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