diff options
Diffstat (limited to 'contrib/llvm-project/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp')
| -rw-r--r-- | contrib/llvm-project/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp | 1376 |
1 files changed, 1376 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp b/contrib/llvm-project/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp new file mode 100644 index 000000000000..3ac335e2ad9d --- /dev/null +++ b/contrib/llvm-project/llvm/lib/Target/CSKY/CSKYConstantIslandPass.cpp @@ -0,0 +1,1376 @@ +//===- CSKYConstantIslandPass.cpp - Emit PC Relative loads ----------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// +// Loading constants inline is expensive on CSKY and it's in general better +// to place the constant nearby in code space and then it can be loaded with a +// simple 16/32 bit load instruction like lrw. +// +// 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 "CSKY.h" +#include "CSKYConstantPoolValue.h" +#include "CSKYMachineFunctionInfo.h" +#include "CSKYSubtarget.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/MachineDominators.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 "CSKY-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"); + +namespace { + +using Iter = MachineBasicBlock::iterator; +using ReverseIter = MachineBasicBlock::reverse_iterator; + +/// CSKYConstantIslands - Due to limited PC-relative displacements, CSKY +/// 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 CSKYConstantIslands : 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; + + unsigned postOffset() const { return Offset + Size; } + }; + + 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; + + public: + bool NegOk; + + CPUser(MachineInstr *Mi, MachineInstr *Cpemi, unsigned Maxdisp, bool Neg) + : MI(Mi), CPEMI(Cpemi), MaxDisp(Maxdisp), NegOk(Neg) { + HighWaterMark = CPEMI->getParent(); + } + + /// getMaxDisp - Returns the maximum displacement supported by MI. + unsigned getMaxDisp() const { return MaxDisp - 16; } + + void setMaxDisp(unsigned Val) { MaxDisp = Val; } + }; + + /// 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; + + const CSKYSubtarget *STI = nullptr; + const CSKYInstrInfo *TII; + CSKYMachineFunctionInfo *MFI; + MachineFunction *MF = nullptr; + MachineConstantPool *MCP = nullptr; + + unsigned PICLabelUId; + + void initPICLabelUId(unsigned UId) { PICLabelUId = UId; } + + unsigned createPICLabelUId() { return PICLabelUId++; } + +public: + static char ID; + + CSKYConstantIslands() : MachineFunctionPass(ID) {} + + StringRef getPassName() const override { return "CSKY Constant Islands"; } + + bool runOnMachineFunction(MachineFunction &F) override; + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.addRequired<MachineDominatorTree>(); + MachineFunctionPass::getAnalysisUsage(AU); + } + + MachineFunctionProperties getRequiredProperties() const override { + return MachineFunctionProperties().set( + MachineFunctionProperties::Property::NoVRegs); + } + + void doInitialPlacement(std::vector<MachineInstr *> &CPEMIs); + CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI); + Align getCPEAlign(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); + 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); +}; +} // end anonymous namespace + +char CSKYConstantIslands::ID = 0; + +bool CSKYConstantIslands::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 CSKYConstantIslands::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 CSKYConstantIslands::runOnMachineFunction(MachineFunction &Mf) { + MF = &Mf; + MCP = Mf.getConstantPool(); + STI = &static_cast<const CSKYSubtarget &>(Mf.getSubtarget()); + + LLVM_DEBUG(dbgs() << "***** CSKYConstantIslands: " + << MCP->getConstants().size() << " CP entries, aligned to " + << MCP->getConstantPoolAlign().value() << " bytes *****\n"); + + TII = STI->getInstrInfo(); + MFI = MF->getInfo<CSKYMachineFunctionInfo>(); + + // 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 CSKYConstantIslands::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). + const Align MaxAlign = MCP->getConstantPoolAlign(); + + // Mark the basic block as required by the const-pool. + BB->setAlignment(Align(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(Log2(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 = CPs[I].getSizeInBytes(TD); + assert(Size >= 4 && "Too small constant pool entry"); + Align Alignment = CPs[I].getAlign(); + // 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(isAligned(Alignment, Size) && "CP Entry not multiple of 4 bytes!"); + + // Insert CONSTPOOL_ENTRY before entries with a smaller alignment. + unsigned LogAlign = Log2(Alignment); + MachineBasicBlock::iterator InsAt = InsPoint[LogAlign]; + + MachineInstr *CPEMI = + BuildMI(*BB, InsAt, DebugLoc(), TII->get(CSKY::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 <= Log2(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 = " << Alignment.value() << '\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. +CSKYConstantIslands::CPEntry * +CSKYConstantIslands::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; +} + +/// getCPEAlign - Returns the required alignment of the constant pool entry +/// represented by CPEMI. Alignment is measured in log2(bytes) units. +Align CSKYConstantIslands::getCPEAlign(const MachineInstr &CPEMI) { + assert(CPEMI.getOpcode() == CSKY::CONSTPOOL_ENTRY); + + unsigned CPI = CPEMI.getOperand(1).getIndex(); + assert(CPI < MCP->getConstants().size() && "Invalid constant pool index."); + return MCP->getConstants()[CPI].getAlign(); +} + +/// 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 CSKYConstantIslands::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() && !MI.isIndirectBranch()) { + bool IsCond = MI.isConditionalBranch(); + unsigned Bits = 0; + unsigned Scale = 1; + int UOpc = CSKY::BR32; + + switch (MI.getOpcode()) { + case CSKY::BR16: + case CSKY::BF16: + case CSKY::BT16: + Bits = 10; + Scale = 2; + break; + default: + Bits = 16; + Scale = 2; + break; + } + + // Record this immediate branch. + unsigned MaxOffs = ((1 << (Bits - 1)) - 1) * Scale; + ImmBranches.push_back(ImmBranch(&MI, MaxOffs, IsCond, UOpc)); + } + + if (Opc == CSKY::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; + + switch (Opc) { + default: + llvm_unreachable("Unknown addressing mode for CP reference!"); + case CSKY::MOVIH32: + case CSKY::ORI32: + continue; + case CSKY::PseudoTLSLA32: + case CSKY::JSRI32: + case CSKY::JMPI32: + case CSKY::LRW32: + case CSKY::LRW32_Gen: + Bits = 16; + Scale = 4; + break; + case CSKY::f2FLRW_S: + case CSKY::f2FLRW_D: + Bits = 8; + Scale = 4; + break; + case CSKY::GRS32: + Bits = 17; + Scale = 2; + 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; + CPUsers.push_back(CPUser(&MI, CPEMI, MaxOffs, NegOk)); + + // 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 CSKYConstantIslands::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 CSKYConstantIslands::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 CSKYConstantIslands::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 = llvm::lower_bound(WaterList, NewBB, compareMbbNumbers); + WaterList.insert(IP, NewBB); +} + +unsigned CSKYConstantIslands::getUserOffset(CPUser &U) const { + unsigned UserOffset = getOffsetOf(U.MI); + + UserOffset &= ~3u; + + return UserOffset; +} + +/// 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 * +CSKYConstantIslands::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. + + // TODO: Add support for 16bit instr. + BuildMI(OrigBB, DebugLoc(), TII->get(CSKY::BR32)).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 = llvm::lower_bound(WaterList, 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 CSKYConstantIslands::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 CSKYConstantIslands::isWaterInRange(unsigned UserOffset, + MachineBasicBlock *Water, CPUser &U, + unsigned &Growth) { + unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(); + unsigned NextBlockOffset; + Align NextBlockAlignment; + MachineFunction::const_iterator NextBlock = ++Water->getIterator(); + if (NextBlock == MF->end()) { + NextBlockOffset = BBInfo[Water->getNumber()].postOffset(); + NextBlockAlignment = Align(4); + } 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, 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 CSKYConstantIslands::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() == CSKY::BR32 /*TODO: change to 16bit instr. */) + return PredMI->getOperand(0).getMBB() == Succ; + return false; +} +#endif + +void CSKYConstantIslands::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 CSKYConstantIslands::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 CSKYConstantIslands::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; +} + +/// getUnconditionalBrDisp - Returns the maximum displacement that can fit in +/// the specific unconditional branch instruction. +static inline unsigned getUnconditionalBrDisp(int Opc) { + unsigned Bits, Scale; + + switch (Opc) { + case CSKY::BR16: + Bits = 10; + Scale = 2; + break; + case CSKY::BR32: + Bits = 16; + Scale = 2; + break; + default: + assert(0); + break; + } + + unsigned MaxOffs = ((1 << (Bits - 1)) - 1) * Scale; + return MaxOffs; +} + +/// 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 CSKYConstantIslands::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 CSKYConstantIslands::createNewWater(unsigned CPUserIndex, + unsigned UserOffset, + MachineBasicBlock *&NewMBB) { + CPUser &U = CPUsers[CPUserIndex]; + MachineInstr *UserMI = U.MI; + MachineInstr *CPEMI = U.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 = 4; + // Compute the offset where the CPE will begin. + unsigned CPEOffset = UserBBI.postOffset() + 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. + + // TODO: Add support for 16bit instr. + int UncondBr = CSKY::BR32; + auto *NewMI = BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)) + .addMBB(NewMBB) + .getInstr(); + unsigned MaxDisp = getUnconditionalBrDisp(UncondBr); + ImmBranches.push_back( + ImmBranch(&UserMBB->back(), MaxDisp, false, UncondBr)); + BBInfo[UserMBB->getNumber()].Size += TII->getInstSizeInBytes(*NewMI); + 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 + // Align which is the largest possible alignment in the function. + const Align Align = MF->getAlignment(); + 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=" << Log2(Align) << '\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(); + 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 -= Align.value(); + EndInsertOffset -= Align.value(); + } + // 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 CSKYConstantIslands::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; + 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 { + 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(CSKY::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(getCPEAlign(*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 CSKYConstantIslands::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(Align(4)); + } else { + // Entries are sorted by descending alignment, so realign from the front. + CPEBB->setAlignment(getCPEAlign(*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 CSKYConstantIslands::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 CSKYConstantIslands::isBBInRange(MachineInstr *MI, + MachineBasicBlock *DestBB, + unsigned MaxDisp) { + unsigned BrOffset = getOffsetOf(MI); + 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 CSKYConstantIslands::fixupImmediateBr(ImmBranch &Br) { + MachineInstr *MI = Br.MI; + MachineBasicBlock *DestBB = TII->getBranchDestBlock(*MI); + + // 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 BSR to implement a far jump. +/// Otherwise, add an intermediate branch instruction to a branch. +bool CSKYConstantIslands::fixupUnconditionalBr(ImmBranch &Br) { + MachineInstr *MI = Br.MI; + MachineBasicBlock *MBB = MI->getParent(); + + if (!MFI->isLRSpilled()) + report_fatal_error("underestimated function size"); + + // Use BSR to implement far jump. + Br.MaxDisp = ((1 << (26 - 1)) - 1) * 2; + MI->setDesc(TII->get(CSKY::BSR32_BR)); + BBInfo[MBB->getNumber()].Size += 4; + adjustBBOffsetsAfter(MBB); + ++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 CSKYConstantIslands::fixupConditionalBr(ImmBranch &Br) { + MachineInstr *MI = Br.MI; + MachineBasicBlock *DestBB = TII->getBranchDestBlock(*MI); + + SmallVector<MachineOperand, 4> Cond; + Cond.push_back(MachineOperand::CreateImm(MI->getOpcode())); + Cond.push_back(MI->getOperand(0)); + TII->reverseBranchCondition(Cond); + + // 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); + + ++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 + MachineBasicBlock *NewDest = TII->getBranchDestBlock(*BMI); + if (isBBInRange(MI, NewDest, Br.MaxDisp)) { + LLVM_DEBUG( + dbgs() << " Invert Bcc condition and swap its destination with " + << *BMI); + BMI->getOperand(BMI->getNumExplicitOperands() - 1).setMBB(DestBB); + MI->getOperand(MI->getNumExplicitOperands() - 1).setMBB(NewDest); + + MI->setDesc(TII->get(Cond[0].getImm())); + 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 + + // The conditional successor will be swapped between the BBs after this, so + // update CFG. + MBB->addSuccessor(DestBB); + std::next(MBB->getIterator())->removeSuccessor(DestBB); + } + 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. + + BuildMI(MBB, DebugLoc(), TII->get(Cond[0].getImm())) + .addReg(MI->getOperand(0).getReg()) + .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; +} + +/// Returns a pass that converts branches to long branches. +FunctionPass *llvm::createCSKYConstantIslandPass() { + return new CSKYConstantIslands(); +} + +INITIALIZE_PASS(CSKYConstantIslands, DEBUG_TYPE, + "CSKY constant island placement and branch shortening pass", + false, false) |