diff options
Diffstat (limited to 'contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp')
| -rw-r--r-- | contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp | 429 |
1 files changed, 311 insertions, 118 deletions
diff --git a/contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp b/contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp index 6fa5ad7..f4ec8c6 100644 --- a/contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp +++ b/contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp @@ -180,9 +180,7 @@ namespace { MachineInstr *MI; MachineInstr *CPEMI; MachineBasicBlock *HighWaterMark; - private: unsigned MaxDisp; - public: bool NegOk; bool IsSoImm; bool KnownAlignment; @@ -216,12 +214,24 @@ namespace { }; /// CPEntries - Keep track of all of the constant pool entry machine - /// instructions. For each original constpool index (i.e. those that - /// existed upon entry to this pass), it keeps a vector of entries. - /// Original elements are cloned as we go along; the clones are - /// put in the vector of the original element, but have distinct CPIs. + /// instructions. For each original constpool index (i.e. those that existed + /// upon entry to this pass), it keeps a vector of entries. Original + /// elements are cloned as we go along; the clones are put in the vector of + /// the original element, but have distinct CPIs. + /// + /// The first half of CPEntries contains generic constants, the second half + /// contains jump tables. Use getCombinedIndex on a generic CPEMI to look up + /// which vector it will be in here. std::vector<std::vector<CPEntry> > CPEntries; + /// Maps a JT index to the offset in CPEntries containing copies of that + /// table. The equivalent map for a CONSTPOOL_ENTRY is the identity. + DenseMap<int, int> JumpTableEntryIndices; + + /// Maps a JT index to the LEA that actually uses the index to calculate its + /// base address. + DenseMap<int, int> JumpTableUserIndices; + /// ImmBranch - One per immediate branch, keeping the machine instruction /// pointer, conditional or unconditional, the max displacement, /// and (if isCond is true) the corresponding unconditional branch @@ -269,7 +279,8 @@ namespace { } private: - void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs); + void doInitialConstPlacement(std::vector<MachineInstr *> &CPEMIs); + void doInitialJumpTablePlacement(std::vector<MachineInstr *> &CPEMIs); bool BBHasFallthrough(MachineBasicBlock *MBB); CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI); unsigned getCPELogAlign(const MachineInstr *CPEMI); @@ -279,6 +290,7 @@ namespace { void updateForInsertedWaterBlock(MachineBasicBlock *NewBB); void adjustBBOffsetsAfter(MachineBasicBlock *BB); bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI); + unsigned getCombinedIndex(const MachineInstr *CPEMI); int findInRangeCPEntry(CPUser& U, unsigned UserOffset); bool findAvailableWater(CPUser&U, unsigned UserOffset, water_iterator &WaterIter); @@ -301,8 +313,9 @@ namespace { bool optimizeThumb2Instructions(); bool optimizeThumb2Branches(); bool reorderThumb2JumpTables(); - unsigned removeDeadDefinitions(MachineInstr *MI, unsigned BaseReg, - unsigned IdxReg); + bool preserveBaseRegister(MachineInstr *JumpMI, MachineInstr *LEAMI, + unsigned &DeadSize, bool &CanDeleteLEA, + bool &BaseRegKill); bool optimizeThumb2JumpTables(); MachineBasicBlock *adjustJTTargetBlockForward(MachineBasicBlock *BB, MachineBasicBlock *JTBB); @@ -413,7 +426,10 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &mf) { // we put them all at the end of the function. std::vector<MachineInstr*> CPEMIs; if (!MCP->isEmpty()) - doInitialPlacement(CPEMIs); + doInitialConstPlacement(CPEMIs); + + if (MF->getJumpTableInfo()) + doInitialJumpTablePlacement(CPEMIs); /// The next UID to take is the first unused one. AFI->initPICLabelUId(CPEMIs.size()); @@ -478,7 +494,8 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &mf) { for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) { for (unsigned j = 0, je = CPEntries[i].size(); j != je; ++j) { const CPEntry & CPE = CPEntries[i][j]; - AFI->recordCPEClone(i, CPE.CPI); + if (CPE.CPEMI && CPE.CPEMI->getOperand(1).isCPI()) + AFI->recordCPEClone(i, CPE.CPI); } } @@ -488,6 +505,8 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &mf) { WaterList.clear(); CPUsers.clear(); CPEntries.clear(); + JumpTableEntryIndices.clear(); + JumpTableUserIndices.clear(); ImmBranches.clear(); PushPopMIs.clear(); T2JumpTables.clear(); @@ -495,10 +514,10 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &mf) { return MadeChange; } -/// doInitialPlacement - Perform the initial placement of the constant pool -/// entries. To start with, we put them all at the end of the function. +/// \brief Perform the initial placement of the regular constant pool entries. +/// To start with, we put them all at the end of the function. void -ARMConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) { +ARMConstantIslands::doInitialConstPlacement(std::vector<MachineInstr*> &CPEMIs) { // Create the basic block to hold the CPE's. MachineBasicBlock *BB = MF->CreateMachineBasicBlock(); MF->push_back(BB); @@ -556,6 +575,66 @@ ARMConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) { DEBUG(BB->dump()); } +/// \brief Do initial placement of the jump tables. Because Thumb2's TBB and TBH +/// instructions can be made more efficient if the jump table immediately +/// follows the instruction, it's best to place them immediately next to their +/// jumps to begin with. In almost all cases they'll never be moved from that +/// position. +void ARMConstantIslands::doInitialJumpTablePlacement( + std::vector<MachineInstr *> &CPEMIs) { + unsigned i = CPEntries.size(); + auto MJTI = MF->getJumpTableInfo(); + const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables(); + + MachineBasicBlock *LastCorrectlyNumberedBB = nullptr; + for (MachineBasicBlock &MBB : *MF) { + auto MI = MBB.getLastNonDebugInstr(); + + unsigned JTOpcode; + switch (MI->getOpcode()) { + default: + continue; + case ARM::BR_JTadd: + case ARM::BR_JTr: + case ARM::tBR_JTr: + case ARM::BR_JTm: + JTOpcode = ARM::JUMPTABLE_ADDRS; + break; + case ARM::t2BR_JT: + JTOpcode = ARM::JUMPTABLE_INSTS; + break; + case ARM::t2TBB_JT: + JTOpcode = ARM::JUMPTABLE_TBB; + break; + case ARM::t2TBH_JT: + JTOpcode = ARM::JUMPTABLE_TBH; + break; + } + + unsigned NumOps = MI->getDesc().getNumOperands(); + MachineOperand JTOp = + MI->getOperand(NumOps - (MI->isPredicable() ? 2 : 1)); + unsigned JTI = JTOp.getIndex(); + unsigned Size = JT[JTI].MBBs.size() * sizeof(uint32_t); + MachineBasicBlock *JumpTableBB = MF->CreateMachineBasicBlock(); + MF->insert(std::next(MachineFunction::iterator(MBB)), JumpTableBB); + MachineInstr *CPEMI = BuildMI(*JumpTableBB, JumpTableBB->begin(), + DebugLoc(), TII->get(JTOpcode)) + .addImm(i++) + .addJumpTableIndex(JTI) + .addImm(Size); + CPEMIs.push_back(CPEMI); + CPEntries.emplace_back(1, CPEntry(CPEMI, JTI)); + JumpTableEntryIndices.insert(std::make_pair(JTI, CPEntries.size() - 1)); + if (!LastCorrectlyNumberedBB) + LastCorrectlyNumberedBB = &MBB; + } + + // If we did anything then we need to renumber the subsequent blocks. + if (LastCorrectlyNumberedBB) + MF->RenumberBlocks(LastCorrectlyNumberedBB); +} + /// BBHasFallthrough - Return true if the specified basic block can fallthrough /// into the block immediately after it. bool ARMConstantIslands::BBHasFallthrough(MachineBasicBlock *MBB) { @@ -595,9 +674,21 @@ ARMConstantIslands::CPEntry /// getCPELogAlign - Returns the required alignment of the constant pool entry /// represented by CPEMI. Alignment is measured in log2(bytes) units. unsigned ARMConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) { - assert(CPEMI && CPEMI->getOpcode() == ARM::CONSTPOOL_ENTRY); + switch (CPEMI->getOpcode()) { + case ARM::CONSTPOOL_ENTRY: + break; + case ARM::JUMPTABLE_TBB: + return 0; + case ARM::JUMPTABLE_TBH: + case ARM::JUMPTABLE_INSTS: + return 1; + case ARM::JUMPTABLE_ADDRS: + return 2; + default: + llvm_unreachable("unknown constpool entry kind"); + } - unsigned CPI = CPEMI->getOperand(1).getIndex(); + unsigned CPI = getCombinedIndex(CPEMI); assert(CPI < MCP->getConstants().size() && "Invalid constant pool index."); unsigned Align = MCP->getConstants()[CPI].getAlignment(); assert(isPowerOf2_32(Align) && "Invalid CPE alignment"); @@ -706,12 +797,14 @@ initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) { if (Opc == ARM::tPUSH || Opc == ARM::tPOP_RET) PushPopMIs.push_back(I); - if (Opc == ARM::CONSTPOOL_ENTRY) + if (Opc == ARM::CONSTPOOL_ENTRY || Opc == ARM::JUMPTABLE_ADDRS || + Opc == ARM::JUMPTABLE_INSTS || Opc == ARM::JUMPTABLE_TBB || + Opc == ARM::JUMPTABLE_TBH) continue; // Scan the instructions for constant pool operands. for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) - if (I->getOperand(op).isCPI()) { + if (I->getOperand(op).isCPI() || I->getOperand(op).isJTI()) { // We found one. The addressing mode tells us the max displacement // from the PC that this instruction permits. @@ -727,6 +820,7 @@ initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) { // Taking the address of a CP entry. case ARM::LEApcrel: + case ARM::LEApcrelJT: // This takes a SoImm, which is 8 bit immediate rotated. We'll // pretend the maximum offset is 255 * 4. Since each instruction // 4 byte wide, this is always correct. We'll check for other @@ -737,10 +831,12 @@ initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) { IsSoImm = true; break; case ARM::t2LEApcrel: + case ARM::t2LEApcrelJT: Bits = 12; NegOk = true; break; case ARM::tLEApcrel: + case ARM::tLEApcrelJT: Bits = 8; Scale = 4; break; @@ -768,6 +864,11 @@ initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) { // Remember that this is a user of a CP entry. unsigned CPI = I->getOperand(op).getIndex(); + if (I->getOperand(op).isJTI()) { + JumpTableUserIndices.insert(std::make_pair(CPI, CPUsers.size())); + CPI = JumpTableEntryIndices[CPI]; + } + MachineInstr *CPEMI = CPEMIs[CPI]; unsigned MaxOffs = ((1 << Bits)-1) * Scale; CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk, IsSoImm)); @@ -1101,6 +1202,13 @@ bool ARMConstantIslands::decrementCPEReferenceCount(unsigned CPI, return false; } +unsigned ARMConstantIslands::getCombinedIndex(const MachineInstr *CPEMI) { + if (CPEMI->getOperand(1).isCPI()) + return CPEMI->getOperand(1).getIndex(); + + return JumpTableEntryIndices[CPEMI->getOperand(1).getIndex()]; +} + /// LookForCPEntryInRange - see if the currently referenced CPE is in range; /// if not, see if an in-range clone of the CPE is in range, and if so, /// change the data structures so the user references the clone. Returns: @@ -1120,7 +1228,7 @@ int ARMConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset) } // No. Look for previously created clones of the CPE that are in range. - unsigned CPI = CPEMI->getOperand(1).getIndex(); + unsigned CPI = getCombinedIndex(CPEMI); std::vector<CPEntry> &CPEs = CPEntries[CPI]; for (unsigned i = 0, e = CPEs.size(); i != e; ++i) { // We already tried this one @@ -1365,7 +1473,7 @@ bool ARMConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) { CPUser &U = CPUsers[CPUserIndex]; MachineInstr *UserMI = U.MI; MachineInstr *CPEMI = U.CPEMI; - unsigned CPI = CPEMI->getOperand(1).getIndex(); + unsigned CPI = getCombinedIndex(CPEMI); unsigned Size = CPEMI->getOperand(2).getImm(); // Compute this only once, it's expensive. unsigned UserOffset = getUserOffset(U); @@ -1429,17 +1537,17 @@ bool ARMConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) { // Update internal data structures to account for the newly inserted MBB. updateForInsertedWaterBlock(NewIsland); - // Decrement the old entry, and remove it if refcount becomes 0. - decrementCPEReferenceCount(CPI, CPEMI); - // Now that we have an island to add the CPE to, clone the original CPE and // add it to the island. U.HighWaterMark = NewIsland; - U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(ARM::CONSTPOOL_ENTRY)) - .addImm(ID).addConstantPoolIndex(CPI).addImm(Size); + U.CPEMI = BuildMI(NewIsland, DebugLoc(), CPEMI->getDesc()) + .addImm(ID).addOperand(CPEMI->getOperand(1)).addImm(Size); CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1)); ++NumCPEs; + // Decrement the old entry, and remove it if refcount becomes 0. + decrementCPEReferenceCount(CPI, CPEMI); + // Mark the basic block as aligned as required by the const-pool entry. NewIsland->setAlignment(getCPELogAlign(U.CPEMI)); @@ -1844,77 +1952,120 @@ bool ARMConstantIslands::optimizeThumb2Branches() { return MadeChange; } -/// If we've formed a TBB or TBH instruction, the base register is now -/// redundant. In most cases, the instructions defining it will now be dead and -/// can be tidied up. This function removes them if so, and returns the number -/// of bytes saved. -unsigned ARMConstantIslands::removeDeadDefinitions(MachineInstr *MI, - unsigned BaseReg, - unsigned IdxReg) { - unsigned BytesRemoved = 0; - MachineBasicBlock *MBB = MI->getParent(); +static bool isSimpleIndexCalc(MachineInstr &I, unsigned EntryReg, + unsigned BaseReg) { + if (I.getOpcode() != ARM::t2ADDrs) + return false; - // Scan backwards to find the instruction that defines the base - // register. Due to post-RA scheduling, we can't count on it - // immediately preceding the branch instruction. - MachineBasicBlock::iterator PrevI = MI; - MachineBasicBlock::iterator B = MBB->begin(); - while (PrevI != B && !PrevI->definesRegister(BaseReg)) - --PrevI; - - // If for some reason we didn't find it, we can't do anything, so - // just skip this one. - if (!PrevI->definesRegister(BaseReg) || PrevI->hasUnmodeledSideEffects() || - PrevI->mayStore()) - return BytesRemoved; - - MachineInstr *AddrMI = PrevI; - unsigned NewBaseReg = BytesRemoved; - - // Examine the instruction that calculates the jumptable entry address. Make - // sure it only defines the base register and kills any uses other than the - // index register. We also need precisely one use to trace backwards to - // (hopefully) the LEA. - for (unsigned k = 0, eee = AddrMI->getNumOperands(); k != eee; ++k) { - const MachineOperand &MO = AddrMI->getOperand(k); - if (!MO.isReg() || !MO.getReg()) - continue; - if (MO.isDef() && MO.getReg() != BaseReg) - return BytesRemoved; + if (I.getOperand(0).getReg() != EntryReg) + return false; - if (MO.isUse() && MO.getReg() != IdxReg) { - if (!MO.isKill() || (NewBaseReg != 0 && NewBaseReg != MO.getReg())) - return BytesRemoved; - NewBaseReg = MO.getReg(); + if (I.getOperand(1).getReg() != BaseReg) + return false; + + // FIXME: what about CC and IdxReg? + return true; +} + +/// \brief While trying to form a TBB/TBH instruction, we may (if the table +/// doesn't immediately follow the BR_JT) need access to the start of the +/// jump-table. We know one instruction that produces such a register; this +/// function works out whether that definition can be preserved to the BR_JT, +/// possibly by removing an intervening addition (which is usually needed to +/// calculate the actual entry to jump to). +bool ARMConstantIslands::preserveBaseRegister(MachineInstr *JumpMI, + MachineInstr *LEAMI, + unsigned &DeadSize, + bool &CanDeleteLEA, + bool &BaseRegKill) { + if (JumpMI->getParent() != LEAMI->getParent()) + return false; + + // Now we hope that we have at least these instructions in the basic block: + // BaseReg = t2LEA ... + // [...] + // EntryReg = t2ADDrs BaseReg, ... + // [...] + // t2BR_JT EntryReg + // + // We have to be very conservative about what we recognise here though. The + // main perturbing factors to watch out for are: + // + Spills at any point in the chain: not direct problems but we would + // expect a blocking Def of the spilled register so in practice what we + // can do is limited. + // + EntryReg == BaseReg: this is the one situation we should allow a Def + // of BaseReg, but only if the t2ADDrs can be removed. + // + Some instruction other than t2ADDrs computing the entry. Not seen in + // the wild, but we should be careful. + unsigned EntryReg = JumpMI->getOperand(0).getReg(); + unsigned BaseReg = LEAMI->getOperand(0).getReg(); + + CanDeleteLEA = true; + BaseRegKill = false; + MachineInstr *RemovableAdd = nullptr; + MachineBasicBlock::iterator I(LEAMI); + for (++I; &*I != JumpMI; ++I) { + if (isSimpleIndexCalc(*I, EntryReg, BaseReg)) { + RemovableAdd = &*I; + break; + } + + for (unsigned K = 0, E = I->getNumOperands(); K != E; ++K) { + const MachineOperand &MO = I->getOperand(K); + if (!MO.isReg() || !MO.getReg()) + continue; + if (MO.isDef() && MO.getReg() == BaseReg) + return false; + if (MO.isUse() && MO.getReg() == BaseReg) { + BaseRegKill = BaseRegKill || MO.isKill(); + CanDeleteLEA = false; + } + } + } + + if (!RemovableAdd) + return true; + + // Check the add really is removable, and that nothing else in the block + // clobbers BaseReg. + for (++I; &*I != JumpMI; ++I) { + for (unsigned K = 0, E = I->getNumOperands(); K != E; ++K) { + const MachineOperand &MO = I->getOperand(K); + if (!MO.isReg() || !MO.getReg()) + continue; + if (MO.isDef() && MO.getReg() == BaseReg) + return false; + if (MO.isUse() && MO.getReg() == EntryReg) + RemovableAdd = nullptr; } } - // Want to continue searching for AddrMI, but there are 2 problems: AddrMI is - // going away soon, and even decrementing once may be invalid. - if (PrevI != B) - PrevI = std::prev(PrevI); - - DEBUG(dbgs() << "remove addr: " << *AddrMI); - BytesRemoved += TII->GetInstSizeInBytes(AddrMI); - AddrMI->eraseFromParent(); - - // Now scan back again to find the tLEApcrel or t2LEApcrelJT instruction - // that gave us the initial base register definition. - for (; PrevI != B && !PrevI->definesRegister(NewBaseReg); --PrevI) - ; - - // The instruction should be a tLEApcrel or t2LEApcrelJT; we want - // to delete it as well. - MachineInstr *LeaMI = PrevI; - if ((LeaMI->getOpcode() != ARM::tLEApcrelJT && - LeaMI->getOpcode() != ARM::t2LEApcrelJT) || - LeaMI->getOperand(0).getReg() != NewBaseReg) - return BytesRemoved; - - DEBUG(dbgs() << "remove lea: " << *LeaMI); - BytesRemoved += TII->GetInstSizeInBytes(LeaMI); - LeaMI->eraseFromParent(); - return BytesRemoved; + if (RemovableAdd) { + RemovableAdd->eraseFromParent(); + DeadSize += 4; + } else if (BaseReg == EntryReg) { + // The add wasn't removable, but clobbered the base for the TBB. So we can't + // preserve it. + return false; + } + + // We reached the end of the block without seeing another definition of + // BaseReg (except, possibly the t2ADDrs, which was removed). BaseReg can be + // used in the TBB/TBH if necessary. + return true; +} + +/// \brief Returns whether CPEMI is the first instruction in the block +/// immediately following JTMI (assumed to be a TBB or TBH terminator). If so, +/// we can switch the first register to PC and usually remove the address +/// calculation that preceeded it. +static bool jumpTableFollowsTB(MachineInstr *JTMI, MachineInstr *CPEMI) { + MachineFunction::iterator MBB = JTMI->getParent(); + MachineFunction *MF = MBB->getParent(); + ++MBB; + + return MBB != MF->end() && MBB->begin() != MBB->end() && + &*MBB->begin() == CPEMI; } /// optimizeThumb2JumpTables - Use tbb / tbh instructions to generate smaller @@ -1955,37 +2106,79 @@ bool ARMConstantIslands::optimizeThumb2JumpTables() { break; } - if (ByteOk || HalfWordOk) { - MachineBasicBlock *MBB = MI->getParent(); - unsigned BaseReg = MI->getOperand(0).getReg(); - bool BaseRegKill = MI->getOperand(0).isKill(); - if (!BaseRegKill) - continue; - unsigned IdxReg = MI->getOperand(1).getReg(); - bool IdxRegKill = MI->getOperand(1).isKill(); + if (!ByteOk && !HalfWordOk) + continue; - DEBUG(dbgs() << "Shrink JT: " << *MI); - unsigned Opc = ByteOk ? ARM::t2TBB_JT : ARM::t2TBH_JT; - MachineBasicBlock::iterator MI_JT = MI; - MachineInstr *NewJTMI = - BuildMI(*MBB, MI_JT, MI->getDebugLoc(), TII->get(Opc)) - .addReg(IdxReg, getKillRegState(IdxRegKill)) - .addJumpTableIndex(JTI, JTOP.getTargetFlags()); - DEBUG(dbgs() << "BB#" << MBB->getNumber() << ": " << *NewJTMI); - // FIXME: Insert an "ALIGN" instruction to ensure the next instruction - // is 2-byte aligned. For now, asm printer will fix it up. - unsigned NewSize = TII->GetInstSizeInBytes(NewJTMI); - unsigned OrigSize = TII->GetInstSizeInBytes(MI); - unsigned DeadSize = removeDeadDefinitions(MI, BaseReg, IdxReg); - MI->eraseFromParent(); + MachineBasicBlock *MBB = MI->getParent(); + if (!MI->getOperand(0).isKill()) // FIXME: needed now? + continue; + unsigned IdxReg = MI->getOperand(1).getReg(); + bool IdxRegKill = MI->getOperand(1).isKill(); - int delta = OrigSize - NewSize + DeadSize; - BBInfo[MBB->getNumber()].Size -= delta; - adjustBBOffsetsAfter(MBB); + CPUser &User = CPUsers[JumpTableUserIndices[JTI]]; + unsigned DeadSize = 0; + bool CanDeleteLEA = false; + bool BaseRegKill = false; + bool PreservedBaseReg = + preserveBaseRegister(MI, User.MI, DeadSize, CanDeleteLEA, BaseRegKill); - ++NumTBs; - MadeChange = true; + if (!jumpTableFollowsTB(MI, User.CPEMI) && !PreservedBaseReg) + continue; + + DEBUG(dbgs() << "Shrink JT: " << *MI); + MachineInstr *CPEMI = User.CPEMI; + unsigned Opc = ByteOk ? ARM::t2TBB_JT : ARM::t2TBH_JT; + MachineBasicBlock::iterator MI_JT = MI; + MachineInstr *NewJTMI = + BuildMI(*MBB, MI_JT, MI->getDebugLoc(), TII->get(Opc)) + .addReg(User.MI->getOperand(0).getReg(), + getKillRegState(BaseRegKill)) + .addReg(IdxReg, getKillRegState(IdxRegKill)) + .addJumpTableIndex(JTI, JTOP.getTargetFlags()) + .addImm(CPEMI->getOperand(0).getImm()); + DEBUG(dbgs() << "BB#" << MBB->getNumber() << ": " << *NewJTMI); + + unsigned JTOpc = ByteOk ? ARM::JUMPTABLE_TBB : ARM::JUMPTABLE_TBH; + CPEMI->setDesc(TII->get(JTOpc)); + + if (jumpTableFollowsTB(MI, User.CPEMI)) { + NewJTMI->getOperand(0).setReg(ARM::PC); + NewJTMI->getOperand(0).setIsKill(false); + + if (CanDeleteLEA) { + User.MI->eraseFromParent(); + DeadSize += 4; + + // The LEA was eliminated, the TBB instruction becomes the only new user + // of the jump table. + User.MI = NewJTMI; + User.MaxDisp = 4; + User.NegOk = false; + User.IsSoImm = false; + User.KnownAlignment = false; + } else { + // The LEA couldn't be eliminated, so we must add another CPUser to + // record the TBB or TBH use. + int CPEntryIdx = JumpTableEntryIndices[JTI]; + auto &CPEs = CPEntries[CPEntryIdx]; + auto Entry = std::find_if(CPEs.begin(), CPEs.end(), [&](CPEntry &E) { + return E.CPEMI == User.CPEMI; + }); + ++Entry->RefCount; + CPUsers.emplace_back(CPUser(NewJTMI, User.CPEMI, 4, false, false)); + } } + + unsigned NewSize = TII->GetInstSizeInBytes(NewJTMI); + unsigned OrigSize = TII->GetInstSizeInBytes(MI); + MI->eraseFromParent(); + + int Delta = OrigSize - NewSize + DeadSize; + BBInfo[MBB->getNumber()].Size -= Delta; + adjustBBOffsetsAfter(MBB); + + ++NumTBs; + MadeChange = true; } return MadeChange; |
