LLVM  4.0.0
MipsConstantIslandPass.cpp
Go to the documentation of this file.
1 //===-- MipsConstantIslandPass.cpp - Emit Pc Relative loads----------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //
11 // This pass is used to make Pc relative loads of constants.
12 // For now, only Mips16 will use this.
13 //
14 // Loading constants inline is expensive on Mips16 and it's in general better
15 // to place the constant nearby in code space and then it can be loaded with a
16 // simple 16 bit load instruction.
17 //
18 // The constants can be not just numbers but addresses of functions and labels.
19 // This can be particularly helpful in static relocation mode for embedded
20 // non-linux targets.
21 //
22 //
23 
24 #include "Mips.h"
26 #include "Mips16InstrInfo.h"
27 #include "MipsMachineFunction.h"
28 #include "MipsTargetMachine.h"
29 #include "llvm/ADT/Statistic.h"
35 #include "llvm/IR/Function.h"
36 #include "llvm/IR/InstIterator.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/Format.h"
45 #include <algorithm>
46 
47 using namespace llvm;
48 
49 #define DEBUG_TYPE "mips-constant-islands"
50 
51 STATISTIC(NumCPEs, "Number of constpool entries");
52 STATISTIC(NumSplit, "Number of uncond branches inserted");
53 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
54 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
55 
56 // FIXME: This option should be removed once it has received sufficient testing.
57 static cl::opt<bool>
58 AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true),
59  cl::desc("Align constant islands in code"));
60 
61 
62 // Rather than do make check tests with huge amounts of code, we force
63 // the test to use this amount.
64 //
66  "mips-constant-islands-small-offset",
67  cl::init(0),
68  cl::desc("Make small offsets be this amount for testing purposes"),
69  cl::Hidden);
70 
71 //
72 // For testing purposes we tell it to not use relaxed load forms so that it
73 // will split blocks.
74 //
76  "mips-constant-islands-no-load-relaxation",
77  cl::init(false),
78  cl::desc("Don't relax loads to long loads - for testing purposes"),
79  cl::Hidden);
80 
81 static unsigned int branchTargetOperand(MachineInstr *MI) {
82  switch (MI->getOpcode()) {
83  case Mips::Bimm16:
84  case Mips::BimmX16:
85  case Mips::Bteqz16:
86  case Mips::BteqzX16:
87  case Mips::Btnez16:
88  case Mips::BtnezX16:
89  case Mips::JalB16:
90  return 0;
91  case Mips::BeqzRxImm16:
92  case Mips::BeqzRxImmX16:
93  case Mips::BnezRxImm16:
94  case Mips::BnezRxImmX16:
95  return 1;
96  }
97  llvm_unreachable("Unknown branch type");
98 }
99 
100 static unsigned int longformBranchOpcode(unsigned int Opcode) {
101  switch (Opcode) {
102  case Mips::Bimm16:
103  case Mips::BimmX16:
104  return Mips::BimmX16;
105  case Mips::Bteqz16:
106  case Mips::BteqzX16:
107  return Mips::BteqzX16;
108  case Mips::Btnez16:
109  case Mips::BtnezX16:
110  return Mips::BtnezX16;
111  case Mips::JalB16:
112  return Mips::JalB16;
113  case Mips::BeqzRxImm16:
114  case Mips::BeqzRxImmX16:
115  return Mips::BeqzRxImmX16;
116  case Mips::BnezRxImm16:
117  case Mips::BnezRxImmX16:
118  return Mips::BnezRxImmX16;
119  }
120  llvm_unreachable("Unknown branch type");
121 }
122 
123 //
124 // FIXME: need to go through this whole constant islands port and check the math
125 // for branch ranges and clean this up and make some functions to calculate things
126 // that are done many times identically.
127 // Need to refactor some of the code to call this routine.
128 //
129 static unsigned int branchMaxOffsets(unsigned int Opcode) {
130  unsigned Bits, Scale;
131  switch (Opcode) {
132  case Mips::Bimm16:
133  Bits = 11;
134  Scale = 2;
135  break;
136  case Mips::BimmX16:
137  Bits = 16;
138  Scale = 2;
139  break;
140  case Mips::BeqzRxImm16:
141  Bits = 8;
142  Scale = 2;
143  break;
144  case Mips::BeqzRxImmX16:
145  Bits = 16;
146  Scale = 2;
147  break;
148  case Mips::BnezRxImm16:
149  Bits = 8;
150  Scale = 2;
151  break;
152  case Mips::BnezRxImmX16:
153  Bits = 16;
154  Scale = 2;
155  break;
156  case Mips::Bteqz16:
157  Bits = 8;
158  Scale = 2;
159  break;
160  case Mips::BteqzX16:
161  Bits = 16;
162  Scale = 2;
163  break;
164  case Mips::Btnez16:
165  Bits = 8;
166  Scale = 2;
167  break;
168  case Mips::BtnezX16:
169  Bits = 16;
170  Scale = 2;
171  break;
172  default:
173  llvm_unreachable("Unknown branch type");
174  }
175  unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
176  return MaxOffs;
177 }
178 
179 namespace {
180 
181 
182  typedef MachineBasicBlock::iterator Iter;
183  typedef MachineBasicBlock::reverse_iterator ReverseIter;
184 
185  /// MipsConstantIslands - Due to limited PC-relative displacements, Mips
186  /// requires constant pool entries to be scattered among the instructions
187  /// inside a function. To do this, it completely ignores the normal LLVM
188  /// constant pool; instead, it places constants wherever it feels like with
189  /// special instructions.
190  ///
191  /// The terminology used in this pass includes:
192  /// Islands - Clumps of constants placed in the function.
193  /// Water - Potential places where an island could be formed.
194  /// CPE - A constant pool entry that has been placed somewhere, which
195  /// tracks a list of users.
196 
197  class MipsConstantIslands : public MachineFunctionPass {
198 
199  /// BasicBlockInfo - Information about the offset and size of a single
200  /// basic block.
201  struct BasicBlockInfo {
202  /// Offset - Distance from the beginning of the function to the beginning
203  /// of this basic block.
204  ///
205  /// Offsets are computed assuming worst case padding before an aligned
206  /// block. This means that subtracting basic block offsets always gives a
207  /// conservative estimate of the real distance which may be smaller.
208  ///
209  /// Because worst case padding is used, the computed offset of an aligned
210  /// block may not actually be aligned.
211  unsigned Offset;
212 
213  /// Size - Size of the basic block in bytes. If the block contains
214  /// inline assembly, this is a worst case estimate.
215  ///
216  /// The size does not include any alignment padding whether from the
217  /// beginning of the block, or from an aligned jump table at the end.
218  unsigned Size;
219 
220  // FIXME: ignore LogAlign for this patch
221  //
222  unsigned postOffset(unsigned LogAlign = 0) const {
223  unsigned PO = Offset + Size;
224  return PO;
225  }
226 
227  BasicBlockInfo() : Offset(0), Size(0) {}
228 
229  };
230 
231  std::vector<BasicBlockInfo> BBInfo;
232 
233  /// WaterList - A sorted list of basic blocks where islands could be placed
234  /// (i.e. blocks that don't fall through to the following block, due
235  /// to a return, unreachable, or unconditional branch).
236  std::vector<MachineBasicBlock*> WaterList;
237 
238  /// NewWaterList - The subset of WaterList that was created since the
239  /// previous iteration by inserting unconditional branches.
240  SmallSet<MachineBasicBlock*, 4> NewWaterList;
241 
242  typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
243 
244  /// CPUser - One user of a constant pool, keeping the machine instruction
245  /// pointer, the constant pool being referenced, and the max displacement
246  /// allowed from the instruction to the CP. The HighWaterMark records the
247  /// highest basic block where a new CPEntry can be placed. To ensure this
248  /// pass terminates, the CP entries are initially placed at the end of the
249  /// function and then move monotonically to lower addresses. The
250  /// exception to this rule is when the current CP entry for a particular
251  /// CPUser is out of range, but there is another CP entry for the same
252  /// constant value in range. We want to use the existing in-range CP
253  /// entry, but if it later moves out of range, the search for new water
254  /// should resume where it left off. The HighWaterMark is used to record
255  /// that point.
256  struct CPUser {
257  MachineInstr *MI;
258  MachineInstr *CPEMI;
259  MachineBasicBlock *HighWaterMark;
260  private:
261  unsigned MaxDisp;
262  unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions
263  // with different displacements
264  unsigned LongFormOpcode;
265  public:
266  bool NegOk;
267  CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
268  bool neg,
269  unsigned longformmaxdisp, unsigned longformopcode)
270  : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp),
271  LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode),
272  NegOk(neg){
273  HighWaterMark = CPEMI->getParent();
274  }
275  /// getMaxDisp - Returns the maximum displacement supported by MI.
276  unsigned getMaxDisp() const {
277  unsigned xMaxDisp = ConstantIslandsSmallOffset?
279  return xMaxDisp;
280  }
281  void setMaxDisp(unsigned val) {
282  MaxDisp = val;
283  }
284  unsigned getLongFormMaxDisp() const {
285  return LongFormMaxDisp;
286  }
287  unsigned getLongFormOpcode() const {
288  return LongFormOpcode;
289  }
290  };
291 
292  /// CPUsers - Keep track of all of the machine instructions that use various
293  /// constant pools and their max displacement.
294  std::vector<CPUser> CPUsers;
295 
296  /// CPEntry - One per constant pool entry, keeping the machine instruction
297  /// pointer, the constpool index, and the number of CPUser's which
298  /// reference this entry.
299  struct CPEntry {
300  MachineInstr *CPEMI;
301  unsigned CPI;
302  unsigned RefCount;
303  CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
304  : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
305  };
306 
307  /// CPEntries - Keep track of all of the constant pool entry machine
308  /// instructions. For each original constpool index (i.e. those that
309  /// existed upon entry to this pass), it keeps a vector of entries.
310  /// Original elements are cloned as we go along; the clones are
311  /// put in the vector of the original element, but have distinct CPIs.
312  std::vector<std::vector<CPEntry> > CPEntries;
313 
314  /// ImmBranch - One per immediate branch, keeping the machine instruction
315  /// pointer, conditional or unconditional, the max displacement,
316  /// and (if isCond is true) the corresponding unconditional branch
317  /// opcode.
318  struct ImmBranch {
319  MachineInstr *MI;
320  unsigned MaxDisp : 31;
321  bool isCond : 1;
322  int UncondBr;
323  ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
324  : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
325  };
326 
327  /// ImmBranches - Keep track of all the immediate branch instructions.
328  ///
329  std::vector<ImmBranch> ImmBranches;
330 
331  /// HasFarJump - True if any far jump instruction has been emitted during
332  /// the branch fix up pass.
333  bool HasFarJump;
334 
335  const MipsSubtarget *STI;
336  const Mips16InstrInfo *TII;
337  MipsFunctionInfo *MFI;
338  MachineFunction *MF;
339  MachineConstantPool *MCP;
340 
341  unsigned PICLabelUId;
342  bool PrescannedForConstants;
343 
344  void initPICLabelUId(unsigned UId) {
345  PICLabelUId = UId;
346  }
347 
348 
349  unsigned createPICLabelUId() {
350  return PICLabelUId++;
351  }
352 
353  public:
354  static char ID;
355  MipsConstantIslands()
356  : MachineFunctionPass(ID), STI(nullptr), MF(nullptr), MCP(nullptr),
357  PrescannedForConstants(false) {}
358 
359  StringRef getPassName() const override { return "Mips Constant Islands"; }
360 
361  bool runOnMachineFunction(MachineFunction &F) override;
362 
363  MachineFunctionProperties getRequiredProperties() const override {
366  }
367 
368  void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs);
369  CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
370  unsigned getCPELogAlign(const MachineInstr &CPEMI);
371  void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs);
372  unsigned getOffsetOf(MachineInstr *MI) const;
373  unsigned getUserOffset(CPUser&) const;
374  void dumpBBs();
375 
376  bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
377  unsigned Disp, bool NegativeOK);
378  bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset,
379  const CPUser &U);
380 
382  MachineBasicBlock *splitBlockBeforeInstr(MachineInstr &MI);
383  void updateForInsertedWaterBlock(MachineBasicBlock *NewBB);
384  void adjustBBOffsetsAfter(MachineBasicBlock *BB);
385  bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI);
386  int findInRangeCPEntry(CPUser& U, unsigned UserOffset);
387  int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset);
388  bool findAvailableWater(CPUser&U, unsigned UserOffset,
389  water_iterator &WaterIter);
390  void createNewWater(unsigned CPUserIndex, unsigned UserOffset,
391  MachineBasicBlock *&NewMBB);
392  bool handleConstantPoolUser(unsigned CPUserIndex);
393  void removeDeadCPEMI(MachineInstr *CPEMI);
394  bool removeUnusedCPEntries();
395  bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset,
396  MachineInstr *CPEMI, unsigned Disp, bool NegOk,
397  bool DoDump = false);
398  bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water,
399  CPUser &U, unsigned &Growth);
400  bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
401  bool fixupImmediateBr(ImmBranch &Br);
402  bool fixupConditionalBr(ImmBranch &Br);
403  bool fixupUnconditionalBr(ImmBranch &Br);
404 
405  void prescanForConstants();
406 
407  private:
408 
409  };
410 
411  char MipsConstantIslands::ID = 0;
412 } // end of anonymous namespace
413 
414 bool MipsConstantIslands::isOffsetInRange
415  (unsigned UserOffset, unsigned TrialOffset,
416  const CPUser &U) {
417  return isOffsetInRange(UserOffset, TrialOffset,
418  U.getMaxDisp(), U.NegOk);
419 }
420 /// print block size and offset information - debugging
421 void MipsConstantIslands::dumpBBs() {
422  DEBUG({
423  for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) {
424  const BasicBlockInfo &BBI = BBInfo[J];
425  dbgs() << format("%08x BB#%u\t", BBI.Offset, J)
426  << format(" size=%#x\n", BBInfo[J].Size);
427  }
428  });
429 }
430 /// Returns a pass that converts branches to long branches.
432  return new MipsConstantIslands();
433 }
434 
435 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) {
436  // The intention is for this to be a mips16 only pass for now
437  // FIXME:
438  MF = &mf;
439  MCP = mf.getConstantPool();
440  STI = &static_cast<const MipsSubtarget &>(mf.getSubtarget());
441  DEBUG(dbgs() << "constant island machine function " << "\n");
442  if (!STI->inMips16Mode() || !MipsSubtarget::useConstantIslands()) {
443  return false;
444  }
445  TII = (const Mips16InstrInfo *)STI->getInstrInfo();
446  MFI = MF->getInfo<MipsFunctionInfo>();
447  DEBUG(dbgs() << "constant island processing " << "\n");
448  //
449  // will need to make predermination if there is any constants we need to
450  // put in constant islands. TBD.
451  //
452  if (!PrescannedForConstants) prescanForConstants();
453 
454  HasFarJump = false;
455  // This pass invalidates liveness information when it splits basic blocks.
456  MF->getRegInfo().invalidateLiveness();
457 
458  // Renumber all of the machine basic blocks in the function, guaranteeing that
459  // the numbers agree with the position of the block in the function.
460  MF->RenumberBlocks();
461 
462  bool MadeChange = false;
463 
464  // Perform the initial placement of the constant pool entries. To start with,
465  // we put them all at the end of the function.
466  std::vector<MachineInstr*> CPEMIs;
467  if (!MCP->isEmpty())
468  doInitialPlacement(CPEMIs);
469 
470  /// The next UID to take is the first unused one.
471  initPICLabelUId(CPEMIs.size());
472 
473  // Do the initial scan of the function, building up information about the
474  // sizes of each block, the location of all the water, and finding all of the
475  // constant pool users.
476  initializeFunctionInfo(CPEMIs);
477  CPEMIs.clear();
478  DEBUG(dumpBBs());
479 
480  /// Remove dead constant pool entries.
481  MadeChange |= removeUnusedCPEntries();
482 
483  // Iteratively place constant pool entries and fix up branches until there
484  // is no change.
485  unsigned NoCPIters = 0, NoBRIters = 0;
486  (void)NoBRIters;
487  while (true) {
488  DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n');
489  bool CPChange = false;
490  for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
491  CPChange |= handleConstantPoolUser(i);
492  if (CPChange && ++NoCPIters > 30)
493  report_fatal_error("Constant Island pass failed to converge!");
494  DEBUG(dumpBBs());
495 
496  // Clear NewWaterList now. If we split a block for branches, it should
497  // appear as "new water" for the next iteration of constant pool placement.
498  NewWaterList.clear();
499 
500  DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n');
501  bool BRChange = false;
502  for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
503  BRChange |= fixupImmediateBr(ImmBranches[i]);
504  if (BRChange && ++NoBRIters > 30)
505  report_fatal_error("Branch Fix Up pass failed to converge!");
506  DEBUG(dumpBBs());
507  if (!CPChange && !BRChange)
508  break;
509  MadeChange = true;
510  }
511 
512  DEBUG(dbgs() << '\n'; dumpBBs());
513 
514  BBInfo.clear();
515  WaterList.clear();
516  CPUsers.clear();
517  CPEntries.clear();
518  ImmBranches.clear();
519  return MadeChange;
520 }
521 
522 /// doInitialPlacement - Perform the initial placement of the constant pool
523 /// entries. To start with, we put them all at the end of the function.
524 void
525 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) {
526  // Create the basic block to hold the CPE's.
527  MachineBasicBlock *BB = MF->CreateMachineBasicBlock();
528  MF->push_back(BB);
529 
530 
531  // MachineConstantPool measures alignment in bytes. We measure in log2(bytes).
532  unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment());
533 
534  // Mark the basic block as required by the const-pool.
535  // If AlignConstantIslands isn't set, use 4-byte alignment for everything.
536  BB->setAlignment(AlignConstantIslands ? MaxAlign : 2);
537 
538  // The function needs to be as aligned as the basic blocks. The linker may
539  // move functions around based on their alignment.
540  MF->ensureAlignment(BB->getAlignment());
541 
542  // Order the entries in BB by descending alignment. That ensures correct
543  // alignment of all entries as long as BB is sufficiently aligned. Keep
544  // track of the insertion point for each alignment. We are going to bucket
545  // sort the entries as they are created.
546  SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end());
547 
548  // Add all of the constants from the constant pool to the end block, use an
549  // identity mapping of CPI's to CPE's.
550  const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants();
551 
552  const DataLayout &TD = MF->getDataLayout();
553  for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
554  unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
555  assert(Size >= 4 && "Too small constant pool entry");
556  unsigned Align = CPs[i].getAlignment();
557  assert(isPowerOf2_32(Align) && "Invalid alignment");
558  // Verify that all constant pool entries are a multiple of their alignment.
559  // If not, we would have to pad them out so that instructions stay aligned.
560  assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!");
561 
562  // Insert CONSTPOOL_ENTRY before entries with a smaller alignment.
563  unsigned LogAlign = Log2_32(Align);
564  MachineBasicBlock::iterator InsAt = InsPoint[LogAlign];
565 
566  MachineInstr *CPEMI =
567  BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
568  .addImm(i).addConstantPoolIndex(i).addImm(Size);
569 
570  CPEMIs.push_back(CPEMI);
571 
572  // Ensure that future entries with higher alignment get inserted before
573  // CPEMI. This is bucket sort with iterators.
574  for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a)
575  if (InsPoint[a] == InsAt)
576  InsPoint[a] = CPEMI;
577  // Add a new CPEntry, but no corresponding CPUser yet.
578  CPEntries.emplace_back(1, CPEntry(CPEMI, i));
579  ++NumCPEs;
580  DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = "
581  << Size << ", align = " << Align <<'\n');
582  }
583  DEBUG(BB->dump());
584 }
585 
586 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
587 /// into the block immediately after it.
589  // Get the next machine basic block in the function.
591  // Can't fall off end of function.
592  if (std::next(MBBI) == MBB->getParent()->end())
593  return false;
594 
595  MachineBasicBlock *NextBB = &*std::next(MBBI);
597  E = MBB->succ_end(); I != E; ++I)
598  if (*I == NextBB)
599  return true;
600 
601  return false;
602 }
603 
604 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
605 /// look up the corresponding CPEntry.
606 MipsConstantIslands::CPEntry
607 *MipsConstantIslands::findConstPoolEntry(unsigned CPI,
608  const MachineInstr *CPEMI) {
609  std::vector<CPEntry> &CPEs = CPEntries[CPI];
610  // Number of entries per constpool index should be small, just do a
611  // linear search.
612  for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
613  if (CPEs[i].CPEMI == CPEMI)
614  return &CPEs[i];
615  }
616  return nullptr;
617 }
618 
619 /// getCPELogAlign - Returns the required alignment of the constant pool entry
620 /// represented by CPEMI. Alignment is measured in log2(bytes) units.
621 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr &CPEMI) {
622  assert(CPEMI.getOpcode() == Mips::CONSTPOOL_ENTRY);
623 
624  // Everything is 4-byte aligned unless AlignConstantIslands is set.
626  return 2;
627 
628  unsigned CPI = CPEMI.getOperand(1).getIndex();
629  assert(CPI < MCP->getConstants().size() && "Invalid constant pool index.");
630  unsigned Align = MCP->getConstants()[CPI].getAlignment();
631  assert(isPowerOf2_32(Align) && "Invalid CPE alignment");
632  return Log2_32(Align);
633 }
634 
635 /// initializeFunctionInfo - Do the initial scan of the function, building up
636 /// information about the sizes of each block, the location of all the water,
637 /// and finding all of the constant pool users.
638 void MipsConstantIslands::
639 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
640  BBInfo.clear();
641  BBInfo.resize(MF->getNumBlockIDs());
642 
643  // First thing, compute the size of all basic blocks, and see if the function
644  // has any inline assembly in it. If so, we have to be conservative about
645  // alignment assumptions, as we don't know for sure the size of any
646  // instructions in the inline assembly.
647  for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I)
648  computeBlockSize(&*I);
649 
650 
651  // Compute block offsets.
652  adjustBBOffsetsAfter(&MF->front());
653 
654  // Now go back through the instructions and build up our data structures.
655  for (MachineBasicBlock &MBB : *MF) {
656  // If this block doesn't fall through into the next MBB, then this is
657  // 'water' that a constant pool island could be placed.
658  if (!BBHasFallthrough(&MBB))
659  WaterList.push_back(&MBB);
660  for (MachineInstr &MI : MBB) {
661  if (MI.isDebugValue())
662  continue;
663 
664  int Opc = MI.getOpcode();
665  if (MI.isBranch()) {
666  bool isCond = false;
667  unsigned Bits = 0;
668  unsigned Scale = 1;
669  int UOpc = Opc;
670  switch (Opc) {
671  default:
672  continue; // Ignore other branches for now
673  case Mips::Bimm16:
674  Bits = 11;
675  Scale = 2;
676  isCond = false;
677  break;
678  case Mips::BimmX16:
679  Bits = 16;
680  Scale = 2;
681  isCond = false;
682  break;
683  case Mips::BeqzRxImm16:
684  UOpc=Mips::Bimm16;
685  Bits = 8;
686  Scale = 2;
687  isCond = true;
688  break;
689  case Mips::BeqzRxImmX16:
690  UOpc=Mips::Bimm16;
691  Bits = 16;
692  Scale = 2;
693  isCond = true;
694  break;
695  case Mips::BnezRxImm16:
696  UOpc=Mips::Bimm16;
697  Bits = 8;
698  Scale = 2;
699  isCond = true;
700  break;
701  case Mips::BnezRxImmX16:
702  UOpc=Mips::Bimm16;
703  Bits = 16;
704  Scale = 2;
705  isCond = true;
706  break;
707  case Mips::Bteqz16:
708  UOpc=Mips::Bimm16;
709  Bits = 8;
710  Scale = 2;
711  isCond = true;
712  break;
713  case Mips::BteqzX16:
714  UOpc=Mips::Bimm16;
715  Bits = 16;
716  Scale = 2;
717  isCond = true;
718  break;
719  case Mips::Btnez16:
720  UOpc=Mips::Bimm16;
721  Bits = 8;
722  Scale = 2;
723  isCond = true;
724  break;
725  case Mips::BtnezX16:
726  UOpc=Mips::Bimm16;
727  Bits = 16;
728  Scale = 2;
729  isCond = true;
730  break;
731  }
732  // Record this immediate branch.
733  unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
734  ImmBranches.push_back(ImmBranch(&MI, MaxOffs, isCond, UOpc));
735  }
736 
737  if (Opc == Mips::CONSTPOOL_ENTRY)
738  continue;
739 
740 
741  // Scan the instructions for constant pool operands.
742  for (unsigned op = 0, e = MI.getNumOperands(); op != e; ++op)
743  if (MI.getOperand(op).isCPI()) {
744 
745  // We found one. The addressing mode tells us the max displacement
746  // from the PC that this instruction permits.
747 
748  // Basic size info comes from the TSFlags field.
749  unsigned Bits = 0;
750  unsigned Scale = 1;
751  bool NegOk = false;
752  unsigned LongFormBits = 0;
753  unsigned LongFormScale = 0;
754  unsigned LongFormOpcode = 0;
755  switch (Opc) {
756  default:
757  llvm_unreachable("Unknown addressing mode for CP reference!");
758  case Mips::LwRxPcTcp16:
759  Bits = 8;
760  Scale = 4;
761  LongFormOpcode = Mips::LwRxPcTcpX16;
762  LongFormBits = 14;
763  LongFormScale = 1;
764  break;
765  case Mips::LwRxPcTcpX16:
766  Bits = 14;
767  Scale = 1;
768  NegOk = true;
769  break;
770  }
771  // Remember that this is a user of a CP entry.
772  unsigned CPI = MI.getOperand(op).getIndex();
773  MachineInstr *CPEMI = CPEMIs[CPI];
774  unsigned MaxOffs = ((1 << Bits)-1) * Scale;
775  unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale;
776  CPUsers.push_back(CPUser(&MI, CPEMI, MaxOffs, NegOk, LongFormMaxOffs,
777  LongFormOpcode));
778 
779  // Increment corresponding CPEntry reference count.
780  CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
781  assert(CPE && "Cannot find a corresponding CPEntry!");
782  CPE->RefCount++;
783 
784  // Instructions can only use one CP entry, don't bother scanning the
785  // rest of the operands.
786  break;
787 
788  }
789 
790  }
791  }
792 
793 }
794 
795 /// computeBlockSize - Compute the size and some alignment information for MBB.
796 /// This function updates BBInfo directly.
798  BasicBlockInfo &BBI = BBInfo[MBB->getNumber()];
799  BBI.Size = 0;
800 
801  for (const MachineInstr &MI : *MBB)
802  BBI.Size += TII->getInstSizeInBytes(MI);
803 }
804 
805 /// getOffsetOf - Return the current offset of the specified machine instruction
806 /// from the start of the function. This offset changes as stuff is moved
807 /// around inside the function.
808 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const {
809  MachineBasicBlock *MBB = MI->getParent();
810 
811  // The offset is composed of two things: the sum of the sizes of all MBB's
812  // before this instruction's block, and the offset from the start of the block
813  // it is in.
814  unsigned Offset = BBInfo[MBB->getNumber()].Offset;
815 
816  // Sum instructions before MI in MBB.
817  for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) {
818  assert(I != MBB->end() && "Didn't find MI in its own basic block?");
819  Offset += TII->getInstSizeInBytes(*I);
820  }
821  return Offset;
822 }
823 
824 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
825 /// ID.
826 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
827  const MachineBasicBlock *RHS) {
828  return LHS->getNumber() < RHS->getNumber();
829 }
830 
831 /// updateForInsertedWaterBlock - When a block is newly inserted into the
832 /// machine function, it upsets all of the block numbers. Renumber the blocks
833 /// and update the arrays that parallel this numbering.
834 void MipsConstantIslands::updateForInsertedWaterBlock
835  (MachineBasicBlock *NewBB) {
836  // Renumber the MBB's to keep them consecutive.
837  NewBB->getParent()->RenumberBlocks(NewBB);
838 
839  // Insert an entry into BBInfo to align it properly with the (newly
840  // renumbered) block numbers.
841  BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
842 
843  // Next, update WaterList. Specifically, we need to add NewMBB as having
844  // available water after it.
845  water_iterator IP =
846  std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
848  WaterList.insert(IP, NewBB);
849 }
850 
851 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const {
852  return getOffsetOf(U.MI);
853 }
854 
855 /// Split the basic block containing MI into two blocks, which are joined by
856 /// an unconditional branch. Update data structures and renumber blocks to
857 /// account for this change and returns the newly created block.
859 MipsConstantIslands::splitBlockBeforeInstr(MachineInstr &MI) {
860  MachineBasicBlock *OrigBB = MI.getParent();
861 
862  // Create a new MBB for the code after the OrigBB.
863  MachineBasicBlock *NewBB =
864  MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
865  MachineFunction::iterator MBBI = ++OrigBB->getIterator();
866  MF->insert(MBBI, NewBB);
867 
868  // Splice the instructions starting with MI over to NewBB.
869  NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
870 
871  // Add an unconditional branch from OrigBB to NewBB.
872  // Note the new unconditional branch is not being recorded.
873  // There doesn't seem to be meaningful DebugInfo available; this doesn't
874  // correspond to anything in the source.
875  BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB);
876  ++NumSplit;
877 
878  // Update the CFG. All succs of OrigBB are now succs of NewBB.
879  NewBB->transferSuccessors(OrigBB);
880 
881  // OrigBB branches to NewBB.
882  OrigBB->addSuccessor(NewBB);
883 
884  // Update internal data structures to account for the newly inserted MBB.
885  // This is almost the same as updateForInsertedWaterBlock, except that
886  // the Water goes after OrigBB, not NewBB.
887  MF->RenumberBlocks(NewBB);
888 
889  // Insert an entry into BBInfo to align it properly with the (newly
890  // renumbered) block numbers.
891  BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo());
892 
893  // Next, update WaterList. Specifically, we need to add OrigMBB as having
894  // available water after it (but not if it's already there, which happens
895  // when splitting before a conditional branch that is followed by an
896  // unconditional branch - in that case we want to insert NewBB).
897  water_iterator IP =
898  std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
900  MachineBasicBlock* WaterBB = *IP;
901  if (WaterBB == OrigBB)
902  WaterList.insert(std::next(IP), NewBB);
903  else
904  WaterList.insert(IP, OrigBB);
905  NewWaterList.insert(OrigBB);
906 
907  // Figure out how large the OrigBB is. As the first half of the original
908  // block, it cannot contain a tablejump. The size includes
909  // the new jump we added. (It should be possible to do this without
910  // recounting everything, but it's very confusing, and this is rarely
911  // executed.)
912  computeBlockSize(OrigBB);
913 
914  // Figure out how large the NewMBB is. As the second half of the original
915  // block, it may contain a tablejump.
916  computeBlockSize(NewBB);
917 
918  // All BBOffsets following these blocks must be modified.
919  adjustBBOffsetsAfter(OrigBB);
920 
921  return NewBB;
922 }
923 
924 
925 
926 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool
927 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
928 /// constant pool entry).
929 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset,
930  unsigned TrialOffset, unsigned MaxDisp,
931  bool NegativeOK) {
932  if (UserOffset <= TrialOffset) {
933  // User before the Trial.
934  if (TrialOffset - UserOffset <= MaxDisp)
935  return true;
936  } else if (NegativeOK) {
937  if (UserOffset - TrialOffset <= MaxDisp)
938  return true;
939  }
940  return false;
941 }
942 
943 /// isWaterInRange - Returns true if a CPE placed after the specified
944 /// Water (a basic block) will be in range for the specific MI.
945 ///
946 /// Compute how much the function will grow by inserting a CPE after Water.
947 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset,
948  MachineBasicBlock* Water, CPUser &U,
949  unsigned &Growth) {
950  unsigned CPELogAlign = getCPELogAlign(*U.CPEMI);
951  unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign);
952  unsigned NextBlockOffset, NextBlockAlignment;
953  MachineFunction::const_iterator NextBlock = ++Water->getIterator();
954  if (NextBlock == MF->end()) {
955  NextBlockOffset = BBInfo[Water->getNumber()].postOffset();
956  NextBlockAlignment = 0;
957  } else {
958  NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset;
959  NextBlockAlignment = NextBlock->getAlignment();
960  }
961  unsigned Size = U.CPEMI->getOperand(2).getImm();
962  unsigned CPEEnd = CPEOffset + Size;
963 
964  // The CPE may be able to hide in the alignment padding before the next
965  // block. It may also cause more padding to be required if it is more aligned
966  // that the next block.
967  if (CPEEnd > NextBlockOffset) {
968  Growth = CPEEnd - NextBlockOffset;
969  // Compute the padding that would go at the end of the CPE to align the next
970  // block.
971  Growth += OffsetToAlignment(CPEEnd, 1ULL << NextBlockAlignment);
972 
973  // If the CPE is to be inserted before the instruction, that will raise
974  // the offset of the instruction. Also account for unknown alignment padding
975  // in blocks between CPE and the user.
976  if (CPEOffset < UserOffset)
977  UserOffset += Growth;
978  } else
979  // CPE fits in existing padding.
980  Growth = 0;
981 
982  return isOffsetInRange(UserOffset, CPEOffset, U);
983 }
984 
985 /// isCPEntryInRange - Returns true if the distance between specific MI and
986 /// specific ConstPool entry instruction can fit in MI's displacement field.
987 bool MipsConstantIslands::isCPEntryInRange
988  (MachineInstr *MI, unsigned UserOffset,
989  MachineInstr *CPEMI, unsigned MaxDisp,
990  bool NegOk, bool DoDump) {
991  unsigned CPEOffset = getOffsetOf(CPEMI);
992 
993  if (DoDump) {
994  DEBUG({
995  unsigned Block = MI->getParent()->getNumber();
996  const BasicBlockInfo &BBI = BBInfo[Block];
997  dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
998  << " max delta=" << MaxDisp
999  << format(" insn address=%#x", UserOffset)
1000  << " in BB#" << Block << ": "
1001  << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI
1002  << format("CPE address=%#x offset=%+d: ", CPEOffset,
1003  int(CPEOffset-UserOffset));
1004  });
1005  }
1006 
1007  return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
1008 }
1009 
1010 #ifndef NDEBUG
1011 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
1012 /// unconditionally branches to its only successor.
1014  if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
1015  return false;
1016  MachineBasicBlock *Succ = *MBB->succ_begin();
1017  MachineBasicBlock *Pred = *MBB->pred_begin();
1018  MachineInstr *PredMI = &Pred->back();
1019  if (PredMI->getOpcode() == Mips::Bimm16)
1020  return PredMI->getOperand(0).getMBB() == Succ;
1021  return false;
1022 }
1023 #endif
1024 
1025 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) {
1026  unsigned BBNum = BB->getNumber();
1027  for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) {
1028  // Get the offset and known bits at the end of the layout predecessor.
1029  // Include the alignment of the current block.
1030  unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size;
1031  BBInfo[i].Offset = Offset;
1032  }
1033 }
1034 
1035 /// decrementCPEReferenceCount - find the constant pool entry with index CPI
1036 /// and instruction CPEMI, and decrement its refcount. If the refcount
1037 /// becomes 0 remove the entry and instruction. Returns true if we removed
1038 /// the entry, false if we didn't.
1039 
1040 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI,
1041  MachineInstr *CPEMI) {
1042  // Find the old entry. Eliminate it if it is no longer used.
1043  CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
1044  assert(CPE && "Unexpected!");
1045  if (--CPE->RefCount == 0) {
1046  removeDeadCPEMI(CPEMI);
1047  CPE->CPEMI = nullptr;
1048  --NumCPEs;
1049  return true;
1050  }
1051  return false;
1052 }
1053 
1054 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1055 /// if not, see if an in-range clone of the CPE is in range, and if so,
1056 /// change the data structures so the user references the clone. Returns:
1057 /// 0 = no existing entry found
1058 /// 1 = entry found, and there were no code insertions or deletions
1059 /// 2 = entry found, and there were code insertions or deletions
1060 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset)
1061 {
1062  MachineInstr *UserMI = U.MI;
1063  MachineInstr *CPEMI = U.CPEMI;
1064 
1065  // Check to see if the CPE is already in-range.
1066  if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk,
1067  true)) {
1068  DEBUG(dbgs() << "In range\n");
1069  return 1;
1070  }
1071 
1072  // No. Look for previously created clones of the CPE that are in range.
1073  unsigned CPI = CPEMI->getOperand(1).getIndex();
1074  std::vector<CPEntry> &CPEs = CPEntries[CPI];
1075  for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1076  // We already tried this one
1077  if (CPEs[i].CPEMI == CPEMI)
1078  continue;
1079  // Removing CPEs can leave empty entries, skip
1080  if (CPEs[i].CPEMI == nullptr)
1081  continue;
1082  if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(),
1083  U.NegOk)) {
1084  DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1085  << CPEs[i].CPI << "\n");
1086  // Point the CPUser node to the replacement
1087  U.CPEMI = CPEs[i].CPEMI;
1088  // Change the CPI in the instruction operand to refer to the clone.
1089  for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1090  if (UserMI->getOperand(j).isCPI()) {
1091  UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1092  break;
1093  }
1094  // Adjust the refcount of the clone...
1095  CPEs[i].RefCount++;
1096  // ...and the original. If we didn't remove the old entry, none of the
1097  // addresses changed, so we don't need another pass.
1098  return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1099  }
1100  }
1101  return 0;
1102 }
1103 
1104 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
1105 /// This version checks if the longer form of the instruction can be used to
1106 /// to satisfy things.
1107 /// if not, see if an in-range clone of the CPE is in range, and if so,
1108 /// change the data structures so the user references the clone. Returns:
1109 /// 0 = no existing entry found
1110 /// 1 = entry found, and there were no code insertions or deletions
1111 /// 2 = entry found, and there were code insertions or deletions
1112 int MipsConstantIslands::findLongFormInRangeCPEntry
1113  (CPUser& U, unsigned UserOffset)
1114 {
1115  MachineInstr *UserMI = U.MI;
1116  MachineInstr *CPEMI = U.CPEMI;
1117 
1118  // Check to see if the CPE is already in-range.
1119  if (isCPEntryInRange(UserMI, UserOffset, CPEMI,
1120  U.getLongFormMaxDisp(), U.NegOk,
1121  true)) {
1122  DEBUG(dbgs() << "In range\n");
1123  UserMI->setDesc(TII->get(U.getLongFormOpcode()));
1124  U.setMaxDisp(U.getLongFormMaxDisp());
1125  return 2; // instruction is longer length now
1126  }
1127 
1128  // No. Look for previously created clones of the CPE that are in range.
1129  unsigned CPI = CPEMI->getOperand(1).getIndex();
1130  std::vector<CPEntry> &CPEs = CPEntries[CPI];
1131  for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
1132  // We already tried this one
1133  if (CPEs[i].CPEMI == CPEMI)
1134  continue;
1135  // Removing CPEs can leave empty entries, skip
1136  if (CPEs[i].CPEMI == nullptr)
1137  continue;
1138  if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI,
1139  U.getLongFormMaxDisp(), U.NegOk)) {
1140  DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#"
1141  << CPEs[i].CPI << "\n");
1142  // Point the CPUser node to the replacement
1143  U.CPEMI = CPEs[i].CPEMI;
1144  // Change the CPI in the instruction operand to refer to the clone.
1145  for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
1146  if (UserMI->getOperand(j).isCPI()) {
1147  UserMI->getOperand(j).setIndex(CPEs[i].CPI);
1148  break;
1149  }
1150  // Adjust the refcount of the clone...
1151  CPEs[i].RefCount++;
1152  // ...and the original. If we didn't remove the old entry, none of the
1153  // addresses changed, so we don't need another pass.
1154  return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1;
1155  }
1156  }
1157  return 0;
1158 }
1159 
1160 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1161 /// the specific unconditional branch instruction.
1162 static inline unsigned getUnconditionalBrDisp(int Opc) {
1163  switch (Opc) {
1164  case Mips::Bimm16:
1165  return ((1<<10)-1)*2;
1166  case Mips::BimmX16:
1167  return ((1<<16)-1)*2;
1168  default:
1169  break;
1170  }
1171  return ((1<<16)-1)*2;
1172 }
1173 
1174 /// findAvailableWater - Look for an existing entry in the WaterList in which
1175 /// we can place the CPE referenced from U so it's within range of U's MI.
1176 /// Returns true if found, false if not. If it returns true, WaterIter
1177 /// is set to the WaterList entry.
1178 /// To ensure that this pass
1179 /// terminates, the CPE location for a particular CPUser is only allowed to
1180 /// move to a lower address, so search backward from the end of the list and
1181 /// prefer the first water that is in range.
1182 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset,
1183  water_iterator &WaterIter) {
1184  if (WaterList.empty())
1185  return false;
1186 
1187  unsigned BestGrowth = ~0u;
1188  for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();;
1189  --IP) {
1190  MachineBasicBlock* WaterBB = *IP;
1191  // Check if water is in range and is either at a lower address than the
1192  // current "high water mark" or a new water block that was created since
1193  // the previous iteration by inserting an unconditional branch. In the
1194  // latter case, we want to allow resetting the high water mark back to
1195  // this new water since we haven't seen it before. Inserting branches
1196  // should be relatively uncommon and when it does happen, we want to be
1197  // sure to take advantage of it for all the CPEs near that block, so that
1198  // we don't insert more branches than necessary.
1199  unsigned Growth;
1200  if (isWaterInRange(UserOffset, WaterBB, U, Growth) &&
1201  (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1202  NewWaterList.count(WaterBB)) && Growth < BestGrowth) {
1203  // This is the least amount of required padding seen so far.
1204  BestGrowth = Growth;
1205  WaterIter = IP;
1206  DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber()
1207  << " Growth=" << Growth << '\n');
1208 
1209  // Keep looking unless it is perfect.
1210  if (BestGrowth == 0)
1211  return true;
1212  }
1213  if (IP == B)
1214  break;
1215  }
1216  return BestGrowth != ~0u;
1217 }
1218 
1219 /// createNewWater - No existing WaterList entry will work for
1220 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1221 /// block is used if in range, and the conditional branch munged so control
1222 /// flow is correct. Otherwise the block is split to create a hole with an
1223 /// unconditional branch around it. In either case NewMBB is set to a
1224 /// block following which the new island can be inserted (the WaterList
1225 /// is not adjusted).
1226 void MipsConstantIslands::createNewWater(unsigned CPUserIndex,
1227  unsigned UserOffset,
1228  MachineBasicBlock *&NewMBB) {
1229  CPUser &U = CPUsers[CPUserIndex];
1230  MachineInstr *UserMI = U.MI;
1231  MachineInstr *CPEMI = U.CPEMI;
1232  unsigned CPELogAlign = getCPELogAlign(*CPEMI);
1233  MachineBasicBlock *UserMBB = UserMI->getParent();
1234  const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()];
1235 
1236  // If the block does not end in an unconditional branch already, and if the
1237  // end of the block is within range, make new water there.
1238  if (BBHasFallthrough(UserMBB)) {
1239  // Size of branch to insert.
1240  unsigned Delta = 2;
1241  // Compute the offset where the CPE will begin.
1242  unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta;
1243 
1244  if (isOffsetInRange(UserOffset, CPEOffset, U)) {
1245  DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber()
1246  << format(", expected CPE offset %#x\n", CPEOffset));
1247  NewMBB = &*++UserMBB->getIterator();
1248  // Add an unconditional branch from UserMBB to fallthrough block. Record
1249  // it for branch lengthening; this new branch will not get out of range,
1250  // but if the preceding conditional branch is out of range, the targets
1251  // will be exchanged, and the altered branch may be out of range, so the
1252  // machinery has to know about it.
1253  int UncondBr = Mips::Bimm16;
1254  BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB);
1255  unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1256  ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1257  MaxDisp, false, UncondBr));
1258  BBInfo[UserMBB->getNumber()].Size += Delta;
1259  adjustBBOffsetsAfter(UserMBB);
1260  return;
1261  }
1262  }
1263 
1264  // What a big block. Find a place within the block to split it.
1265 
1266  // Try to split the block so it's fully aligned. Compute the latest split
1267  // point where we can add a 4-byte branch instruction, and then align to
1268  // LogAlign which is the largest possible alignment in the function.
1269  unsigned LogAlign = MF->getAlignment();
1270  assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry");
1271  unsigned BaseInsertOffset = UserOffset + U.getMaxDisp();
1272  DEBUG(dbgs() << format("Split in middle of big block before %#x",
1273  BaseInsertOffset));
1274 
1275  // The 4 in the following is for the unconditional branch we'll be inserting
1276  // Alignment of the island is handled
1277  // inside isOffsetInRange.
1278  BaseInsertOffset -= 4;
1279 
1280  DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset)
1281  << " la=" << LogAlign << '\n');
1282 
1283  // This could point off the end of the block if we've already got constant
1284  // pool entries following this block; only the last one is in the water list.
1285  // Back past any possible branches (allow for a conditional and a maximally
1286  // long unconditional).
1287  if (BaseInsertOffset + 8 >= UserBBI.postOffset()) {
1288  BaseInsertOffset = UserBBI.postOffset() - 8;
1289  DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset));
1290  }
1291  unsigned EndInsertOffset = BaseInsertOffset + 4 +
1292  CPEMI->getOperand(2).getImm();
1293  MachineBasicBlock::iterator MI = UserMI;
1294  ++MI;
1295  unsigned CPUIndex = CPUserIndex+1;
1296  unsigned NumCPUsers = CPUsers.size();
1297  //MachineInstr *LastIT = 0;
1298  for (unsigned Offset = UserOffset + TII->getInstSizeInBytes(*UserMI);
1299  Offset < BaseInsertOffset;
1300  Offset += TII->getInstSizeInBytes(*MI), MI = std::next(MI)) {
1301  assert(MI != UserMBB->end() && "Fell off end of block");
1302  if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) {
1303  CPUser &U = CPUsers[CPUIndex];
1304  if (!isOffsetInRange(Offset, EndInsertOffset, U)) {
1305  // Shift intertion point by one unit of alignment so it is within reach.
1306  BaseInsertOffset -= 1u << LogAlign;
1307  EndInsertOffset -= 1u << LogAlign;
1308  }
1309  // This is overly conservative, as we don't account for CPEMIs being
1310  // reused within the block, but it doesn't matter much. Also assume CPEs
1311  // are added in order with alignment padding. We may eventually be able
1312  // to pack the aligned CPEs better.
1313  EndInsertOffset += U.CPEMI->getOperand(2).getImm();
1314  CPUIndex++;
1315  }
1316  }
1317 
1318  NewMBB = splitBlockBeforeInstr(*--MI);
1319 }
1320 
1321 /// handleConstantPoolUser - Analyze the specified user, checking to see if it
1322 /// is out-of-range. If so, pick up the constant pool value and move it some
1323 /// place in-range. Return true if we changed any addresses (thus must run
1324 /// another pass of branch lengthening), false otherwise.
1325 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) {
1326  CPUser &U = CPUsers[CPUserIndex];
1327  MachineInstr *UserMI = U.MI;
1328  MachineInstr *CPEMI = U.CPEMI;
1329  unsigned CPI = CPEMI->getOperand(1).getIndex();
1330  unsigned Size = CPEMI->getOperand(2).getImm();
1331  // Compute this only once, it's expensive.
1332  unsigned UserOffset = getUserOffset(U);
1333 
1334  // See if the current entry is within range, or there is a clone of it
1335  // in range.
1336  int result = findInRangeCPEntry(U, UserOffset);
1337  if (result==1) return false;
1338  else if (result==2) return true;
1339 
1340 
1341  // Look for water where we can place this CPE.
1342  MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock();
1343  MachineBasicBlock *NewMBB;
1344  water_iterator IP;
1345  if (findAvailableWater(U, UserOffset, IP)) {
1346  DEBUG(dbgs() << "Found water in range\n");
1347  MachineBasicBlock *WaterBB = *IP;
1348 
1349  // If the original WaterList entry was "new water" on this iteration,
1350  // propagate that to the new island. This is just keeping NewWaterList
1351  // updated to match the WaterList, which will be updated below.
1352  if (NewWaterList.erase(WaterBB))
1353  NewWaterList.insert(NewIsland);
1354 
1355  // The new CPE goes before the following block (NewMBB).
1356  NewMBB = &*++WaterBB->getIterator();
1357  } else {
1358  // No water found.
1359  // we first see if a longer form of the instrucion could have reached
1360  // the constant. in that case we won't bother to split
1361  if (!NoLoadRelaxation) {
1362  result = findLongFormInRangeCPEntry(U, UserOffset);
1363  if (result != 0) return true;
1364  }
1365  DEBUG(dbgs() << "No water found\n");
1366  createNewWater(CPUserIndex, UserOffset, NewMBB);
1367 
1368  // splitBlockBeforeInstr adds to WaterList, which is important when it is
1369  // called while handling branches so that the water will be seen on the
1370  // next iteration for constant pools, but in this context, we don't want
1371  // it. Check for this so it will be removed from the WaterList.
1372  // Also remove any entry from NewWaterList.
1373  MachineBasicBlock *WaterBB = &*--NewMBB->getIterator();
1374  IP = find(WaterList, WaterBB);
1375  if (IP != WaterList.end())
1376  NewWaterList.erase(WaterBB);
1377 
1378  // We are adding new water. Update NewWaterList.
1379  NewWaterList.insert(NewIsland);
1380  }
1381 
1382  // Remove the original WaterList entry; we want subsequent insertions in
1383  // this vicinity to go after the one we're about to insert. This
1384  // considerably reduces the number of times we have to move the same CPE
1385  // more than once and is also important to ensure the algorithm terminates.
1386  if (IP != WaterList.end())
1387  WaterList.erase(IP);
1388 
1389  // Okay, we know we can put an island before NewMBB now, do it!
1390  MF->insert(NewMBB->getIterator(), NewIsland);
1391 
1392  // Update internal data structures to account for the newly inserted MBB.
1393  updateForInsertedWaterBlock(NewIsland);
1394 
1395  // Decrement the old entry, and remove it if refcount becomes 0.
1396  decrementCPEReferenceCount(CPI, CPEMI);
1397 
1398  // No existing clone of this CPE is within range.
1399  // We will be generating a new clone. Get a UID for it.
1400  unsigned ID = createPICLabelUId();
1401 
1402  // Now that we have an island to add the CPE to, clone the original CPE and
1403  // add it to the island.
1404  U.HighWaterMark = NewIsland;
1405  U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY))
1406  .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1407  CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1408  ++NumCPEs;
1409 
1410  // Mark the basic block as aligned as required by the const-pool entry.
1411  NewIsland->setAlignment(getCPELogAlign(*U.CPEMI));
1412 
1413  // Increase the size of the island block to account for the new entry.
1414  BBInfo[NewIsland->getNumber()].Size += Size;
1415  adjustBBOffsetsAfter(&*--NewIsland->getIterator());
1416 
1417  // Finally, change the CPI in the instruction operand to be ID.
1418  for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1419  if (UserMI->getOperand(i).isCPI()) {
1420  UserMI->getOperand(i).setIndex(ID);
1421  break;
1422  }
1423 
1424  DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI
1425  << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset));
1426 
1427  return true;
1428 }
1429 
1430 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update
1431 /// sizes and offsets of impacted basic blocks.
1432 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) {
1433  MachineBasicBlock *CPEBB = CPEMI->getParent();
1434  unsigned Size = CPEMI->getOperand(2).getImm();
1435  CPEMI->eraseFromParent();
1436  BBInfo[CPEBB->getNumber()].Size -= Size;
1437  // All succeeding offsets have the current size value added in, fix this.
1438  if (CPEBB->empty()) {
1439  BBInfo[CPEBB->getNumber()].Size = 0;
1440 
1441  // This block no longer needs to be aligned.
1442  CPEBB->setAlignment(0);
1443  } else
1444  // Entries are sorted by descending alignment, so realign from the front.
1445  CPEBB->setAlignment(getCPELogAlign(*CPEBB->begin()));
1446 
1447  adjustBBOffsetsAfter(CPEBB);
1448  // An island has only one predecessor BB and one successor BB. Check if
1449  // this BB's predecessor jumps directly to this BB's successor. This
1450  // shouldn't happen currently.
1451  assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1452  // FIXME: remove the empty blocks after all the work is done?
1453 }
1454 
1455 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts
1456 /// are zero.
1457 bool MipsConstantIslands::removeUnusedCPEntries() {
1458  unsigned MadeChange = false;
1459  for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1460  std::vector<CPEntry> &CPEs = CPEntries[i];
1461  for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1462  if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1463  removeDeadCPEMI(CPEs[j].CPEMI);
1464  CPEs[j].CPEMI = nullptr;
1465  MadeChange = true;
1466  }
1467  }
1468  }
1469  return MadeChange;
1470 }
1471 
1472 /// isBBInRange - Returns true if the distance between specific MI and
1473 /// specific BB can fit in MI's displacement field.
1474 bool MipsConstantIslands::isBBInRange
1475  (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) {
1476 
1477 unsigned PCAdj = 4;
1478 
1479  unsigned BrOffset = getOffsetOf(MI) + PCAdj;
1480  unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset;
1481 
1482  DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber()
1483  << " from BB#" << MI->getParent()->getNumber()
1484  << " max delta=" << MaxDisp
1485  << " from " << getOffsetOf(MI) << " to " << DestOffset
1486  << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1487 
1488  if (BrOffset <= DestOffset) {
1489  // Branch before the Dest.
1490  if (DestOffset-BrOffset <= MaxDisp)
1491  return true;
1492  } else {
1493  if (BrOffset-DestOffset <= MaxDisp)
1494  return true;
1495  }
1496  return false;
1497 }
1498 
1499 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far
1500 /// away to fit in its displacement field.
1501 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
1502  MachineInstr *MI = Br.MI;
1503  unsigned TargetOperand = branchTargetOperand(MI);
1504  MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1505 
1506  // Check to see if the DestBB is already in-range.
1507  if (isBBInRange(MI, DestBB, Br.MaxDisp))
1508  return false;
1509 
1510  if (!Br.isCond)
1511  return fixupUnconditionalBr(Br);
1512  return fixupConditionalBr(Br);
1513 }
1514 
1515 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is
1516 /// too far away to fit in its displacement field. If the LR register has been
1517 /// spilled in the epilogue, then we can use BL to implement a far jump.
1518 /// Otherwise, add an intermediate branch instruction to a branch.
1519 bool
1520 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
1521  MachineInstr *MI = Br.MI;
1522  MachineBasicBlock *MBB = MI->getParent();
1523  MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1524  // Use BL to implement far jump.
1525  unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2;
1526  if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) {
1527  Br.MaxDisp = BimmX16MaxDisp;
1528  MI->setDesc(TII->get(Mips::BimmX16));
1529  }
1530  else {
1531  // need to give the math a more careful look here
1532  // this is really a segment address and not
1533  // a PC relative address. FIXME. But I think that
1534  // just reducing the bits by 1 as I've done is correct.
1535  // The basic block we are branching too much be longword aligned.
1536  // we know that RA is saved because we always save it right now.
1537  // this requirement will be relaxed later but we also have an alternate
1538  // way to implement this that I will implement that does not need jal.
1539  // We should have a way to back out this alignment restriction if we "can" later.
1540  // but it is not harmful.
1541  //
1542  DestBB->setAlignment(2);
1543  Br.MaxDisp = ((1<<24)-1) * 2;
1544  MI->setDesc(TII->get(Mips::JalB16));
1545  }
1546  BBInfo[MBB->getNumber()].Size += 2;
1547  adjustBBOffsetsAfter(MBB);
1548  HasFarJump = true;
1549  ++NumUBrFixed;
1550 
1551  DEBUG(dbgs() << " Changed B to long jump " << *MI);
1552 
1553  return true;
1554 }
1555 
1556 
1557 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
1558 /// far away to fit in its displacement field. It is converted to an inverse
1559 /// conditional branch + an unconditional branch to the destination.
1560 bool
1561 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
1562  MachineInstr *MI = Br.MI;
1563  unsigned TargetOperand = branchTargetOperand(MI);
1564  MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
1565  unsigned Opcode = MI->getOpcode();
1566  unsigned LongFormOpcode = longformBranchOpcode(Opcode);
1567  unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode);
1568 
1569  // Check to see if the DestBB is already in-range.
1570  if (isBBInRange(MI, DestBB, LongFormMaxOff)) {
1571  Br.MaxDisp = LongFormMaxOff;
1572  MI->setDesc(TII->get(LongFormOpcode));
1573  return true;
1574  }
1575 
1576  // Add an unconditional branch to the destination and invert the branch
1577  // condition to jump over it:
1578  // bteqz L1
1579  // =>
1580  // bnez L2
1581  // b L1
1582  // L2:
1583 
1584  // If the branch is at the end of its MBB and that has a fall-through block,
1585  // direct the updated conditional branch to the fall-through block. Otherwise,
1586  // split the MBB before the next instruction.
1587  MachineBasicBlock *MBB = MI->getParent();
1588  MachineInstr *BMI = &MBB->back();
1589  bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1590  unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode);
1591 
1592  ++NumCBrFixed;
1593  if (BMI != MI) {
1594  if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) &&
1595  BMI->isUnconditionalBranch()) {
1596  // Last MI in the BB is an unconditional branch. Can we simply invert the
1597  // condition and swap destinations:
1598  // beqz L1
1599  // b L2
1600  // =>
1601  // bnez L2
1602  // b L1
1603  unsigned BMITargetOperand = branchTargetOperand(BMI);
1604  MachineBasicBlock *NewDest =
1605  BMI->getOperand(BMITargetOperand).getMBB();
1606  if (isBBInRange(MI, NewDest, Br.MaxDisp)) {
1607  DEBUG(dbgs() << " Invert Bcc condition and swap its destination with "
1608  << *BMI);
1609  MI->setDesc(TII->get(OppositeBranchOpcode));
1610  BMI->getOperand(BMITargetOperand).setMBB(DestBB);
1611  MI->getOperand(TargetOperand).setMBB(NewDest);
1612  return true;
1613  }
1614  }
1615  }
1616 
1617 
1618  if (NeedSplit) {
1619  splitBlockBeforeInstr(*MI);
1620  // No need for the branch to the next block. We're adding an unconditional
1621  // branch to the destination.
1622  int delta = TII->getInstSizeInBytes(MBB->back());
1623  BBInfo[MBB->getNumber()].Size -= delta;
1624  MBB->back().eraseFromParent();
1625  // BBInfo[SplitBB].Offset is wrong temporarily, fixed below
1626  }
1627  MachineBasicBlock *NextBB = &*++MBB->getIterator();
1628 
1629  DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber()
1630  << " also invert condition and change dest. to BB#"
1631  << NextBB->getNumber() << "\n");
1632 
1633  // Insert a new conditional branch and a new unconditional branch.
1634  // Also update the ImmBranch as well as adding a new entry for the new branch.
1635  if (MI->getNumExplicitOperands() == 2) {
1636  BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1637  .addReg(MI->getOperand(0).getReg())
1638  .addMBB(NextBB);
1639  } else {
1640  BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode))
1641  .addMBB(NextBB);
1642  }
1643  Br.MI = &MBB->back();
1644  BBInfo[MBB->getNumber()].Size += TII->getInstSizeInBytes(MBB->back());
1645  BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1646  BBInfo[MBB->getNumber()].Size += TII->getInstSizeInBytes(MBB->back());
1647  unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1648  ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1649 
1650  // Remove the old conditional branch. It may or may not still be in MBB.
1651  BBInfo[MI->getParent()->getNumber()].Size -= TII->getInstSizeInBytes(*MI);
1652  MI->eraseFromParent();
1653  adjustBBOffsetsAfter(MBB);
1654  return true;
1655 }
1656 
1657 
1658 void MipsConstantIslands::prescanForConstants() {
1659  unsigned J = 0;
1660  (void)J;
1662  MF->begin(), E = MF->end(); B != E; ++B) {
1664  B->instr_begin(), EB = B->instr_end(); I != EB; ++I) {
1665  switch(I->getDesc().getOpcode()) {
1666  case Mips::LwConstant32: {
1667  PrescannedForConstants = true;
1668  DEBUG(dbgs() << "constant island constant " << *I << "\n");
1669  J = I->getNumOperands();
1670  DEBUG(dbgs() << "num operands " << J << "\n");
1671  MachineOperand& Literal = I->getOperand(1);
1672  if (Literal.isImm()) {
1673  int64_t V = Literal.getImm();
1674  DEBUG(dbgs() << "literal " << V << "\n");
1675  Type *Int32Ty =
1676  Type::getInt32Ty(MF->getFunction()->getContext());
1677  const Constant *C = ConstantInt::get(Int32Ty, V);
1678  unsigned index = MCP->getConstantPoolIndex(C, 4);
1679  I->getOperand(2).ChangeToImmediate(index);
1680  DEBUG(dbgs() << "constant island constant " << *I << "\n");
1681  I->setDesc(TII->get(Mips::LwRxPcTcp16));
1682  I->RemoveOperand(1);
1683  I->RemoveOperand(1);
1684  I->addOperand(MachineOperand::CreateCPI(index, 0));
1685  I->addOperand(MachineOperand::CreateImm(4));
1686  }
1687  break;
1688  }
1689  default:
1690  break;
1691  }
1692  }
1693  }
1694 }
unsigned succ_size() const
const MachineFunction * getParent() const
Return the MachineFunction containing this basic block.
A parsed version of the target data layout string in and methods for querying it. ...
Definition: DataLayout.h:102
The MachineConstantPool class keeps track of constants referenced by a function which must be spilled...
static unsigned int branchTargetOperand(MachineInstr *MI)
static bool CompareMBBNumbers(const MachineBasicBlock *LHS, const MachineBasicBlock *RHS)
CompareMBBNumbers - Little predicate function to sort the WaterList by MBB ID.
STATISTIC(NumFunctions,"Total number of functions")
LLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
size_t i
void RenumberBlocks(MachineBasicBlock *MBBFrom=nullptr)
RenumberBlocks - This discards all of the MachineBasicBlock numbers and recomputes them...
MachineBasicBlock * getMBB() const
int getNumber() const
MachineBasicBlocks are uniquely numbered at the function level, unless they're not in a MachineFuncti...
void transferSuccessors(MachineBasicBlock *FromMBB)
Transfers all the successors from MBB to this machine basic block (i.e., copies all the successors Fr...
unsigned Offset
Offset - Distance from the beginning of the function to the beginning of this basic block...
static unsigned int branchMaxOffsets(unsigned int Opcode)
A debug info location.
Definition: DebugLoc.h:34
FunctionType * getType(LLVMContext &Context, ID id, ArrayRef< Type * > Tys=None)
Return the function type for an intrinsic.
Definition: Function.cpp:905
#define op(i)
void computeBlockSize(MachineFunction *MF, MachineBasicBlock *MBB, BasicBlockInfo &BBI)
void setAlignment(unsigned Align)
Set alignment of the basic block.
BasicBlockInfo - Information about the offset and size of a single basic block.
const TargetSubtargetInfo & getSubtarget() const
getSubtarget - Return the subtarget for which this machine code is being compiled.
This file declares the MachineConstantPool class which is an abstract constant pool to keep track of ...
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
const HexagonInstrInfo * TII
bool isImm() const
isImm - Tests if this is a MO_Immediate operand.
void eraseFromParent()
Unlink 'this' from the containing basic block and delete it.
std::vector< MachineBasicBlock * >::iterator succ_iterator
void setIndex(int Idx)
static cl::opt< bool > AlignConstantIslands("mips-align-constant-islands", cl::Hidden, cl::init(true), cl::desc("Align constant islands in code"))
const MachineInstrBuilder & addImm(int64_t Val) const
Add a new immediate operand.
unsigned getNumOperands() const
Access to explicit operands of the instruction.
Definition: MachineInstr.h:277
bool isCPI() const
isCPI - Tests if this is a MO_ConstantPoolIndex operand.
#define F(x, y, z)
Definition: MD5.cpp:51
MachineBasicBlock * MBB
Function Alias Analysis false
static GCRegistry::Add< OcamlGC > B("ocaml","ocaml 3.10-compatible GC")
int64_t getImm() const
const BasicBlock * getBasicBlock() const
Return the LLVM basic block that this instance corresponded to originally.
unsigned getOpcode() const
Returns the opcode of this MachineInstr.
Definition: MachineInstr.h:273
static GCRegistry::Add< CoreCLRGC > E("coreclr","CoreCLR-compatible GC")
const MachineBasicBlock * getParent() const
Definition: MachineInstr.h:131
format_object< Ts...> format(const char *Fmt, const Ts &...Vals)
These are helper functions used to produce formatted output.
Definition: Format.h:124
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)
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)
MachineInstrBuilder BuildMI(MachineFunction &MF, const DebugLoc &DL, const MCInstrDesc &MCID)
Builder interface. Specify how to create the initial instruction itself.
#define rc(i)
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:395
static unsigned int longformBranchOpcode(unsigned int Opcode)
constexpr bool isPowerOf2_32(uint32_t Value)
isPowerOf2_32 - This function returns true if the argument is a power of two > 0. ...
Definition: MathExtras.h:399
static MachineOperand CreateCPI(unsigned Idx, int Offset, unsigned char TargetFlags=0)
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
static bool BBIsJumpedOver(MachineBasicBlock *MBB)
BBIsJumpedOver - Return true of the specified basic block's only predecessor unconditionally branches...
This is an important base class in LLVM.
Definition: Constant.h:42
SmallSet - This maintains a set of unique values, optimizing for the case when the set is small (less...
Definition: SmallSet.h:36
const MachineOperand & getOperand(unsigned i) const
Definition: MachineInstr.h:279
void setMBB(MachineBasicBlock *MBB)
unsigned getNumExplicitOperands() const
Returns the number of non-implicit operands.
uint32_t Offset
void neg(uint64_t &Value)
FunctionPass class - This class is used to implement most global optimizations.
Definition: Pass.h:298
FunctionPass * createMipsConstantIslandPass()
Returns a pass that converts branches to long branches.
self_iterator getIterator()
Definition: ilist_node.h:81
MachineConstantPool * getConstantPool()
getConstantPool - Return the constant pool object for the current function.
static unsigned getUnconditionalBrDisp(int Opc)
getUnconditionalBrDisp - Returns the maximum displacement that can fit in the specific unconditional ...
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
static bool useConstantIslands()
Iterator for intrusive lists based on ilist_node.
void addSuccessor(MachineBasicBlock *Succ, BranchProbability Prob=BranchProbability::getUnknown())
Add Succ as a successor of this MachineBasicBlock.
void setDesc(const MCInstrDesc &tid)
Replace the instruction descriptor (thus opcode) of the current instruction with a new one...
auto find(R &&Range, const T &Val) -> decltype(std::begin(Range))
Provide wrappers to std::find which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:757
uint64_t getTypeAllocSize(Type *Ty) const
Returns the offset in bytes between successive objects of the specified type, including alignment pad...
Definition: DataLayout.h:408
MachineOperand class - Representation of each machine instruction operand.
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:843
unsigned Size
Size - Size of the basic block in bytes.
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:558
static GCRegistry::Add< ShadowStackGC > C("shadow-stack","Very portable GC for uncooperative code generators")
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
unsigned Log2_32(uint32_t Value)
Log2_32 - This function returns the floor log base 2 of the specified value, -1 if the value is zero...
Definition: MathExtras.h:513
MachineFunctionProperties & set(Property P)
Representation of each machine instruction.
Definition: MachineInstr.h:52
void splice(iterator Where, MachineBasicBlock *Other, iterator From)
Take an instruction from MBB 'Other' at the position From, and insert it into this MBB right before '...
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:169
static bool BBHasFallthrough(MachineBasicBlock *MBB)
BBHasFallthrough - Return true if the specified basic block can fallthrough into the block immediatel...
const MachineInstrBuilder & addConstantPoolIndex(unsigned Idx, int Offset=0, unsigned char TargetFlags=0) const
static MachineOperand CreateImm(int64_t Val)
void push_back(MachineInstr *MI)
#define I(x, y, z)
Definition: MD5.cpp:54
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:135
MipsFunctionInfo - This class is derived from MachineFunction private Mips target-specific informatio...
instr_iterator insert(instr_iterator I, MachineInstr *M)
Insert MI into the instruction list before I, possibly inside a bundle.
unsigned getReg() const
getReg - Returns the register number.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
uint64_t OffsetToAlignment(uint64_t Value, uint64_t Align)
Returns the offset to the next integer (mod 2**64) that is greater than or equal to Value and is a mu...
Definition: MathExtras.h:701
#define DEBUG(X)
Definition: Debug.h:100
IRTranslator LLVM IR MI
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:47
unsigned pred_size() const
Properties which a MachineFunction may have at a given point in time.
IntegerType * Int32Ty
bool isUnconditionalBranch(QueryType Type=AnyInBundle) const
Return true if this is a branch which always transfers control flow to some other block...
Definition: MachineInstr.h:470
unsigned postOffset(unsigned LogAlign=0) const
Compute the offset immediately following this block.
unsigned getAlignment() const
Return alignment of the basic block.