Coverage Report

Created: 2019-07-24 05:18

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/lib/Target/Hexagon/HexagonCFGOptimizer.cpp
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//===- HexagonCFGOptimizer.cpp - CFG optimizations ------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "Hexagon.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineOperand.h"
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#include "llvm/CodeGen/TargetInstrInfo.h"
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#include "llvm/CodeGen/TargetSubtargetInfo.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/ErrorHandling.h"
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#include <cassert>
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#include <vector>
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using namespace llvm;
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#define DEBUG_TYPE "hexagon_cfg"
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namespace llvm {
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FunctionPass *createHexagonCFGOptimizer();
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void initializeHexagonCFGOptimizerPass(PassRegistry&);
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} // end namespace llvm
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namespace {
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class HexagonCFGOptimizer : public MachineFunctionPass {
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private:
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  void InvertAndChangeJumpTarget(MachineInstr &, MachineBasicBlock *);
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  bool isOnFallThroughPath(MachineBasicBlock *MBB);
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public:
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  static char ID;
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  HexagonCFGOptimizer() : MachineFunctionPass(ID) {
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    initializeHexagonCFGOptimizerPass(*PassRegistry::getPassRegistry());
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  }
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  StringRef getPassName() const override { return "Hexagon CFG Optimizer"; }
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  bool runOnMachineFunction(MachineFunction &Fn) override;
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  MachineFunctionProperties getRequiredProperties() const override {
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    return MachineFunctionProperties().set(
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        MachineFunctionProperties::Property::NoVRegs);
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  }
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};
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} // end anonymous namespace
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char HexagonCFGOptimizer::ID = 0;
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static bool IsConditionalBranch(int Opc) {
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  switch (Opc) {
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    case Hexagon::J2_jumpt:
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    case Hexagon::J2_jumptpt:
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    case Hexagon::J2_jumpf:
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    case Hexagon::J2_jumpfpt:
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    case Hexagon::J2_jumptnew:
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    case Hexagon::J2_jumpfnew:
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    case Hexagon::J2_jumptnewpt:
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    case Hexagon::J2_jumpfnewpt:
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      return true;
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  }
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  return false;
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}
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static bool IsUnconditionalJump(int Opc) {
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  return (Opc == Hexagon::J2_jump);
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}
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void HexagonCFGOptimizer::InvertAndChangeJumpTarget(
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    MachineInstr &MI, MachineBasicBlock *NewTarget) {
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  const TargetInstrInfo *TII =
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      MI.getParent()->getParent()->getSubtarget().getInstrInfo();
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  int NewOpcode = 0;
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  switch (MI.getOpcode()) {
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  case Hexagon::J2_jumpt:
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    NewOpcode = Hexagon::J2_jumpf;
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    break;
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  case Hexagon::J2_jumpf:
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    NewOpcode = Hexagon::J2_jumpt;
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    break;
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  case Hexagon::J2_jumptnewpt:
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    NewOpcode = Hexagon::J2_jumpfnewpt;
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    break;
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  case Hexagon::J2_jumpfnewpt:
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    NewOpcode = Hexagon::J2_jumptnewpt;
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    break;
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  default:
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    llvm_unreachable("Cannot handle this case");
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  }
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  MI.setDesc(TII->get(NewOpcode));
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  MI.getOperand(1).setMBB(NewTarget);
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}
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bool HexagonCFGOptimizer::isOnFallThroughPath(MachineBasicBlock *MBB) {
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  if (MBB->canFallThrough())
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    return true;
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  for (MachineBasicBlock *PB : MBB->predecessors())
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    if (PB->isLayoutSuccessor(MBB) && PB->canFallThrough())
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      return true;
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  return false;
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}
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bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
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  if (skipFunction(Fn.getFunction()))
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    return false;
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  // Loop over all of the basic blocks.
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  for (MachineFunction::iterator MBBb = Fn.begin(), MBBe = Fn.end();
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       MBBb != MBBe; 
++MBBb5.55k
) {
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    MachineBasicBlock *MBB = &*MBBb;
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    // Traverse the basic block.
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    MachineBasicBlock::iterator MII = MBB->getFirstTerminator();
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    if (MII != MBB->end()) {
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      MachineInstr &MI = *MII;
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      int Opc = MI.getOpcode();
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      if (IsConditionalBranch(Opc)) {
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        // (Case 1) Transform the code if the following condition occurs:
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        //   BB1: if (p0) jump BB3
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        //   ...falls-through to BB2 ...
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        //   BB2: jump BB4
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        //   ...next block in layout is BB3...
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        //   BB3: ...
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        //
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        //  Transform this to:
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        //  BB1: if (!p0) jump BB4
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        //  Remove BB2
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        //  BB3: ...
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        //
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        // (Case 2) A variation occurs when BB3 contains a JMP to BB4:
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        //   BB1: if (p0) jump BB3
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        //   ...falls-through to BB2 ...
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        //   BB2: jump BB4
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        //   ...other basic blocks ...
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        //   BB4:
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        //   ...not a fall-thru
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        //   BB3: ...
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        //     jump BB4
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        //
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        // Transform this to:
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        //   BB1: if (!p0) jump BB4
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        //   Remove BB2
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        //   BB3: ...
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        //   BB4: ...
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        unsigned NumSuccs = MBB->succ_size();
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        MachineBasicBlock::succ_iterator SI = MBB->succ_begin();
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        MachineBasicBlock* FirstSucc = *SI;
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        MachineBasicBlock* SecondSucc = *(++SI);
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        MachineBasicBlock* LayoutSucc = nullptr;
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        MachineBasicBlock* JumpAroundTarget = nullptr;
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        if (MBB->isLayoutSuccessor(FirstSucc)) {
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          LayoutSucc = FirstSucc;
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          JumpAroundTarget = SecondSucc;
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        } else 
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MBB->isLayoutSuccessor(SecondSucc)350
) {
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          LayoutSucc = SecondSucc;
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          JumpAroundTarget = FirstSucc;
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        } else {
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          // Odd case...cannot handle.
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        }
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        // The target of the unconditional branch must be JumpAroundTarget.
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        // TODO: If not, we should not invert the unconditional branch.
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        MachineBasicBlock* CondBranchTarget = nullptr;
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        if (MI.getOpcode() == Hexagon::J2_jumpt ||
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MI.getOpcode() == Hexagon::J2_jumpf462
) {
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          CondBranchTarget = MI.getOperand(1).getMBB();
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        }
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        if (!LayoutSucc || 
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) {
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          continue;
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        }
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        if ((NumSuccs == 2) && LayoutSucc && (LayoutSucc->pred_size() == 1)) {
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          // Ensure that BB2 has one instruction -- an unconditional jump.
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          if ((LayoutSucc->size() == 1) &&
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IsUnconditionalJump(LayoutSucc->front().getOpcode())129
) {
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            assert(JumpAroundTarget && "jump target is needed to process second basic block");
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            MachineBasicBlock* UncondTarget =
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              LayoutSucc->front().getOperand(0).getMBB();
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            // Check if the layout successor of BB2 is BB3.
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            bool case1 = LayoutSucc->isLayoutSuccessor(JumpAroundTarget);
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            bool case2 = JumpAroundTarget->isSuccessor(UncondTarget) &&
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!JumpAroundTarget->empty()15
&&
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IsUnconditionalJump(JumpAroundTarget->back().getOpcode())15
&&
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JumpAroundTarget->pred_size() == 16
&&
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JumpAroundTarget->succ_size() == 16
;
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            if (case1 || 
case210
) {
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              InvertAndChangeJumpTarget(MI, UncondTarget);
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              MBB->replaceSuccessor(JumpAroundTarget, UncondTarget);
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              // Remove the unconditional branch in LayoutSucc.
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              LayoutSucc->erase(LayoutSucc->begin());
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              LayoutSucc->replaceSuccessor(UncondTarget, JumpAroundTarget);
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              // This code performs the conversion for case 2, which moves
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              // the block to the fall-thru case (BB3 in the code above).
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              if (case2 && 
!case13
) {
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                JumpAroundTarget->moveAfter(LayoutSucc);
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                // only move a block if it doesn't have a fall-thru. otherwise
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                // the CFG will be incorrect.
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                if (!isOnFallThroughPath(UncondTarget))
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                  UncondTarget->moveAfter(JumpAroundTarget);
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              }
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              // Correct live-in information. Is used by post-RA scheduler
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              // The live-in to LayoutSucc is now all values live-in to
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              // JumpAroundTarget.
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              std::vector<MachineBasicBlock::RegisterMaskPair> OrigLiveIn(
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                  LayoutSucc->livein_begin(), LayoutSucc->livein_end());
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              std::vector<MachineBasicBlock::RegisterMaskPair> NewLiveIn(
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                  JumpAroundTarget->livein_begin(),
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                  JumpAroundTarget->livein_end());
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              for (const auto &OrigLI : OrigLiveIn)
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                LayoutSucc->removeLiveIn(OrigLI.PhysReg);
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              for (const auto &NewLI : NewLiveIn)
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                LayoutSucc->addLiveIn(NewLI);
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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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  return true;
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}
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//===----------------------------------------------------------------------===//
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//                         Public Constructor Functions
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//===----------------------------------------------------------------------===//
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INITIALIZE_PASS(HexagonCFGOptimizer, "hexagon-cfg", "Hexagon CFG Optimizer",
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                false, false)
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FunctionPass *llvm::createHexagonCFGOptimizer() {
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  return new HexagonCFGOptimizer();
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}