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" 25 #include "MCTargetDesc/MipsBaseInfo.h" 26 #include "Mips16InstrInfo.h" 27 #include "MipsMachineFunction.h" 28 #include "MipsTargetMachine.h" 29 #include "llvm/ADT/Statistic.h" 30 #include "llvm/CodeGen/MachineBasicBlock.h" 31 #include "llvm/CodeGen/MachineConstantPool.h" 32 #include "llvm/CodeGen/MachineFunctionPass.h" 33 #include "llvm/CodeGen/MachineInstrBuilder.h" 34 #include "llvm/CodeGen/MachineRegisterInfo.h" 35 #include "llvm/IR/Function.h" 36 #include "llvm/IR/InstIterator.h" 37 #include "llvm/Support/CommandLine.h" 38 #include "llvm/Support/Debug.h" 39 #include "llvm/Support/Format.h" 40 #include "llvm/Support/MathExtras.h" 41 #include "llvm/Support/raw_ostream.h" 42 #include "llvm/Target/TargetInstrInfo.h" 43 #include "llvm/Target/TargetMachine.h" 44 #include "llvm/Target/TargetRegisterInfo.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 // 65 static cl::opt<int> ConstantIslandsSmallOffset( 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 // 75 static cl::opt<bool> NoLoadRelaxation( 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 bool isUnconditionalBranch(unsigned int Opcode) { 101 switch (Opcode) { 102 default: return false; 103 case Mips::Bimm16: 104 case Mips::BimmX16: 105 case Mips::JalB16: 106 return true; 107 } 108 } 109 110 static unsigned int longformBranchOpcode(unsigned int Opcode) { 111 switch (Opcode) { 112 case Mips::Bimm16: 113 case Mips::BimmX16: 114 return Mips::BimmX16; 115 case Mips::Bteqz16: 116 case Mips::BteqzX16: 117 return Mips::BteqzX16; 118 case Mips::Btnez16: 119 case Mips::BtnezX16: 120 return Mips::BtnezX16; 121 case Mips::JalB16: 122 return Mips::JalB16; 123 case Mips::BeqzRxImm16: 124 case Mips::BeqzRxImmX16: 125 return Mips::BeqzRxImmX16; 126 case Mips::BnezRxImm16: 127 case Mips::BnezRxImmX16: 128 return Mips::BnezRxImmX16; 129 } 130 llvm_unreachable("Unknown branch type"); 131 } 132 133 // 134 // FIXME: need to go through this whole constant islands port and check the math 135 // for branch ranges and clean this up and make some functions to calculate things 136 // that are done many times identically. 137 // Need to refactor some of the code to call this routine. 138 // 139 static unsigned int branchMaxOffsets(unsigned int Opcode) { 140 unsigned Bits, Scale; 141 switch (Opcode) { 142 case Mips::Bimm16: 143 Bits = 11; 144 Scale = 2; 145 break; 146 case Mips::BimmX16: 147 Bits = 16; 148 Scale = 2; 149 break; 150 case Mips::BeqzRxImm16: 151 Bits = 8; 152 Scale = 2; 153 break; 154 case Mips::BeqzRxImmX16: 155 Bits = 16; 156 Scale = 2; 157 break; 158 case Mips::BnezRxImm16: 159 Bits = 8; 160 Scale = 2; 161 break; 162 case Mips::BnezRxImmX16: 163 Bits = 16; 164 Scale = 2; 165 break; 166 case Mips::Bteqz16: 167 Bits = 8; 168 Scale = 2; 169 break; 170 case Mips::BteqzX16: 171 Bits = 16; 172 Scale = 2; 173 break; 174 case Mips::Btnez16: 175 Bits = 8; 176 Scale = 2; 177 break; 178 case Mips::BtnezX16: 179 Bits = 16; 180 Scale = 2; 181 break; 182 default: 183 llvm_unreachable("Unknown branch type"); 184 } 185 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale; 186 return MaxOffs; 187 } 188 189 namespace { 190 191 192 typedef MachineBasicBlock::iterator Iter; 193 typedef MachineBasicBlock::reverse_iterator ReverseIter; 194 195 /// MipsConstantIslands - Due to limited PC-relative displacements, Mips 196 /// requires constant pool entries to be scattered among the instructions 197 /// inside a function. To do this, it completely ignores the normal LLVM 198 /// constant pool; instead, it places constants wherever it feels like with 199 /// special instructions. 200 /// 201 /// The terminology used in this pass includes: 202 /// Islands - Clumps of constants placed in the function. 203 /// Water - Potential places where an island could be formed. 204 /// CPE - A constant pool entry that has been placed somewhere, which 205 /// tracks a list of users. 206 207 class MipsConstantIslands : public MachineFunctionPass { 208 209 /// BasicBlockInfo - Information about the offset and size of a single 210 /// basic block. 211 struct BasicBlockInfo { 212 /// Offset - Distance from the beginning of the function to the beginning 213 /// of this basic block. 214 /// 215 /// Offsets are computed assuming worst case padding before an aligned 216 /// block. This means that subtracting basic block offsets always gives a 217 /// conservative estimate of the real distance which may be smaller. 218 /// 219 /// Because worst case padding is used, the computed offset of an aligned 220 /// block may not actually be aligned. 221 unsigned Offset; 222 223 /// Size - Size of the basic block in bytes. If the block contains 224 /// inline assembly, this is a worst case estimate. 225 /// 226 /// The size does not include any alignment padding whether from the 227 /// beginning of the block, or from an aligned jump table at the end. 228 unsigned Size; 229 230 // FIXME: ignore LogAlign for this patch 231 // 232 unsigned postOffset(unsigned LogAlign = 0) const { 233 unsigned PO = Offset + Size; 234 return PO; 235 } 236 237 BasicBlockInfo() : Offset(0), Size(0) {} 238 239 }; 240 241 std::vector<BasicBlockInfo> BBInfo; 242 243 /// WaterList - A sorted list of basic blocks where islands could be placed 244 /// (i.e. blocks that don't fall through to the following block, due 245 /// to a return, unreachable, or unconditional branch). 246 std::vector<MachineBasicBlock*> WaterList; 247 248 /// NewWaterList - The subset of WaterList that was created since the 249 /// previous iteration by inserting unconditional branches. 250 SmallSet<MachineBasicBlock*, 4> NewWaterList; 251 252 typedef std::vector<MachineBasicBlock*>::iterator water_iterator; 253 254 /// CPUser - One user of a constant pool, keeping the machine instruction 255 /// pointer, the constant pool being referenced, and the max displacement 256 /// allowed from the instruction to the CP. The HighWaterMark records the 257 /// highest basic block where a new CPEntry can be placed. To ensure this 258 /// pass terminates, the CP entries are initially placed at the end of the 259 /// function and then move monotonically to lower addresses. The 260 /// exception to this rule is when the current CP entry for a particular 261 /// CPUser is out of range, but there is another CP entry for the same 262 /// constant value in range. We want to use the existing in-range CP 263 /// entry, but if it later moves out of range, the search for new water 264 /// should resume where it left off. The HighWaterMark is used to record 265 /// that point. 266 struct CPUser { 267 MachineInstr *MI; 268 MachineInstr *CPEMI; 269 MachineBasicBlock *HighWaterMark; 270 private: 271 unsigned MaxDisp; 272 unsigned LongFormMaxDisp; // mips16 has 16/32 bit instructions 273 // with different displacements 274 unsigned LongFormOpcode; 275 public: 276 bool NegOk; 277 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp, 278 bool neg, 279 unsigned longformmaxdisp, unsigned longformopcode) 280 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), 281 LongFormMaxDisp(longformmaxdisp), LongFormOpcode(longformopcode), 282 NegOk(neg){ 283 HighWaterMark = CPEMI->getParent(); 284 } 285 /// getMaxDisp - Returns the maximum displacement supported by MI. 286 unsigned getMaxDisp() const { 287 unsigned xMaxDisp = ConstantIslandsSmallOffset? 288 ConstantIslandsSmallOffset: MaxDisp; 289 return xMaxDisp; 290 } 291 void setMaxDisp(unsigned val) { 292 MaxDisp = val; 293 } 294 unsigned getLongFormMaxDisp() const { 295 return LongFormMaxDisp; 296 } 297 unsigned getLongFormOpcode() const { 298 return LongFormOpcode; 299 } 300 }; 301 302 /// CPUsers - Keep track of all of the machine instructions that use various 303 /// constant pools and their max displacement. 304 std::vector<CPUser> CPUsers; 305 306 /// CPEntry - One per constant pool entry, keeping the machine instruction 307 /// pointer, the constpool index, and the number of CPUser's which 308 /// reference this entry. 309 struct CPEntry { 310 MachineInstr *CPEMI; 311 unsigned CPI; 312 unsigned RefCount; 313 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0) 314 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {} 315 }; 316 317 /// CPEntries - Keep track of all of the constant pool entry machine 318 /// instructions. For each original constpool index (i.e. those that 319 /// existed upon entry to this pass), it keeps a vector of entries. 320 /// Original elements are cloned as we go along; the clones are 321 /// put in the vector of the original element, but have distinct CPIs. 322 std::vector<std::vector<CPEntry> > CPEntries; 323 324 /// ImmBranch - One per immediate branch, keeping the machine instruction 325 /// pointer, conditional or unconditional, the max displacement, 326 /// and (if isCond is true) the corresponding unconditional branch 327 /// opcode. 328 struct ImmBranch { 329 MachineInstr *MI; 330 unsigned MaxDisp : 31; 331 bool isCond : 1; 332 int UncondBr; 333 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr) 334 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {} 335 }; 336 337 /// ImmBranches - Keep track of all the immediate branch instructions. 338 /// 339 std::vector<ImmBranch> ImmBranches; 340 341 /// HasFarJump - True if any far jump instruction has been emitted during 342 /// the branch fix up pass. 343 bool HasFarJump; 344 345 const TargetMachine &TM; 346 bool IsPIC; 347 const MipsSubtarget *STI; 348 const Mips16InstrInfo *TII; 349 MipsFunctionInfo *MFI; 350 MachineFunction *MF; 351 MachineConstantPool *MCP; 352 353 unsigned PICLabelUId; 354 bool PrescannedForConstants; 355 356 void initPICLabelUId(unsigned UId) { 357 PICLabelUId = UId; 358 } 359 360 361 unsigned createPICLabelUId() { 362 return PICLabelUId++; 363 } 364 365 public: 366 static char ID; 367 MipsConstantIslands(TargetMachine &tm) 368 : MachineFunctionPass(ID), TM(tm), 369 IsPIC(TM.getRelocationModel() == Reloc::PIC_), STI(nullptr), 370 MF(nullptr), MCP(nullptr), PrescannedForConstants(false) {} 371 372 const char *getPassName() const override { 373 return "Mips Constant Islands"; 374 } 375 376 bool runOnMachineFunction(MachineFunction &F) override; 377 378 void doInitialPlacement(std::vector<MachineInstr*> &CPEMIs); 379 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI); 380 unsigned getCPELogAlign(const MachineInstr *CPEMI); 381 void initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs); 382 unsigned getOffsetOf(MachineInstr *MI) const; 383 unsigned getUserOffset(CPUser&) const; 384 void dumpBBs(); 385 386 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset, 387 unsigned Disp, bool NegativeOK); 388 bool isOffsetInRange(unsigned UserOffset, unsigned TrialOffset, 389 const CPUser &U); 390 391 void computeBlockSize(MachineBasicBlock *MBB); 392 MachineBasicBlock *splitBlockBeforeInstr(MachineInstr *MI); 393 void updateForInsertedWaterBlock(MachineBasicBlock *NewBB); 394 void adjustBBOffsetsAfter(MachineBasicBlock *BB); 395 bool decrementCPEReferenceCount(unsigned CPI, MachineInstr* CPEMI); 396 int findInRangeCPEntry(CPUser& U, unsigned UserOffset); 397 int findLongFormInRangeCPEntry(CPUser& U, unsigned UserOffset); 398 bool findAvailableWater(CPUser&U, unsigned UserOffset, 399 water_iterator &WaterIter); 400 void createNewWater(unsigned CPUserIndex, unsigned UserOffset, 401 MachineBasicBlock *&NewMBB); 402 bool handleConstantPoolUser(unsigned CPUserIndex); 403 void removeDeadCPEMI(MachineInstr *CPEMI); 404 bool removeUnusedCPEntries(); 405 bool isCPEntryInRange(MachineInstr *MI, unsigned UserOffset, 406 MachineInstr *CPEMI, unsigned Disp, bool NegOk, 407 bool DoDump = false); 408 bool isWaterInRange(unsigned UserOffset, MachineBasicBlock *Water, 409 CPUser &U, unsigned &Growth); 410 bool isBBInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp); 411 bool fixupImmediateBr(ImmBranch &Br); 412 bool fixupConditionalBr(ImmBranch &Br); 413 bool fixupUnconditionalBr(ImmBranch &Br); 414 415 void prescanForConstants(); 416 417 private: 418 419 }; 420 421 char MipsConstantIslands::ID = 0; 422 } // end of anonymous namespace 423 424 bool MipsConstantIslands::isOffsetInRange 425 (unsigned UserOffset, unsigned TrialOffset, 426 const CPUser &U) { 427 return isOffsetInRange(UserOffset, TrialOffset, 428 U.getMaxDisp(), U.NegOk); 429 } 430 /// print block size and offset information - debugging 431 void MipsConstantIslands::dumpBBs() { 432 DEBUG({ 433 for (unsigned J = 0, E = BBInfo.size(); J !=E; ++J) { 434 const BasicBlockInfo &BBI = BBInfo[J]; 435 dbgs() << format("%08x BB#%u\t", BBI.Offset, J) 436 << format(" size=%#x\n", BBInfo[J].Size); 437 } 438 }); 439 } 440 /// createMipsLongBranchPass - Returns a pass that converts branches to long 441 /// branches. 442 FunctionPass *llvm::createMipsConstantIslandPass(MipsTargetMachine &tm) { 443 return new MipsConstantIslands(tm); 444 } 445 446 bool MipsConstantIslands::runOnMachineFunction(MachineFunction &mf) { 447 // The intention is for this to be a mips16 only pass for now 448 // FIXME: 449 MF = &mf; 450 MCP = mf.getConstantPool(); 451 STI = &static_cast<const MipsSubtarget &>(mf.getSubtarget()); 452 DEBUG(dbgs() << "constant island machine function " << "\n"); 453 if (!STI->inMips16Mode() || !MipsSubtarget::useConstantIslands()) { 454 return false; 455 } 456 TII = (const Mips16InstrInfo *)STI->getInstrInfo(); 457 MFI = MF->getInfo<MipsFunctionInfo>(); 458 DEBUG(dbgs() << "constant island processing " << "\n"); 459 // 460 // will need to make predermination if there is any constants we need to 461 // put in constant islands. TBD. 462 // 463 if (!PrescannedForConstants) prescanForConstants(); 464 465 HasFarJump = false; 466 // This pass invalidates liveness information when it splits basic blocks. 467 MF->getRegInfo().invalidateLiveness(); 468 469 // Renumber all of the machine basic blocks in the function, guaranteeing that 470 // the numbers agree with the position of the block in the function. 471 MF->RenumberBlocks(); 472 473 bool MadeChange = false; 474 475 // Perform the initial placement of the constant pool entries. To start with, 476 // we put them all at the end of the function. 477 std::vector<MachineInstr*> CPEMIs; 478 if (!MCP->isEmpty()) 479 doInitialPlacement(CPEMIs); 480 481 /// The next UID to take is the first unused one. 482 initPICLabelUId(CPEMIs.size()); 483 484 // Do the initial scan of the function, building up information about the 485 // sizes of each block, the location of all the water, and finding all of the 486 // constant pool users. 487 initializeFunctionInfo(CPEMIs); 488 CPEMIs.clear(); 489 DEBUG(dumpBBs()); 490 491 /// Remove dead constant pool entries. 492 MadeChange |= removeUnusedCPEntries(); 493 494 // Iteratively place constant pool entries and fix up branches until there 495 // is no change. 496 unsigned NoCPIters = 0, NoBRIters = 0; 497 (void)NoBRIters; 498 while (true) { 499 DEBUG(dbgs() << "Beginning CP iteration #" << NoCPIters << '\n'); 500 bool CPChange = false; 501 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) 502 CPChange |= handleConstantPoolUser(i); 503 if (CPChange && ++NoCPIters > 30) 504 report_fatal_error("Constant Island pass failed to converge!"); 505 DEBUG(dumpBBs()); 506 507 // Clear NewWaterList now. If we split a block for branches, it should 508 // appear as "new water" for the next iteration of constant pool placement. 509 NewWaterList.clear(); 510 511 DEBUG(dbgs() << "Beginning BR iteration #" << NoBRIters << '\n'); 512 bool BRChange = false; 513 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) 514 BRChange |= fixupImmediateBr(ImmBranches[i]); 515 if (BRChange && ++NoBRIters > 30) 516 report_fatal_error("Branch Fix Up pass failed to converge!"); 517 DEBUG(dumpBBs()); 518 if (!CPChange && !BRChange) 519 break; 520 MadeChange = true; 521 } 522 523 DEBUG(dbgs() << '\n'; dumpBBs()); 524 525 BBInfo.clear(); 526 WaterList.clear(); 527 CPUsers.clear(); 528 CPEntries.clear(); 529 ImmBranches.clear(); 530 return MadeChange; 531 } 532 533 /// doInitialPlacement - Perform the initial placement of the constant pool 534 /// entries. To start with, we put them all at the end of the function. 535 void 536 MipsConstantIslands::doInitialPlacement(std::vector<MachineInstr*> &CPEMIs) { 537 // Create the basic block to hold the CPE's. 538 MachineBasicBlock *BB = MF->CreateMachineBasicBlock(); 539 MF->push_back(BB); 540 541 542 // MachineConstantPool measures alignment in bytes. We measure in log2(bytes). 543 unsigned MaxAlign = Log2_32(MCP->getConstantPoolAlignment()); 544 545 // Mark the basic block as required by the const-pool. 546 // If AlignConstantIslands isn't set, use 4-byte alignment for everything. 547 BB->setAlignment(AlignConstantIslands ? MaxAlign : 2); 548 549 // The function needs to be as aligned as the basic blocks. The linker may 550 // move functions around based on their alignment. 551 MF->ensureAlignment(BB->getAlignment()); 552 553 // Order the entries in BB by descending alignment. That ensures correct 554 // alignment of all entries as long as BB is sufficiently aligned. Keep 555 // track of the insertion point for each alignment. We are going to bucket 556 // sort the entries as they are created. 557 SmallVector<MachineBasicBlock::iterator, 8> InsPoint(MaxAlign + 1, BB->end()); 558 559 // Add all of the constants from the constant pool to the end block, use an 560 // identity mapping of CPI's to CPE's. 561 const std::vector<MachineConstantPoolEntry> &CPs = MCP->getConstants(); 562 563 const DataLayout &TD = MF->getDataLayout(); 564 for (unsigned i = 0, e = CPs.size(); i != e; ++i) { 565 unsigned Size = TD.getTypeAllocSize(CPs[i].getType()); 566 assert(Size >= 4 && "Too small constant pool entry"); 567 unsigned Align = CPs[i].getAlignment(); 568 assert(isPowerOf2_32(Align) && "Invalid alignment"); 569 // Verify that all constant pool entries are a multiple of their alignment. 570 // If not, we would have to pad them out so that instructions stay aligned. 571 assert((Size % Align) == 0 && "CP Entry not multiple of 4 bytes!"); 572 573 // Insert CONSTPOOL_ENTRY before entries with a smaller alignment. 574 unsigned LogAlign = Log2_32(Align); 575 MachineBasicBlock::iterator InsAt = InsPoint[LogAlign]; 576 577 MachineInstr *CPEMI = 578 BuildMI(*BB, InsAt, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY)) 579 .addImm(i).addConstantPoolIndex(i).addImm(Size); 580 581 CPEMIs.push_back(CPEMI); 582 583 // Ensure that future entries with higher alignment get inserted before 584 // CPEMI. This is bucket sort with iterators. 585 for (unsigned a = LogAlign + 1; a <= MaxAlign; ++a) 586 if (InsPoint[a] == InsAt) 587 InsPoint[a] = CPEMI; 588 // Add a new CPEntry, but no corresponding CPUser yet. 589 CPEntries.emplace_back(1, CPEntry(CPEMI, i)); 590 ++NumCPEs; 591 DEBUG(dbgs() << "Moved CPI#" << i << " to end of function, size = " 592 << Size << ", align = " << Align <<'\n'); 593 } 594 DEBUG(BB->dump()); 595 } 596 597 /// BBHasFallthrough - Return true if the specified basic block can fallthrough 598 /// into the block immediately after it. 599 static bool BBHasFallthrough(MachineBasicBlock *MBB) { 600 // Get the next machine basic block in the function. 601 MachineFunction::iterator MBBI = MBB->getIterator(); 602 // Can't fall off end of function. 603 if (std::next(MBBI) == MBB->getParent()->end()) 604 return false; 605 606 MachineBasicBlock *NextBB = &*std::next(MBBI); 607 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(), 608 E = MBB->succ_end(); I != E; ++I) 609 if (*I == NextBB) 610 return true; 611 612 return false; 613 } 614 615 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI, 616 /// look up the corresponding CPEntry. 617 MipsConstantIslands::CPEntry 618 *MipsConstantIslands::findConstPoolEntry(unsigned CPI, 619 const MachineInstr *CPEMI) { 620 std::vector<CPEntry> &CPEs = CPEntries[CPI]; 621 // Number of entries per constpool index should be small, just do a 622 // linear search. 623 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) { 624 if (CPEs[i].CPEMI == CPEMI) 625 return &CPEs[i]; 626 } 627 return nullptr; 628 } 629 630 /// getCPELogAlign - Returns the required alignment of the constant pool entry 631 /// represented by CPEMI. Alignment is measured in log2(bytes) units. 632 unsigned MipsConstantIslands::getCPELogAlign(const MachineInstr *CPEMI) { 633 assert(CPEMI && CPEMI->getOpcode() == Mips::CONSTPOOL_ENTRY); 634 635 // Everything is 4-byte aligned unless AlignConstantIslands is set. 636 if (!AlignConstantIslands) 637 return 2; 638 639 unsigned CPI = CPEMI->getOperand(1).getIndex(); 640 assert(CPI < MCP->getConstants().size() && "Invalid constant pool index."); 641 unsigned Align = MCP->getConstants()[CPI].getAlignment(); 642 assert(isPowerOf2_32(Align) && "Invalid CPE alignment"); 643 return Log2_32(Align); 644 } 645 646 /// initializeFunctionInfo - Do the initial scan of the function, building up 647 /// information about the sizes of each block, the location of all the water, 648 /// and finding all of the constant pool users. 649 void MipsConstantIslands:: 650 initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) { 651 BBInfo.clear(); 652 BBInfo.resize(MF->getNumBlockIDs()); 653 654 // First thing, compute the size of all basic blocks, and see if the function 655 // has any inline assembly in it. If so, we have to be conservative about 656 // alignment assumptions, as we don't know for sure the size of any 657 // instructions in the inline assembly. 658 for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I) 659 computeBlockSize(&*I); 660 661 662 // Compute block offsets. 663 adjustBBOffsetsAfter(&MF->front()); 664 665 // Now go back through the instructions and build up our data structures. 666 for (MachineFunction::iterator MBBI = MF->begin(), E = MF->end(); 667 MBBI != E; ++MBBI) { 668 MachineBasicBlock &MBB = *MBBI; 669 670 // If this block doesn't fall through into the next MBB, then this is 671 // 'water' that a constant pool island could be placed. 672 if (!BBHasFallthrough(&MBB)) 673 WaterList.push_back(&MBB); 674 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); 675 I != E; ++I) { 676 if (I->isDebugValue()) 677 continue; 678 679 int Opc = I->getOpcode(); 680 if (I->isBranch()) { 681 bool isCond = false; 682 unsigned Bits = 0; 683 unsigned Scale = 1; 684 int UOpc = Opc; 685 switch (Opc) { 686 default: 687 continue; // Ignore other branches for now 688 case Mips::Bimm16: 689 Bits = 11; 690 Scale = 2; 691 isCond = false; 692 break; 693 case Mips::BimmX16: 694 Bits = 16; 695 Scale = 2; 696 isCond = false; 697 break; 698 case Mips::BeqzRxImm16: 699 UOpc=Mips::Bimm16; 700 Bits = 8; 701 Scale = 2; 702 isCond = true; 703 break; 704 case Mips::BeqzRxImmX16: 705 UOpc=Mips::Bimm16; 706 Bits = 16; 707 Scale = 2; 708 isCond = true; 709 break; 710 case Mips::BnezRxImm16: 711 UOpc=Mips::Bimm16; 712 Bits = 8; 713 Scale = 2; 714 isCond = true; 715 break; 716 case Mips::BnezRxImmX16: 717 UOpc=Mips::Bimm16; 718 Bits = 16; 719 Scale = 2; 720 isCond = true; 721 break; 722 case Mips::Bteqz16: 723 UOpc=Mips::Bimm16; 724 Bits = 8; 725 Scale = 2; 726 isCond = true; 727 break; 728 case Mips::BteqzX16: 729 UOpc=Mips::Bimm16; 730 Bits = 16; 731 Scale = 2; 732 isCond = true; 733 break; 734 case Mips::Btnez16: 735 UOpc=Mips::Bimm16; 736 Bits = 8; 737 Scale = 2; 738 isCond = true; 739 break; 740 case Mips::BtnezX16: 741 UOpc=Mips::Bimm16; 742 Bits = 16; 743 Scale = 2; 744 isCond = true; 745 break; 746 } 747 // Record this immediate branch. 748 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale; 749 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc)); 750 } 751 752 if (Opc == Mips::CONSTPOOL_ENTRY) 753 continue; 754 755 756 // Scan the instructions for constant pool operands. 757 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) 758 if (I->getOperand(op).isCPI()) { 759 760 // We found one. The addressing mode tells us the max displacement 761 // from the PC that this instruction permits. 762 763 // Basic size info comes from the TSFlags field. 764 unsigned Bits = 0; 765 unsigned Scale = 1; 766 bool NegOk = false; 767 unsigned LongFormBits = 0; 768 unsigned LongFormScale = 0; 769 unsigned LongFormOpcode = 0; 770 switch (Opc) { 771 default: 772 llvm_unreachable("Unknown addressing mode for CP reference!"); 773 case Mips::LwRxPcTcp16: 774 Bits = 8; 775 Scale = 4; 776 LongFormOpcode = Mips::LwRxPcTcpX16; 777 LongFormBits = 14; 778 LongFormScale = 1; 779 break; 780 case Mips::LwRxPcTcpX16: 781 Bits = 14; 782 Scale = 1; 783 NegOk = true; 784 break; 785 } 786 // Remember that this is a user of a CP entry. 787 unsigned CPI = I->getOperand(op).getIndex(); 788 MachineInstr *CPEMI = CPEMIs[CPI]; 789 unsigned MaxOffs = ((1 << Bits)-1) * Scale; 790 unsigned LongFormMaxOffs = ((1 << LongFormBits)-1) * LongFormScale; 791 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk, 792 LongFormMaxOffs, LongFormOpcode)); 793 794 // Increment corresponding CPEntry reference count. 795 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI); 796 assert(CPE && "Cannot find a corresponding CPEntry!"); 797 CPE->RefCount++; 798 799 // Instructions can only use one CP entry, don't bother scanning the 800 // rest of the operands. 801 break; 802 803 } 804 805 } 806 } 807 808 } 809 810 /// computeBlockSize - Compute the size and some alignment information for MBB. 811 /// This function updates BBInfo directly. 812 void MipsConstantIslands::computeBlockSize(MachineBasicBlock *MBB) { 813 BasicBlockInfo &BBI = BBInfo[MBB->getNumber()]; 814 BBI.Size = 0; 815 816 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E; 817 ++I) 818 BBI.Size += TII->GetInstSizeInBytes(I); 819 820 } 821 822 /// getOffsetOf - Return the current offset of the specified machine instruction 823 /// from the start of the function. This offset changes as stuff is moved 824 /// around inside the function. 825 unsigned MipsConstantIslands::getOffsetOf(MachineInstr *MI) const { 826 MachineBasicBlock *MBB = MI->getParent(); 827 828 // The offset is composed of two things: the sum of the sizes of all MBB's 829 // before this instruction's block, and the offset from the start of the block 830 // it is in. 831 unsigned Offset = BBInfo[MBB->getNumber()].Offset; 832 833 // Sum instructions before MI in MBB. 834 for (MachineBasicBlock::iterator I = MBB->begin(); &*I != MI; ++I) { 835 assert(I != MBB->end() && "Didn't find MI in its own basic block?"); 836 Offset += TII->GetInstSizeInBytes(I); 837 } 838 return Offset; 839 } 840 841 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB 842 /// ID. 843 static bool CompareMBBNumbers(const MachineBasicBlock *LHS, 844 const MachineBasicBlock *RHS) { 845 return LHS->getNumber() < RHS->getNumber(); 846 } 847 848 /// updateForInsertedWaterBlock - When a block is newly inserted into the 849 /// machine function, it upsets all of the block numbers. Renumber the blocks 850 /// and update the arrays that parallel this numbering. 851 void MipsConstantIslands::updateForInsertedWaterBlock 852 (MachineBasicBlock *NewBB) { 853 // Renumber the MBB's to keep them consecutive. 854 NewBB->getParent()->RenumberBlocks(NewBB); 855 856 // Insert an entry into BBInfo to align it properly with the (newly 857 // renumbered) block numbers. 858 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo()); 859 860 // Next, update WaterList. Specifically, we need to add NewMBB as having 861 // available water after it. 862 water_iterator IP = 863 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB, 864 CompareMBBNumbers); 865 WaterList.insert(IP, NewBB); 866 } 867 868 unsigned MipsConstantIslands::getUserOffset(CPUser &U) const { 869 return getOffsetOf(U.MI); 870 } 871 872 /// Split the basic block containing MI into two blocks, which are joined by 873 /// an unconditional branch. Update data structures and renumber blocks to 874 /// account for this change and returns the newly created block. 875 MachineBasicBlock *MipsConstantIslands::splitBlockBeforeInstr 876 (MachineInstr *MI) { 877 MachineBasicBlock *OrigBB = MI->getParent(); 878 879 // Create a new MBB for the code after the OrigBB. 880 MachineBasicBlock *NewBB = 881 MF->CreateMachineBasicBlock(OrigBB->getBasicBlock()); 882 MachineFunction::iterator MBBI = ++OrigBB->getIterator(); 883 MF->insert(MBBI, NewBB); 884 885 // Splice the instructions starting with MI over to NewBB. 886 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end()); 887 888 // Add an unconditional branch from OrigBB to NewBB. 889 // Note the new unconditional branch is not being recorded. 890 // There doesn't seem to be meaningful DebugInfo available; this doesn't 891 // correspond to anything in the source. 892 BuildMI(OrigBB, DebugLoc(), TII->get(Mips::Bimm16)).addMBB(NewBB); 893 ++NumSplit; 894 895 // Update the CFG. All succs of OrigBB are now succs of NewBB. 896 NewBB->transferSuccessors(OrigBB); 897 898 // OrigBB branches to NewBB. 899 OrigBB->addSuccessor(NewBB); 900 901 // Update internal data structures to account for the newly inserted MBB. 902 // This is almost the same as updateForInsertedWaterBlock, except that 903 // the Water goes after OrigBB, not NewBB. 904 MF->RenumberBlocks(NewBB); 905 906 // Insert an entry into BBInfo to align it properly with the (newly 907 // renumbered) block numbers. 908 BBInfo.insert(BBInfo.begin() + NewBB->getNumber(), BasicBlockInfo()); 909 910 // Next, update WaterList. Specifically, we need to add OrigMBB as having 911 // available water after it (but not if it's already there, which happens 912 // when splitting before a conditional branch that is followed by an 913 // unconditional branch - in that case we want to insert NewBB). 914 water_iterator IP = 915 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB, 916 CompareMBBNumbers); 917 MachineBasicBlock* WaterBB = *IP; 918 if (WaterBB == OrigBB) 919 WaterList.insert(std::next(IP), NewBB); 920 else 921 WaterList.insert(IP, OrigBB); 922 NewWaterList.insert(OrigBB); 923 924 // Figure out how large the OrigBB is. As the first half of the original 925 // block, it cannot contain a tablejump. The size includes 926 // the new jump we added. (It should be possible to do this without 927 // recounting everything, but it's very confusing, and this is rarely 928 // executed.) 929 computeBlockSize(OrigBB); 930 931 // Figure out how large the NewMBB is. As the second half of the original 932 // block, it may contain a tablejump. 933 computeBlockSize(NewBB); 934 935 // All BBOffsets following these blocks must be modified. 936 adjustBBOffsetsAfter(OrigBB); 937 938 return NewBB; 939 } 940 941 942 943 /// isOffsetInRange - Checks whether UserOffset (the location of a constant pool 944 /// reference) is within MaxDisp of TrialOffset (a proposed location of a 945 /// constant pool entry). 946 bool MipsConstantIslands::isOffsetInRange(unsigned UserOffset, 947 unsigned TrialOffset, unsigned MaxDisp, 948 bool NegativeOK) { 949 if (UserOffset <= TrialOffset) { 950 // User before the Trial. 951 if (TrialOffset - UserOffset <= MaxDisp) 952 return true; 953 } else if (NegativeOK) { 954 if (UserOffset - TrialOffset <= MaxDisp) 955 return true; 956 } 957 return false; 958 } 959 960 /// isWaterInRange - Returns true if a CPE placed after the specified 961 /// Water (a basic block) will be in range for the specific MI. 962 /// 963 /// Compute how much the function will grow by inserting a CPE after Water. 964 bool MipsConstantIslands::isWaterInRange(unsigned UserOffset, 965 MachineBasicBlock* Water, CPUser &U, 966 unsigned &Growth) { 967 unsigned CPELogAlign = getCPELogAlign(U.CPEMI); 968 unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign); 969 unsigned NextBlockOffset, NextBlockAlignment; 970 MachineFunction::const_iterator NextBlock = ++Water->getIterator(); 971 if (NextBlock == MF->end()) { 972 NextBlockOffset = BBInfo[Water->getNumber()].postOffset(); 973 NextBlockAlignment = 0; 974 } else { 975 NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset; 976 NextBlockAlignment = NextBlock->getAlignment(); 977 } 978 unsigned Size = U.CPEMI->getOperand(2).getImm(); 979 unsigned CPEEnd = CPEOffset + Size; 980 981 // The CPE may be able to hide in the alignment padding before the next 982 // block. It may also cause more padding to be required if it is more aligned 983 // that the next block. 984 if (CPEEnd > NextBlockOffset) { 985 Growth = CPEEnd - NextBlockOffset; 986 // Compute the padding that would go at the end of the CPE to align the next 987 // block. 988 Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment); 989 990 // If the CPE is to be inserted before the instruction, that will raise 991 // the offset of the instruction. Also account for unknown alignment padding 992 // in blocks between CPE and the user. 993 if (CPEOffset < UserOffset) 994 UserOffset += Growth; 995 } else 996 // CPE fits in existing padding. 997 Growth = 0; 998 999 return isOffsetInRange(UserOffset, CPEOffset, U); 1000 } 1001 1002 /// isCPEntryInRange - Returns true if the distance between specific MI and 1003 /// specific ConstPool entry instruction can fit in MI's displacement field. 1004 bool MipsConstantIslands::isCPEntryInRange 1005 (MachineInstr *MI, unsigned UserOffset, 1006 MachineInstr *CPEMI, unsigned MaxDisp, 1007 bool NegOk, bool DoDump) { 1008 unsigned CPEOffset = getOffsetOf(CPEMI); 1009 1010 if (DoDump) { 1011 DEBUG({ 1012 unsigned Block = MI->getParent()->getNumber(); 1013 const BasicBlockInfo &BBI = BBInfo[Block]; 1014 dbgs() << "User of CPE#" << CPEMI->getOperand(0).getImm() 1015 << " max delta=" << MaxDisp 1016 << format(" insn address=%#x", UserOffset) 1017 << " in BB#" << Block << ": " 1018 << format("%#x-%x\t", BBI.Offset, BBI.postOffset()) << *MI 1019 << format("CPE address=%#x offset=%+d: ", CPEOffset, 1020 int(CPEOffset-UserOffset)); 1021 }); 1022 } 1023 1024 return isOffsetInRange(UserOffset, CPEOffset, MaxDisp, NegOk); 1025 } 1026 1027 #ifndef NDEBUG 1028 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor 1029 /// unconditionally branches to its only successor. 1030 static bool BBIsJumpedOver(MachineBasicBlock *MBB) { 1031 if (MBB->pred_size() != 1 || MBB->succ_size() != 1) 1032 return false; 1033 MachineBasicBlock *Succ = *MBB->succ_begin(); 1034 MachineBasicBlock *Pred = *MBB->pred_begin(); 1035 MachineInstr *PredMI = &Pred->back(); 1036 if (PredMI->getOpcode() == Mips::Bimm16) 1037 return PredMI->getOperand(0).getMBB() == Succ; 1038 return false; 1039 } 1040 #endif 1041 1042 void MipsConstantIslands::adjustBBOffsetsAfter(MachineBasicBlock *BB) { 1043 unsigned BBNum = BB->getNumber(); 1044 for(unsigned i = BBNum + 1, e = MF->getNumBlockIDs(); i < e; ++i) { 1045 // Get the offset and known bits at the end of the layout predecessor. 1046 // Include the alignment of the current block. 1047 unsigned Offset = BBInfo[i - 1].Offset + BBInfo[i - 1].Size; 1048 BBInfo[i].Offset = Offset; 1049 } 1050 } 1051 1052 /// decrementCPEReferenceCount - find the constant pool entry with index CPI 1053 /// and instruction CPEMI, and decrement its refcount. If the refcount 1054 /// becomes 0 remove the entry and instruction. Returns true if we removed 1055 /// the entry, false if we didn't. 1056 1057 bool MipsConstantIslands::decrementCPEReferenceCount(unsigned CPI, 1058 MachineInstr *CPEMI) { 1059 // Find the old entry. Eliminate it if it is no longer used. 1060 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI); 1061 assert(CPE && "Unexpected!"); 1062 if (--CPE->RefCount == 0) { 1063 removeDeadCPEMI(CPEMI); 1064 CPE->CPEMI = nullptr; 1065 --NumCPEs; 1066 return true; 1067 } 1068 return false; 1069 } 1070 1071 /// LookForCPEntryInRange - see if the currently referenced CPE is in range; 1072 /// if not, see if an in-range clone of the CPE is in range, and if so, 1073 /// change the data structures so the user references the clone. Returns: 1074 /// 0 = no existing entry found 1075 /// 1 = entry found, and there were no code insertions or deletions 1076 /// 2 = entry found, and there were code insertions or deletions 1077 int MipsConstantIslands::findInRangeCPEntry(CPUser& U, unsigned UserOffset) 1078 { 1079 MachineInstr *UserMI = U.MI; 1080 MachineInstr *CPEMI = U.CPEMI; 1081 1082 // Check to see if the CPE is already in-range. 1083 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, U.getMaxDisp(), U.NegOk, 1084 true)) { 1085 DEBUG(dbgs() << "In range\n"); 1086 return 1; 1087 } 1088 1089 // No. Look for previously created clones of the CPE that are in range. 1090 unsigned CPI = CPEMI->getOperand(1).getIndex(); 1091 std::vector<CPEntry> &CPEs = CPEntries[CPI]; 1092 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) { 1093 // We already tried this one 1094 if (CPEs[i].CPEMI == CPEMI) 1095 continue; 1096 // Removing CPEs can leave empty entries, skip 1097 if (CPEs[i].CPEMI == nullptr) 1098 continue; 1099 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.getMaxDisp(), 1100 U.NegOk)) { 1101 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#" 1102 << CPEs[i].CPI << "\n"); 1103 // Point the CPUser node to the replacement 1104 U.CPEMI = CPEs[i].CPEMI; 1105 // Change the CPI in the instruction operand to refer to the clone. 1106 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j) 1107 if (UserMI->getOperand(j).isCPI()) { 1108 UserMI->getOperand(j).setIndex(CPEs[i].CPI); 1109 break; 1110 } 1111 // Adjust the refcount of the clone... 1112 CPEs[i].RefCount++; 1113 // ...and the original. If we didn't remove the old entry, none of the 1114 // addresses changed, so we don't need another pass. 1115 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1; 1116 } 1117 } 1118 return 0; 1119 } 1120 1121 /// LookForCPEntryInRange - see if the currently referenced CPE is in range; 1122 /// This version checks if the longer form of the instruction can be used to 1123 /// to satisfy things. 1124 /// if not, see if an in-range clone of the CPE is in range, and if so, 1125 /// change the data structures so the user references the clone. Returns: 1126 /// 0 = no existing entry found 1127 /// 1 = entry found, and there were no code insertions or deletions 1128 /// 2 = entry found, and there were code insertions or deletions 1129 int MipsConstantIslands::findLongFormInRangeCPEntry 1130 (CPUser& U, unsigned UserOffset) 1131 { 1132 MachineInstr *UserMI = U.MI; 1133 MachineInstr *CPEMI = U.CPEMI; 1134 1135 // Check to see if the CPE is already in-range. 1136 if (isCPEntryInRange(UserMI, UserOffset, CPEMI, 1137 U.getLongFormMaxDisp(), U.NegOk, 1138 true)) { 1139 DEBUG(dbgs() << "In range\n"); 1140 UserMI->setDesc(TII->get(U.getLongFormOpcode())); 1141 U.setMaxDisp(U.getLongFormMaxDisp()); 1142 return 2; // instruction is longer length now 1143 } 1144 1145 // No. Look for previously created clones of the CPE that are in range. 1146 unsigned CPI = CPEMI->getOperand(1).getIndex(); 1147 std::vector<CPEntry> &CPEs = CPEntries[CPI]; 1148 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) { 1149 // We already tried this one 1150 if (CPEs[i].CPEMI == CPEMI) 1151 continue; 1152 // Removing CPEs can leave empty entries, skip 1153 if (CPEs[i].CPEMI == nullptr) 1154 continue; 1155 if (isCPEntryInRange(UserMI, UserOffset, CPEs[i].CPEMI, 1156 U.getLongFormMaxDisp(), U.NegOk)) { 1157 DEBUG(dbgs() << "Replacing CPE#" << CPI << " with CPE#" 1158 << CPEs[i].CPI << "\n"); 1159 // Point the CPUser node to the replacement 1160 U.CPEMI = CPEs[i].CPEMI; 1161 // Change the CPI in the instruction operand to refer to the clone. 1162 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j) 1163 if (UserMI->getOperand(j).isCPI()) { 1164 UserMI->getOperand(j).setIndex(CPEs[i].CPI); 1165 break; 1166 } 1167 // Adjust the refcount of the clone... 1168 CPEs[i].RefCount++; 1169 // ...and the original. If we didn't remove the old entry, none of the 1170 // addresses changed, so we don't need another pass. 1171 return decrementCPEReferenceCount(CPI, CPEMI) ? 2 : 1; 1172 } 1173 } 1174 return 0; 1175 } 1176 1177 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in 1178 /// the specific unconditional branch instruction. 1179 static inline unsigned getUnconditionalBrDisp(int Opc) { 1180 switch (Opc) { 1181 case Mips::Bimm16: 1182 return ((1<<10)-1)*2; 1183 case Mips::BimmX16: 1184 return ((1<<16)-1)*2; 1185 default: 1186 break; 1187 } 1188 return ((1<<16)-1)*2; 1189 } 1190 1191 /// findAvailableWater - Look for an existing entry in the WaterList in which 1192 /// we can place the CPE referenced from U so it's within range of U's MI. 1193 /// Returns true if found, false if not. If it returns true, WaterIter 1194 /// is set to the WaterList entry. 1195 /// To ensure that this pass 1196 /// terminates, the CPE location for a particular CPUser is only allowed to 1197 /// move to a lower address, so search backward from the end of the list and 1198 /// prefer the first water that is in range. 1199 bool MipsConstantIslands::findAvailableWater(CPUser &U, unsigned UserOffset, 1200 water_iterator &WaterIter) { 1201 if (WaterList.empty()) 1202 return false; 1203 1204 unsigned BestGrowth = ~0u; 1205 for (water_iterator IP = std::prev(WaterList.end()), B = WaterList.begin();; 1206 --IP) { 1207 MachineBasicBlock* WaterBB = *IP; 1208 // Check if water is in range and is either at a lower address than the 1209 // current "high water mark" or a new water block that was created since 1210 // the previous iteration by inserting an unconditional branch. In the 1211 // latter case, we want to allow resetting the high water mark back to 1212 // this new water since we haven't seen it before. Inserting branches 1213 // should be relatively uncommon and when it does happen, we want to be 1214 // sure to take advantage of it for all the CPEs near that block, so that 1215 // we don't insert more branches than necessary. 1216 unsigned Growth; 1217 if (isWaterInRange(UserOffset, WaterBB, U, Growth) && 1218 (WaterBB->getNumber() < U.HighWaterMark->getNumber() || 1219 NewWaterList.count(WaterBB)) && Growth < BestGrowth) { 1220 // This is the least amount of required padding seen so far. 1221 BestGrowth = Growth; 1222 WaterIter = IP; 1223 DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber() 1224 << " Growth=" << Growth << '\n'); 1225 1226 // Keep looking unless it is perfect. 1227 if (BestGrowth == 0) 1228 return true; 1229 } 1230 if (IP == B) 1231 break; 1232 } 1233 return BestGrowth != ~0u; 1234 } 1235 1236 /// createNewWater - No existing WaterList entry will work for 1237 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the 1238 /// block is used if in range, and the conditional branch munged so control 1239 /// flow is correct. Otherwise the block is split to create a hole with an 1240 /// unconditional branch around it. In either case NewMBB is set to a 1241 /// block following which the new island can be inserted (the WaterList 1242 /// is not adjusted). 1243 void MipsConstantIslands::createNewWater(unsigned CPUserIndex, 1244 unsigned UserOffset, 1245 MachineBasicBlock *&NewMBB) { 1246 CPUser &U = CPUsers[CPUserIndex]; 1247 MachineInstr *UserMI = U.MI; 1248 MachineInstr *CPEMI = U.CPEMI; 1249 unsigned CPELogAlign = getCPELogAlign(CPEMI); 1250 MachineBasicBlock *UserMBB = UserMI->getParent(); 1251 const BasicBlockInfo &UserBBI = BBInfo[UserMBB->getNumber()]; 1252 1253 // If the block does not end in an unconditional branch already, and if the 1254 // end of the block is within range, make new water there. 1255 if (BBHasFallthrough(UserMBB)) { 1256 // Size of branch to insert. 1257 unsigned Delta = 2; 1258 // Compute the offset where the CPE will begin. 1259 unsigned CPEOffset = UserBBI.postOffset(CPELogAlign) + Delta; 1260 1261 if (isOffsetInRange(UserOffset, CPEOffset, U)) { 1262 DEBUG(dbgs() << "Split at end of BB#" << UserMBB->getNumber() 1263 << format(", expected CPE offset %#x\n", CPEOffset)); 1264 NewMBB = &*++UserMBB->getIterator(); 1265 // Add an unconditional branch from UserMBB to fallthrough block. Record 1266 // it for branch lengthening; this new branch will not get out of range, 1267 // but if the preceding conditional branch is out of range, the targets 1268 // will be exchanged, and the altered branch may be out of range, so the 1269 // machinery has to know about it. 1270 int UncondBr = Mips::Bimm16; 1271 BuildMI(UserMBB, DebugLoc(), TII->get(UncondBr)).addMBB(NewMBB); 1272 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr); 1273 ImmBranches.push_back(ImmBranch(&UserMBB->back(), 1274 MaxDisp, false, UncondBr)); 1275 BBInfo[UserMBB->getNumber()].Size += Delta; 1276 adjustBBOffsetsAfter(UserMBB); 1277 return; 1278 } 1279 } 1280 1281 // What a big block. Find a place within the block to split it. 1282 1283 // Try to split the block so it's fully aligned. Compute the latest split 1284 // point where we can add a 4-byte branch instruction, and then align to 1285 // LogAlign which is the largest possible alignment in the function. 1286 unsigned LogAlign = MF->getAlignment(); 1287 assert(LogAlign >= CPELogAlign && "Over-aligned constant pool entry"); 1288 unsigned BaseInsertOffset = UserOffset + U.getMaxDisp(); 1289 DEBUG(dbgs() << format("Split in middle of big block before %#x", 1290 BaseInsertOffset)); 1291 1292 // The 4 in the following is for the unconditional branch we'll be inserting 1293 // Alignment of the island is handled 1294 // inside isOffsetInRange. 1295 BaseInsertOffset -= 4; 1296 1297 DEBUG(dbgs() << format(", adjusted to %#x", BaseInsertOffset) 1298 << " la=" << LogAlign << '\n'); 1299 1300 // This could point off the end of the block if we've already got constant 1301 // pool entries following this block; only the last one is in the water list. 1302 // Back past any possible branches (allow for a conditional and a maximally 1303 // long unconditional). 1304 if (BaseInsertOffset + 8 >= UserBBI.postOffset()) { 1305 BaseInsertOffset = UserBBI.postOffset() - 8; 1306 DEBUG(dbgs() << format("Move inside block: %#x\n", BaseInsertOffset)); 1307 } 1308 unsigned EndInsertOffset = BaseInsertOffset + 4 + 1309 CPEMI->getOperand(2).getImm(); 1310 MachineBasicBlock::iterator MI = UserMI; 1311 ++MI; 1312 unsigned CPUIndex = CPUserIndex+1; 1313 unsigned NumCPUsers = CPUsers.size(); 1314 //MachineInstr *LastIT = 0; 1315 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI); 1316 Offset < BaseInsertOffset; 1317 Offset += TII->GetInstSizeInBytes(MI), MI = std::next(MI)) { 1318 assert(MI != UserMBB->end() && "Fell off end of block"); 1319 if (CPUIndex < NumCPUsers && CPUsers[CPUIndex].MI == MI) { 1320 CPUser &U = CPUsers[CPUIndex]; 1321 if (!isOffsetInRange(Offset, EndInsertOffset, U)) { 1322 // Shift intertion point by one unit of alignment so it is within reach. 1323 BaseInsertOffset -= 1u << LogAlign; 1324 EndInsertOffset -= 1u << LogAlign; 1325 } 1326 // This is overly conservative, as we don't account for CPEMIs being 1327 // reused within the block, but it doesn't matter much. Also assume CPEs 1328 // are added in order with alignment padding. We may eventually be able 1329 // to pack the aligned CPEs better. 1330 EndInsertOffset += U.CPEMI->getOperand(2).getImm(); 1331 CPUIndex++; 1332 } 1333 } 1334 1335 --MI; 1336 NewMBB = splitBlockBeforeInstr(MI); 1337 } 1338 1339 /// handleConstantPoolUser - Analyze the specified user, checking to see if it 1340 /// is out-of-range. If so, pick up the constant pool value and move it some 1341 /// place in-range. Return true if we changed any addresses (thus must run 1342 /// another pass of branch lengthening), false otherwise. 1343 bool MipsConstantIslands::handleConstantPoolUser(unsigned CPUserIndex) { 1344 CPUser &U = CPUsers[CPUserIndex]; 1345 MachineInstr *UserMI = U.MI; 1346 MachineInstr *CPEMI = U.CPEMI; 1347 unsigned CPI = CPEMI->getOperand(1).getIndex(); 1348 unsigned Size = CPEMI->getOperand(2).getImm(); 1349 // Compute this only once, it's expensive. 1350 unsigned UserOffset = getUserOffset(U); 1351 1352 // See if the current entry is within range, or there is a clone of it 1353 // in range. 1354 int result = findInRangeCPEntry(U, UserOffset); 1355 if (result==1) return false; 1356 else if (result==2) return true; 1357 1358 1359 // Look for water where we can place this CPE. 1360 MachineBasicBlock *NewIsland = MF->CreateMachineBasicBlock(); 1361 MachineBasicBlock *NewMBB; 1362 water_iterator IP; 1363 if (findAvailableWater(U, UserOffset, IP)) { 1364 DEBUG(dbgs() << "Found water in range\n"); 1365 MachineBasicBlock *WaterBB = *IP; 1366 1367 // If the original WaterList entry was "new water" on this iteration, 1368 // propagate that to the new island. This is just keeping NewWaterList 1369 // updated to match the WaterList, which will be updated below. 1370 if (NewWaterList.erase(WaterBB)) 1371 NewWaterList.insert(NewIsland); 1372 1373 // The new CPE goes before the following block (NewMBB). 1374 NewMBB = &*++WaterBB->getIterator(); 1375 } else { 1376 // No water found. 1377 // we first see if a longer form of the instrucion could have reached 1378 // the constant. in that case we won't bother to split 1379 if (!NoLoadRelaxation) { 1380 result = findLongFormInRangeCPEntry(U, UserOffset); 1381 if (result != 0) return true; 1382 } 1383 DEBUG(dbgs() << "No water found\n"); 1384 createNewWater(CPUserIndex, UserOffset, NewMBB); 1385 1386 // splitBlockBeforeInstr adds to WaterList, which is important when it is 1387 // called while handling branches so that the water will be seen on the 1388 // next iteration for constant pools, but in this context, we don't want 1389 // it. Check for this so it will be removed from the WaterList. 1390 // Also remove any entry from NewWaterList. 1391 MachineBasicBlock *WaterBB = &*--NewMBB->getIterator(); 1392 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB); 1393 if (IP != WaterList.end()) 1394 NewWaterList.erase(WaterBB); 1395 1396 // We are adding new water. Update NewWaterList. 1397 NewWaterList.insert(NewIsland); 1398 } 1399 1400 // Remove the original WaterList entry; we want subsequent insertions in 1401 // this vicinity to go after the one we're about to insert. This 1402 // considerably reduces the number of times we have to move the same CPE 1403 // more than once and is also important to ensure the algorithm terminates. 1404 if (IP != WaterList.end()) 1405 WaterList.erase(IP); 1406 1407 // Okay, we know we can put an island before NewMBB now, do it! 1408 MF->insert(NewMBB->getIterator(), NewIsland); 1409 1410 // Update internal data structures to account for the newly inserted MBB. 1411 updateForInsertedWaterBlock(NewIsland); 1412 1413 // Decrement the old entry, and remove it if refcount becomes 0. 1414 decrementCPEReferenceCount(CPI, CPEMI); 1415 1416 // No existing clone of this CPE is within range. 1417 // We will be generating a new clone. Get a UID for it. 1418 unsigned ID = createPICLabelUId(); 1419 1420 // Now that we have an island to add the CPE to, clone the original CPE and 1421 // add it to the island. 1422 U.HighWaterMark = NewIsland; 1423 U.CPEMI = BuildMI(NewIsland, DebugLoc(), TII->get(Mips::CONSTPOOL_ENTRY)) 1424 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size); 1425 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1)); 1426 ++NumCPEs; 1427 1428 // Mark the basic block as aligned as required by the const-pool entry. 1429 NewIsland->setAlignment(getCPELogAlign(U.CPEMI)); 1430 1431 // Increase the size of the island block to account for the new entry. 1432 BBInfo[NewIsland->getNumber()].Size += Size; 1433 adjustBBOffsetsAfter(&*--NewIsland->getIterator()); 1434 1435 // Finally, change the CPI in the instruction operand to be ID. 1436 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i) 1437 if (UserMI->getOperand(i).isCPI()) { 1438 UserMI->getOperand(i).setIndex(ID); 1439 break; 1440 } 1441 1442 DEBUG(dbgs() << " Moved CPE to #" << ID << " CPI=" << CPI 1443 << format(" offset=%#x\n", BBInfo[NewIsland->getNumber()].Offset)); 1444 1445 return true; 1446 } 1447 1448 /// removeDeadCPEMI - Remove a dead constant pool entry instruction. Update 1449 /// sizes and offsets of impacted basic blocks. 1450 void MipsConstantIslands::removeDeadCPEMI(MachineInstr *CPEMI) { 1451 MachineBasicBlock *CPEBB = CPEMI->getParent(); 1452 unsigned Size = CPEMI->getOperand(2).getImm(); 1453 CPEMI->eraseFromParent(); 1454 BBInfo[CPEBB->getNumber()].Size -= Size; 1455 // All succeeding offsets have the current size value added in, fix this. 1456 if (CPEBB->empty()) { 1457 BBInfo[CPEBB->getNumber()].Size = 0; 1458 1459 // This block no longer needs to be aligned. 1460 CPEBB->setAlignment(0); 1461 } else 1462 // Entries are sorted by descending alignment, so realign from the front. 1463 CPEBB->setAlignment(getCPELogAlign(CPEBB->begin())); 1464 1465 adjustBBOffsetsAfter(CPEBB); 1466 // An island has only one predecessor BB and one successor BB. Check if 1467 // this BB's predecessor jumps directly to this BB's successor. This 1468 // shouldn't happen currently. 1469 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?"); 1470 // FIXME: remove the empty blocks after all the work is done? 1471 } 1472 1473 /// removeUnusedCPEntries - Remove constant pool entries whose refcounts 1474 /// are zero. 1475 bool MipsConstantIslands::removeUnusedCPEntries() { 1476 unsigned MadeChange = false; 1477 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) { 1478 std::vector<CPEntry> &CPEs = CPEntries[i]; 1479 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) { 1480 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) { 1481 removeDeadCPEMI(CPEs[j].CPEMI); 1482 CPEs[j].CPEMI = nullptr; 1483 MadeChange = true; 1484 } 1485 } 1486 } 1487 return MadeChange; 1488 } 1489 1490 /// isBBInRange - Returns true if the distance between specific MI and 1491 /// specific BB can fit in MI's displacement field. 1492 bool MipsConstantIslands::isBBInRange 1493 (MachineInstr *MI,MachineBasicBlock *DestBB, unsigned MaxDisp) { 1494 1495 unsigned PCAdj = 4; 1496 1497 unsigned BrOffset = getOffsetOf(MI) + PCAdj; 1498 unsigned DestOffset = BBInfo[DestBB->getNumber()].Offset; 1499 1500 DEBUG(dbgs() << "Branch of destination BB#" << DestBB->getNumber() 1501 << " from BB#" << MI->getParent()->getNumber() 1502 << " max delta=" << MaxDisp 1503 << " from " << getOffsetOf(MI) << " to " << DestOffset 1504 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI); 1505 1506 if (BrOffset <= DestOffset) { 1507 // Branch before the Dest. 1508 if (DestOffset-BrOffset <= MaxDisp) 1509 return true; 1510 } else { 1511 if (BrOffset-DestOffset <= MaxDisp) 1512 return true; 1513 } 1514 return false; 1515 } 1516 1517 /// fixupImmediateBr - Fix up an immediate branch whose destination is too far 1518 /// away to fit in its displacement field. 1519 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) { 1520 MachineInstr *MI = Br.MI; 1521 unsigned TargetOperand = branchTargetOperand(MI); 1522 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB(); 1523 1524 // Check to see if the DestBB is already in-range. 1525 if (isBBInRange(MI, DestBB, Br.MaxDisp)) 1526 return false; 1527 1528 if (!Br.isCond) 1529 return fixupUnconditionalBr(Br); 1530 return fixupConditionalBr(Br); 1531 } 1532 1533 /// fixupUnconditionalBr - Fix up an unconditional branch whose destination is 1534 /// too far away to fit in its displacement field. If the LR register has been 1535 /// spilled in the epilogue, then we can use BL to implement a far jump. 1536 /// Otherwise, add an intermediate branch instruction to a branch. 1537 bool 1538 MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) { 1539 MachineInstr *MI = Br.MI; 1540 MachineBasicBlock *MBB = MI->getParent(); 1541 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB(); 1542 // Use BL to implement far jump. 1543 unsigned BimmX16MaxDisp = ((1 << 16)-1) * 2; 1544 if (isBBInRange(MI, DestBB, BimmX16MaxDisp)) { 1545 Br.MaxDisp = BimmX16MaxDisp; 1546 MI->setDesc(TII->get(Mips::BimmX16)); 1547 } 1548 else { 1549 // need to give the math a more careful look here 1550 // this is really a segment address and not 1551 // a PC relative address. FIXME. But I think that 1552 // just reducing the bits by 1 as I've done is correct. 1553 // The basic block we are branching too much be longword aligned. 1554 // we know that RA is saved because we always save it right now. 1555 // this requirement will be relaxed later but we also have an alternate 1556 // way to implement this that I will implement that does not need jal. 1557 // We should have a way to back out this alignment restriction if we "can" later. 1558 // but it is not harmful. 1559 // 1560 DestBB->setAlignment(2); 1561 Br.MaxDisp = ((1<<24)-1) * 2; 1562 MI->setDesc(TII->get(Mips::JalB16)); 1563 } 1564 BBInfo[MBB->getNumber()].Size += 2; 1565 adjustBBOffsetsAfter(MBB); 1566 HasFarJump = true; 1567 ++NumUBrFixed; 1568 1569 DEBUG(dbgs() << " Changed B to long jump " << *MI); 1570 1571 return true; 1572 } 1573 1574 1575 /// fixupConditionalBr - Fix up a conditional branch whose destination is too 1576 /// far away to fit in its displacement field. It is converted to an inverse 1577 /// conditional branch + an unconditional branch to the destination. 1578 bool 1579 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) { 1580 MachineInstr *MI = Br.MI; 1581 unsigned TargetOperand = branchTargetOperand(MI); 1582 MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB(); 1583 unsigned Opcode = MI->getOpcode(); 1584 unsigned LongFormOpcode = longformBranchOpcode(Opcode); 1585 unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode); 1586 1587 // Check to see if the DestBB is already in-range. 1588 if (isBBInRange(MI, DestBB, LongFormMaxOff)) { 1589 Br.MaxDisp = LongFormMaxOff; 1590 MI->setDesc(TII->get(LongFormOpcode)); 1591 return true; 1592 } 1593 1594 // Add an unconditional branch to the destination and invert the branch 1595 // condition to jump over it: 1596 // bteqz L1 1597 // => 1598 // bnez L2 1599 // b L1 1600 // L2: 1601 1602 // If the branch is at the end of its MBB and that has a fall-through block, 1603 // direct the updated conditional branch to the fall-through block. Otherwise, 1604 // split the MBB before the next instruction. 1605 MachineBasicBlock *MBB = MI->getParent(); 1606 MachineInstr *BMI = &MBB->back(); 1607 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB); 1608 unsigned OppositeBranchOpcode = TII->getOppositeBranchOpc(Opcode); 1609 1610 ++NumCBrFixed; 1611 if (BMI != MI) { 1612 if (std::next(MachineBasicBlock::iterator(MI)) == std::prev(MBB->end()) && 1613 isUnconditionalBranch(BMI->getOpcode())) { 1614 // Last MI in the BB is an unconditional branch. Can we simply invert the 1615 // condition and swap destinations: 1616 // beqz L1 1617 // b L2 1618 // => 1619 // bnez L2 1620 // b L1 1621 unsigned BMITargetOperand = branchTargetOperand(BMI); 1622 MachineBasicBlock *NewDest = 1623 BMI->getOperand(BMITargetOperand).getMBB(); 1624 if (isBBInRange(MI, NewDest, Br.MaxDisp)) { 1625 DEBUG(dbgs() << " Invert Bcc condition and swap its destination with " 1626 << *BMI); 1627 MI->setDesc(TII->get(OppositeBranchOpcode)); 1628 BMI->getOperand(BMITargetOperand).setMBB(DestBB); 1629 MI->getOperand(TargetOperand).setMBB(NewDest); 1630 return true; 1631 } 1632 } 1633 } 1634 1635 1636 if (NeedSplit) { 1637 splitBlockBeforeInstr(MI); 1638 // No need for the branch to the next block. We're adding an unconditional 1639 // branch to the destination. 1640 int delta = TII->GetInstSizeInBytes(&MBB->back()); 1641 BBInfo[MBB->getNumber()].Size -= delta; 1642 MBB->back().eraseFromParent(); 1643 // BBInfo[SplitBB].Offset is wrong temporarily, fixed below 1644 } 1645 MachineBasicBlock *NextBB = &*++MBB->getIterator(); 1646 1647 DEBUG(dbgs() << " Insert B to BB#" << DestBB->getNumber() 1648 << " also invert condition and change dest. to BB#" 1649 << NextBB->getNumber() << "\n"); 1650 1651 // Insert a new conditional branch and a new unconditional branch. 1652 // Also update the ImmBranch as well as adding a new entry for the new branch. 1653 if (MI->getNumExplicitOperands() == 2) { 1654 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode)) 1655 .addReg(MI->getOperand(0).getReg()) 1656 .addMBB(NextBB); 1657 } else { 1658 BuildMI(MBB, DebugLoc(), TII->get(OppositeBranchOpcode)) 1659 .addMBB(NextBB); 1660 } 1661 Br.MI = &MBB->back(); 1662 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back()); 1663 BuildMI(MBB, DebugLoc(), TII->get(Br.UncondBr)).addMBB(DestBB); 1664 BBInfo[MBB->getNumber()].Size += TII->GetInstSizeInBytes(&MBB->back()); 1665 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr); 1666 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr)); 1667 1668 // Remove the old conditional branch. It may or may not still be in MBB. 1669 BBInfo[MI->getParent()->getNumber()].Size -= TII->GetInstSizeInBytes(MI); 1670 MI->eraseFromParent(); 1671 adjustBBOffsetsAfter(MBB); 1672 return true; 1673 } 1674 1675 1676 void MipsConstantIslands::prescanForConstants() { 1677 unsigned J = 0; 1678 (void)J; 1679 for (MachineFunction::iterator B = 1680 MF->begin(), E = MF->end(); B != E; ++B) { 1681 for (MachineBasicBlock::instr_iterator I = 1682 B->instr_begin(), EB = B->instr_end(); I != EB; ++I) { 1683 switch(I->getDesc().getOpcode()) { 1684 case Mips::LwConstant32: { 1685 PrescannedForConstants = true; 1686 DEBUG(dbgs() << "constant island constant " << *I << "\n"); 1687 J = I->getNumOperands(); 1688 DEBUG(dbgs() << "num operands " << J << "\n"); 1689 MachineOperand& Literal = I->getOperand(1); 1690 if (Literal.isImm()) { 1691 int64_t V = Literal.getImm(); 1692 DEBUG(dbgs() << "literal " << V << "\n"); 1693 Type *Int32Ty = 1694 Type::getInt32Ty(MF->getFunction()->getContext()); 1695 const Constant *C = ConstantInt::get(Int32Ty, V); 1696 unsigned index = MCP->getConstantPoolIndex(C, 4); 1697 I->getOperand(2).ChangeToImmediate(index); 1698 DEBUG(dbgs() << "constant island constant " << *I << "\n"); 1699 I->setDesc(TII->get(Mips::LwRxPcTcp16)); 1700 I->RemoveOperand(1); 1701 I->RemoveOperand(1); 1702 I->addOperand(MachineOperand::CreateCPI(index, 0)); 1703 I->addOperand(MachineOperand::CreateImm(4)); 1704 } 1705 break; 1706 } 1707 default: 1708 break; 1709 } 1710 } 1711 } 1712 } 1713 1714