>();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
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SmallPtrSet<MachineBasicBlock*, 8> Reachable;
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bool ModifiedPHI = false;
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MMI = getAnalysisIfAvailable<MachineModuleInfo>();
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MachineDominatorTree *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
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MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
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// Mark all reachable blocks.
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for (df_ext_iterator<MachineFunction*, SmallPtrSet<MachineBasicBlock*, 8> >
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I = df_ext_begin(&F, Reachable), E = df_ext_end(&F, Reachable);
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I != E; ++I)
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/* Mark all reachable blocks */;
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// Loop over all dead blocks, remembering them and deleting all instructions
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// in them.
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std::vector<MachineBasicBlock*> DeadBlocks;
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for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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MachineBasicBlock *BB = I;
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// Test for deadness.
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if (!Reachable.count(BB)) {
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DeadBlocks.push_back(BB);
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// Update dominator and loop info.
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if (MLI) MLI->removeBlock(BB);
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if (MDT && MDT->getNode(BB)) MDT->eraseNode(BB);
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while (BB->succ_begin() != BB->succ_end()) {
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MachineBasicBlock* succ = *BB->succ_begin();
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MachineBasicBlock::iterator start = succ->begin();
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while (start != succ->end() && start->isPHI()) {
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for (unsigned i = start->getNumOperands() - 1; i >= 2; i-=2)
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if (start->getOperand(i).isMBB() &&
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start->getOperand(i).getMBB() == BB) {
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start->RemoveOperand(i);
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start->RemoveOperand(i-1);
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}
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start++;
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}
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BB->removeSuccessor(BB->succ_begin());
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}
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}
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}
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// Actually remove the blocks now.
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for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i)
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DeadBlocks[i]->eraseFromParent();
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// Cleanup PHI nodes.
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for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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MachineBasicBlock *BB = I;
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// Prune unneeded PHI entries.
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SmallPtrSet<MachineBasicBlock*, 8> preds(BB->pred_begin(),
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BB->pred_end());
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MachineBasicBlock::iterator phi = BB->begin();
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while (phi != BB->end() && phi->isPHI()) {
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for (unsigned i = phi->getNumOperands() - 1; i >= 2; i-=2)
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if (!preds.count(phi->getOperand(i).getMBB())) {
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phi->RemoveOperand(i);
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phi->RemoveOperand(i-1);
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ModifiedPHI = true;
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}
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if (phi->getNumOperands() == 3) {
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unsigned Input = phi->getOperand(1).getReg();
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unsigned Output = phi->getOperand(0).getReg();
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MachineInstr* temp = phi;
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++phi;
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temp->eraseFromParent();
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ModifiedPHI = true;
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if (Input != Output)
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F.getRegInfo().replaceRegWith(Output, Input);
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continue;
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}
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++phi;
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}
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}
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F.RenumberBlocks();
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return (DeadBlocks.size() || ModifiedPHI);
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}
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