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Diffstat (limited to 'contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp')
| -rw-r--r-- | contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp | 1821 |
1 files changed, 1821 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp b/contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp new file mode 100644 index 0000000..13d8b74 --- /dev/null +++ b/contrib/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp @@ -0,0 +1,1821 @@ +//===-- ARMConstantIslandPass.cpp - ARM constant islands --------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains a pass that splits the constant pool up into 'islands' +// which are scattered through-out the function. This is required due to the +// limited pc-relative displacements that ARM has. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "arm-cp-islands" +#include "ARM.h" +#include "ARMAddressingModes.h" +#include "ARMMachineFunctionInfo.h" +#include "ARMInstrInfo.h" +#include "llvm/CodeGen/MachineConstantPool.h" +#include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineJumpTableInfo.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Target/TargetMachine.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/SmallVector.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Support/CommandLine.h" +#include <algorithm> +using namespace llvm; + +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"); +STATISTIC(NumTBs, "Number of table branches generated"); +STATISTIC(NumT2CPShrunk, "Number of Thumb2 constantpool instructions shrunk"); +STATISTIC(NumT2BrShrunk, "Number of Thumb2 immediate branches shrunk"); +STATISTIC(NumCBZ, "Number of CBZ / CBNZ formed"); +STATISTIC(NumJTMoved, "Number of jump table destination blocks moved"); +STATISTIC(NumJTInserted, "Number of jump table intermediate blocks inserted"); + + +static cl::opt<bool> +AdjustJumpTableBlocks("arm-adjust-jump-tables", cl::Hidden, cl::init(true), + cl::desc("Adjust basic block layout to better use TB[BH]")); + +namespace { + /// ARMConstantIslands - Due to limited PC-relative displacements, ARM + /// 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 ARMConstantIslands : public MachineFunctionPass { + /// BBSizes - The size of each MachineBasicBlock in bytes of code, indexed + /// by MBB Number. The two-byte pads required for Thumb alignment are + /// counted as part of the following block (i.e., the offset and size for + /// a padded block will both be ==2 mod 4). + std::vector<unsigned> BBSizes; + + /// BBOffsets - the offset of each MBB in bytes, starting from 0. + /// The two-byte pads required for Thumb alignment are counted as part of + /// the following block. + std::vector<unsigned> BBOffsets; + + /// 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; + + typedef std::vector<MachineBasicBlock*>::iterator water_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; + unsigned MaxDisp; + bool NegOk; + bool IsSoImm; + CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp, + bool neg, bool soimm) + : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), NegOk(neg), IsSoImm(soimm) { + HighWaterMark = CPEMI->getParent(); + } + }; + + /// 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; + + /// PushPopMIs - Keep track of all the Thumb push / pop instructions. + /// + SmallVector<MachineInstr*, 4> PushPopMIs; + + /// T2JumpTables - Keep track of all the Thumb2 jumptable instructions. + SmallVector<MachineInstr*, 4> T2JumpTables; + + /// HasFarJump - True if any far jump instruction has been emitted during + /// the branch fix up pass. + bool HasFarJump; + + /// HasInlineAsm - True if the function contains inline assembly. + bool HasInlineAsm; + + const TargetInstrInfo *TII; + const ARMSubtarget *STI; + ARMFunctionInfo *AFI; + bool isThumb; + bool isThumb1; + bool isThumb2; + public: + static char ID; + ARMConstantIslands() : MachineFunctionPass(&ID) {} + + virtual bool runOnMachineFunction(MachineFunction &MF); + + virtual const char *getPassName() const { + return "ARM constant island placement and branch shortening pass"; + } + + private: + void DoInitialPlacement(MachineFunction &MF, + std::vector<MachineInstr*> &CPEMIs); + CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI); + void JumpTableFunctionScan(MachineFunction &MF); + void InitialFunctionScan(MachineFunction &MF, + const std::vector<MachineInstr*> &CPEMIs); + MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI); + void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB); + void AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta); + bool DecrementOldEntry(unsigned CPI, MachineInstr* CPEMI); + int LookForExistingCPEntry(CPUser& U, unsigned UserOffset); + bool LookForWater(CPUser&U, unsigned UserOffset, water_iterator &WaterIter); + void CreateNewWater(unsigned CPUserIndex, unsigned UserOffset, + MachineBasicBlock *&NewMBB); + bool HandleConstantPoolUser(MachineFunction &MF, unsigned CPUserIndex); + void RemoveDeadCPEMI(MachineInstr *CPEMI); + bool RemoveUnusedCPEntries(); + bool CPEIsInRange(MachineInstr *MI, unsigned UserOffset, + MachineInstr *CPEMI, unsigned Disp, bool NegOk, + bool DoDump = false); + bool WaterIsInRange(unsigned UserOffset, MachineBasicBlock *Water, + CPUser &U); + bool OffsetIsInRange(unsigned UserOffset, unsigned TrialOffset, + unsigned Disp, bool NegativeOK, bool IsSoImm = false); + bool BBIsInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp); + bool FixUpImmediateBr(MachineFunction &MF, ImmBranch &Br); + bool FixUpConditionalBr(MachineFunction &MF, ImmBranch &Br); + bool FixUpUnconditionalBr(MachineFunction &MF, ImmBranch &Br); + bool UndoLRSpillRestore(); + bool OptimizeThumb2Instructions(MachineFunction &MF); + bool OptimizeThumb2Branches(MachineFunction &MF); + bool ReorderThumb2JumpTables(MachineFunction &MF); + bool OptimizeThumb2JumpTables(MachineFunction &MF); + MachineBasicBlock *AdjustJTTargetBlockForward(MachineBasicBlock *BB, + MachineBasicBlock *JTBB); + + unsigned GetOffsetOf(MachineInstr *MI) const; + void dumpBBs(); + void verify(MachineFunction &MF); + }; + char ARMConstantIslands::ID = 0; +} + +/// verify - check BBOffsets, BBSizes, alignment of islands +void ARMConstantIslands::verify(MachineFunction &MF) { + assert(BBOffsets.size() == BBSizes.size()); + for (unsigned i = 1, e = BBOffsets.size(); i != e; ++i) + assert(BBOffsets[i-1]+BBSizes[i-1] == BBOffsets[i]); + if (!isThumb) + return; +#ifndef NDEBUG + for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); + MBBI != E; ++MBBI) { + MachineBasicBlock *MBB = MBBI; + if (!MBB->empty() && + MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) { + unsigned MBBId = MBB->getNumber(); + assert(HasInlineAsm || + (BBOffsets[MBBId]%4 == 0 && BBSizes[MBBId]%4 == 0) || + (BBOffsets[MBBId]%4 != 0 && BBSizes[MBBId]%4 != 0)); + } + } + for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) { + CPUser &U = CPUsers[i]; + unsigned UserOffset = GetOffsetOf(U.MI) + (isThumb ? 4 : 8); + unsigned CPEOffset = GetOffsetOf(U.CPEMI); + unsigned Disp = UserOffset < CPEOffset ? CPEOffset - UserOffset : + UserOffset - CPEOffset; + assert(Disp <= U.MaxDisp || "Constant pool entry out of range!"); + } +#endif +} + +/// print block size and offset information - debugging +void ARMConstantIslands::dumpBBs() { + for (unsigned J = 0, E = BBOffsets.size(); J !=E; ++J) { + DEBUG(errs() << "block " << J << " offset " << BBOffsets[J] + << " size " << BBSizes[J] << "\n"); + } +} + +/// createARMConstantIslandPass - returns an instance of the constpool +/// island pass. +FunctionPass *llvm::createARMConstantIslandPass() { + return new ARMConstantIslands(); +} + +bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) { + MachineConstantPool &MCP = *MF.getConstantPool(); + + TII = MF.getTarget().getInstrInfo(); + AFI = MF.getInfo<ARMFunctionInfo>(); + STI = &MF.getTarget().getSubtarget<ARMSubtarget>(); + + isThumb = AFI->isThumbFunction(); + isThumb1 = AFI->isThumb1OnlyFunction(); + isThumb2 = AFI->isThumb2Function(); + + HasFarJump = false; + HasInlineAsm = false; + + // 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(); + + // Try to reorder and otherwise adjust the block layout to make good use + // of the TB[BH] instructions. + bool MadeChange = false; + if (isThumb2 && AdjustJumpTableBlocks) { + JumpTableFunctionScan(MF); + MadeChange |= ReorderThumb2JumpTables(MF); + // Data is out of date, so clear it. It'll be re-computed later. + T2JumpTables.clear(); + // Blocks may have shifted around. Keep the numbering up to date. + MF.RenumberBlocks(); + } + + // Thumb1 functions containing constant pools get 4-byte alignment. + // This is so we can keep exact track of where the alignment padding goes. + + // ARM and Thumb2 functions need to be 4-byte aligned. + if (!isThumb1) + MF.EnsureAlignment(2); // 2 = log2(4) + + // 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(MF, CPEMIs); + if (isThumb1) + MF.EnsureAlignment(2); // 2 = log2(4) + } + + /// The next UID to take is the first unused one. + AFI->initConstPoolEntryUId(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. + InitialFunctionScan(MF, CPEMIs); + CPEMIs.clear(); + + /// Remove dead constant pool entries. + RemoveUnusedCPEntries(); + + // Iteratively place constant pool entries and fix up branches until there + // is no change. + unsigned NoCPIters = 0, NoBRIters = 0; + while (true) { + bool CPChange = false; + for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) + CPChange |= HandleConstantPoolUser(MF, i); + if (CPChange && ++NoCPIters > 30) + llvm_unreachable("Constant Island pass failed to converge!"); + 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(); + + bool BRChange = false; + for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) + BRChange |= FixUpImmediateBr(MF, ImmBranches[i]); + if (BRChange && ++NoBRIters > 30) + llvm_unreachable("Branch Fix Up pass failed to converge!"); + DEBUG(dumpBBs()); + + if (!CPChange && !BRChange) + break; + MadeChange = true; + } + + // Shrink 32-bit Thumb2 branch, load, and store instructions. + if (isThumb2) + MadeChange |= OptimizeThumb2Instructions(MF); + + // After a while, this might be made debug-only, but it is not expensive. + verify(MF); + + // If LR has been forced spilled and no far jumps (i.e. BL) has been issued. + // Undo the spill / restore of LR if possible. + if (isThumb && !HasFarJump && AFI->isLRSpilledForFarJump()) + MadeChange |= UndoLRSpillRestore(); + + BBSizes.clear(); + BBOffsets.clear(); + WaterList.clear(); + CPUsers.clear(); + CPEntries.clear(); + ImmBranches.clear(); + PushPopMIs.clear(); + T2JumpTables.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 ARMConstantIslands::DoInitialPlacement(MachineFunction &MF, + std::vector<MachineInstr*> &CPEMIs) { + // Create the basic block to hold the CPE's. + MachineBasicBlock *BB = MF.CreateMachineBasicBlock(); + MF.push_back(BB); + + // 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 = + MF.getConstantPool()->getConstants(); + + const TargetData &TD = *MF.getTarget().getTargetData(); + for (unsigned i = 0, e = CPs.size(); i != e; ++i) { + unsigned Size = TD.getTypeAllocSize(CPs[i].getType()); + // Verify that all constant pool entries are a multiple of 4 bytes. If not, + // we would have to pad them out or something so that instructions stay + // aligned. + assert((Size & 3) == 0 && "CP Entry not multiple of 4 bytes!"); + MachineInstr *CPEMI = + BuildMI(BB, DebugLoc(), TII->get(ARM::CONSTPOOL_ENTRY)) + .addImm(i).addConstantPoolIndex(i).addImm(Size); + CPEMIs.push_back(CPEMI); + + // Add a new CPEntry, but no corresponding CPUser yet. + std::vector<CPEntry> CPEs; + CPEs.push_back(CPEntry(CPEMI, i)); + CPEntries.push_back(CPEs); + NumCPEs++; + DEBUG(errs() << "Moved CPI#" << i << " to end of function as #" << i + << "\n"); + } +} + +/// 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; + if (llvm::next(MBBI) == MBB->getParent()->end()) // Can't fall off end of function. + return false; + + MachineBasicBlock *NextBB = llvm::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. +ARMConstantIslands::CPEntry +*ARMConstantIslands::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 NULL; +} + +/// JumpTableFunctionScan - Do a scan of the function, building up +/// information about the sizes of each block and the locations of all +/// the jump tables. +void ARMConstantIslands::JumpTableFunctionScan(MachineFunction &MF) { + for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); + MBBI != E; ++MBBI) { + MachineBasicBlock &MBB = *MBBI; + + for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); + I != E; ++I) + if (I->getDesc().isBranch() && I->getOpcode() == ARM::t2BR_JT) + T2JumpTables.push_back(I); + } +} + +/// InitialFunctionScan - 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 ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, + const std::vector<MachineInstr*> &CPEMIs) { + // First thing, 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 MBBI = MF.begin(), E = MF.end(); + MBBI != E; ++MBBI) { + MachineBasicBlock &MBB = *MBBI; + for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); + I != E; ++I) + if (I->getOpcode() == ARM::INLINEASM) + HasInlineAsm = true; + } + + // Now go back through the instructions and build up our data structures + unsigned Offset = 0; + for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); + MBBI != E; ++MBBI) { + MachineBasicBlock &MBB = *MBBI; + + // 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); + + unsigned MBBSize = 0; + for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); + I != E; ++I) { + // Add instruction size to MBBSize. + MBBSize += TII->GetInstSizeInBytes(I); + + int Opc = I->getOpcode(); + if (I->getDesc().isBranch()) { + bool isCond = false; + unsigned Bits = 0; + unsigned Scale = 1; + int UOpc = Opc; + switch (Opc) { + default: + continue; // Ignore other JT branches + case ARM::tBR_JTr: + // A Thumb1 table jump may involve padding; for the offsets to + // be right, functions containing these must be 4-byte aligned. + MF.EnsureAlignment(2U); + if ((Offset+MBBSize)%4 != 0 || HasInlineAsm) + // FIXME: Add a pseudo ALIGN instruction instead. + MBBSize += 2; // padding + continue; // Does not get an entry in ImmBranches + case ARM::t2BR_JT: + T2JumpTables.push_back(I); + continue; // Does not get an entry in ImmBranches + case ARM::Bcc: + isCond = true; + UOpc = ARM::B; + // Fallthrough + case ARM::B: + Bits = 24; + Scale = 4; + break; + case ARM::tBcc: + isCond = true; + UOpc = ARM::tB; + Bits = 8; + Scale = 2; + break; + case ARM::tB: + Bits = 11; + Scale = 2; + break; + case ARM::t2Bcc: + isCond = true; + UOpc = ARM::t2B; + Bits = 20; + Scale = 2; + break; + case ARM::t2B: + Bits = 24; + Scale = 2; + break; + } + + // Record this immediate branch. + unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale; + ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc)); + } + + if (Opc == ARM::tPUSH || Opc == ARM::tPOP_RET) + PushPopMIs.push_back(I); + + if (Opc == ARM::CONSTPOOL_ENTRY) + continue; + + // Scan the instructions for constant pool operands. + for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) + if (I->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; + bool IsSoImm = false; + + switch (Opc) { + default: + llvm_unreachable("Unknown addressing mode for CP reference!"); + break; + + // Taking the address of a CP entry. + case ARM::LEApcrel: + // 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 + // displacements that fits in a SoImm as well. + Bits = 8; + Scale = 4; + NegOk = true; + IsSoImm = true; + break; + case ARM::t2LEApcrel: + Bits = 12; + NegOk = true; + break; + case ARM::tLEApcrel: + Bits = 8; + Scale = 4; + break; + + case ARM::LDR: + case ARM::LDRcp: + case ARM::t2LDRpci: + Bits = 12; // +-offset_12 + NegOk = true; + break; + + case ARM::tLDRpci: + case ARM::tLDRcp: + Bits = 8; + Scale = 4; // +(offset_8*4) + break; + + case ARM::VLDRD: + case ARM::VLDRS: + Bits = 8; + Scale = 4; // +-(offset_8*4) + NegOk = true; + break; + } + + // Remember that this is a user of a CP entry. + unsigned CPI = I->getOperand(op).getIndex(); + MachineInstr *CPEMI = CPEMIs[CPI]; + unsigned MaxOffs = ((1 << Bits)-1) * Scale; + CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk, IsSoImm)); + + // 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; + } + } + + // In thumb mode, if this block is a constpool island, we may need padding + // so it's aligned on 4 byte boundary. + if (isThumb && + !MBB.empty() && + MBB.begin()->getOpcode() == ARM::CONSTPOOL_ENTRY && + ((Offset%4) != 0 || HasInlineAsm)) + MBBSize += 2; + + BBSizes.push_back(MBBSize); + BBOffsets.push_back(Offset); + Offset += MBBSize; + } +} + +/// 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 ARMConstantIslands::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 = BBOffsets[MBB->getNumber()]; + + // If we're looking for a CONSTPOOL_ENTRY in Thumb, see if this block has + // alignment padding, and compensate if so. + if (isThumb && + MI->getOpcode() == ARM::CONSTPOOL_ENTRY && + (Offset%4 != 0 || HasInlineAsm)) + Offset += 2; + + // Sum instructions before MI in MBB. + for (MachineBasicBlock::iterator I = MBB->begin(); ; ++I) { + assert(I != MBB->end() && "Didn't find MI in its own basic block?"); + if (&*I == MI) return Offset; + Offset += TII->GetInstSizeInBytes(I); + } +} + +/// 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 ARMConstantIslands::UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB) { + // Renumber the MBB's to keep them consequtive. + NewBB->getParent()->RenumberBlocks(NewBB); + + // Insert a size into BBSizes to align it properly with the (newly + // renumbered) block numbers. + BBSizes.insert(BBSizes.begin()+NewBB->getNumber(), 0); + + // Likewise for BBOffsets. + BBOffsets.insert(BBOffsets.begin()+NewBB->getNumber(), 0); + + // 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); +} + + +/// 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 *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) { + MachineBasicBlock *OrigBB = MI->getParent(); + MachineFunction &MF = *OrigBB->getParent(); + + // Create a new MBB for the code after the OrigBB. + MachineBasicBlock *NewBB = + MF.CreateMachineBasicBlock(OrigBB->getBasicBlock()); + MachineFunction::iterator MBBI = OrigBB; ++MBBI; + 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. + unsigned Opc = isThumb ? (isThumb2 ? ARM::t2B : ARM::tB) : ARM::B; + BuildMI(OrigBB, DebugLoc(), TII->get(Opc)).addMBB(NewBB); + NumSplit++; + + // Update the CFG. All succs of OrigBB are now succs of NewBB. + while (!OrigBB->succ_empty()) { + MachineBasicBlock *Succ = *OrigBB->succ_begin(); + OrigBB->removeSuccessor(Succ); + NewBB->addSuccessor(Succ); + + // This pass should be run after register allocation, so there should be no + // PHI nodes to update. + assert((Succ->empty() || !Succ->begin()->isPHI()) + && "PHI nodes should be eliminated by now!"); + } + + // 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 a size into BBSizes to align it properly with the (newly + // renumbered) block numbers. + BBSizes.insert(BBSizes.begin()+NewBB->getNumber(), 0); + + // Likewise for BBOffsets. + BBOffsets.insert(BBOffsets.begin()+NewBB->getNumber(), 0); + + // 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(llvm::next(IP), NewBB); + else + WaterList.insert(IP, OrigBB); + NewWaterList.insert(OrigBB); + + // Figure out how large the first NewMBB is. (It cannot + // contain a constpool_entry or tablejump.) + unsigned NewBBSize = 0; + for (MachineBasicBlock::iterator I = NewBB->begin(), E = NewBB->end(); + I != E; ++I) + NewBBSize += TII->GetInstSizeInBytes(I); + + unsigned OrigBBI = OrigBB->getNumber(); + unsigned NewBBI = NewBB->getNumber(); + // Set the size of NewBB in BBSizes. + BBSizes[NewBBI] = NewBBSize; + + // We removed instructions from UserMBB, subtract that off from its size. + // Add 2 or 4 to the block to count the unconditional branch we added to it. + int delta = isThumb1 ? 2 : 4; + BBSizes[OrigBBI] -= NewBBSize - delta; + + // ...and adjust BBOffsets for NewBB accordingly. + BBOffsets[NewBBI] = BBOffsets[OrigBBI] + BBSizes[OrigBBI]; + + // All BBOffsets following these blocks must be modified. + AdjustBBOffsetsAfter(NewBB, delta); + + return NewBB; +} + +/// OffsetIsInRange - Checks whether UserOffset (the location of a constant pool +/// reference) is within MaxDisp of TrialOffset (a proposed location of a +/// constant pool entry). +bool ARMConstantIslands::OffsetIsInRange(unsigned UserOffset, + unsigned TrialOffset, unsigned MaxDisp, + bool NegativeOK, bool IsSoImm) { + // On Thumb offsets==2 mod 4 are rounded down by the hardware for + // purposes of the displacement computation; compensate for that here. + // Effectively, the valid range of displacements is 2 bytes smaller for such + // references. + unsigned TotalAdj = 0; + if (isThumb && UserOffset%4 !=0) { + UserOffset -= 2; + TotalAdj = 2; + } + // CPEs will be rounded up to a multiple of 4. + if (isThumb && TrialOffset%4 != 0) { + TrialOffset += 2; + TotalAdj += 2; + } + + // In Thumb2 mode, later branch adjustments can shift instructions up and + // cause alignment change. In the worst case scenario this can cause the + // user's effective address to be subtracted by 2 and the CPE's address to + // be plus 2. + if (isThumb2 && TotalAdj != 4) + MaxDisp -= (4 - TotalAdj); + + if (UserOffset <= TrialOffset) { + // User before the Trial. + if (TrialOffset - UserOffset <= MaxDisp) + return true; + // FIXME: Make use full range of soimm values. + } else if (NegativeOK) { + if (UserOffset - TrialOffset <= MaxDisp) + return true; + // FIXME: Make use full range of soimm values. + } + return false; +} + +/// WaterIsInRange - Returns true if a CPE placed after the specified +/// Water (a basic block) will be in range for the specific MI. + +bool ARMConstantIslands::WaterIsInRange(unsigned UserOffset, + MachineBasicBlock* Water, CPUser &U) { + unsigned MaxDisp = U.MaxDisp; + unsigned CPEOffset = BBOffsets[Water->getNumber()] + + BBSizes[Water->getNumber()]; + + // If the CPE is to be inserted before the instruction, that will raise + // the offset of the instruction. + if (CPEOffset < UserOffset) + UserOffset += U.CPEMI->getOperand(2).getImm(); + + return OffsetIsInRange(UserOffset, CPEOffset, MaxDisp, U.NegOk, U.IsSoImm); +} + +/// CPEIsInRange - Returns true if the distance between specific MI and +/// specific ConstPool entry instruction can fit in MI's displacement field. +bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, unsigned UserOffset, + MachineInstr *CPEMI, unsigned MaxDisp, + bool NegOk, bool DoDump) { + unsigned CPEOffset = GetOffsetOf(CPEMI); + assert((CPEOffset%4 == 0 || HasInlineAsm) && "Misaligned CPE"); + + if (DoDump) { + DEBUG(errs() << "User of CPE#" << CPEMI->getOperand(0).getImm() + << " max delta=" << MaxDisp + << " insn address=" << UserOffset + << " CPE address=" << CPEOffset + << " offset=" << int(CPEOffset-UserOffset) << "\t" << *MI); + } + + return OffsetIsInRange(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() == ARM::B || PredMI->getOpcode() == ARM::tB + || PredMI->getOpcode() == ARM::t2B) + return PredMI->getOperand(0).getMBB() == Succ; + return false; +} +#endif // NDEBUG + +void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB, + int delta) { + MachineFunction::iterator MBBI = BB; MBBI = llvm::next(MBBI); + for(unsigned i = BB->getNumber()+1, e = BB->getParent()->getNumBlockIDs(); + i < e; ++i) { + BBOffsets[i] += delta; + // If some existing blocks have padding, adjust the padding as needed, a + // bit tricky. delta can be negative so don't use % on that. + if (!isThumb) + continue; + MachineBasicBlock *MBB = MBBI; + if (!MBB->empty() && !HasInlineAsm) { + // Constant pool entries require padding. + if (MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) { + unsigned OldOffset = BBOffsets[i] - delta; + if ((OldOffset%4) == 0 && (BBOffsets[i]%4) != 0) { + // add new padding + BBSizes[i] += 2; + delta += 2; + } else if ((OldOffset%4) != 0 && (BBOffsets[i]%4) == 0) { + // remove existing padding + BBSizes[i] -= 2; + delta -= 2; + } + } + // Thumb1 jump tables require padding. They should be at the end; + // following unconditional branches are removed by AnalyzeBranch. + MachineInstr *ThumbJTMI = prior(MBB->end()); + if (ThumbJTMI->getOpcode() == ARM::tBR_JTr) { + unsigned NewMIOffset = GetOffsetOf(ThumbJTMI); + unsigned OldMIOffset = NewMIOffset - delta; + if ((OldMIOffset%4) == 0 && (NewMIOffset%4) != 0) { + // remove existing padding + BBSizes[i] -= 2; + delta -= 2; + } else if ((OldMIOffset%4) != 0 && (NewMIOffset%4) == 0) { + // add new padding + BBSizes[i] += 2; + delta += 2; + } + } + if (delta==0) + return; + } + MBBI = llvm::next(MBBI); + } +} + +/// DecrementOldEntry - 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 ARMConstantIslands::DecrementOldEntry(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 = NULL; + 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 ARMConstantIslands::LookForExistingCPEntry(CPUser& U, unsigned UserOffset) +{ + MachineInstr *UserMI = U.MI; + MachineInstr *CPEMI = U.CPEMI; + + // Check to see if the CPE is already in-range. + if (CPEIsInRange(UserMI, UserOffset, CPEMI, U.MaxDisp, U.NegOk, true)) { + DEBUG(errs() << "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 == NULL) + continue; + if (CPEIsInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.MaxDisp, U.NegOk)) { + DEBUG(errs() << "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 DecrementOldEntry(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 ARM::tB: + return ((1<<10)-1)*2; + case ARM::t2B: + return ((1<<23)-1)*2; + default: + break; + } + + return ((1<<23)-1)*4; +} + +/// LookForWater - 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. For Thumb, prefer water that will not +/// introduce padding to water that will. 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 ARMConstantIslands::LookForWater(CPUser &U, unsigned UserOffset, + water_iterator &WaterIter) { + if (WaterList.empty()) + return false; + + bool FoundWaterThatWouldPad = false; + water_iterator IPThatWouldPad; + for (water_iterator IP = prior(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. + if (WaterIsInRange(UserOffset, WaterBB, U) && + (WaterBB->getNumber() < U.HighWaterMark->getNumber() || + NewWaterList.count(WaterBB))) { + unsigned WBBId = WaterBB->getNumber(); + if (isThumb && + (BBOffsets[WBBId] + BBSizes[WBBId])%4 != 0) { + // This is valid Water, but would introduce padding. Remember + // it in case we don't find any Water that doesn't do this. + if (!FoundWaterThatWouldPad) { + FoundWaterThatWouldPad = true; + IPThatWouldPad = IP; + } + } else { + WaterIter = IP; + return true; + } + } + if (IP == B) + break; + } + if (FoundWaterThatWouldPad) { + WaterIter = IPThatWouldPad; + return true; + } + return false; +} + +/// 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 ARMConstantIslands::CreateNewWater(unsigned CPUserIndex, + unsigned UserOffset, + MachineBasicBlock *&NewMBB) { + CPUser &U = CPUsers[CPUserIndex]; + MachineInstr *UserMI = U.MI; + MachineInstr *CPEMI = U.CPEMI; + MachineBasicBlock *UserMBB = UserMI->getParent(); + unsigned OffsetOfNextBlock = BBOffsets[UserMBB->getNumber()] + + BBSizes[UserMBB->getNumber()]; + assert(OffsetOfNextBlock== BBOffsets[UserMBB->getNumber()+1]); + + // 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. (The addition + // below is for the unconditional branch we will be adding: 4 bytes on ARM + + // Thumb2, 2 on Thumb1. Possible Thumb1 alignment padding is allowed for + // inside OffsetIsInRange. + if (BBHasFallthrough(UserMBB) && + OffsetIsInRange(UserOffset, OffsetOfNextBlock + (isThumb1 ? 2: 4), + U.MaxDisp, U.NegOk, U.IsSoImm)) { + DEBUG(errs() << "Split at end of block\n"); + if (&UserMBB->back() == UserMI) + assert(BBHasFallthrough(UserMBB) && "Expected a fallthrough BB!"); + NewMBB = llvm::next(MachineFunction::iterator(UserMBB)); + // 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 = isThumb ? ((isThumb2) ? ARM::t2B : ARM::tB) : ARM::B; + BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB); + unsigned MaxDisp = getUnconditionalBrDisp(UncondBr); + ImmBranches.push_back(ImmBranch(&UserMBB->back(), + MaxDisp, false, UncondBr)); + int delta = isThumb1 ? 2 : 4; + BBSizes[UserMBB->getNumber()] += delta; + AdjustBBOffsetsAfter(UserMBB, delta); + } else { + // What a big block. Find a place within the block to split it. + // This is a little tricky on Thumb1 since instructions are 2 bytes + // and constant pool entries are 4 bytes: if instruction I references + // island CPE, and instruction I+1 references CPE', it will + // not work well to put CPE as far forward as possible, since then + // CPE' cannot immediately follow it (that location is 2 bytes + // farther away from I+1 than CPE was from I) and we'd need to create + // a new island. So, we make a first guess, then walk through the + // instructions between the one currently being looked at and the + // possible insertion point, and make sure any other instructions + // that reference CPEs will be able to use the same island area; + // if not, we back up the insertion point. + + // The 4 in the following is for the unconditional branch we'll be + // inserting (allows for long branch on Thumb1). Alignment of the + // island is handled inside OffsetIsInRange. + unsigned BaseInsertOffset = UserOffset + U.MaxDisp -4; + // 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 >= BBOffsets[UserMBB->getNumber()+1]) + BaseInsertOffset = BBOffsets[UserMBB->getNumber()+1] - + (isThumb1 ? 6 : 8); + unsigned EndInsertOffset = BaseInsertOffset + + CPEMI->getOperand(2).getImm(); + MachineBasicBlock::iterator MI = UserMI; + ++MI; + unsigned CPUIndex = CPUserIndex+1; + for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI); + Offset < BaseInsertOffset; + Offset += TII->GetInstSizeInBytes(MI), + MI = llvm::next(MI)) { + if (CPUIndex < CPUsers.size() && CPUsers[CPUIndex].MI == MI) { + CPUser &U = CPUsers[CPUIndex]; + if (!OffsetIsInRange(Offset, EndInsertOffset, + U.MaxDisp, U.NegOk, U.IsSoImm)) { + BaseInsertOffset -= (isThumb1 ? 2 : 4); + EndInsertOffset -= (isThumb1 ? 2 : 4); + } + // This is overly conservative, as we don't account for CPEMIs + // being reused within the block, but it doesn't matter much. + EndInsertOffset += CPUsers[CPUIndex].CPEMI->getOperand(2).getImm(); + CPUIndex++; + } + } + DEBUG(errs() << "Split in middle of big block\n"); + NewMBB = SplitBlockBeforeInstr(prior(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 ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF, + 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. The 4 or 8 is the value the + // hardware keeps in the PC. + unsigned UserOffset = GetOffsetOf(UserMI) + (isThumb ? 4 : 8); + + // See if the current entry is within range, or there is a clone of it + // in range. + int result = LookForExistingCPEntry(U, UserOffset); + if (result==1) return false; + else if (result==2) return true; + + // No existing clone of this CPE is within range. + // We will be generating a new clone. Get a UID for it. + unsigned ID = AFI->createConstPoolEntryUId(); + + // Look for water where we can place this CPE. + MachineBasicBlock *NewIsland = MF.CreateMachineBasicBlock(); + MachineBasicBlock *NewMBB; + water_iterator IP; + if (LookForWater(U, UserOffset, IP)) { + DEBUG(errs() << "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.count(WaterBB)) { + NewWaterList.erase(WaterBB); + NewWaterList.insert(NewIsland); + } + // The new CPE goes before the following block (NewMBB). + NewMBB = llvm::next(MachineFunction::iterator(WaterBB)); + + } else { + // No water found. + DEBUG(errs() << "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 = prior(MachineFunction::iterator(NewMBB)); + IP = std::find(WaterList.begin(), WaterList.end(), 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, 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. + DecrementOldEntry(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); + CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1)); + NumCPEs++; + + BBOffsets[NewIsland->getNumber()] = BBOffsets[NewMBB->getNumber()]; + // Compensate for .align 2 in thumb mode. + if (isThumb && (BBOffsets[NewIsland->getNumber()]%4 != 0 || HasInlineAsm)) + Size += 2; + // Increase the size of the island block to account for the new entry. + BBSizes[NewIsland->getNumber()] += Size; + AdjustBBOffsetsAfter(NewIsland, Size); + + // 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; + } + + DEBUG(errs() << " Moved CPE to #" << ID << " CPI=" << CPI + << '\t' << *UserMI); + + return true; +} + +/// RemoveDeadCPEMI - Remove a dead constant pool entry instruction. Update +/// sizes and offsets of impacted basic blocks. +void ARMConstantIslands::RemoveDeadCPEMI(MachineInstr *CPEMI) { + MachineBasicBlock *CPEBB = CPEMI->getParent(); + unsigned Size = CPEMI->getOperand(2).getImm(); + CPEMI->eraseFromParent(); + BBSizes[CPEBB->getNumber()] -= Size; + // All succeeding offsets have the current size value added in, fix this. + if (CPEBB->empty()) { + // In thumb1 mode, the size of island may be padded by two to compensate for + // the alignment requirement. Then it will now be 2 when the block is + // empty, so fix this. + // All succeeding offsets have the current size value added in, fix this. + if (BBSizes[CPEBB->getNumber()] != 0) { + Size += BBSizes[CPEBB->getNumber()]; + BBSizes[CPEBB->getNumber()] = 0; + } + } + AdjustBBOffsetsAfter(CPEBB, -Size); + // 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 ARMConstantIslands::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 = NULL; + MadeChange = true; + } + } + } + return MadeChange; +} + +/// BBIsInRange - Returns true if the distance between specific MI and +/// specific BB can fit in MI's displacement field. +bool ARMConstantIslands::BBIsInRange(MachineInstr *MI,MachineBasicBlock *DestBB, + unsigned MaxDisp) { + unsigned PCAdj = isThumb ? 4 : 8; + unsigned BrOffset = GetOffsetOf(MI) + PCAdj; + unsigned DestOffset = BBOffsets[DestBB->getNumber()]; + + DEBUG(errs() << "Branch of destination BB#" << DestBB->getNumber() + << " from BB#" << MI->getParent()->getNumber() + << " 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 ARMConstantIslands::FixUpImmediateBr(MachineFunction &MF, ImmBranch &Br) { + MachineInstr *MI = Br.MI; + MachineBasicBlock *DestBB = MI->getOperand(0).getMBB(); + + // Check to see if the DestBB is already in-range. + if (BBIsInRange(MI, DestBB, Br.MaxDisp)) + return false; + + if (!Br.isCond) + return FixUpUnconditionalBr(MF, Br); + return FixUpConditionalBr(MF, 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 +ARMConstantIslands::FixUpUnconditionalBr(MachineFunction &MF, ImmBranch &Br) { + MachineInstr *MI = Br.MI; + MachineBasicBlock *MBB = MI->getParent(); + if (!isThumb1) + llvm_unreachable("FixUpUnconditionalBr is Thumb1 only!"); + + // Use BL to implement far jump. + Br.MaxDisp = (1 << 21) * 2; + MI->setDesc(TII->get(ARM::tBfar)); + BBSizes[MBB->getNumber()] += 2; + AdjustBBOffsetsAfter(MBB, 2); + HasFarJump = true; + NumUBrFixed++; + + DEBUG(errs() << " 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 +ARMConstantIslands::FixUpConditionalBr(MachineFunction &MF, ImmBranch &Br) { + MachineInstr *MI = Br.MI; + MachineBasicBlock *DestBB = MI->getOperand(0).getMBB(); + + // Add an unconditional branch to the destination and invert the branch + // condition to jump over it: + // blt L1 + // => + // bge L2 + // b L1 + // L2: + ARMCC::CondCodes CC = (ARMCC::CondCodes)MI->getOperand(1).getImm(); + CC = ARMCC::getOppositeCondition(CC); + unsigned CCReg = MI->getOperand(2).getReg(); + + // 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); + + NumCBrFixed++; + if (BMI != MI) { + if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) && + BMI->getOpcode() == Br.UncondBr) { + // Last MI in the BB is an unconditional branch. Can we simply invert the + // condition and swap destinations: + // beq L1 + // b L2 + // => + // bne L2 + // b L1 + MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB(); + if (BBIsInRange(MI, NewDest, Br.MaxDisp)) { + DEBUG(errs() << " Invert Bcc condition and swap its destination with " + << *BMI); + BMI->getOperand(0).setMBB(DestBB); + MI->getOperand(0).setMBB(NewDest); + MI->getOperand(1).setImm(CC); + 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()); + BBSizes[MBB->getNumber()] -= delta; + MachineBasicBlock* SplitBB = llvm::next(MachineFunction::iterator(MBB)); + AdjustBBOffsetsAfter(SplitBB, -delta); + MBB->back().eraseFromParent(); + // BBOffsets[SplitBB] is wrong temporarily, fixed below + } + MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB)); + + DEBUG(errs() << " Insert B to BB#" << DestBB->getNumber() + << " also invert condition and change dest. to BB#" + << NextBB->getNumber() << "\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. + BuildMI(MBB, DebugLoc(), TII->get(MI->getOpcode())) + .addMBB(NextBB).addImm(CC).addReg(CCReg); + Br.MI = &MBB->back(); + BBSizes[MBB->getNumber()] += TII->GetInstSizeInBytes(&MBB->back()); + BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB); + BBSizes[MBB->getNumber()] += 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. + BBSizes[MI->getParent()->getNumber()] -= TII->GetInstSizeInBytes(MI); + MI->eraseFromParent(); + + // The net size change is an addition of one unconditional branch. + int delta = TII->GetInstSizeInBytes(&MBB->back()); + AdjustBBOffsetsAfter(MBB, delta); + return true; +} + +/// UndoLRSpillRestore - Remove Thumb push / pop instructions that only spills +/// LR / restores LR to pc. FIXME: This is done here because it's only possible +/// to do this if tBfar is not used. +bool ARMConstantIslands::UndoLRSpillRestore() { + bool MadeChange = false; + for (unsigned i = 0, e = PushPopMIs.size(); i != e; ++i) { + MachineInstr *MI = PushPopMIs[i]; + // First two operands are predicates. + if (MI->getOpcode() == ARM::tPOP_RET && + MI->getOperand(2).getReg() == ARM::PC && + MI->getNumExplicitOperands() == 3) { + BuildMI(MI->getParent(), MI->getDebugLoc(), TII->get(ARM::tBX_RET)); + MI->eraseFromParent(); + MadeChange = true; + } + } + return MadeChange; +} + +bool ARMConstantIslands::OptimizeThumb2Instructions(MachineFunction &MF) { + bool MadeChange = false; + + // Shrink ADR and LDR from constantpool. + for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) { + CPUser &U = CPUsers[i]; + unsigned Opcode = U.MI->getOpcode(); + unsigned NewOpc = 0; + unsigned Scale = 1; + unsigned Bits = 0; + switch (Opcode) { + default: break; + case ARM::t2LEApcrel: + if (isARMLowRegister(U.MI->getOperand(0).getReg())) { + NewOpc = ARM::tLEApcrel; + Bits = 8; + Scale = 4; + } + break; + case ARM::t2LDRpci: + if (isARMLowRegister(U.MI->getOperand(0).getReg())) { + NewOpc = ARM::tLDRpci; + Bits = 8; + Scale = 4; + } + break; + } + + if (!NewOpc) + continue; + + unsigned UserOffset = GetOffsetOf(U.MI) + 4; + unsigned MaxOffs = ((1 << Bits) - 1) * Scale; + // FIXME: Check if offset is multiple of scale if scale is not 4. + if (CPEIsInRange(U.MI, UserOffset, U.CPEMI, MaxOffs, false, true)) { + U.MI->setDesc(TII->get(NewOpc)); + MachineBasicBlock *MBB = U.MI->getParent(); + BBSizes[MBB->getNumber()] -= 2; + AdjustBBOffsetsAfter(MBB, -2); + ++NumT2CPShrunk; + MadeChange = true; + } + } + + MadeChange |= OptimizeThumb2Branches(MF); + MadeChange |= OptimizeThumb2JumpTables(MF); + return MadeChange; +} + +bool ARMConstantIslands::OptimizeThumb2Branches(MachineFunction &MF) { + bool MadeChange = false; + + for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) { + ImmBranch &Br = ImmBranches[i]; + unsigned Opcode = Br.MI->getOpcode(); + unsigned NewOpc = 0; + unsigned Scale = 1; + unsigned Bits = 0; + switch (Opcode) { + default: break; + case ARM::t2B: + NewOpc = ARM::tB; + Bits = 11; + Scale = 2; + break; + case ARM::t2Bcc: { + NewOpc = ARM::tBcc; + Bits = 8; + Scale = 2; + break; + } + } + if (NewOpc) { + unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale; + MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB(); + if (BBIsInRange(Br.MI, DestBB, MaxOffs)) { + Br.MI->setDesc(TII->get(NewOpc)); + MachineBasicBlock *MBB = Br.MI->getParent(); + BBSizes[MBB->getNumber()] -= 2; + AdjustBBOffsetsAfter(MBB, -2); + ++NumT2BrShrunk; + MadeChange = true; + } + } + + Opcode = Br.MI->getOpcode(); + if (Opcode != ARM::tBcc) + continue; + + NewOpc = 0; + unsigned PredReg = 0; + ARMCC::CondCodes Pred = llvm::getInstrPredicate(Br.MI, PredReg); + if (Pred == ARMCC::EQ) + NewOpc = ARM::tCBZ; + else if (Pred == ARMCC::NE) + NewOpc = ARM::tCBNZ; + if (!NewOpc) + continue; + MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB(); + // Check if the distance is within 126. Subtract starting offset by 2 + // because the cmp will be eliminated. + unsigned BrOffset = GetOffsetOf(Br.MI) + 4 - 2; + unsigned DestOffset = BBOffsets[DestBB->getNumber()]; + if (BrOffset < DestOffset && (DestOffset - BrOffset) <= 126) { + MachineBasicBlock::iterator CmpMI = Br.MI; --CmpMI; + if (CmpMI->getOpcode() == ARM::tCMPzi8) { + unsigned Reg = CmpMI->getOperand(0).getReg(); + Pred = llvm::getInstrPredicate(CmpMI, PredReg); + if (Pred == ARMCC::AL && + CmpMI->getOperand(1).getImm() == 0 && + isARMLowRegister(Reg)) { + MachineBasicBlock *MBB = Br.MI->getParent(); + MachineInstr *NewBR = + BuildMI(*MBB, CmpMI, Br.MI->getDebugLoc(), TII->get(NewOpc)) + .addReg(Reg).addMBB(DestBB, Br.MI->getOperand(0).getTargetFlags()); + CmpMI->eraseFromParent(); + Br.MI->eraseFromParent(); + Br.MI = NewBR; + BBSizes[MBB->getNumber()] -= 2; + AdjustBBOffsetsAfter(MBB, -2); + ++NumCBZ; + MadeChange = true; + } + } + } + } + + return MadeChange; +} + +/// OptimizeThumb2JumpTables - Use tbb / tbh instructions to generate smaller +/// jumptables when it's possible. +bool ARMConstantIslands::OptimizeThumb2JumpTables(MachineFunction &MF) { + bool MadeChange = false; + + // FIXME: After the tables are shrunk, can we get rid some of the + // constantpool tables? + MachineJumpTableInfo *MJTI = MF.getJumpTableInfo(); + if (MJTI == 0) return false; + + const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables(); + for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) { + MachineInstr *MI = T2JumpTables[i]; + const TargetInstrDesc &TID = MI->getDesc(); + unsigned NumOps = TID.getNumOperands(); + unsigned JTOpIdx = NumOps - (TID.isPredicable() ? 3 : 2); + MachineOperand JTOP = MI->getOperand(JTOpIdx); + unsigned JTI = JTOP.getIndex(); + assert(JTI < JT.size()); + + bool ByteOk = true; + bool HalfWordOk = true; + unsigned JTOffset = GetOffsetOf(MI) + 4; + const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs; + for (unsigned j = 0, ee = JTBBs.size(); j != ee; ++j) { + MachineBasicBlock *MBB = JTBBs[j]; + unsigned DstOffset = BBOffsets[MBB->getNumber()]; + // Negative offset is not ok. FIXME: We should change BB layout to make + // sure all the branches are forward. + if (ByteOk && (DstOffset - JTOffset) > ((1<<8)-1)*2) + ByteOk = false; + unsigned TBHLimit = ((1<<16)-1)*2; + if (HalfWordOk && (DstOffset - JTOffset) > TBHLimit) + HalfWordOk = false; + if (!ByteOk && !HalfWordOk) + 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(); + MachineBasicBlock::iterator PrevI = MI; + if (PrevI == MBB->begin()) + continue; + + MachineInstr *AddrMI = --PrevI; + bool OptOk = true; + // Examine the instruction that calculate the jumptable entry address. + // If it's not the one just before the t2BR_JT, we won't delete it, then + // it's not worth doing the optimization. + 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) { + OptOk = false; + break; + } + if (MO.isUse() && !MO.isKill() && MO.getReg() != IdxReg) { + OptOk = false; + break; + } + } + if (!OptOk) + continue; + + // The previous 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() != BaseReg) + OptOk = false; + + if (!OptOk) + continue; + + unsigned Opc = ByteOk ? ARM::t2TBB : ARM::t2TBH; + MachineInstr *NewJTMI = BuildMI(MBB, MI->getDebugLoc(), TII->get(Opc)) + .addReg(IdxReg, getKillRegState(IdxRegKill)) + .addJumpTableIndex(JTI, JTOP.getTargetFlags()) + .addImm(MI->getOperand(JTOpIdx+1).getImm()); + // 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(AddrMI); + OrigSize += TII->GetInstSizeInBytes(LeaMI); + OrigSize += TII->GetInstSizeInBytes(MI); + + AddrMI->eraseFromParent(); + LeaMI->eraseFromParent(); + MI->eraseFromParent(); + + int delta = OrigSize - NewSize; + BBSizes[MBB->getNumber()] -= delta; + AdjustBBOffsetsAfter(MBB, -delta); + + ++NumTBs; + MadeChange = true; + } + } + + return MadeChange; +} + +/// ReorderThumb2JumpTables - Adjust the function's block layout to ensure that +/// jump tables always branch forwards, since that's what tbb and tbh need. +bool ARMConstantIslands::ReorderThumb2JumpTables(MachineFunction &MF) { + bool MadeChange = false; + + MachineJumpTableInfo *MJTI = MF.getJumpTableInfo(); + if (MJTI == 0) return false; + + const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables(); + for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) { + MachineInstr *MI = T2JumpTables[i]; + const TargetInstrDesc &TID = MI->getDesc(); + unsigned NumOps = TID.getNumOperands(); + unsigned JTOpIdx = NumOps - (TID.isPredicable() ? 3 : 2); + MachineOperand JTOP = MI->getOperand(JTOpIdx); + unsigned JTI = JTOP.getIndex(); + assert(JTI < JT.size()); + + // We prefer if target blocks for the jump table come after the jump + // instruction so we can use TB[BH]. Loop through the target blocks + // and try to adjust them such that that's true. + int JTNumber = MI->getParent()->getNumber(); + const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs; + for (unsigned j = 0, ee = JTBBs.size(); j != ee; ++j) { + MachineBasicBlock *MBB = JTBBs[j]; + int DTNumber = MBB->getNumber(); + + if (DTNumber < JTNumber) { + // The destination precedes the switch. Try to move the block forward + // so we have a positive offset. + MachineBasicBlock *NewBB = + AdjustJTTargetBlockForward(MBB, MI->getParent()); + if (NewBB) + MJTI->ReplaceMBBInJumpTable(JTI, JTBBs[j], NewBB); + MadeChange = true; + } + } + } + + return MadeChange; +} + +MachineBasicBlock *ARMConstantIslands:: +AdjustJTTargetBlockForward(MachineBasicBlock *BB, MachineBasicBlock *JTBB) +{ + MachineFunction &MF = *BB->getParent(); + + // If it's the destination block is terminated by an unconditional branch, + // try to move it; otherwise, create a new block following the jump + // table that branches back to the actual target. This is a very simple + // heuristic. FIXME: We can definitely improve it. + MachineBasicBlock *TBB = 0, *FBB = 0; + SmallVector<MachineOperand, 4> Cond; + SmallVector<MachineOperand, 4> CondPrior; + MachineFunction::iterator BBi = BB; + MachineFunction::iterator OldPrior = prior(BBi); + + // If the block terminator isn't analyzable, don't try to move the block + bool B = TII->AnalyzeBranch(*BB, TBB, FBB, Cond); + + // If the block ends in an unconditional branch, move it. The prior block + // has to have an analyzable terminator for us to move this one. Be paranoid + // and make sure we're not trying to move the entry block of the function. + if (!B && Cond.empty() && BB != MF.begin() && + !TII->AnalyzeBranch(*OldPrior, TBB, FBB, CondPrior)) { + BB->moveAfter(JTBB); + OldPrior->updateTerminator(); + BB->updateTerminator(); + // Update numbering to account for the block being moved. + MF.RenumberBlocks(); + ++NumJTMoved; + return NULL; + } + + // Create a new MBB for the code after the jump BB. + MachineBasicBlock *NewBB = + MF.CreateMachineBasicBlock(JTBB->getBasicBlock()); + MachineFunction::iterator MBBI = JTBB; ++MBBI; + MF.insert(MBBI, NewBB); + + // Add an unconditional branch from NewBB to BB. + // There doesn't seem to be meaningful DebugInfo available; this doesn't + // correspond directly to anything in the source. + assert (isThumb2 && "Adjusting for TB[BH] but not in Thumb2?"); + BuildMI(NewBB, DebugLoc(), TII->get(ARM::t2B)).addMBB(BB); + + // Update internal data structures to account for the newly inserted MBB. + MF.RenumberBlocks(NewBB); + + // Update the CFG. + NewBB->addSuccessor(BB); + JTBB->removeSuccessor(BB); + JTBB->addSuccessor(NewBB); + + ++NumJTInserted; + return NewBB; +} |
