| //===- MipsConstantIslandPass.cpp - Emit Pc Relative loads ----------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass is used to make Pc relative loads of constants. |
| // For now, only Mips16 will use this. |
| // |
| // Loading constants inline is expensive on Mips16 and it's in general better |
| // to place the constant nearby in code space and then it can be loaded with a |
| // simple 16 bit load instruction. |
| // |
| // The constants can be not just numbers but addresses of functions and labels. |
| // This can be particularly helpful in static relocation mode for embedded |
| // non-linux targets. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "Mips.h" |
| #include "Mips16InstrInfo.h" |
| #include "MipsMachineFunction.h" |
| #include "MipsSubtarget.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/StringRef.h" |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/MachineConstantPool.h" |
| #include "llvm/CodeGen/MachineFunction.h" |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/MachineOperand.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/Config/llvm-config.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DebugLoc.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/Type.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/Format.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <algorithm> |
| #include <cassert> |
| #include <cstdint> |
| #include <iterator> |
| #include <vector> |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "mips-constant-islands" |
| |
| STATISTIC(NumCPEs, "Number of constpool entries"); |
| STATISTIC(NumSplit, "Number of uncond branches inserted"); |
| STATISTIC(NumCBrFixed, "Number of cond branches fixed"); |
| STATISTIC(NumUBrFixed, "Number of uncond branches fixed"); |
| |
| // FIXME: This option should be removed once it has received sufficient testing. |
| static cl::opt<bool> |
| AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true), |
| cl::desc("Align constant islands in code")); |
| |
| // Rather than do make check tests with huge amounts of code, we force |
| // the test to use this amount. |
| static cl::opt<int> ConstantIslandsSmallOffset( |
| "mips-constant-islands-small-offset", |
| cl::init(0), |
| cl::desc("Make small offsets be this amount for testing purposes"), |
| cl::Hidden); |
| |
| // For testing purposes we tell it to not use relaxed load forms so that it |
| // will split blocks. |
| static cl::opt<bool> NoLoadRelaxation( |
| "mips-constant-islands-no-load-relaxation", |
| cl::init(false), |
| cl::desc("Don't relax loads to long loads - for testing purposes"), |
| cl::Hidden); |
| |
| static unsigned int branchTargetOperand(MachineInstr *MI) { |
| switch (MI->getOpcode()) { |
| case Mips::Bimm16: |
| case Mips::BimmX16: |
| case Mips::Bteqz16: |
| case Mips::BteqzX16: |
| case Mips::Btnez16: |
| case Mips::BtnezX16: |
| case Mips::JalB16: |
| return 0; |
| case Mips::BeqzRxImm16: |
| case Mips::BeqzRxImmX16: |
| case Mips::BnezRxImm16: |
| case Mips::BnezRxImmX16: |
| return 1; |
| } |
| llvm_unreachable("Unknown branch type"); |
| } |
| |
| static unsigned int longformBranchOpcode(unsigned int Opcode) { |
| switch (Opcode) { |
| case Mips::Bimm16: |
| case Mips::BimmX16: |
| return Mips::BimmX16; |
| case Mips::Bteqz16: |
| case Mips::BteqzX16: |
| return Mips::BteqzX16; |
| case Mips::Btnez16: |
| case Mips::BtnezX16: |
| return Mips::BtnezX16; |
| case Mips::JalB16: |
| return Mips::JalB16; |
| case Mips::BeqzRxImm16: |
| case Mips::BeqzRxImmX16: |
| return Mips::BeqzRxImmX16; |
| case Mips::BnezRxImm16: |
| case Mips::BnezRxImmX16: |
| return Mips::BnezRxImmX16; |
| } |
| llvm_unreachable("Unknown branch type"); |
| } |
| |
| // FIXME: need to go through this whole constant islands port and check the math |
| // for branch ranges and clean this up and make some functions to calculate things |
| // that are done many times identically. |
| // Need to refactor some of the code to call this routine. |
| static unsigned int branchMaxOffsets(unsigned int Opcode) { |
| unsigned Bits, Scale; |
| switch (Opcode) { |
| case Mips::Bimm16: |
| Bits = 11; |
| Scale = 2; |
| break; |
| case Mips::BimmX16: |
| Bits = 16; |
| Scale = 2; |
| break; |
| case Mips::BeqzRxImm16: |
| Bits = 8; |
| Scale = 2; |
| break; |
| case Mips::BeqzRxImmX16: |
| Bits = 16; |
| Scale = 2; |
| break; |
| case Mips::BnezRxImm16: |
| Bits = 8; |
| Scale = 2; |
| break; |
| case Mips::BnezRxImmX16: |
| Bits = 16; |
| Scale = 2; |
| break; |
| case Mips::Bteqz16: |
| Bits = 8; |
| Scale = 2; |
| break; |
| case Mips::BteqzX16: |
| Bits = 16; |
| Scale = 2; |
| break; |
| case Mips::Btnez16: |
| Bits = 8; |
| Scale = 2; |
| break; |
| case Mips::BtnezX16: |
| Bits = 16; |
| Scale = 2; |
| break; |
| default: |
| llvm_unreachable("Unknown branch type"); |
| } |
| unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale; |
| return MaxOffs; |
| } |
| |
| namespace { |
| |
| using Iter = MachineBasicBlock::iterator; |
| using ReverseIter = MachineBasicBlock::reverse_iterator; |
| |
| /// MipsConstantIslands - Due to limited PC-relative displacements, Mips |
| /// requires constant pool entries to be scattered among the instructions |
| /// inside a function. To do this, it completely ignores the normal LLVM |
| /// constant pool; instead, it places constants wherever it feels like with |
| /// special instructions. |
| /// |
| /// The terminology used in this pass includes: |
| /// Islands - Clumps of constants placed in the function. |
| /// Water - Potential places where an island could be formed. |
| /// CPE - A constant pool entry that has been placed somewhere, which |
| /// tracks a list of users. |
| |
| class MipsConstantIslands : public MachineFunctionPass { |
| /// BasicBlockInfo - Information about the offset and size of a single |
| /// basic block. |
| struct BasicBlockInfo { |
| /// Offset - Distance from the beginning of the function to the beginning |
| /// of this basic block. |
| /// |
| /// Offsets are computed assuming worst case padding before an aligned |
| /// block. This means that subtracting basic block offsets always gives a |
| /// conservative estimate of the real distance which may be smaller. |
| /// |
| /// Because worst case padding is used, the computed offset of an aligned |
| /// block may not actually be aligned. |
| unsigned Offset = 0; |
| |
| /// Size - Size of the basic block in bytes. If the block contains |
| /// inline assembly, this is a worst case estimate. |
| /// |
| /// The size does not include any alignment padding whether from the |
| /// beginning of the block, or from an aligned jump table at the end. |
| unsigned Size = 0; |
| |
| BasicBlockInfo() = default; |
| |
| // FIXME: ignore LogAlign for this patch |
| // |
| unsigned postOffset(unsigned LogAlign = 0) const { |
| unsigned PO = Offset + Size; |
| return PO; |
| } |
| }; |
| |
| std::vector<BasicBlockInfo> BBInfo; |
| |
| /// WaterList - A sorted list of basic blocks where islands could be placed |
| /// (i.e. blocks that don't fall through to the following block, due |
| /// to a return, unreachable, or unconditional branch). |
| std::vector<MachineBasicBlock*> WaterList; |
| |
| /// NewWaterList - The subset of WaterList that was created since the |
| /// previous iteration by inserting unconditional branches. |
| SmallSet<MachineBasicBlock*, 4> NewWaterList; |
| |
| using water_iterator = std::vector<MachineBasicBlock *>::iterator; |
| |
| /// CPUser - One user of a constant pool, keeping the machine instruction |
| /// pointer, the constant pool being referenced, and the max displacement |
| /// allowed from the instruction to the CP. The HighWaterMark records the |
| /// highest basic block where a new CPEntry can be placed. To ensure this |
| /// pass terminates, the CP entries are initially placed at the end of the |
| /// function and then move monotonically to lower addresses. The |
| /// exception to this rule is when the current CP entry for a particular |
| /// CPUser is out of range, but there is another CP entry for the same |
| /// constant value in range. We want to use the existing in-range CP |
| /// entry, but if it later moves out of range, the search for new water |
| /// should resume where it left off. The HighWaterMark is used to record |
| /// that point. |
| struct CPUser { |
| MachineInstr *MI; |
| MachineInstr *CPEMI; |
| MachineBasicBlock *HighWaterMark; |
| |
| private: |
| unsigned MaxDisp; |
| unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions |
| // with different displacements |
| unsigned LongFormOpcode; |
| |
| public: |
| bool NegOk; |
| |
| CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp, |
| bool neg, |
| unsigned longformmaxdisp, unsigned longformopcode) |
| : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), |
| LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode), |
| NegOk(neg){ |
| HighWaterMark = CPEMI->getParent(); |
| } |
| |
| /// getMaxDisp - Returns the maximum displacement supported by MI. |
| unsigned getMaxDisp() const { |
| unsigned xMaxDisp = ConstantIslandsSmallOffset? |
| ConstantIslandsSmallOffset: MaxDisp; |
| return xMaxDisp; |
| } |
| |
| void setMaxDisp(unsigned val) { |
| MaxDisp = val; |
| } |
| |
| unsigned getLongFormMaxDisp() const { |
| return LongFormMaxDisp; |
| } |
| |
| unsigned getLongFormOpcode() const { |
| return LongFormOpcode; |
| } |
| }; |
| |
| /// CPUsers - Keep track of all of the machine instructions that use various |
| /// constant pools and their max displacement. |
| std::vector<CPUser> CPUsers; |
| |
| /// CPEntry - One per constant pool entry, keeping the machine instruction |
| /// pointer, the constpool index, and the number of CPUser's which |
| /// reference this entry. |
| struct CPEntry { |
| MachineInstr *CPEMI; |
| unsigned CPI; |
| unsigned RefCount; |
| |
| CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0) |
| : CPEMI(cpemi), CPI(cpi), RefCount(rc) {} |
| }; |
| |
| /// 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. |
| std::vector<std::vector<CPEntry>> CPEntries; |
| |
| /// 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 |
| /// opcode. |
| struct ImmBranch { |
| MachineInstr *MI; |
| unsigned MaxDisp : 31; |
| bool isCond : 1; |
| int UncondBr; |
| |
| ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr) |
| : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {} |
| }; |
| |
| /// ImmBranches - Keep track of all the immediate branch instructions. |
| /// |
| std::vector<ImmBranch> ImmBranches; |
| |
| /// HasFarJump - True if any far jump instruction has been emitted during |
| /// the branch fix up pass. |
| bool HasFarJump; |
| |
| const MipsSubtarget *STI = nullptr; |
| const Mips16InstrInfo *TII; |
| MipsFunctionInfo *MFI; |
| MachineFunction *MF = nullptr; |
| MachineConstantPool *MCP = nullptr; |
| |
| unsigned PICLabelUId; |
| bool PrescannedForConstants = false; |
| |
| void initPICLabelUId(unsigned UId) { |
| PICLabelUId = UId; |
| } |
| |
| unsigned createPICLabelUId() { |
| return PICLabelUId++; |
| } |
| |
| public: |
| static char ID; |
| |
| MipsConstantIslands() : MachineFunctionPass(ID) {} |
| |
| StringRef getPassName() const override { return "Mips Constant Islands"; } |
| |
| bool runOnMachineFunction(MachineFunction &F) override; |
| |
| MachineFunctionProperties getRequiredProperties() const override { |
| return MachineFunctionProperties().set( |
| MachineFunctionProperties::Property::NoVRegs); |
| } |
| |
| void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs); |
| CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI); |
| unsigned getCPELogAlign(const MachineInstr &CPEMI); |
| void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs); |
| unsigned getOffsetOf(MachineInstr *MI) const; |
| unsigned getUserOffset(CPUser&) const; |
| void dumpBBs(); |
| |
| bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset, |
| unsigned Disp, bool NegativeOK); |
| bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset, |
| const CPUser &U); |
| |
| void computeBlockSize(MachineBasicBlock *MBB); |
| MachineBasicBlock *splitBlockBeforeInstr(MachineInstr &MI); |
| void updateForInsertedWaterBlock(MachineBasicBlock *NewBB); |
| void adjustBBOffsetsAfter(MachineBasicBlock *BB); |
| bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI); |
| int findInRangeCPEntry(CPUser& U, unsigned UserOffset); |
| int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset); |
| bool findAvailableWater(CPUser&U, unsigned UserOffset, |
| water_iterator &WaterIter); |
| void createNewWater(unsigned CPUserIndex, unsigned UserOffset, |
| MachineBasicBlock *&NewMBB); |
| bool handleConstantPoolUser(unsigned CPUserIndex); |
| void removeDeadCPEMI(MachineInstr *CPEMI); |
| bool removeUnusedCPEntries(); |
| bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset, |
| MachineInstr *CPEMI, unsigned Disp, bool NegOk, |
| bool DoDump = false); |
| bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water, |
| CPUser &U, unsigned &Growth); |
| bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp); |
| bool fixupImmediateBr(ImmBranch &Br); |
| bool fixupConditionalBr(ImmBranch &Br); |
| bool fixupUnconditionalBr(ImmBranch &Br); |
| |
| void prescanForConstants(); |
| }; |
| |
| } // end anonymous namespace |
| |
| char MipsConstantIslands::ID = 0; |
| |
| bool MipsConstantIslands::isOffsetInRange |
| (unsigned UserOffset, unsigned TrialOffset, |
| const CPUser &U) { |
| return isOffsetInRange(UserOffset, TrialOffset, |
| U.getMaxDisp(), U.NegOk); |
| } |
| |
| #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) |
| /// print block size and offset information - debugging |
| LLVM_DUMP_METHOD void MipsConstantIslands::dumpBBs() { |
| for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) { |
| const BasicBlockInfo &BBI = BBInfo[J]; |
| dbgs() << format("%08x %bb.%u\t", BBI.Offset, J) |
| << format(" size=%#x\n", BBInfo[J].Size); |
| } |
| } |
| #endif |
| |
| bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) { |
| // The intention is for this to be a mips16 only pass for now |
| // FIXME: |
| MF = &mf; |
| MCP = mf.getConstantPool(); |
| STI = &static_cast<const MipsSubtarget &>(mf.getSubtarget()); |
| LLVM_DEBUG(dbgs() << "constant island machine function " |
| << "\n"); |
| if (!STI->inMips16Mode() || !MipsSubtarget::useConstantIslands()) { |
| return false; |
| } |
| TII = (const Mips16InstrInfo *)STI->getInstrInfo(); |
| MFI = MF->getInfo<MipsFunctionInfo>(); |
| LLVM_DEBUG(dbgs() << "constant island processing " |
| << "\n"); |
| // |
| // will need to make predermination if there is any constants we need to |
| // put in constant islands. TBD. |
| // |
| if (!PrescannedForConstants) prescanForConstants(); |
| |
| HasFarJump = false; |
| // This pass invalidates liveness information when it splits basic blocks. |
| MF->getRegInfo().invalidateLiveness(); |
| |
| // Renumber all of the machine basic blocks in the function, guaranteeing that |
| // the numbers agree with the position of the block in the function. |
| MF->RenumberBlocks(); |
| |
| bool MadeChange = false; |
| |
| // Perform the initial placement of the constant pool entries. To start with, |
| // we put them all at the end of the function. |
| std::vector<MachineInstr*> CPEMIs; |
| if (!MCP->isEmpty()) |
| doInitialPlacement(CPEMIs); |
| |
| /// The next UID to take is the first unused one. |
| initPICLabelUId(CPEMIs.size()); |
| |
| // Do the initial scan of the function, building up information about the |
| // sizes of each block, the location of all the water, and finding all of the |
| // constant pool users. |
| initializeFunctionInfo(CPEMIs); |
| CPEMIs.clear(); |
| LLVM_DEBUG(dumpBBs()); |
| |
| /// Remove dead constant pool entries. |
| MadeChange |= removeUnusedCPEntries(); |
| |
| // Iteratively place constant pool entries and fix up branches until there |
| // is no change. |
| unsigned NoCPIters = 0, NoBRIters = 0; |
| (void)NoBRIters; |
| while (true) { |
| LLVM_DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n'); |
| bool CPChange = false; |
| for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) |
| CPChange |= handleConstantPoolUser(i); |
| if (CPChange && ++NoCPIters > 30) |
| report_fatal_error("Constant Island pass failed to converge!"); |
| LLVM_DEBUG(dumpBBs()); |
| |
| // Clear NewWaterList now. If we split a block for branches, it should |
| // appear as "new water" for the next iteration of constant pool placement. |
| NewWaterList.clear(); |
| |
| LLVM_DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n'); |
| bool BRChange = false; |
| for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) |
| BRChange |= fixupImmediateBr(ImmBranches[i]); |
| if (BRChange && ++NoBRIters > 30) |
| report_fatal_error("Branch Fix Up pass failed to converge!"); |
| LLVM_DEBUG(dumpBBs()); |
| if (!CPChange && !BRChange) |
| break; |
| MadeChange = true; |
| } |
| |
| LLVM_DEBUG(dbgs() << '\n'; dumpBBs()); |
| |
| BBInfo.clear(); |
| WaterList.clear(); |
| CPUsers.clear(); |
| CPEntries.clear(); |
| ImmBranches.clear(); |
| 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. |
| void |
| MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) { |
| // Create the basic block to hold the CPE's. |
| MachineBasicBlock *BB = MF->CreateMachineBasicBlock(); |
| MF->push_back(BB); |
| |
| // MachineConstantPool measures alignment in bytes. We measure in log2(bytes). |
| unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment()); |
| |
| // Mark the basic block as required by the const-pool. |
| // If AlignConstantIslands isn't set, use 4-byte alignment for everything. |
| BB->setAlignment(AlignConstantIslands ? MaxAlign : 2); |
| |
| // The function needs to be as aligned as the basic blocks. The linker may |
| // move functions around based on their alignment. |
| MF->ensureAlignment(BB->getAlignment()); |
| |
| // Order the entries in BB by descending alignment. That ensures correct |
| // alignment of all entries as long as BB is sufficiently aligned. Keep |
| // track of the insertion point for each alignment. We are going to bucket |
| // sort the entries as they are created. |
| SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end()); |
| |
| // Add all of the constants from the constant pool to the end block, use an |
| // identity mapping of CPI's to CPE's. |
| const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants(); |
| |
| const DataLayout &TD = MF->getDataLayout(); |
| for (unsigned i = 0, e = CPs.size(); i != e; ++i) { |
| unsigned Size = TD.getTypeAllocSize(CPs[i].getType()); |
| assert(Size >= 4 && "Too small constant pool entry"); |
| unsigned Align = CPs[i].getAlignment(); |
| assert(isPowerOf2_32(Align) && "Invalid alignment"); |
| // Verify that all constant pool entries are a multiple of their alignment. |
| // If not, we would have to pad them out so that instructions stay aligned. |
| assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!"); |
| |
| // Insert CONSTPOOL_ENTRY before entries with a smaller alignment. |
| unsigned LogAlign = Log2_32(Align); |
| MachineBasicBlock::iterator InsAt = InsPoint[LogAlign]; |
| |
| MachineInstr *CPEMI = |
| BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY)) |
| .addImm(i).addConstantPoolIndex(i).addImm(Size); |
| |
| CPEMIs.push_back(CPEMI); |
| |
| // Ensure that future entries with higher alignment get inserted before |
| // CPEMI. This is bucket sort with iterators. |
| for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a) |
| if (InsPoint[a] == InsAt) |
| InsPoint[a] = CPEMI; |
| // Add a new CPEntry, but no corresponding CPUser yet. |
| CPEntries.emplace_back(1, CPEntry(CPEMI, i)); |
| ++NumCPEs; |
| LLVM_DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = " |
| << Size << ", align = " << Align << '\n'); |
| } |
| LLVM_DEBUG(BB->dump()); |
| } |
| |
| /// BBHasFallthrough - Return true if the specified basic block can fallthrough |
| /// into the block immediately after it. |
| static bool BBHasFallthrough(MachineBasicBlock *MBB) { |
| // Get the next machine basic block in the function. |
| MachineFunction::iterator MBBI = MBB->getIterator(); |
| // Can't fall off end of function. |
| if (std::next(MBBI) == MBB->getParent()->end()) |
| return false; |
| |
| MachineBasicBlock *NextBB = &*std::next(MBBI); |
| for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(), |
| E = MBB->succ_end(); I != E; ++I) |
| if (*I == NextBB) |
| return true; |
| |
| return false; |
| } |
| |
| /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI, |
| /// look up the corresponding CPEntry. |
| MipsConstantIslands::CPEntry |
| *MipsConstantIslands::findConstPoolEntry(unsigned CPI, |
| const MachineInstr *CPEMI) { |
| std::vector<CPEntry> &CPEs = CPEntries[CPI]; |
| // Number of entries per constpool index should be small, just do a |
| // linear search. |
| for (unsigned i = 0, e = CPEs.size(); i != e; ++i) { |
| if (CPEs[i].CPEMI == CPEMI) |
| return &CPEs[i]; |
| } |
| return nullptr; |
| } |
| |
| /// getCPELogAlign - Returns the required alignment of the constant pool entry |
| /// represented by CPEMI. Alignment is measured in log2(bytes) units. |
| unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr &CPEMI) { |
| assert(CPEMI.getOpcode() == Mips::CONSTPOOL_ENTRY); |
| |
| // Everything is 4-byte aligned unless AlignConstantIslands is set. |
| if (!AlignConstantIslands) |
| return 2; |
| |
| unsigned CPI = CPEMI.getOperand(1).getIndex(); |
| assert(CPI < MCP->getConstants().size() && "Invalid constant pool index."); |
| unsigned Align = MCP->getConstants()[CPI].getAlignment(); |
| assert(isPowerOf2_32(Align) && "Invalid CPE alignment"); |
| return Log2_32(Align); |
| } |
| |
| /// initializeFunctionInfo - Do the initial scan of the function, building up |
| /// information about the sizes of each block, the location of all the water, |
| /// and finding all of the constant pool users. |
| void MipsConstantIslands:: |
| initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) { |
| BBInfo.clear(); |
| BBInfo.resize(MF->getNumBlockIDs()); |
| |
| // First thing, compute the size of all basic blocks, and see if the function |
| // has any inline assembly in it. If so, we have to be conservative about |
| // alignment assumptions, as we don't know for sure the size of any |
| // instructions in the inline assembly. |
| for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I) |
| computeBlockSize(&*I); |
| |
| // Compute block offsets. |
| adjustBBOffsetsAfter(&MF->front()); |
| |
| // Now go back through the instructions and build up our data structures. |
| for (MachineBasicBlock &MBB : *MF) { |
| // If this block doesn't fall through into the next MBB, then this is |
| // 'water' that a constant pool island could be placed. |
| if (!BBHasFallthrough(&MBB)) |
| WaterList.push_back(&MBB); |
| for (MachineInstr &MI : MBB) { |
| if (MI.isDebugInstr()) |
| continue; |
| |
| int Opc = MI.getOpcode(); |
| if (MI.isBranch()) { |
| bool isCond = false; |
| unsigned Bits = 0; |
| unsigned Scale = 1; |
| int UOpc = Opc; |
| switch (Opc) { |
| default: |
| continue; // Ignore other branches for now |
| case Mips::Bimm16: |
| Bits = 11; |
| Scale = 2; |
| isCond = false; |
| break; |
| case Mips::BimmX16: |
| Bits = 16; |
| Scale = 2; |
| isCond = false; |
| break; |
| case Mips::BeqzRxImm16: |
| UOpc=Mips::Bimm16; |
| Bits = 8; |
| Scale = 2; |
| isCond = true; |
| break; |
| case Mips::BeqzRxImmX16: |
| UOpc=Mips::Bimm16; |
| Bits = 16; |
| Scale = 2; |
| isCond = true; |
| break; |
| case Mips::BnezRxImm16: |
| UOpc=Mips::Bimm16; |
| Bits = 8; |
| Scale = 2; |
| isCond = true; |
| break; |
| case Mips::BnezRxImmX16: |
| UOpc=Mips::Bimm16; |
| Bits = 16; |
| Scale = 2; |
| isCond = true; |
| break; |
| case Mips::Bteqz16: |
| UOpc=Mips::Bimm16; |
| Bits = 8; |
| Scale = 2; |
| isCond = true; |
| break; |
| case Mips::BteqzX16: |
| UOpc=Mips::Bimm16; |
| Bits = 16; |
| Scale = 2; |
| isCond = true; |
| break; |
| case Mips::Btnez16: |
| UOpc=Mips::Bimm16; |
| Bits = 8; |
| Scale = 2; |
| isCond = true; |
| break; |
| case Mips::BtnezX16: |
| UOpc=Mips::Bimm16; |
| Bits = 16; |
| Scale = 2; |
| isCond = true; |
| break; |
| } |
| // Record this immediate branch. |
| unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale; |
| ImmBranches.push_back(ImmBranch(&MI, MaxOffs, isCond, UOpc)); |
| } |
| |
| if (Opc == Mips::CONSTPOOL_ENTRY) |
| continue; |
| |
| // Scan the instructions for constant pool operands. |
| for (unsigned op = 0, e = MI.getNumOperands(); op != e; ++op) |
| if (MI.getOperand(op).isCPI()) { |
| // We found one. The addressing mode tells us the max displacement |
| // from the PC that this instruction permits. |
| |
| // Basic size info comes from the TSFlags field. |
| unsigned Bits = 0; |
| unsigned Scale = 1; |
| bool NegOk = false; |
| unsigned LongFormBits = 0; |
| unsigned LongFormScale = 0; |
| unsigned LongFormOpcode = 0; |
| switch (Opc) { |
| default: |
| llvm_unreachable("Unknown addressing mode for CP reference!"); |
| case Mips::LwRxPcTcp16: |
| Bits = 8; |
| Scale = 4; |
| LongFormOpcode = Mips::LwRxPcTcpX16; |
| LongFormBits = 14; |
| LongFormScale = 1; |
| break; |
| case Mips::LwRxPcTcpX16: |
| Bits = 14; |
| Scale = 1; |
| NegOk = true; |
| break; |
| } |
| // Remember that this is a user of a CP entry. |
| unsigned CPI = MI.getOperand(op).getIndex(); |
| MachineInstr *CPEMI = CPEMIs[CPI]; |
| unsigned MaxOffs = ((1 << Bits)-1) * Scale; |
| unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale; |
| CPUsers.push_back(CPUser(&MI, CPEMI, MaxOffs, NegOk, LongFormMaxOffs, |
| LongFormOpcode)); |
| |
| // Increment corresponding CPEntry reference count. |
| CPEntry *CPE = findConstPoolEntry(CPI, CPEMI); |
| assert(CPE && "Cannot find a corresponding CPEntry!"); |
| CPE->RefCount++; |
| |
| // Instructions can only use one CP entry, don't bother scanning the |
| // rest of the operands. |
| break; |
| } |
| } |
| } |
| } |
| |
| /// computeBlockSize - Compute the size and some alignment information for MBB. |
| /// This function updates BBInfo directly. |
| void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) { |
| BasicBlockInfo &BBI = BBInfo[MBB->getNumber()]; |
| BBI.Size = 0; |
| |
| for (const MachineInstr &MI : *MBB) |
| BBI.Size += TII->getInstSizeInBytes(MI); |
| } |
| |
| /// getOffsetOf - Return the current offset of the specified machine instruction |
| /// from the start of the function. This offset changes as stuff is moved |
| /// around inside the function. |
| unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const { |
| MachineBasicBlock *MBB = MI->getParent(); |
| |
| // The offset is composed of two things: the sum of the sizes of all MBB's |
| // before this instruction's block, and the offset from the start of the block |
| // it is in. |
| unsigned Offset = BBInfo[MBB->getNumber()].Offset; |
| |
| // Sum instructions before MI in MBB. |
| for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) { |
| assert(I != MBB->end() && "Didn't find MI in its own basic block?"); |
| Offset += TII->getInstSizeInBytes(*I); |
| } |
| return Offset; |
| } |
| |
| /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB |
| /// ID. |
| static bool CompareMBBNumbers(const MachineBasicBlock *LHS, |
| const MachineBasicBlock *RHS) { |
| return LHS->getNumber() < RHS->getNumber(); |
| } |
| |
| /// updateForInsertedWaterBlock - When a block is newly inserted into the |
| /// machine function, it upsets all of the block numbers. Renumber the blocks |
| /// and update the arrays that parallel this numbering. |
| void MipsConstantIslands::updateForInsertedWaterBlock |
| (MachineBasicBlock *NewBB) { |
| // Renumber the MBB's to keep them consecutive. |
| NewBB->getParent()->RenumberBlocks(NewBB); |
| |
| // Insert an entry into BBInfo to align it properly with the (newly |
| // renumbered) block numbers. |
| BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo()); |
| |
| // Next, update WaterList. Specifically, we need to add NewMBB as having |
| // available water after it. |
| water_iterator IP = |
| std::lower_bound(WaterList.begin(), WaterList.end(), NewBB, |
| CompareMBBNumbers); |
| WaterList.insert(IP, NewBB); |
| } |
| |
| unsigned MipsConstantIslands::getUserOffset(CPUser &U) const { |
| return getOffsetOf(U.MI); |
| } |
| |
| /// Split the basic block containing MI into two blocks, which are joined by |
| /// an unconditional branch. Update data structures and renumber blocks to |
| /// account for this change and returns the newly created block. |
| MachineBasicBlock * |
| MipsConstantIslands::splitBlockBeforeInstr(MachineInstr &MI) { |
| MachineBasicBlock *OrigBB = MI.getParent(); |
| |
| // Create a new MBB for the code after the OrigBB. |
| MachineBasicBlock *NewBB = |
| MF->CreateMachineBasicBlock(OrigBB->getBasicBlock()); |
| MachineFunction::iterator MBBI = ++OrigBB->getIterator(); |
| MF->insert(MBBI, NewBB); |
| |
| // Splice the instructions starting with MI over to NewBB. |
| NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end()); |
| |
| // Add an unconditional branch from OrigBB to NewBB. |
| // Note the new unconditional branch is not being recorded. |
| // There doesn't seem to be meaningful DebugInfo available; this doesn't |
| // correspond to anything in the source. |
| BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB); |
| ++NumSplit; |
| |
| // Update the CFG. All succs of OrigBB are now succs of NewBB. |
| NewBB->transferSuccessors(OrigBB); |
| |
| // OrigBB branches to NewBB. |
| OrigBB->addSuccessor(NewBB); |
| |
| // Update internal data structures to account for the newly inserted MBB. |
| // This is almost the same as updateForInsertedWaterBlock, except that |
| // the Water goes after OrigBB, not NewBB. |
| MF->RenumberBlocks(NewBB); |
| |
| // Insert an entry into BBInfo to align it properly with the (newly |
| // renumbered) block numbers. |
| BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo()); |
| |
| // Next, update WaterList. Specifically, we need to add OrigMBB as having |
| // available water after it (but not if it's already there, which happens |
| // when splitting before a conditional branch that is followed by an |
| // unconditional branch - in that case we want to insert NewBB). |
| water_iterator IP = |
| std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB, |
| CompareMBBNumbers); |
| MachineBasicBlock* WaterBB = *IP; |
| if (WaterBB == OrigBB) |
| WaterList.insert(std::next(IP), NewBB); |
| else |
| WaterList.insert(IP, OrigBB); |
| NewWaterList.insert(OrigBB); |
| |
| // Figure out how large the OrigBB is. As the first half of the original |
| // block, it cannot contain a tablejump. The size includes |
| // the new jump we added. (It should be possible to do this without |
| // recounting everything, but it's very confusing, and this is rarely |
| // executed.) |
| computeBlockSize(OrigBB); |
| |
| // Figure out how large the NewMBB is. As the second half of the original |
| // block, it may contain a tablejump. |
| computeBlockSize(NewBB); |
| |
| // All BBOffsets following these blocks must be modified. |
| adjustBBOffsetsAfter(OrigBB); |
| |
| return NewBB; |
| } |
| |
| /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool |
| /// reference) is within MaxDisp of TrialOffset (a proposed location of a |
| /// constant pool entry). |
| bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset, |
| unsigned TrialOffset, unsigned MaxDisp, |
| bool NegativeOK) { |
| if (UserOffset <= TrialOffset) { |
| // User before the Trial. |
| if (TrialOffset - UserOffset <= MaxDisp) |
| return true; |
| } else if (NegativeOK) { |
| if (UserOffset - TrialOffset <= MaxDisp) |
| return true; |
| } |
| return false; |
| } |
| |
| /// isWaterInRange - Returns true if a CPE placed after the specified |
| /// Water (a basic block) will be in range for the specific MI. |
| /// |
| /// Compute how much the function will grow by inserting a CPE after Water. |
| bool MipsConstantIslands::isWaterInRange(unsigned UserOffset, |
| MachineBasicBlock* Water, CPUser &U, |
| unsigned &Growth) { |
| unsigned CPELogAlign = getCPELogAlign(*U.CPEMI); |
| unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign); |
| unsigned NextBlockOffset, NextBlockAlignment; |
| MachineFunction::const_iterator NextBlock = ++Water->getIterator(); |
| if (NextBlock == MF->end()) { |
| NextBlockOffset = BBInfo[Water->getNumber()].postOffset(); |
| NextBlockAlignment = 0; |
| } else { |
| NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset; |
| NextBlockAlignment = NextBlock->getAlignment(); |
| } |
| unsigned Size = U.CPEMI->getOperand(2).getImm(); |
| unsigned CPEEnd = CPEOffset + Size; |
| |
| // The CPE may be able to hide in the alignment padding before the next |
| // block. It may also cause more padding to be required if it is more aligned |
| // that the next block. |
| if (CPEEnd > NextBlockOffset) { |
| Growth = CPEEnd - NextBlockOffset; |
| // Compute the padding that would go at the end of the CPE to align the next |
| // block. |
| Growth += OffsetToAlignment(CPEEnd, 1ULL << NextBlockAlignment); |
| |
| // If the CPE is to be inserted before the instruction, that will raise |
| // the offset of the instruction. Also account for unknown alignment padding |
| // in blocks between CPE and the user. |
| if (CPEOffset < UserOffset) |
| UserOffset += Growth; |
| } else |
| // CPE fits in existing padding. |
| Growth = 0; |
| |
| return isOffsetInRange(UserOffset, CPEOffset, U); |
| } |
| |
| /// isCPEntryInRange - Returns true if the distance between specific MI and |
| /// specific ConstPool entry instruction can fit in MI's displacement field. |
| bool MipsConstantIslands::isCPEntryInRange |
| (MachineInstr *MI, unsigned UserOffset, |
| MachineInstr *CPEMI, unsigned MaxDisp, |
| bool NegOk, bool DoDump) { |
| unsigned CPEOffset = getOffsetOf(CPEMI); |
| |
| if (DoDump) { |
| LLVM_DEBUG({ |
| unsigned Block = MI->getParent()->getNumber(); |
| const BasicBlockInfo &BBI = BBInfo[Block]; |
| dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm() |
| << " max delta=" << MaxDisp |
| << format(" insn address=%#x", UserOffset) << " in " |
| << printMBBReference(*MI->getParent()) << ": " |
| << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI |
| << format("CPE address=%#x offset=%+d: ", CPEOffset, |
| int(CPEOffset - UserOffset)); |
| }); |
| } |
| |
| return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk); |
| } |
| |
| #ifndef NDEBUG |
| /// BBIsJumpedOver - Return true of the specified basic block's only predecessor |
| /// unconditionally branches to its only successor. |
| static bool BBIsJumpedOver(MachineBasicBlock *MBB) { |
| if (MBB->pred_size() != 1 || MBB->succ_size() != 1) |
| return false; |
| MachineBasicBlock *Succ = *MBB->succ_begin(); |
| MachineBasicBlock *Pred = *MBB->pred_begin(); |
| MachineInstr *PredMI = &Pred->back(); |
| if (PredMI->getOpcode() == Mips::Bimm16) |
| return PredMI->getOperand(0).getMBB() == Succ; |
| return false; |
| } |
| #endif |
| |
| void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) { |
| unsigned BBNum = BB->getNumber(); |
| for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) { |
| // Get the offset and known bits at the end of the layout predecessor. |
| // Include the alignment of the current block. |
| unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size; |
| BBInfo[i].Offset = Offset; |
| } |
| } |
| |
| /// decrementCPEReferenceCount - find the constant pool entry with index CPI |
| /// and instruction CPEMI, and decrement its refcount. If the refcount |
| /// becomes 0 remove the entry and instruction. Returns true if we removed |
| /// the entry, false if we didn't. |
| bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI, |
| MachineInstr *CPEMI) { |
| // Find the old entry. Eliminate it if it is no longer used. |
| CPEntry *CPE = findConstPoolEntry(CPI, CPEMI); |
| assert(CPE && "Unexpected!"); |
| if (--CPE->RefCount == 0) { |
| removeDeadCPEMI(CPEMI); |
| CPE->CPEMI = nullptr; |
| --NumCPEs; |
| return true; |
| } |
| return false; |
| } |
| |
| /// 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: |
| /// 0 = no existing entry found |
| /// 1 = entry found, and there were no code insertions or deletions |
| /// 2 = entry found, and there were code insertions or deletions |
| int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset) |
| { |
| MachineInstr *UserMI = U.MI; |
| MachineInstr *CPEMI = U.CPEMI; |
| |
| // Check to see if the CPE is already in-range. |
| if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk, |
| true)) { |
| LLVM_DEBUG(dbgs() << "In range\n"); |
| return 1; |
| } |
| |
| // No. Look for previously created clones of the CPE that are in range. |
| unsigned CPI = CPEMI->getOperand(1).getIndex(); |
| std::vector<CPEntry> &CPEs = CPEntries[CPI]; |
| for (unsigned i = 0, e = CPEs.size(); i != e; ++i) { |
| // We already tried this one |
| if (CPEs[i].CPEMI == CPEMI) |
| continue; |
| // Removing CPEs can leave empty entries, skip |
| if (CPEs[i].CPEMI == nullptr) |
| continue; |
| if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(), |
| U.NegOk)) { |
| LLVM_DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#" |
| << CPEs[i].CPI << "\n"); |
| // Point the CPUser node to the replacement |
| U.CPEMI = CPEs[i].CPEMI; |
| // Change the CPI in the instruction operand to refer to the clone. |
| for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j) |
| if (UserMI->getOperand(j).isCPI()) { |
| UserMI->getOperand(j).setIndex(CPEs[i].CPI); |
| break; |
| } |
| // Adjust the refcount of the clone... |
| CPEs[i].RefCount++; |
| // ...and the original. If we didn't remove the old entry, none of the |
| // addresses changed, so we don't need another pass. |
| return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1; |
| } |
| } |
| return 0; |
| } |
| |
| /// LookForCPEntryInRange - see if the currently referenced CPE is in range; |
| /// This version checks if the longer form of the instruction can be used to |
| /// to satisfy things. |
| /// 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: |
| /// 0 = no existing entry found |
| /// 1 = entry found, and there were no code insertions or deletions |
| /// 2 = entry found, and there were code insertions or deletions |
| int MipsConstantIslands::findLongFormInRangeCPEntry |
| (CPUser& U, unsigned UserOffset) |
| { |
| MachineInstr *UserMI = U.MI; |
| MachineInstr *CPEMI = U.CPEMI; |
| |
| // Check to see if the CPE is already in-range. |
| if (isCPEntryInRange(UserMI, UserOffset, CPEMI, |
| U.getLongFormMaxDisp(), U.NegOk, |
| true)) { |
| LLVM_DEBUG(dbgs() << "In range\n"); |
| UserMI->setDesc(TII->get(U.getLongFormOpcode())); |
| U.setMaxDisp(U.getLongFormMaxDisp()); |
| return 2; // instruction is longer length now |
| } |
| |
| // No. Look for previously created clones of the CPE that are in range. |
| unsigned CPI = CPEMI->getOperand(1).getIndex(); |
| std::vector<CPEntry> &CPEs = CPEntries[CPI]; |
| for (unsigned i = 0, e = CPEs.size(); i != e; ++i) { |
| // We already tried this one |
| if (CPEs[i].CPEMI == CPEMI) |
| continue; |
| // Removing CPEs can leave empty entries, skip |
| if (CPEs[i].CPEMI == nullptr) |
| continue; |
| if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, |
| U.getLongFormMaxDisp(), U.NegOk)) { |
| LLVM_DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#" |
| << CPEs[i].CPI << "\n"); |
| // Point the CPUser node to the replacement |
| U.CPEMI = CPEs[i].CPEMI; |
| // Change the CPI in the instruction operand to refer to the clone. |
| for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j) |
| if (UserMI->getOperand(j).isCPI()) { |
| UserMI->getOperand(j).setIndex(CPEs[i].CPI); |
| break; |
| } |
| // Adjust the refcount of the clone... |
| CPEs[i].RefCount++; |
| // ...and the original. If we didn't remove the old entry, none of the |
| // addresses changed, so we don't need another pass. |
| return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1; |
| } |
| } |
| return 0; |
| } |
| |
| /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in |
| /// the specific unconditional branch instruction. |
| static inline unsigned getUnconditionalBrDisp(int Opc) { |
| switch (Opc) { |
| case Mips::Bimm16: |
| return ((1<<10)-1)*2; |
| case Mips::BimmX16: |
| return ((1<<16)-1)*2; |
| default: |
| break; |
| } |
| return ((1<<16)-1)*2; |
| } |
| |
| /// findAvailableWater - Look for an existing entry in the WaterList in which |
| /// we can place the CPE referenced from U so it's within range of U's MI. |
| /// Returns true if found, false if not. If it returns true, WaterIter |
| /// is set to the WaterList entry. |
| /// To ensure that this pass |
| /// terminates, the CPE location for a particular CPUser is only allowed to |
| /// move to a lower address, so search backward from the end of the list and |
| /// prefer the first water that is in range. |
| bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset, |
| water_iterator &WaterIter) { |
| if (WaterList.empty()) |
| return false; |
| |
| unsigned BestGrowth = ~0u; |
| for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();; |
| --IP) { |
| MachineBasicBlock* WaterBB = *IP; |
| // Check if water is in range and is either at a lower address than the |
| // current "high water mark" or a new water block that was created since |
| // the previous iteration by inserting an unconditional branch. In the |
| // latter case, we want to allow resetting the high water mark back to |
| // this new water since we haven't seen it before. Inserting branches |
| // should be relatively uncommon and when it does happen, we want to be |
| // sure to take advantage of it for all the CPEs near that block, so that |
| // we don't insert more branches than necessary. |
| unsigned Growth; |
| if (isWaterInRange(UserOffset, WaterBB, U, Growth) && |
| (WaterBB->getNumber() < U.HighWaterMark->getNumber() || |
| NewWaterList.count(WaterBB)) && Growth < BestGrowth) { |
| // This is the least amount of required padding seen so far. |
| BestGrowth = Growth; |
| WaterIter = IP; |
| LLVM_DEBUG(dbgs() << "Found water after " << printMBBReference(*WaterBB) |
| << " Growth=" << Growth << '\n'); |
| |
| // Keep looking unless it is perfect. |
| if (BestGrowth == 0) |
| return true; |
| } |
| if (IP == B) |
| break; |
| } |
| return BestGrowth != ~0u; |
| } |
| |
| /// createNewWater - No existing WaterList entry will work for |
| /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the |
| /// block is used if in range, and the conditional branch munged so control |
| /// flow is correct. Otherwise the block is split to create a hole with an |
| /// unconditional branch around it. In either case NewMBB is set to a |
| /// block following which the new island can be inserted (the WaterList |
| /// is not adjusted). |
| void MipsConstantIslands::createNewWater(unsigned CPUserIndex, |
| unsigned UserOffset, |
| MachineBasicBlock *&NewMBB) { |
| CPUser &U = CPUsers[CPUserIndex]; |
| MachineInstr *UserMI = U.MI; |
| MachineInstr *CPEMI = U.CPEMI; |
| unsigned CPELogAlign = getCPELogAlign(*CPEMI); |
| MachineBasicBlock *UserMBB = UserMI->getParent(); |
| const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()]; |
| |
| // If the block does not end in an unconditional branch already, and if the |
| // end of the block is within range, make new water there. |
| if (BBHasFallthrough(UserMBB)) { |
| // Size of branch to insert. |
| unsigned Delta = 2; |
| // Compute the offset where the CPE will begin. |
| unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta; |
| |
| if (isOffsetInRange(UserOffset, CPEOffset, U)) { |
| LLVM_DEBUG(dbgs() << "Split at end of " << printMBBReference(*UserMBB) |
| << format(", expected CPE offset %#x\n", CPEOffset)); |
| NewMBB = &*++UserMBB->getIterator(); |
| // Add an unconditional branch from UserMBB to fallthrough block. Record |
| // it for branch lengthening; this new branch will not get out of range, |
| // but if the preceding conditional branch is out of range, the targets |
| // will be exchanged, and the altered branch may be out of range, so the |
| // machinery has to know about it. |
| int UncondBr = Mips::Bimm16; |
| BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB); |
| unsigned MaxDisp = getUnconditionalBrDisp(UncondBr); |
| ImmBranches.push_back(ImmBranch(&UserMBB->back(), |
| MaxDisp, false, UncondBr)); |
| BBInfo[UserMBB->getNumber()].Size += Delta; |
| adjustBBOffsetsAfter(UserMBB); |
| return; |
| } |
| } |
| |
| // What a big block. Find a place within the block to split it. |
| |
| // Try to split the block so it's fully aligned. Compute the latest split |
| // point where we can add a 4-byte branch instruction, and then align to |
| // LogAlign which is the largest possible alignment in the function. |
| unsigned LogAlign = MF->getAlignment(); |
| assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry"); |
| unsigned BaseInsertOffset = UserOffset + U.getMaxDisp(); |
| LLVM_DEBUG(dbgs() << format("Split in middle of big block before %#x", |
| BaseInsertOffset)); |
| |
| // The 4 in the following is for the unconditional branch we'll be inserting |
| // Alignment of the island is handled |
| // inside isOffsetInRange. |
| BaseInsertOffset -= 4; |
| |
| LLVM_DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset) |
| << " la=" << LogAlign << '\n'); |
| |
| // This could point off the end of the block if we've already got constant |
| // pool entries following this block; only the last one is in the water list. |
| // Back past any possible branches (allow for a conditional and a maximally |
| // long unconditional). |
| if (BaseInsertOffset + 8 >= UserBBI.postOffset()) { |
| BaseInsertOffset = UserBBI.postOffset() - 8; |
| LLVM_DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset)); |
| } |
| unsigned EndInsertOffset = BaseInsertOffset + 4 + |
| CPEMI->getOperand(2).getImm(); |
| MachineBasicBlock::iterator MI = UserMI; |
| ++MI; |
| unsigned CPUIndex = CPUserIndex+1; |
| unsigned NumCPUsers = CPUsers.size(); |
| //MachineInstr *LastIT = 0; |
| for (unsigned Offset = UserOffset + TII->getInstSizeInBytes(*UserMI); |
| Offset < BaseInsertOffset; |
| Offset += TII->getInstSizeInBytes(*MI), MI = std::next(MI)) { |
| assert(MI != UserMBB->end() && "Fell off end of block"); |
| if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) { |
| CPUser &U = CPUsers[CPUIndex]; |
| if (!isOffsetInRange(Offset, EndInsertOffset, U)) { |
| // Shift intertion point by one unit of alignment so it is within reach. |
| BaseInsertOffset -= 1u << LogAlign; |
| EndInsertOffset -= 1u << LogAlign; |
| } |
| // This is overly conservative, as we don't account for CPEMIs being |
| // reused within the block, but it doesn't matter much. Also assume CPEs |
| // are added in order with alignment padding. We may eventually be able |
| // to pack the aligned CPEs better. |
| EndInsertOffset += U.CPEMI->getOperand(2).getImm(); |
| CPUIndex++; |
| } |
| } |
| |
| NewMBB = splitBlockBeforeInstr(*--MI); |
| } |
| |
| /// handleConstantPoolUser - Analyze the specified user, checking to see if it |
| /// is out-of-range. If so, pick up the constant pool value and move it some |
| /// place in-range. Return true if we changed any addresses (thus must run |
| /// another pass of branch lengthening), false otherwise. |
| bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) { |
| CPUser &U = CPUsers[CPUserIndex]; |
| MachineInstr *UserMI = U.MI; |
| MachineInstr *CPEMI = U.CPEMI; |
| unsigned CPI = CPEMI->getOperand(1).getIndex(); |
| unsigned Size = CPEMI->getOperand(2).getImm(); |
| // Compute this only once, it's expensive. |
| unsigned UserOffset = getUserOffset(U); |
| |
| // See if the current entry is within range, or there is a clone of it |
| // in range. |
| int result = findInRangeCPEntry(U, UserOffset); |
| if (result==1) return false; |
| else if (result==2) return true; |
| |
| // Look for water where we can place this CPE. |
| MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock(); |
| MachineBasicBlock *NewMBB; |
| water_iterator IP; |
| if (findAvailableWater(U, UserOffset, IP)) { |
| LLVM_DEBUG(dbgs() << "Found water in range\n"); |
| MachineBasicBlock *WaterBB = *IP; |
| |
| // If the original WaterList entry was "new water" on this iteration, |
| // propagate that to the new island. This is just keeping NewWaterList |
| // updated to match the WaterList, which will be updated below. |
| if (NewWaterList.erase(WaterBB)) |
| NewWaterList.insert(NewIsland); |
| |
| // The new CPE goes before the following block (NewMBB). |
| NewMBB = &*++WaterBB->getIterator(); |
| } else { |
| // No water found. |
| // we first see if a longer form of the instrucion could have reached |
| // the constant. in that case we won't bother to split |
| if (!NoLoadRelaxation) { |
| result = findLongFormInRangeCPEntry(U, UserOffset); |
| if (result != 0) return true; |
| } |
| LLVM_DEBUG(dbgs() << "No water found\n"); |
| createNewWater(CPUserIndex, UserOffset, NewMBB); |
| |
| // splitBlockBeforeInstr adds to WaterList, which is important when it is |
| // called while handling branches so that the water will be seen on the |
| // next iteration for constant pools, but in this context, we don't want |
| // it. Check for this so it will be removed from the WaterList. |
| // Also remove any entry from NewWaterList. |
| MachineBasicBlock *WaterBB = &*--NewMBB->getIterator(); |
| IP = llvm::find(WaterList, WaterBB); |
| if (IP != WaterList.end()) |
| NewWaterList.erase(WaterBB); |
| |
| // We are adding new water. Update NewWaterList. |
| NewWaterList.insert(NewIsland); |
| } |
| |
| // Remove the original WaterList entry; we want subsequent insertions in |
| // this vicinity to go after the one we're about to insert. This |
| // considerably reduces the number of times we have to move the same CPE |
| // more than once and is also important to ensure the algorithm terminates. |
| if (IP != WaterList.end()) |
| WaterList.erase(IP); |
| |
| // Okay, we know we can put an island before NewMBB now, do it! |
| MF->insert(NewMBB->getIterator(), NewIsland); |
| |
| // 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); |
| |
| // No existing clone of this CPE is within range. |
| // We will be generating a new clone. Get a UID for it. |
| unsigned ID = createPICLabelUId(); |
| |
| // 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(Mips::CONSTPOOL_ENTRY)) |
| .addImm(ID).addConstantPoolIndex(CPI).addImm(Size); |
| CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1)); |
| ++NumCPEs; |
| |
| // Mark the basic block as aligned as required by the const-pool entry. |
| NewIsland->setAlignment(getCPELogAlign(*U.CPEMI)); |
| |
| // Increase the size of the island block to account for the new entry. |
| BBInfo[NewIsland->getNumber()].Size += Size; |
| adjustBBOffsetsAfter(&*--NewIsland->getIterator()); |
| |
| // Finally, change the CPI in the instruction operand to be ID. |
| for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i) |
| if (UserMI->getOperand(i).isCPI()) { |
| UserMI->getOperand(i).setIndex(ID); |
| break; |
| } |
| |
| LLVM_DEBUG( |
| dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI |
| << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset)); |
| |
| return true; |
| } |
| |
| /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update |
| /// sizes and offsets of impacted basic blocks. |
| void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) { |
| MachineBasicBlock *CPEBB = CPEMI->getParent(); |
| unsigned Size = CPEMI->getOperand(2).getImm(); |
| CPEMI->eraseFromParent(); |
| BBInfo[CPEBB->getNumber()].Size -= Size; |
| // All succeeding offsets have the current size value added in, fix this. |
| if (CPEBB->empty()) { |
| BBInfo[CPEBB->getNumber()].Size = 0; |
| |
| // This block no longer needs to be aligned. |
| CPEBB->setAlignment(0); |
| } else |
| // Entries are sorted by descending alignment, so realign from the front. |
| CPEBB->setAlignment(getCPELogAlign(*CPEBB->begin())); |
| |
| adjustBBOffsetsAfter(CPEBB); |
| // An island has only one predecessor BB and one successor BB. Check if |
| // this BB's predecessor jumps directly to this BB's successor. This |
| // shouldn't happen currently. |
| assert(!BBIsJumpedOver(CPEBB) && "How did this happen?"); |
| // FIXME: remove the empty blocks after all the work is done? |
| } |
| |
| /// removeUnusedCPEntries - Remove constant pool entries whose refcounts |
| /// are zero. |
| bool MipsConstantIslands::removeUnusedCPEntries() { |
| unsigned MadeChange = false; |
| for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) { |
| std::vector<CPEntry> &CPEs = CPEntries[i]; |
| for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) { |
| if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) { |
| removeDeadCPEMI(CPEs[j].CPEMI); |
| CPEs[j].CPEMI = nullptr; |
| MadeChange = true; |
| } |
| } |
| } |
| return MadeChange; |
| } |
| |
| /// isBBInRange - Returns true if the distance between specific MI and |
| /// specific BB can fit in MI's displacement field. |
| bool MipsConstantIslands::isBBInRange |
| (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) { |
| unsigned PCAdj = 4; |
| unsigned BrOffset = getOffsetOf(MI) + PCAdj; |
| unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset; |
| |
| LLVM_DEBUG(dbgs() << "Branch of destination " << printMBBReference(*DestBB) |
| << " from " << printMBBReference(*MI->getParent()) |
| << " max delta=" << MaxDisp << " from " << getOffsetOf(MI) |
| << " to " << DestOffset << " offset " |
| << int(DestOffset - BrOffset) << "\t" << *MI); |
| |
| if (BrOffset <= DestOffset) { |
| // Branch before the Dest. |
| if (DestOffset-BrOffset <= MaxDisp) |
| return true; |
| } else { |
| if (BrOffset-DestOffset <= MaxDisp) |
| return true; |
| } |
| return false; |
| } |
| |
| /// fixupImmediateBr - Fix up an immediate branch whose destination is too far |
| /// away to fit in its displacement field. |
| bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) { |
| MachineInstr *MI = Br.MI; |
| unsigned TargetOperand = branchTargetOperand(MI); |
| MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB(); |
| |
| // Check to see if the DestBB is already in-range. |
| if (isBBInRange(MI, DestBB, Br.MaxDisp)) |
| return false; |
| |
| if (!Br.isCond) |
| return fixupUnconditionalBr(Br); |
| return fixupConditionalBr(Br); |
| } |
| |
| /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is |
| /// too far away to fit in its displacement field. If the LR register has been |
| /// spilled in the epilogue, then we can use BL to implement a far jump. |
| /// Otherwise, add an intermediate branch instruction to a branch. |
| bool |
| MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) { |
| MachineInstr *MI = Br.MI; |
| MachineBasicBlock *MBB = MI->getParent(); |
| MachineBasicBlock *DestBB = MI->getOperand(0).getMBB(); |
| // Use BL to implement far jump. |
| unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2; |
| if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) { |
| Br.MaxDisp = BimmX16MaxDisp; |
| MI->setDesc(TII->get(Mips::BimmX16)); |
| } |
| else { |
| // need to give the math a more careful look here |
| // this is really a segment address and not |
| // a PC relative address. FIXME. But I think that |
| // just reducing the bits by 1 as I've done is correct. |
| // The basic block we are branching too much be longword aligned. |
| // we know that RA is saved because we always save it right now. |
| // this requirement will be relaxed later but we also have an alternate |
| // way to implement this that I will implement that does not need jal. |
| // We should have a way to back out this alignment restriction if we "can" later. |
| // but it is not harmful. |
| // |
| DestBB->setAlignment(2); |
| Br.MaxDisp = ((1<<24)-1) * 2; |
| MI->setDesc(TII->get(Mips::JalB16)); |
| } |
| BBInfo[MBB->getNumber()].Size += 2; |
| adjustBBOffsetsAfter(MBB); |
| HasFarJump = true; |
| ++NumUBrFixed; |
| |
| LLVM_DEBUG(dbgs() << " Changed B to long jump " << *MI); |
| |
| return true; |
| } |
| |
| /// fixupConditionalBr - Fix up a conditional branch whose destination is too |
| /// far away to fit in its displacement field. It is converted to an inverse |
| /// conditional branch + an unconditional branch to the destination. |
| bool |
| MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) { |
| MachineInstr *MI = Br.MI; |
| unsigned TargetOperand = branchTargetOperand(MI); |
| MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB(); |
| unsigned Opcode = MI->getOpcode(); |
| unsigned LongFormOpcode = longformBranchOpcode(Opcode); |
| unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode); |
| |
| // Check to see if the DestBB is already in-range. |
| if (isBBInRange(MI, DestBB, LongFormMaxOff)) { |
| Br.MaxDisp = LongFormMaxOff; |
| MI->setDesc(TII->get(LongFormOpcode)); |
| return true; |
| } |
| |
| // Add an unconditional branch to the destination and invert the branch |
| // condition to jump over it: |
| // bteqz L1 |
| // => |
| // bnez L2 |
| // b L1 |
| // L2: |
| |
| // If the branch is at the end of its MBB and that has a fall-through block, |
| // direct the updated conditional branch to the fall-through block. Otherwise, |
| // split the MBB before the next instruction. |
| MachineBasicBlock *MBB = MI->getParent(); |
| MachineInstr *BMI = &MBB->back(); |
| bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB); |
| unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode); |
| |
| ++NumCBrFixed; |
| if (BMI != MI) { |
| if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) && |
| BMI->isUnconditionalBranch()) { |
| // Last MI in the BB is an unconditional branch. Can we simply invert the |
| // condition and swap destinations: |
| // beqz L1 |
| // b L2 |
| // => |
| // bnez L2 |
| // b L1 |
| unsigned BMITargetOperand = branchTargetOperand(BMI); |
| MachineBasicBlock *NewDest = |
| BMI->getOperand(BMITargetOperand).getMBB(); |
| if (isBBInRange(MI, NewDest, Br.MaxDisp)) { |
| LLVM_DEBUG( |
| dbgs() << " Invert Bcc condition and swap its destination with " |
| << *BMI); |
| MI->setDesc(TII->get(OppositeBranchOpcode)); |
| BMI->getOperand(BMITargetOperand).setMBB(DestBB); |
| MI->getOperand(TargetOperand).setMBB(NewDest); |
| return true; |
| } |
| } |
| } |
| |
| if (NeedSplit) { |
| splitBlockBeforeInstr(*MI); |
| // No need for the branch to the next block. We're adding an unconditional |
| // branch to the destination. |
| int delta = TII->getInstSizeInBytes(MBB->back()); |
| BBInfo[MBB->getNumber()].Size -= delta; |
| MBB->back().eraseFromParent(); |
| // BBInfo[SplitBB].Offset is wrong temporarily, fixed below |
| } |
| MachineBasicBlock *NextBB = &*++MBB->getIterator(); |
| |
| LLVM_DEBUG(dbgs() << " Insert B to " << printMBBReference(*DestBB) |
| << " also invert condition and change dest. to " |
| << printMBBReference(*NextBB) << "\n"); |
| |
| // Insert a new conditional branch and a new unconditional branch. |
| // Also update the ImmBranch as well as adding a new entry for the new branch. |
| if (MI->getNumExplicitOperands() == 2) { |
| BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode)) |
| .addReg(MI->getOperand(0).getReg()) |
| .addMBB(NextBB); |
| } else { |
| BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode)) |
| .addMBB(NextBB); |
| } |
| Br.MI = &MBB->back(); |
| BBInfo[MBB->getNumber()].Size += TII->getInstSizeInBytes(MBB->back()); |
| BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB); |
| BBInfo[MBB->getNumber()].Size += TII->getInstSizeInBytes(MBB->back()); |
| unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr); |
| ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr)); |
| |
| // Remove the old conditional branch. It may or may not still be in MBB. |
| BBInfo[MI->getParent()->getNumber()].Size -= TII->getInstSizeInBytes(*MI); |
| MI->eraseFromParent(); |
| adjustBBOffsetsAfter(MBB); |
| return true; |
| } |
| |
| void MipsConstantIslands::prescanForConstants() { |
| unsigned J = 0; |
| (void)J; |
| for (MachineFunction::iterator B = |
| MF->begin(), E = MF->end(); B != E; ++B) { |
| for (MachineBasicBlock::instr_iterator I = |
| B->instr_begin(), EB = B->instr_end(); I != EB; ++I) { |
| switch(I->getDesc().getOpcode()) { |
| case Mips::LwConstant32: { |
| PrescannedForConstants = true; |
| LLVM_DEBUG(dbgs() << "constant island constant " << *I << "\n"); |
| J = I->getNumOperands(); |
| LLVM_DEBUG(dbgs() << "num operands " << J << "\n"); |
| MachineOperand& Literal = I->getOperand(1); |
| if (Literal.isImm()) { |
| int64_t V = Literal.getImm(); |
| LLVM_DEBUG(dbgs() << "literal " << V << "\n"); |
| Type *Int32Ty = |
| Type::getInt32Ty(MF->getFunction().getContext()); |
| const Constant *C = ConstantInt::get(Int32Ty, V); |
| unsigned index = MCP->getConstantPoolIndex(C, 4); |
| I->getOperand(2).ChangeToImmediate(index); |
| LLVM_DEBUG(dbgs() << "constant island constant " << *I << "\n"); |
| I->setDesc(TII->get(Mips::LwRxPcTcp16)); |
| I->RemoveOperand(1); |
| I->RemoveOperand(1); |
| I->addOperand(MachineOperand::CreateCPI(index, 0)); |
| I->addOperand(MachineOperand::CreateImm(4)); |
| } |
| break; |
| } |
| default: |
| break; |
| } |
| } |
| } |
| } |
| |
| /// Returns a pass that converts branches to long branches. |
| FunctionPass *llvm::createMipsConstantIslandPass() { |
| return new MipsConstantIslands(); |
| } |
