Coverage Report

Created: 2017-10-03 07:32

/Users/buildslave/jenkins/sharedspace/clang-stage2-coverage-R@2/llvm/lib/CodeGen/UnreachableBlockElim.cpp
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Source (jump to first uncovered line)
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//===-- 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/UnreachableBlockElim.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SmallPtrSet.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/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Constant.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Type.h"
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#include "llvm/Pass.h"
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#include "llvm/Target/TargetInstrInfo.h"
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using namespace llvm;
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614k
static bool eliminateUnreachableBlock(Function &F) {
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  df_iterator_default_set<BasicBlock*> Reachable;
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614k
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614k
  // Mark all reachable blocks.
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614k
  for (BasicBlock *BB : depth_first_ext(&F, Reachable))
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4.00M
    (void)BB/* Mark all reachable blocks */;
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614k
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614k
  // Loop over all dead blocks, remembering them and deleting all instructions
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614k
  // in them.
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614k
  std::vector<BasicBlock*> DeadBlocks;
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4.61M
  for (Function::iterator I = F.begin(), E = F.end(); 
I != E4.61M
;
++I4.00M
)
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4.00M
    
if (4.00M
!Reachable.count(&*I)4.00M
) {
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114
      BasicBlock *BB = &*I;
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114
      DeadBlocks.push_back(BB);
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115
      while (PHINode *
PN115
= dyn_cast<PHINode>(BB->begin())) {
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1
        PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
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1
        BB->getInstList().pop_front();
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1
      }
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163
      for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); 
SI != E163
;
++SI49
)
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49
        (*SI)->removePredecessor(BB);
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4.00M
      BB->dropAllReferences();
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4.00M
    }
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614k
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614k
  // Actually remove the blocks now.
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  for (unsigned i = 0, e = DeadBlocks.size(); 
i != e614k
;
++i114
) {
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    DeadBlocks[i]->eraseFromParent();
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114
  }
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614k
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  return !DeadBlocks.empty();
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614k
}
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namespace {
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class UnreachableBlockElimLegacyPass : public FunctionPass {
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614k
  bool runOnFunction(Function &F) override {
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    return eliminateUnreachableBlock(F);
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  }
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public:
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  static char ID; // Pass identification, replacement for typeid
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35.6k
  UnreachableBlockElimLegacyPass() : FunctionPass(ID) {
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35.6k
    initializeUnreachableBlockElimLegacyPassPass(
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35.6k
        *PassRegistry::getPassRegistry());
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35.6k
  }
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35.5k
  void getAnalysisUsage(AnalysisUsage &AU) const override {
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35.5k
    AU.addPreserved<DominatorTreeWrapperPass>();
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35.5k
  }
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};
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}
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char UnreachableBlockElimLegacyPass::ID = 0;
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INITIALIZE_PASS(UnreachableBlockElimLegacyPass, "unreachableblockelim",
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                "Remove unreachable blocks from the CFG", false, false)
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35.6k
FunctionPass *llvm::createUnreachableBlockEliminationPass() {
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35.6k
  return new UnreachableBlockElimLegacyPass();
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35.6k
}
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PreservedAnalyses UnreachableBlockElimPass::run(Function &F,
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1
                                                FunctionAnalysisManager &AM) {
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  bool Changed = eliminateUnreachableBlock(F);
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1
  if (!Changed)
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0
    return PreservedAnalyses::all();
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1
  PreservedAnalyses PA;
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1
  PA.preserve<DominatorTreeAnalysis>();
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1
  return PA;
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1
}
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namespace {
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  class UnreachableMachineBlockElim : public MachineFunctionPass {
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    bool runOnMachineFunction(MachineFunction &F) override;
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    void getAnalysisUsage(AnalysisUsage &AU) const override;
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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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33.3k
    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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33.3k
  MachineFunctionPass::getAnalysisUsage(AU);
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33.3k
}
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bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
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  df_iterator_default_set<MachineBasicBlock*> 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 (MachineBasicBlock *BB : depth_first_ext(&F, Reachable))
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4.09M
    (void)BB/* 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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4.69M
  for (MachineFunction::iterator I = F.begin(), E = F.end(); 
I != E4.69M
;
++I4.09M
) {
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4.09M
    MachineBasicBlock *BB = &*I;
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4.09M
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4.09M
    // Test for deadness.
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4.09M
    if (
!Reachable.count(BB)4.09M
) {
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      DeadBlocks.push_back(BB);
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      // Update dominator and loop info.
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      if (
MLI156
)
MLI->removeBlock(BB)32
;
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      if (
MDT && 156
MDT->getNode(BB)37
)
MDT->eraseNode(BB)0
;
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156
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      while (
BB->succ_begin() != BB->succ_end()163
) {
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7
        MachineBasicBlock* succ = *BB->succ_begin();
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        MachineBasicBlock::iterator start = succ->begin();
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10
        while (
start != succ->end() && 10
start->isPHI()9
) {
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8
          for (unsigned i = start->getNumOperands() - 1; 
i >= 28
;
i-=25
)
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5
            
if (5
start->getOperand(i).isMBB() &&
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5
                
start->getOperand(i).getMBB() == BB5
) {
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              start->RemoveOperand(i);
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              start->RemoveOperand(i-1);
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            }
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3
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3
          start++;
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3
        }
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        BB->removeSuccessor(BB->succ_begin());
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      }
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    }
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4.09M
  }
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595k
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  // Actually remove the blocks now.
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  for (unsigned i = 0, e = DeadBlocks.size(); 
i != e595k
;
++i156
)
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    DeadBlocks[i]->eraseFromParent();
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  // Cleanup PHI nodes.
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4.69M
  for (MachineFunction::iterator I = F.begin(), E = F.end(); 
I != E4.69M
;
++I4.09M
) {
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4.09M
    MachineBasicBlock *BB = &*I;
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4.09M
    // Prune unneeded PHI entries.
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4.09M
    SmallPtrSet<MachineBasicBlock*, 8> preds(BB->pred_begin(),
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4.09M
                                             BB->pred_end());
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4.09M
    MachineBasicBlock::iterator phi = BB->begin();
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5.03M
    while (
phi != BB->end() && 5.03M
phi->isPHI()4.98M
) {
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3.25M
      for (unsigned i = phi->getNumOperands() - 1; 
i >= 23.25M
;
i-=22.31M
)
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2.31M
        
if (2.31M
!preds.count(phi->getOperand(i).getMBB())2.31M
) {
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0
          phi->RemoveOperand(i);
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0
          phi->RemoveOperand(i-1);
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0
          ModifiedPHI = true;
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0
        }
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      if (
phi->getNumOperands() == 3937k
) {
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        const MachineOperand &Input = phi->getOperand(1);
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        const MachineOperand &Output = phi->getOperand(0);
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        unsigned InputReg = Input.getReg();
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        unsigned OutputReg = Output.getReg();
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        assert(Output.getSubReg() == 0 && "Cannot have output subregister");
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        ModifiedPHI = true;
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        if (
InputReg != OutputReg38
) {
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          MachineRegisterInfo &MRI = F.getRegInfo();
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          unsigned InputSub = Input.getSubReg();
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          if (InputSub == 0 &&
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MRI.constrainRegClass(InputReg, MRI.getRegClass(OutputReg))37
) {
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            MRI.replaceRegWith(OutputReg, InputReg);
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          } else {
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            // The input register to the PHI has a subregister or it can't be
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1
            // constrained to the proper register class:
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            // insert a COPY instead of simply replacing the output
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1
            // with the input.
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1
            const TargetInstrInfo *TII = F.getSubtarget().getInstrInfo();
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1
            BuildMI(*BB, BB->getFirstNonPHI(), phi->getDebugLoc(),
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1
                    TII->get(TargetOpcode::COPY), OutputReg)
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1
                .addReg(InputReg, getRegState(Input), InputSub);
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1
          }
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          phi++->eraseFromParent();
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        }
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        continue;
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      }
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937k
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937k
      ++phi;
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937k
    }
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4.09M
  }
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595k
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595k
  F.RenumberBlocks();
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595k
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595k
  return (!DeadBlocks.empty() || ModifiedPHI);
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595k
}