Check in LLVM r95781.
diff --git a/lib/CodeGen/TailDuplication.cpp b/lib/CodeGen/TailDuplication.cpp
new file mode 100644
index 0000000..9ab4058
--- /dev/null
+++ b/lib/CodeGen/TailDuplication.cpp
@@ -0,0 +1,646 @@
+//===-- TailDuplication.cpp - Duplicate blocks into predecessors' tails ---===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass duplicates basic blocks ending in unconditional branches into
+// the tails of their predecessors.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "tailduplication"
+#include "llvm/Function.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/MachineSSAUpdater.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/Statistic.h"
+using namespace llvm;
+
+STATISTIC(NumTails , "Number of tails duplicated");
+STATISTIC(NumTailDups , "Number of tail duplicated blocks");
+STATISTIC(NumInstrDups , "Additional instructions due to tail duplication");
+STATISTIC(NumDeadBlocks, "Number of dead blocks removed");
+
+// Heuristic for tail duplication.
+static cl::opt<unsigned>
+TailDuplicateSize("tail-dup-size",
+ cl::desc("Maximum instructions to consider tail duplicating"),
+ cl::init(2), cl::Hidden);
+
+static cl::opt<bool>
+TailDupVerify("tail-dup-verify",
+ cl::desc("Verify sanity of PHI instructions during taildup"),
+ cl::init(false), cl::Hidden);
+
+static cl::opt<unsigned>
+TailDupLimit("tail-dup-limit", cl::init(~0U), cl::Hidden);
+
+typedef std::vector<std::pair<MachineBasicBlock*,unsigned> > AvailableValsTy;
+
+namespace {
+ /// TailDuplicatePass - Perform tail duplication.
+ class TailDuplicatePass : public MachineFunctionPass {
+ bool PreRegAlloc;
+ const TargetInstrInfo *TII;
+ MachineModuleInfo *MMI;
+ MachineRegisterInfo *MRI;
+
+ // SSAUpdateVRs - A list of virtual registers for which to update SSA form.
+ SmallVector<unsigned, 16> SSAUpdateVRs;
+
+ // SSAUpdateVals - For each virtual register in SSAUpdateVals keep a list of
+ // source virtual registers.
+ DenseMap<unsigned, AvailableValsTy> SSAUpdateVals;
+
+ public:
+ static char ID;
+ explicit TailDuplicatePass(bool PreRA) :
+ MachineFunctionPass(&ID), PreRegAlloc(PreRA) {}
+
+ virtual bool runOnMachineFunction(MachineFunction &MF);
+ virtual const char *getPassName() const { return "Tail Duplication"; }
+
+ private:
+ void AddSSAUpdateEntry(unsigned OrigReg, unsigned NewReg,
+ MachineBasicBlock *BB);
+ void ProcessPHI(MachineInstr *MI, MachineBasicBlock *TailBB,
+ MachineBasicBlock *PredBB,
+ DenseMap<unsigned, unsigned> &LocalVRMap,
+ SmallVector<std::pair<unsigned,unsigned>, 4> &Copies);
+ void DuplicateInstruction(MachineInstr *MI,
+ MachineBasicBlock *TailBB,
+ MachineBasicBlock *PredBB,
+ MachineFunction &MF,
+ DenseMap<unsigned, unsigned> &LocalVRMap);
+ void UpdateSuccessorsPHIs(MachineBasicBlock *FromBB, bool isDead,
+ SmallVector<MachineBasicBlock*, 8> &TDBBs,
+ SmallSetVector<MachineBasicBlock*, 8> &Succs);
+ bool TailDuplicateBlocks(MachineFunction &MF);
+ bool TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF,
+ SmallVector<MachineBasicBlock*, 8> &TDBBs,
+ SmallVector<MachineInstr*, 16> &Copies);
+ void RemoveDeadBlock(MachineBasicBlock *MBB);
+ };
+
+ char TailDuplicatePass::ID = 0;
+}
+
+FunctionPass *llvm::createTailDuplicatePass(bool PreRegAlloc) {
+ return new TailDuplicatePass(PreRegAlloc);
+}
+
+bool TailDuplicatePass::runOnMachineFunction(MachineFunction &MF) {
+ TII = MF.getTarget().getInstrInfo();
+ MRI = &MF.getRegInfo();
+ MMI = getAnalysisIfAvailable<MachineModuleInfo>();
+
+ bool MadeChange = false;
+ while (TailDuplicateBlocks(MF))
+ MadeChange = true;
+
+ return MadeChange;
+}
+
+static void VerifyPHIs(MachineFunction &MF, bool CheckExtra) {
+ for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ++I) {
+ MachineBasicBlock *MBB = I;
+ SmallSetVector<MachineBasicBlock*, 8> Preds(MBB->pred_begin(),
+ MBB->pred_end());
+ MachineBasicBlock::iterator MI = MBB->begin();
+ while (MI != MBB->end()) {
+ if (!MI->isPHI())
+ break;
+ for (SmallSetVector<MachineBasicBlock *, 8>::iterator PI = Preds.begin(),
+ PE = Preds.end(); PI != PE; ++PI) {
+ MachineBasicBlock *PredBB = *PI;
+ bool Found = false;
+ for (unsigned i = 1, e = MI->getNumOperands(); i != e; i += 2) {
+ MachineBasicBlock *PHIBB = MI->getOperand(i+1).getMBB();
+ if (PHIBB == PredBB) {
+ Found = true;
+ break;
+ }
+ }
+ if (!Found) {
+ dbgs() << "Malformed PHI in BB#" << MBB->getNumber() << ": " << *MI;
+ dbgs() << " missing input from predecessor BB#"
+ << PredBB->getNumber() << '\n';
+ llvm_unreachable(0);
+ }
+ }
+
+ for (unsigned i = 1, e = MI->getNumOperands(); i != e; i += 2) {
+ MachineBasicBlock *PHIBB = MI->getOperand(i+1).getMBB();
+ if (CheckExtra && !Preds.count(PHIBB)) {
+ // This is not a hard error.
+ dbgs() << "Warning: malformed PHI in BB#" << MBB->getNumber()
+ << ": " << *MI;
+ dbgs() << " extra input from predecessor BB#"
+ << PHIBB->getNumber() << '\n';
+ }
+ if (PHIBB->getNumber() < 0) {
+ dbgs() << "Malformed PHI in BB#" << MBB->getNumber() << ": " << *MI;
+ dbgs() << " non-existing BB#" << PHIBB->getNumber() << '\n';
+ llvm_unreachable(0);
+ }
+ }
+ ++MI;
+ }
+ }
+}
+
+/// TailDuplicateBlocks - Look for small blocks that are unconditionally
+/// branched to and do not fall through. Tail-duplicate their instructions
+/// into their predecessors to eliminate (dynamic) branches.
+bool TailDuplicatePass::TailDuplicateBlocks(MachineFunction &MF) {
+ bool MadeChange = false;
+
+ if (PreRegAlloc && TailDupVerify) {
+ DEBUG(dbgs() << "\n*** Before tail-duplicating\n");
+ VerifyPHIs(MF, true);
+ }
+
+ SmallVector<MachineInstr*, 8> NewPHIs;
+ MachineSSAUpdater SSAUpdate(MF, &NewPHIs);
+
+ for (MachineFunction::iterator I = ++MF.begin(), E = MF.end(); I != E; ) {
+ MachineBasicBlock *MBB = I++;
+
+ if (NumTails == TailDupLimit)
+ break;
+
+ // Only duplicate blocks that end with unconditional branches.
+ if (MBB->canFallThrough())
+ continue;
+
+ // Save the successors list.
+ SmallSetVector<MachineBasicBlock*, 8> Succs(MBB->succ_begin(),
+ MBB->succ_end());
+
+ SmallVector<MachineBasicBlock*, 8> TDBBs;
+ SmallVector<MachineInstr*, 16> Copies;
+ if (TailDuplicate(MBB, MF, TDBBs, Copies)) {
+ ++NumTails;
+
+ // TailBB's immediate successors are now successors of those predecessors
+ // which duplicated TailBB. Add the predecessors as sources to the PHI
+ // instructions.
+ bool isDead = MBB->pred_empty();
+ if (PreRegAlloc)
+ UpdateSuccessorsPHIs(MBB, isDead, TDBBs, Succs);
+
+ // If it is dead, remove it.
+ if (isDead) {
+ NumInstrDups -= MBB->size();
+ RemoveDeadBlock(MBB);
+ ++NumDeadBlocks;
+ }
+
+ // Update SSA form.
+ if (!SSAUpdateVRs.empty()) {
+ for (unsigned i = 0, e = SSAUpdateVRs.size(); i != e; ++i) {
+ unsigned VReg = SSAUpdateVRs[i];
+ SSAUpdate.Initialize(VReg);
+
+ // If the original definition is still around, add it as an available
+ // value.
+ MachineInstr *DefMI = MRI->getVRegDef(VReg);
+ MachineBasicBlock *DefBB = 0;
+ if (DefMI) {
+ DefBB = DefMI->getParent();
+ SSAUpdate.AddAvailableValue(DefBB, VReg);
+ }
+
+ // Add the new vregs as available values.
+ DenseMap<unsigned, AvailableValsTy>::iterator LI =
+ SSAUpdateVals.find(VReg);
+ for (unsigned j = 0, ee = LI->second.size(); j != ee; ++j) {
+ MachineBasicBlock *SrcBB = LI->second[j].first;
+ unsigned SrcReg = LI->second[j].second;
+ SSAUpdate.AddAvailableValue(SrcBB, SrcReg);
+ }
+
+ // Rewrite uses that are outside of the original def's block.
+ MachineRegisterInfo::use_iterator UI = MRI->use_begin(VReg);
+ while (UI != MRI->use_end()) {
+ MachineOperand &UseMO = UI.getOperand();
+ MachineInstr *UseMI = &*UI;
+ ++UI;
+ if (UseMI->getParent() == DefBB)
+ continue;
+ SSAUpdate.RewriteUse(UseMO);
+ }
+ }
+
+ SSAUpdateVRs.clear();
+ SSAUpdateVals.clear();
+ }
+
+ // Eliminate some of the copies inserted by tail duplication to maintain
+ // SSA form.
+ for (unsigned i = 0, e = Copies.size(); i != e; ++i) {
+ MachineInstr *Copy = Copies[i];
+ unsigned Src, Dst, SrcSR, DstSR;
+ if (TII->isMoveInstr(*Copy, Src, Dst, SrcSR, DstSR)) {
+ MachineRegisterInfo::use_iterator UI = MRI->use_begin(Src);
+ if (++UI == MRI->use_end()) {
+ // Copy is the only use. Do trivial copy propagation here.
+ MRI->replaceRegWith(Dst, Src);
+ Copy->eraseFromParent();
+ }
+ }
+ }
+
+ if (PreRegAlloc && TailDupVerify)
+ VerifyPHIs(MF, false);
+ MadeChange = true;
+ }
+ }
+
+ return MadeChange;
+}
+
+static bool isDefLiveOut(unsigned Reg, MachineBasicBlock *BB,
+ const MachineRegisterInfo *MRI) {
+ for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
+ UE = MRI->use_end(); UI != UE; ++UI) {
+ MachineInstr *UseMI = &*UI;
+ if (UseMI->getParent() != BB)
+ return true;
+ }
+ return false;
+}
+
+static unsigned getPHISrcRegOpIdx(MachineInstr *MI, MachineBasicBlock *SrcBB) {
+ for (unsigned i = 1, e = MI->getNumOperands(); i != e; i += 2)
+ if (MI->getOperand(i+1).getMBB() == SrcBB)
+ return i;
+ return 0;
+}
+
+/// AddSSAUpdateEntry - Add a definition and source virtual registers pair for
+/// SSA update.
+void TailDuplicatePass::AddSSAUpdateEntry(unsigned OrigReg, unsigned NewReg,
+ MachineBasicBlock *BB) {
+ DenseMap<unsigned, AvailableValsTy>::iterator LI= SSAUpdateVals.find(OrigReg);
+ if (LI != SSAUpdateVals.end())
+ LI->second.push_back(std::make_pair(BB, NewReg));
+ else {
+ AvailableValsTy Vals;
+ Vals.push_back(std::make_pair(BB, NewReg));
+ SSAUpdateVals.insert(std::make_pair(OrigReg, Vals));
+ SSAUpdateVRs.push_back(OrigReg);
+ }
+}
+
+/// ProcessPHI - Process PHI node in TailBB by turning it into a copy in PredBB.
+/// Remember the source register that's contributed by PredBB and update SSA
+/// update map.
+void TailDuplicatePass::ProcessPHI(MachineInstr *MI,
+ MachineBasicBlock *TailBB,
+ MachineBasicBlock *PredBB,
+ DenseMap<unsigned, unsigned> &LocalVRMap,
+ SmallVector<std::pair<unsigned,unsigned>, 4> &Copies) {
+ unsigned DefReg = MI->getOperand(0).getReg();
+ unsigned SrcOpIdx = getPHISrcRegOpIdx(MI, PredBB);
+ assert(SrcOpIdx && "Unable to find matching PHI source?");
+ unsigned SrcReg = MI->getOperand(SrcOpIdx).getReg();
+ const TargetRegisterClass *RC = MRI->getRegClass(DefReg);
+ LocalVRMap.insert(std::make_pair(DefReg, SrcReg));
+
+ // Insert a copy from source to the end of the block. The def register is the
+ // available value liveout of the block.
+ unsigned NewDef = MRI->createVirtualRegister(RC);
+ Copies.push_back(std::make_pair(NewDef, SrcReg));
+ if (isDefLiveOut(DefReg, TailBB, MRI))
+ AddSSAUpdateEntry(DefReg, NewDef, PredBB);
+
+ // Remove PredBB from the PHI node.
+ MI->RemoveOperand(SrcOpIdx+1);
+ MI->RemoveOperand(SrcOpIdx);
+ if (MI->getNumOperands() == 1)
+ MI->eraseFromParent();
+}
+
+/// DuplicateInstruction - Duplicate a TailBB instruction to PredBB and update
+/// the source operands due to earlier PHI translation.
+void TailDuplicatePass::DuplicateInstruction(MachineInstr *MI,
+ MachineBasicBlock *TailBB,
+ MachineBasicBlock *PredBB,
+ MachineFunction &MF,
+ DenseMap<unsigned, unsigned> &LocalVRMap) {
+ MachineInstr *NewMI = TII->duplicate(MI, MF);
+ for (unsigned i = 0, e = NewMI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = NewMI->getOperand(i);
+ if (!MO.isReg())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg))
+ continue;
+ if (MO.isDef()) {
+ const TargetRegisterClass *RC = MRI->getRegClass(Reg);
+ unsigned NewReg = MRI->createVirtualRegister(RC);
+ MO.setReg(NewReg);
+ LocalVRMap.insert(std::make_pair(Reg, NewReg));
+ if (isDefLiveOut(Reg, TailBB, MRI))
+ AddSSAUpdateEntry(Reg, NewReg, PredBB);
+ } else {
+ DenseMap<unsigned, unsigned>::iterator VI = LocalVRMap.find(Reg);
+ if (VI != LocalVRMap.end())
+ MO.setReg(VI->second);
+ }
+ }
+ PredBB->insert(PredBB->end(), NewMI);
+}
+
+/// UpdateSuccessorsPHIs - After FromBB is tail duplicated into its predecessor
+/// blocks, the successors have gained new predecessors. Update the PHI
+/// instructions in them accordingly.
+void
+TailDuplicatePass::UpdateSuccessorsPHIs(MachineBasicBlock *FromBB, bool isDead,
+ SmallVector<MachineBasicBlock*, 8> &TDBBs,
+ SmallSetVector<MachineBasicBlock*,8> &Succs) {
+ for (SmallSetVector<MachineBasicBlock*, 8>::iterator SI = Succs.begin(),
+ SE = Succs.end(); SI != SE; ++SI) {
+ MachineBasicBlock *SuccBB = *SI;
+ for (MachineBasicBlock::iterator II = SuccBB->begin(), EE = SuccBB->end();
+ II != EE; ++II) {
+ if (!II->isPHI())
+ break;
+ unsigned Idx = 0;
+ for (unsigned i = 1, e = II->getNumOperands(); i != e; i += 2) {
+ MachineOperand &MO = II->getOperand(i+1);
+ if (MO.getMBB() == FromBB) {
+ Idx = i;
+ break;
+ }
+ }
+
+ assert(Idx != 0);
+ MachineOperand &MO0 = II->getOperand(Idx);
+ unsigned Reg = MO0.getReg();
+ if (isDead) {
+ // Folded into the previous BB.
+ // There could be duplicate phi source entries. FIXME: Should sdisel
+ // or earlier pass fixed this?
+ for (unsigned i = II->getNumOperands()-2; i != Idx; i -= 2) {
+ MachineOperand &MO = II->getOperand(i+1);
+ if (MO.getMBB() == FromBB) {
+ II->RemoveOperand(i+1);
+ II->RemoveOperand(i);
+ }
+ }
+ II->RemoveOperand(Idx+1);
+ II->RemoveOperand(Idx);
+ }
+ DenseMap<unsigned,AvailableValsTy>::iterator LI=SSAUpdateVals.find(Reg);
+ if (LI != SSAUpdateVals.end()) {
+ // This register is defined in the tail block.
+ for (unsigned j = 0, ee = LI->second.size(); j != ee; ++j) {
+ MachineBasicBlock *SrcBB = LI->second[j].first;
+ unsigned SrcReg = LI->second[j].second;
+ II->addOperand(MachineOperand::CreateReg(SrcReg, false));
+ II->addOperand(MachineOperand::CreateMBB(SrcBB));
+ }
+ } else {
+ // Live in tail block, must also be live in predecessors.
+ for (unsigned j = 0, ee = TDBBs.size(); j != ee; ++j) {
+ MachineBasicBlock *SrcBB = TDBBs[j];
+ II->addOperand(MachineOperand::CreateReg(Reg, false));
+ II->addOperand(MachineOperand::CreateMBB(SrcBB));
+ }
+ }
+ }
+ }
+}
+
+/// TailDuplicate - If it is profitable, duplicate TailBB's contents in each
+/// of its predecessors.
+bool
+TailDuplicatePass::TailDuplicate(MachineBasicBlock *TailBB, MachineFunction &MF,
+ SmallVector<MachineBasicBlock*, 8> &TDBBs,
+ SmallVector<MachineInstr*, 16> &Copies) {
+ // Set the limit on the number of instructions to duplicate, with a default
+ // of one less than the tail-merge threshold. When optimizing for size,
+ // duplicate only one, because one branch instruction can be eliminated to
+ // compensate for the duplication.
+ unsigned MaxDuplicateCount;
+ if (MF.getFunction()->hasFnAttr(Attribute::OptimizeForSize))
+ MaxDuplicateCount = 1;
+ else
+ MaxDuplicateCount = TailDuplicateSize;
+
+ if (PreRegAlloc) {
+ // Pre-regalloc tail duplication hurts compile time and doesn't help
+ // much except for indirect branches.
+ if (TailBB->empty() || !TailBB->back().getDesc().isIndirectBranch())
+ return false;
+ // If the target has hardware branch prediction that can handle indirect
+ // branches, duplicating them can often make them predictable when there
+ // are common paths through the code. The limit needs to be high enough
+ // to allow undoing the effects of tail merging and other optimizations
+ // that rearrange the predecessors of the indirect branch.
+ MaxDuplicateCount = 20;
+ }
+
+ // Don't try to tail-duplicate single-block loops.
+ if (TailBB->isSuccessor(TailBB))
+ return false;
+
+ // Check the instructions in the block to determine whether tail-duplication
+ // is invalid or unlikely to be profitable.
+ unsigned InstrCount = 0;
+ bool HasCall = false;
+ for (MachineBasicBlock::iterator I = TailBB->begin();
+ I != TailBB->end(); ++I) {
+ // Non-duplicable things shouldn't be tail-duplicated.
+ if (I->getDesc().isNotDuplicable()) return false;
+ // Do not duplicate 'return' instructions if this is a pre-regalloc run.
+ // A return may expand into a lot more instructions (e.g. reload of callee
+ // saved registers) after PEI.
+ if (PreRegAlloc && I->getDesc().isReturn()) return false;
+ // Don't duplicate more than the threshold.
+ if (InstrCount == MaxDuplicateCount) return false;
+ // Remember if we saw a call.
+ if (I->getDesc().isCall()) HasCall = true;
+ if (!I->isPHI())
+ InstrCount += 1;
+ }
+ // Heuristically, don't tail-duplicate calls if it would expand code size,
+ // as it's less likely to be worth the extra cost.
+ if (InstrCount > 1 && HasCall)
+ return false;
+
+ DEBUG(dbgs() << "\n*** Tail-duplicating BB#" << TailBB->getNumber() << '\n');
+
+ // Iterate through all the unique predecessors and tail-duplicate this
+ // block into them, if possible. Copying the list ahead of time also
+ // avoids trouble with the predecessor list reallocating.
+ bool Changed = false;
+ SmallSetVector<MachineBasicBlock*, 8> Preds(TailBB->pred_begin(),
+ TailBB->pred_end());
+ for (SmallSetVector<MachineBasicBlock *, 8>::iterator PI = Preds.begin(),
+ PE = Preds.end(); PI != PE; ++PI) {
+ MachineBasicBlock *PredBB = *PI;
+
+ assert(TailBB != PredBB &&
+ "Single-block loop should have been rejected earlier!");
+ if (PredBB->succ_size() > 1) continue;
+
+ MachineBasicBlock *PredTBB, *PredFBB;
+ SmallVector<MachineOperand, 4> PredCond;
+ if (TII->AnalyzeBranch(*PredBB, PredTBB, PredFBB, PredCond, true))
+ continue;
+ if (!PredCond.empty())
+ continue;
+ // EH edges are ignored by AnalyzeBranch.
+ if (PredBB->succ_size() != 1)
+ continue;
+ // Don't duplicate into a fall-through predecessor (at least for now).
+ if (PredBB->isLayoutSuccessor(TailBB) && PredBB->canFallThrough())
+ continue;
+
+ DEBUG(dbgs() << "\nTail-duplicating into PredBB: " << *PredBB
+ << "From Succ: " << *TailBB);
+
+ TDBBs.push_back(PredBB);
+
+ // Remove PredBB's unconditional branch.
+ TII->RemoveBranch(*PredBB);
+
+ // Clone the contents of TailBB into PredBB.
+ DenseMap<unsigned, unsigned> LocalVRMap;
+ SmallVector<std::pair<unsigned,unsigned>, 4> CopyInfos;
+ MachineBasicBlock::iterator I = TailBB->begin();
+ while (I != TailBB->end()) {
+ MachineInstr *MI = &*I;
+ ++I;
+ if (MI->isPHI()) {
+ // Replace the uses of the def of the PHI with the register coming
+ // from PredBB.
+ ProcessPHI(MI, TailBB, PredBB, LocalVRMap, CopyInfos);
+ } else {
+ // Replace def of virtual registers with new registers, and update
+ // uses with PHI source register or the new registers.
+ DuplicateInstruction(MI, TailBB, PredBB, MF, LocalVRMap);
+ }
+ }
+ MachineBasicBlock::iterator Loc = PredBB->getFirstTerminator();
+ for (unsigned i = 0, e = CopyInfos.size(); i != e; ++i) {
+ const TargetRegisterClass *RC = MRI->getRegClass(CopyInfos[i].first);
+ TII->copyRegToReg(*PredBB, Loc, CopyInfos[i].first,
+ CopyInfos[i].second, RC,RC);
+ MachineInstr *CopyMI = prior(Loc);
+ Copies.push_back(CopyMI);
+ }
+ NumInstrDups += TailBB->size() - 1; // subtract one for removed branch
+
+ // Update the CFG.
+ PredBB->removeSuccessor(PredBB->succ_begin());
+ assert(PredBB->succ_empty() &&
+ "TailDuplicate called on block with multiple successors!");
+ for (MachineBasicBlock::succ_iterator I = TailBB->succ_begin(),
+ E = TailBB->succ_end(); I != E; ++I)
+ PredBB->addSuccessor(*I);
+
+ Changed = true;
+ ++NumTailDups;
+ }
+
+ // If TailBB was duplicated into all its predecessors except for the prior
+ // block, which falls through unconditionally, move the contents of this
+ // block into the prior block.
+ MachineBasicBlock *PrevBB = prior(MachineFunction::iterator(TailBB));
+ MachineBasicBlock *PriorTBB = 0, *PriorFBB = 0;
+ SmallVector<MachineOperand, 4> PriorCond;
+ bool PriorUnAnalyzable =
+ TII->AnalyzeBranch(*PrevBB, PriorTBB, PriorFBB, PriorCond, true);
+ // This has to check PrevBB->succ_size() because EH edges are ignored by
+ // AnalyzeBranch.
+ if (!PriorUnAnalyzable && PriorCond.empty() && !PriorTBB &&
+ TailBB->pred_size() == 1 && PrevBB->succ_size() == 1 &&
+ !TailBB->hasAddressTaken()) {
+ DEBUG(dbgs() << "\nMerging into block: " << *PrevBB
+ << "From MBB: " << *TailBB);
+ if (PreRegAlloc) {
+ DenseMap<unsigned, unsigned> LocalVRMap;
+ SmallVector<std::pair<unsigned,unsigned>, 4> CopyInfos;
+ MachineBasicBlock::iterator I = TailBB->begin();
+ // Process PHI instructions first.
+ while (I != TailBB->end() && I->isPHI()) {
+ // Replace the uses of the def of the PHI with the register coming
+ // from PredBB.
+ MachineInstr *MI = &*I++;
+ ProcessPHI(MI, TailBB, PrevBB, LocalVRMap, CopyInfos);
+ if (MI->getParent())
+ MI->eraseFromParent();
+ }
+
+ // Now copy the non-PHI instructions.
+ while (I != TailBB->end()) {
+ // Replace def of virtual registers with new registers, and update
+ // uses with PHI source register or the new registers.
+ MachineInstr *MI = &*I++;
+ DuplicateInstruction(MI, TailBB, PrevBB, MF, LocalVRMap);
+ MI->eraseFromParent();
+ }
+ MachineBasicBlock::iterator Loc = PrevBB->getFirstTerminator();
+ for (unsigned i = 0, e = CopyInfos.size(); i != e; ++i) {
+ const TargetRegisterClass *RC = MRI->getRegClass(CopyInfos[i].first);
+ TII->copyRegToReg(*PrevBB, Loc, CopyInfos[i].first,
+ CopyInfos[i].second, RC, RC);
+ MachineInstr *CopyMI = prior(Loc);
+ Copies.push_back(CopyMI);
+ }
+ } else {
+ // No PHIs to worry about, just splice the instructions over.
+ PrevBB->splice(PrevBB->end(), TailBB, TailBB->begin(), TailBB->end());
+ }
+ PrevBB->removeSuccessor(PrevBB->succ_begin());
+ assert(PrevBB->succ_empty());
+ PrevBB->transferSuccessors(TailBB);
+ TDBBs.push_back(PrevBB);
+ Changed = true;
+ }
+
+ return Changed;
+}
+
+/// RemoveDeadBlock - Remove the specified dead machine basic block from the
+/// function, updating the CFG.
+void TailDuplicatePass::RemoveDeadBlock(MachineBasicBlock *MBB) {
+ assert(MBB->pred_empty() && "MBB must be dead!");
+ DEBUG(dbgs() << "\nRemoving MBB: " << *MBB);
+
+ // Remove all successors.
+ while (!MBB->succ_empty())
+ MBB->removeSuccessor(MBB->succ_end()-1);
+
+ // If there are any labels in the basic block, unregister them from
+ // MachineModuleInfo.
+ if (MMI && !MBB->empty()) {
+ for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
+ I != E; ++I) {
+ if (I->isLabel())
+ // The label ID # is always operand #0, an immediate.
+ MMI->InvalidateLabel(I->getOperand(0).getImm());
+ }
+ }
+
+ // Remove the block.
+ MBB->eraseFromParent();
+}
+