1 //===- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function ---===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This pass is responsible for finalizing the functions frame layout, saving 10 // callee saved registers, and for emitting prolog & epilog code for the 11 // function. 12 // 13 // This pass must be run after register allocation. After this pass is 14 // executed, it is illegal to construct MO_FrameIndex operands. 15 // 16 //===----------------------------------------------------------------------===// 17 18 #include "llvm/ADT/ArrayRef.h" 19 #include "llvm/ADT/BitVector.h" 20 #include "llvm/ADT/DepthFirstIterator.h" 21 #include "llvm/ADT/STLExtras.h" 22 #include "llvm/ADT/SetVector.h" 23 #include "llvm/ADT/SmallPtrSet.h" 24 #include "llvm/ADT/SmallSet.h" 25 #include "llvm/ADT/SmallVector.h" 26 #include "llvm/ADT/Statistic.h" 27 #include "llvm/Analysis/OptimizationRemarkEmitter.h" 28 #include "llvm/CodeGen/MachineBasicBlock.h" 29 #include "llvm/CodeGen/MachineDominators.h" 30 #include "llvm/CodeGen/MachineFrameInfo.h" 31 #include "llvm/CodeGen/MachineFunction.h" 32 #include "llvm/CodeGen/MachineFunctionPass.h" 33 #include "llvm/CodeGen/MachineInstr.h" 34 #include "llvm/CodeGen/MachineInstrBuilder.h" 35 #include "llvm/CodeGen/MachineLoopInfo.h" 36 #include "llvm/CodeGen/MachineModuleInfo.h" 37 #include "llvm/CodeGen/MachineOperand.h" 38 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h" 39 #include "llvm/CodeGen/MachineRegisterInfo.h" 40 #include "llvm/CodeGen/RegisterScavenging.h" 41 #include "llvm/CodeGen/TargetFrameLowering.h" 42 #include "llvm/CodeGen/TargetInstrInfo.h" 43 #include "llvm/CodeGen/TargetOpcodes.h" 44 #include "llvm/CodeGen/TargetRegisterInfo.h" 45 #include "llvm/CodeGen/TargetSubtargetInfo.h" 46 #include "llvm/CodeGen/WinEHFuncInfo.h" 47 #include "llvm/IR/Attributes.h" 48 #include "llvm/IR/CallingConv.h" 49 #include "llvm/IR/DebugInfoMetadata.h" 50 #include "llvm/IR/DiagnosticInfo.h" 51 #include "llvm/IR/Function.h" 52 #include "llvm/IR/InlineAsm.h" 53 #include "llvm/IR/LLVMContext.h" 54 #include "llvm/InitializePasses.h" 55 #include "llvm/MC/MCRegisterInfo.h" 56 #include "llvm/Pass.h" 57 #include "llvm/Support/CodeGen.h" 58 #include "llvm/Support/CommandLine.h" 59 #include "llvm/Support/Debug.h" 60 #include "llvm/Support/ErrorHandling.h" 61 #include "llvm/Support/MathExtras.h" 62 #include "llvm/Support/raw_ostream.h" 63 #include "llvm/Target/TargetMachine.h" 64 #include "llvm/Target/TargetOptions.h" 65 #include <algorithm> 66 #include <cassert> 67 #include <cstdint> 68 #include <functional> 69 #include <limits> 70 #include <utility> 71 #include <vector> 72 73 using namespace llvm; 74 75 #define DEBUG_TYPE "prologepilog" 76 77 using MBBVector = SmallVector<MachineBasicBlock *, 4>; 78 79 STATISTIC(NumLeafFuncWithSpills, "Number of leaf functions with CSRs"); 80 STATISTIC(NumFuncSeen, "Number of functions seen in PEI"); 81 82 83 namespace { 84 85 class PEI : public MachineFunctionPass { 86 public: 87 static char ID; 88 89 PEI() : MachineFunctionPass(ID) { 90 initializePEIPass(*PassRegistry::getPassRegistry()); 91 } 92 93 void getAnalysisUsage(AnalysisUsage &AU) const override; 94 95 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract 96 /// frame indexes with appropriate references. 97 bool runOnMachineFunction(MachineFunction &MF) override; 98 99 private: 100 RegScavenger *RS; 101 102 // MinCSFrameIndex, MaxCSFrameIndex - Keeps the range of callee saved 103 // stack frame indexes. 104 unsigned MinCSFrameIndex = std::numeric_limits<unsigned>::max(); 105 unsigned MaxCSFrameIndex = 0; 106 107 // Save and Restore blocks of the current function. Typically there is a 108 // single save block, unless Windows EH funclets are involved. 109 MBBVector SaveBlocks; 110 MBBVector RestoreBlocks; 111 112 // Flag to control whether to use the register scavenger to resolve 113 // frame index materialization registers. Set according to 114 // TRI->requiresFrameIndexScavenging() for the current function. 115 bool FrameIndexVirtualScavenging; 116 117 // Flag to control whether the scavenger should be passed even though 118 // FrameIndexVirtualScavenging is used. 119 bool FrameIndexEliminationScavenging; 120 121 // Emit remarks. 122 MachineOptimizationRemarkEmitter *ORE = nullptr; 123 124 void calculateCallFrameInfo(MachineFunction &MF); 125 void calculateSaveRestoreBlocks(MachineFunction &MF); 126 void spillCalleeSavedRegs(MachineFunction &MF); 127 128 void calculateFrameObjectOffsets(MachineFunction &MF); 129 void replaceFrameIndices(MachineFunction &MF); 130 void replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &MF, 131 int &SPAdj); 132 void insertPrologEpilogCode(MachineFunction &MF); 133 }; 134 135 } // end anonymous namespace 136 137 char PEI::ID = 0; 138 139 char &llvm::PrologEpilogCodeInserterID = PEI::ID; 140 141 static cl::opt<unsigned> 142 WarnStackSize("warn-stack-size", cl::Hidden, cl::init((unsigned)-1), 143 cl::desc("Warn for stack size bigger than the given" 144 " number")); 145 146 INITIALIZE_PASS_BEGIN(PEI, DEBUG_TYPE, "Prologue/Epilogue Insertion", false, 147 false) 148 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) 149 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) 150 INITIALIZE_PASS_DEPENDENCY(MachineOptimizationRemarkEmitterPass) 151 INITIALIZE_PASS_END(PEI, DEBUG_TYPE, 152 "Prologue/Epilogue Insertion & Frame Finalization", false, 153 false) 154 155 MachineFunctionPass *llvm::createPrologEpilogInserterPass() { 156 return new PEI(); 157 } 158 159 STATISTIC(NumBytesStackSpace, 160 "Number of bytes used for stack in all functions"); 161 162 void PEI::getAnalysisUsage(AnalysisUsage &AU) const { 163 AU.setPreservesCFG(); 164 AU.addPreserved<MachineLoopInfo>(); 165 AU.addPreserved<MachineDominatorTree>(); 166 AU.addRequired<MachineOptimizationRemarkEmitterPass>(); 167 MachineFunctionPass::getAnalysisUsage(AU); 168 } 169 170 /// StackObjSet - A set of stack object indexes 171 using StackObjSet = SmallSetVector<int, 8>; 172 173 using SavedDbgValuesMap = 174 SmallDenseMap<MachineBasicBlock *, SmallVector<MachineInstr *, 4>, 4>; 175 176 /// Stash DBG_VALUEs that describe parameters and which are placed at the start 177 /// of the block. Later on, after the prologue code has been emitted, the 178 /// stashed DBG_VALUEs will be reinserted at the start of the block. 179 static void stashEntryDbgValues(MachineBasicBlock &MBB, 180 SavedDbgValuesMap &EntryDbgValues) { 181 SmallVector<const MachineInstr *, 4> FrameIndexValues; 182 183 for (auto &MI : MBB) { 184 if (!MI.isDebugInstr()) 185 break; 186 if (!MI.isDebugValue() || !MI.getDebugVariable()->isParameter()) 187 continue; 188 if (MI.getOperand(0).isFI()) { 189 // We can only emit valid locations for frame indices after the frame 190 // setup, so do not stash away them. 191 FrameIndexValues.push_back(&MI); 192 continue; 193 } 194 const DILocalVariable *Var = MI.getDebugVariable(); 195 const DIExpression *Expr = MI.getDebugExpression(); 196 auto Overlaps = [Var, Expr](const MachineInstr *DV) { 197 return Var == DV->getDebugVariable() && 198 Expr->fragmentsOverlap(DV->getDebugExpression()); 199 }; 200 // See if the debug value overlaps with any preceding debug value that will 201 // not be stashed. If that is the case, then we can't stash this value, as 202 // we would then reorder the values at reinsertion. 203 if (llvm::none_of(FrameIndexValues, Overlaps)) 204 EntryDbgValues[&MBB].push_back(&MI); 205 } 206 207 // Remove stashed debug values from the block. 208 if (EntryDbgValues.count(&MBB)) 209 for (auto *MI : EntryDbgValues[&MBB]) 210 MI->removeFromParent(); 211 } 212 213 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract 214 /// frame indexes with appropriate references. 215 bool PEI::runOnMachineFunction(MachineFunction &MF) { 216 NumFuncSeen++; 217 const Function &F = MF.getFunction(); 218 const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); 219 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 220 221 RS = TRI->requiresRegisterScavenging(MF) ? new RegScavenger() : nullptr; 222 FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(MF); 223 ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE(); 224 225 // Calculate the MaxCallFrameSize and AdjustsStack variables for the 226 // function's frame information. Also eliminates call frame pseudo 227 // instructions. 228 calculateCallFrameInfo(MF); 229 230 // Determine placement of CSR spill/restore code and prolog/epilog code: 231 // place all spills in the entry block, all restores in return blocks. 232 calculateSaveRestoreBlocks(MF); 233 234 // Stash away DBG_VALUEs that should not be moved by insertion of prolog code. 235 SavedDbgValuesMap EntryDbgValues; 236 for (MachineBasicBlock *SaveBlock : SaveBlocks) 237 stashEntryDbgValues(*SaveBlock, EntryDbgValues); 238 239 // Handle CSR spilling and restoring, for targets that need it. 240 if (MF.getTarget().usesPhysRegsForPEI()) 241 spillCalleeSavedRegs(MF); 242 243 // Allow the target machine to make final modifications to the function 244 // before the frame layout is finalized. 245 TFI->processFunctionBeforeFrameFinalized(MF, RS); 246 247 // Calculate actual frame offsets for all abstract stack objects... 248 calculateFrameObjectOffsets(MF); 249 250 // Add prolog and epilog code to the function. This function is required 251 // to align the stack frame as necessary for any stack variables or 252 // called functions. Because of this, calculateCalleeSavedRegisters() 253 // must be called before this function in order to set the AdjustsStack 254 // and MaxCallFrameSize variables. 255 if (!F.hasFnAttribute(Attribute::Naked)) 256 insertPrologEpilogCode(MF); 257 258 // Reinsert stashed debug values at the start of the entry blocks. 259 for (auto &I : EntryDbgValues) 260 I.first->insert(I.first->begin(), I.second.begin(), I.second.end()); 261 262 // Replace all MO_FrameIndex operands with physical register references 263 // and actual offsets. 264 // 265 replaceFrameIndices(MF); 266 267 // If register scavenging is needed, as we've enabled doing it as a 268 // post-pass, scavenge the virtual registers that frame index elimination 269 // inserted. 270 if (TRI->requiresRegisterScavenging(MF) && FrameIndexVirtualScavenging) 271 scavengeFrameVirtualRegs(MF, *RS); 272 273 // Warn on stack size when we exceeds the given limit. 274 MachineFrameInfo &MFI = MF.getFrameInfo(); 275 uint64_t StackSize = MFI.getStackSize(); 276 if (WarnStackSize.getNumOccurrences() > 0 && WarnStackSize < StackSize) { 277 DiagnosticInfoStackSize DiagStackSize(F, StackSize); 278 F.getContext().diagnose(DiagStackSize); 279 } 280 ORE->emit([&]() { 281 return MachineOptimizationRemarkAnalysis(DEBUG_TYPE, "StackSize", 282 MF.getFunction().getSubprogram(), 283 &MF.front()) 284 << ore::NV("NumStackBytes", StackSize) << " stack bytes in function"; 285 }); 286 287 delete RS; 288 SaveBlocks.clear(); 289 RestoreBlocks.clear(); 290 MFI.setSavePoint(nullptr); 291 MFI.setRestorePoint(nullptr); 292 return true; 293 } 294 295 /// Calculate the MaxCallFrameSize and AdjustsStack 296 /// variables for the function's frame information and eliminate call frame 297 /// pseudo instructions. 298 void PEI::calculateCallFrameInfo(MachineFunction &MF) { 299 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 300 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 301 MachineFrameInfo &MFI = MF.getFrameInfo(); 302 303 unsigned MaxCallFrameSize = 0; 304 bool AdjustsStack = MFI.adjustsStack(); 305 306 // Get the function call frame set-up and tear-down instruction opcode 307 unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode(); 308 unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode(); 309 310 // Early exit for targets which have no call frame setup/destroy pseudo 311 // instructions. 312 if (FrameSetupOpcode == ~0u && FrameDestroyOpcode == ~0u) 313 return; 314 315 std::vector<MachineBasicBlock::iterator> FrameSDOps; 316 for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); BB != E; ++BB) 317 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) 318 if (TII.isFrameInstr(*I)) { 319 unsigned Size = TII.getFrameSize(*I); 320 if (Size > MaxCallFrameSize) MaxCallFrameSize = Size; 321 AdjustsStack = true; 322 FrameSDOps.push_back(I); 323 } else if (I->isInlineAsm()) { 324 // Some inline asm's need a stack frame, as indicated by operand 1. 325 unsigned ExtraInfo = I->getOperand(InlineAsm::MIOp_ExtraInfo).getImm(); 326 if (ExtraInfo & InlineAsm::Extra_IsAlignStack) 327 AdjustsStack = true; 328 } 329 330 assert(!MFI.isMaxCallFrameSizeComputed() || 331 (MFI.getMaxCallFrameSize() == MaxCallFrameSize && 332 MFI.adjustsStack() == AdjustsStack)); 333 MFI.setAdjustsStack(AdjustsStack); 334 MFI.setMaxCallFrameSize(MaxCallFrameSize); 335 336 for (std::vector<MachineBasicBlock::iterator>::iterator 337 i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) { 338 MachineBasicBlock::iterator I = *i; 339 340 // If call frames are not being included as part of the stack frame, and 341 // the target doesn't indicate otherwise, remove the call frame pseudos 342 // here. The sub/add sp instruction pairs are still inserted, but we don't 343 // need to track the SP adjustment for frame index elimination. 344 if (TFI->canSimplifyCallFramePseudos(MF)) 345 TFI->eliminateCallFramePseudoInstr(MF, *I->getParent(), I); 346 } 347 } 348 349 /// Compute the sets of entry and return blocks for saving and restoring 350 /// callee-saved registers, and placing prolog and epilog code. 351 void PEI::calculateSaveRestoreBlocks(MachineFunction &MF) { 352 const MachineFrameInfo &MFI = MF.getFrameInfo(); 353 354 // Even when we do not change any CSR, we still want to insert the 355 // prologue and epilogue of the function. 356 // So set the save points for those. 357 358 // Use the points found by shrink-wrapping, if any. 359 if (MFI.getSavePoint()) { 360 SaveBlocks.push_back(MFI.getSavePoint()); 361 assert(MFI.getRestorePoint() && "Both restore and save must be set"); 362 MachineBasicBlock *RestoreBlock = MFI.getRestorePoint(); 363 // If RestoreBlock does not have any successor and is not a return block 364 // then the end point is unreachable and we do not need to insert any 365 // epilogue. 366 if (!RestoreBlock->succ_empty() || RestoreBlock->isReturnBlock()) 367 RestoreBlocks.push_back(RestoreBlock); 368 return; 369 } 370 371 // Save refs to entry and return blocks. 372 SaveBlocks.push_back(&MF.front()); 373 for (MachineBasicBlock &MBB : MF) { 374 if (MBB.isEHFuncletEntry()) 375 SaveBlocks.push_back(&MBB); 376 if (MBB.isReturnBlock()) 377 RestoreBlocks.push_back(&MBB); 378 } 379 } 380 381 static void assignCalleeSavedSpillSlots(MachineFunction &F, 382 const BitVector &SavedRegs, 383 unsigned &MinCSFrameIndex, 384 unsigned &MaxCSFrameIndex) { 385 if (SavedRegs.empty()) 386 return; 387 388 const TargetRegisterInfo *RegInfo = F.getSubtarget().getRegisterInfo(); 389 const MCPhysReg *CSRegs = F.getRegInfo().getCalleeSavedRegs(); 390 391 std::vector<CalleeSavedInfo> CSI; 392 for (unsigned i = 0; CSRegs[i]; ++i) { 393 unsigned Reg = CSRegs[i]; 394 if (SavedRegs.test(Reg)) 395 CSI.push_back(CalleeSavedInfo(Reg)); 396 } 397 398 const TargetFrameLowering *TFI = F.getSubtarget().getFrameLowering(); 399 MachineFrameInfo &MFI = F.getFrameInfo(); 400 if (!TFI->assignCalleeSavedSpillSlots(F, RegInfo, CSI)) { 401 // If target doesn't implement this, use generic code. 402 403 if (CSI.empty()) 404 return; // Early exit if no callee saved registers are modified! 405 406 unsigned NumFixedSpillSlots; 407 const TargetFrameLowering::SpillSlot *FixedSpillSlots = 408 TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots); 409 410 // Now that we know which registers need to be saved and restored, allocate 411 // stack slots for them. 412 for (auto &CS : CSI) { 413 // If the target has spilled this register to another register, we don't 414 // need to allocate a stack slot. 415 if (CS.isSpilledToReg()) 416 continue; 417 418 unsigned Reg = CS.getReg(); 419 const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg); 420 421 int FrameIdx; 422 if (RegInfo->hasReservedSpillSlot(F, Reg, FrameIdx)) { 423 CS.setFrameIdx(FrameIdx); 424 continue; 425 } 426 427 // Check to see if this physreg must be spilled to a particular stack slot 428 // on this target. 429 const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots; 430 while (FixedSlot != FixedSpillSlots + NumFixedSpillSlots && 431 FixedSlot->Reg != Reg) 432 ++FixedSlot; 433 434 unsigned Size = RegInfo->getSpillSize(*RC); 435 if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) { 436 // Nope, just spill it anywhere convenient. 437 unsigned Align = RegInfo->getSpillAlignment(*RC); 438 unsigned StackAlign = TFI->getStackAlignment(); 439 440 // We may not be able to satisfy the desired alignment specification of 441 // the TargetRegisterClass if the stack alignment is smaller. Use the 442 // min. 443 Align = std::min(Align, StackAlign); 444 FrameIdx = MFI.CreateStackObject(Size, Align, true); 445 if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx; 446 if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx; 447 } else { 448 // Spill it to the stack where we must. 449 FrameIdx = MFI.CreateFixedSpillStackObject(Size, FixedSlot->Offset); 450 } 451 452 CS.setFrameIdx(FrameIdx); 453 } 454 } 455 456 MFI.setCalleeSavedInfo(CSI); 457 } 458 459 /// Helper function to update the liveness information for the callee-saved 460 /// registers. 461 static void updateLiveness(MachineFunction &MF) { 462 MachineFrameInfo &MFI = MF.getFrameInfo(); 463 // Visited will contain all the basic blocks that are in the region 464 // where the callee saved registers are alive: 465 // - Anything that is not Save or Restore -> LiveThrough. 466 // - Save -> LiveIn. 467 // - Restore -> LiveOut. 468 // The live-out is not attached to the block, so no need to keep 469 // Restore in this set. 470 SmallPtrSet<MachineBasicBlock *, 8> Visited; 471 SmallVector<MachineBasicBlock *, 8> WorkList; 472 MachineBasicBlock *Entry = &MF.front(); 473 MachineBasicBlock *Save = MFI.getSavePoint(); 474 475 if (!Save) 476 Save = Entry; 477 478 if (Entry != Save) { 479 WorkList.push_back(Entry); 480 Visited.insert(Entry); 481 } 482 Visited.insert(Save); 483 484 MachineBasicBlock *Restore = MFI.getRestorePoint(); 485 if (Restore) 486 // By construction Restore cannot be visited, otherwise it 487 // means there exists a path to Restore that does not go 488 // through Save. 489 WorkList.push_back(Restore); 490 491 while (!WorkList.empty()) { 492 const MachineBasicBlock *CurBB = WorkList.pop_back_val(); 493 // By construction, the region that is after the save point is 494 // dominated by the Save and post-dominated by the Restore. 495 if (CurBB == Save && Save != Restore) 496 continue; 497 // Enqueue all the successors not already visited. 498 // Those are by construction either before Save or after Restore. 499 for (MachineBasicBlock *SuccBB : CurBB->successors()) 500 if (Visited.insert(SuccBB).second) 501 WorkList.push_back(SuccBB); 502 } 503 504 const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo(); 505 506 MachineRegisterInfo &MRI = MF.getRegInfo(); 507 for (unsigned i = 0, e = CSI.size(); i != e; ++i) { 508 for (MachineBasicBlock *MBB : Visited) { 509 MCPhysReg Reg = CSI[i].getReg(); 510 // Add the callee-saved register as live-in. 511 // It's killed at the spill. 512 if (!MRI.isReserved(Reg) && !MBB->isLiveIn(Reg)) 513 MBB->addLiveIn(Reg); 514 } 515 // If callee-saved register is spilled to another register rather than 516 // spilling to stack, the destination register has to be marked as live for 517 // each MBB between the prologue and epilogue so that it is not clobbered 518 // before it is reloaded in the epilogue. The Visited set contains all 519 // blocks outside of the region delimited by prologue/epilogue. 520 if (CSI[i].isSpilledToReg()) { 521 for (MachineBasicBlock &MBB : MF) { 522 if (Visited.count(&MBB)) 523 continue; 524 MCPhysReg DstReg = CSI[i].getDstReg(); 525 if (!MBB.isLiveIn(DstReg)) 526 MBB.addLiveIn(DstReg); 527 } 528 } 529 } 530 531 } 532 533 /// Insert restore code for the callee-saved registers used in the function. 534 static void insertCSRSaves(MachineBasicBlock &SaveBlock, 535 ArrayRef<CalleeSavedInfo> CSI) { 536 MachineFunction &MF = *SaveBlock.getParent(); 537 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 538 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 539 const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); 540 541 MachineBasicBlock::iterator I = SaveBlock.begin(); 542 if (!TFI->spillCalleeSavedRegisters(SaveBlock, I, CSI, TRI)) { 543 for (const CalleeSavedInfo &CS : CSI) { 544 // Insert the spill to the stack frame. 545 unsigned Reg = CS.getReg(); 546 547 if (CS.isSpilledToReg()) { 548 BuildMI(SaveBlock, I, DebugLoc(), 549 TII.get(TargetOpcode::COPY), CS.getDstReg()) 550 .addReg(Reg, getKillRegState(true)); 551 } else { 552 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg); 553 TII.storeRegToStackSlot(SaveBlock, I, Reg, true, CS.getFrameIdx(), RC, 554 TRI); 555 } 556 } 557 } 558 } 559 560 /// Insert restore code for the callee-saved registers used in the function. 561 static void insertCSRRestores(MachineBasicBlock &RestoreBlock, 562 std::vector<CalleeSavedInfo> &CSI) { 563 MachineFunction &MF = *RestoreBlock.getParent(); 564 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 565 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 566 const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); 567 568 // Restore all registers immediately before the return and any 569 // terminators that precede it. 570 MachineBasicBlock::iterator I = RestoreBlock.getFirstTerminator(); 571 572 if (!TFI->restoreCalleeSavedRegisters(RestoreBlock, I, CSI, TRI)) { 573 for (const CalleeSavedInfo &CI : reverse(CSI)) { 574 unsigned Reg = CI.getReg(); 575 if (CI.isSpilledToReg()) { 576 BuildMI(RestoreBlock, I, DebugLoc(), TII.get(TargetOpcode::COPY), Reg) 577 .addReg(CI.getDstReg(), getKillRegState(true)); 578 } else { 579 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg); 580 TII.loadRegFromStackSlot(RestoreBlock, I, Reg, CI.getFrameIdx(), RC, TRI); 581 assert(I != RestoreBlock.begin() && 582 "loadRegFromStackSlot didn't insert any code!"); 583 // Insert in reverse order. loadRegFromStackSlot can insert 584 // multiple instructions. 585 } 586 } 587 } 588 } 589 590 void PEI::spillCalleeSavedRegs(MachineFunction &MF) { 591 // We can't list this requirement in getRequiredProperties because some 592 // targets (WebAssembly) use virtual registers past this point, and the pass 593 // pipeline is set up without giving the passes a chance to look at the 594 // TargetMachine. 595 // FIXME: Find a way to express this in getRequiredProperties. 596 assert(MF.getProperties().hasProperty( 597 MachineFunctionProperties::Property::NoVRegs)); 598 599 const Function &F = MF.getFunction(); 600 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 601 MachineFrameInfo &MFI = MF.getFrameInfo(); 602 MinCSFrameIndex = std::numeric_limits<unsigned>::max(); 603 MaxCSFrameIndex = 0; 604 605 // Determine which of the registers in the callee save list should be saved. 606 BitVector SavedRegs; 607 TFI->determineCalleeSaves(MF, SavedRegs, RS); 608 609 // Assign stack slots for any callee-saved registers that must be spilled. 610 assignCalleeSavedSpillSlots(MF, SavedRegs, MinCSFrameIndex, MaxCSFrameIndex); 611 612 // Add the code to save and restore the callee saved registers. 613 if (!F.hasFnAttribute(Attribute::Naked)) { 614 MFI.setCalleeSavedInfoValid(true); 615 616 std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo(); 617 if (!CSI.empty()) { 618 if (!MFI.hasCalls()) 619 NumLeafFuncWithSpills++; 620 621 for (MachineBasicBlock *SaveBlock : SaveBlocks) { 622 insertCSRSaves(*SaveBlock, CSI); 623 // Update the live-in information of all the blocks up to the save 624 // point. 625 updateLiveness(MF); 626 } 627 for (MachineBasicBlock *RestoreBlock : RestoreBlocks) 628 insertCSRRestores(*RestoreBlock, CSI); 629 } 630 } 631 } 632 633 /// AdjustStackOffset - Helper function used to adjust the stack frame offset. 634 static inline void 635 AdjustStackOffset(MachineFrameInfo &MFI, int FrameIdx, 636 bool StackGrowsDown, int64_t &Offset, 637 unsigned &MaxAlign, unsigned Skew) { 638 // If the stack grows down, add the object size to find the lowest address. 639 if (StackGrowsDown) 640 Offset += MFI.getObjectSize(FrameIdx); 641 642 unsigned Align = MFI.getObjectAlignment(FrameIdx); 643 644 // If the alignment of this object is greater than that of the stack, then 645 // increase the stack alignment to match. 646 MaxAlign = std::max(MaxAlign, Align); 647 648 // Adjust to alignment boundary. 649 Offset = alignTo(Offset, Align, Skew); 650 651 if (StackGrowsDown) { 652 LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset 653 << "]\n"); 654 MFI.setObjectOffset(FrameIdx, -Offset); // Set the computed offset 655 } else { 656 LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset 657 << "]\n"); 658 MFI.setObjectOffset(FrameIdx, Offset); 659 Offset += MFI.getObjectSize(FrameIdx); 660 } 661 } 662 663 /// Compute which bytes of fixed and callee-save stack area are unused and keep 664 /// track of them in StackBytesFree. 665 static inline void 666 computeFreeStackSlots(MachineFrameInfo &MFI, bool StackGrowsDown, 667 unsigned MinCSFrameIndex, unsigned MaxCSFrameIndex, 668 int64_t FixedCSEnd, BitVector &StackBytesFree) { 669 // Avoid undefined int64_t -> int conversion below in extreme case. 670 if (FixedCSEnd > std::numeric_limits<int>::max()) 671 return; 672 673 StackBytesFree.resize(FixedCSEnd, true); 674 675 SmallVector<int, 16> AllocatedFrameSlots; 676 // Add fixed objects. 677 for (int i = MFI.getObjectIndexBegin(); i != 0; ++i) 678 // StackSlot scavenging is only implemented for the default stack. 679 if (MFI.getStackID(i) == TargetStackID::Default) 680 AllocatedFrameSlots.push_back(i); 681 // Add callee-save objects. 682 for (int i = MinCSFrameIndex; i <= (int)MaxCSFrameIndex; ++i) 683 if (MFI.getStackID(i) == TargetStackID::Default) 684 AllocatedFrameSlots.push_back(i); 685 686 for (int i : AllocatedFrameSlots) { 687 // These are converted from int64_t, but they should always fit in int 688 // because of the FixedCSEnd check above. 689 int ObjOffset = MFI.getObjectOffset(i); 690 int ObjSize = MFI.getObjectSize(i); 691 int ObjStart, ObjEnd; 692 if (StackGrowsDown) { 693 // ObjOffset is negative when StackGrowsDown is true. 694 ObjStart = -ObjOffset - ObjSize; 695 ObjEnd = -ObjOffset; 696 } else { 697 ObjStart = ObjOffset; 698 ObjEnd = ObjOffset + ObjSize; 699 } 700 // Ignore fixed holes that are in the previous stack frame. 701 if (ObjEnd > 0) 702 StackBytesFree.reset(ObjStart, ObjEnd); 703 } 704 } 705 706 /// Assign frame object to an unused portion of the stack in the fixed stack 707 /// object range. Return true if the allocation was successful. 708 static inline bool scavengeStackSlot(MachineFrameInfo &MFI, int FrameIdx, 709 bool StackGrowsDown, unsigned MaxAlign, 710 BitVector &StackBytesFree) { 711 if (MFI.isVariableSizedObjectIndex(FrameIdx)) 712 return false; 713 714 if (StackBytesFree.none()) { 715 // clear it to speed up later scavengeStackSlot calls to 716 // StackBytesFree.none() 717 StackBytesFree.clear(); 718 return false; 719 } 720 721 unsigned ObjAlign = MFI.getObjectAlignment(FrameIdx); 722 if (ObjAlign > MaxAlign) 723 return false; 724 725 int64_t ObjSize = MFI.getObjectSize(FrameIdx); 726 int FreeStart; 727 for (FreeStart = StackBytesFree.find_first(); FreeStart != -1; 728 FreeStart = StackBytesFree.find_next(FreeStart)) { 729 730 // Check that free space has suitable alignment. 731 unsigned ObjStart = StackGrowsDown ? FreeStart + ObjSize : FreeStart; 732 if (alignTo(ObjStart, ObjAlign) != ObjStart) 733 continue; 734 735 if (FreeStart + ObjSize > StackBytesFree.size()) 736 return false; 737 738 bool AllBytesFree = true; 739 for (unsigned Byte = 0; Byte < ObjSize; ++Byte) 740 if (!StackBytesFree.test(FreeStart + Byte)) { 741 AllBytesFree = false; 742 break; 743 } 744 if (AllBytesFree) 745 break; 746 } 747 748 if (FreeStart == -1) 749 return false; 750 751 if (StackGrowsDown) { 752 int ObjStart = -(FreeStart + ObjSize); 753 LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") scavenged at SP[" 754 << ObjStart << "]\n"); 755 MFI.setObjectOffset(FrameIdx, ObjStart); 756 } else { 757 LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") scavenged at SP[" 758 << FreeStart << "]\n"); 759 MFI.setObjectOffset(FrameIdx, FreeStart); 760 } 761 762 StackBytesFree.reset(FreeStart, FreeStart + ObjSize); 763 return true; 764 } 765 766 /// AssignProtectedObjSet - Helper function to assign large stack objects (i.e., 767 /// those required to be close to the Stack Protector) to stack offsets. 768 static void 769 AssignProtectedObjSet(const StackObjSet &UnassignedObjs, 770 SmallSet<int, 16> &ProtectedObjs, 771 MachineFrameInfo &MFI, bool StackGrowsDown, 772 int64_t &Offset, unsigned &MaxAlign, unsigned Skew) { 773 774 for (StackObjSet::const_iterator I = UnassignedObjs.begin(), 775 E = UnassignedObjs.end(); I != E; ++I) { 776 int i = *I; 777 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign, Skew); 778 ProtectedObjs.insert(i); 779 } 780 } 781 782 /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the 783 /// abstract stack objects. 784 void PEI::calculateFrameObjectOffsets(MachineFunction &MF) { 785 const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering(); 786 787 bool StackGrowsDown = 788 TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown; 789 790 // Loop over all of the stack objects, assigning sequential addresses... 791 MachineFrameInfo &MFI = MF.getFrameInfo(); 792 793 // Start at the beginning of the local area. 794 // The Offset is the distance from the stack top in the direction 795 // of stack growth -- so it's always nonnegative. 796 int LocalAreaOffset = TFI.getOffsetOfLocalArea(); 797 if (StackGrowsDown) 798 LocalAreaOffset = -LocalAreaOffset; 799 assert(LocalAreaOffset >= 0 800 && "Local area offset should be in direction of stack growth"); 801 int64_t Offset = LocalAreaOffset; 802 803 // Skew to be applied to alignment. 804 unsigned Skew = TFI.getStackAlignmentSkew(MF); 805 806 #ifdef EXPENSIVE_CHECKS 807 for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) 808 if (!MFI.isDeadObjectIndex(i) && 809 MFI.getStackID(i) == TargetStackID::Default) 810 assert(MFI.getObjectAlignment(i) <= MFI.getMaxAlignment() && 811 "MaxAlignment is invalid"); 812 #endif 813 814 // If there are fixed sized objects that are preallocated in the local area, 815 // non-fixed objects can't be allocated right at the start of local area. 816 // Adjust 'Offset' to point to the end of last fixed sized preallocated 817 // object. 818 for (int i = MFI.getObjectIndexBegin(); i != 0; ++i) { 819 if (MFI.getStackID(i) != 820 TargetStackID::Default) // Only allocate objects on the default stack. 821 continue; 822 823 int64_t FixedOff; 824 if (StackGrowsDown) { 825 // The maximum distance from the stack pointer is at lower address of 826 // the object -- which is given by offset. For down growing stack 827 // the offset is negative, so we negate the offset to get the distance. 828 FixedOff = -MFI.getObjectOffset(i); 829 } else { 830 // The maximum distance from the start pointer is at the upper 831 // address of the object. 832 FixedOff = MFI.getObjectOffset(i) + MFI.getObjectSize(i); 833 } 834 if (FixedOff > Offset) Offset = FixedOff; 835 } 836 837 // First assign frame offsets to stack objects that are used to spill 838 // callee saved registers. 839 if (StackGrowsDown) { 840 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) { 841 if (MFI.getStackID(i) != 842 TargetStackID::Default) // Only allocate objects on the default stack. 843 continue; 844 845 // If the stack grows down, we need to add the size to find the lowest 846 // address of the object. 847 Offset += MFI.getObjectSize(i); 848 849 unsigned Align = MFI.getObjectAlignment(i); 850 // Adjust to alignment boundary 851 Offset = alignTo(Offset, Align, Skew); 852 853 LLVM_DEBUG(dbgs() << "alloc FI(" << i << ") at SP[" << -Offset << "]\n"); 854 MFI.setObjectOffset(i, -Offset); // Set the computed offset 855 } 856 } else if (MaxCSFrameIndex >= MinCSFrameIndex) { 857 // Be careful about underflow in comparisons agains MinCSFrameIndex. 858 for (unsigned i = MaxCSFrameIndex; i != MinCSFrameIndex - 1; --i) { 859 if (MFI.getStackID(i) != 860 TargetStackID::Default) // Only allocate objects on the default stack. 861 continue; 862 863 if (MFI.isDeadObjectIndex(i)) 864 continue; 865 866 unsigned Align = MFI.getObjectAlignment(i); 867 // Adjust to alignment boundary 868 Offset = alignTo(Offset, Align, Skew); 869 870 LLVM_DEBUG(dbgs() << "alloc FI(" << i << ") at SP[" << Offset << "]\n"); 871 MFI.setObjectOffset(i, Offset); 872 Offset += MFI.getObjectSize(i); 873 } 874 } 875 876 // FixedCSEnd is the stack offset to the end of the fixed and callee-save 877 // stack area. 878 int64_t FixedCSEnd = Offset; 879 unsigned MaxAlign = MFI.getMaxAlignment(); 880 881 // Make sure the special register scavenging spill slot is closest to the 882 // incoming stack pointer if a frame pointer is required and is closer 883 // to the incoming rather than the final stack pointer. 884 const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo(); 885 bool EarlyScavengingSlots = (TFI.hasFP(MF) && 886 TFI.isFPCloseToIncomingSP() && 887 RegInfo->useFPForScavengingIndex(MF) && 888 !RegInfo->needsStackRealignment(MF)); 889 if (RS && EarlyScavengingSlots) { 890 SmallVector<int, 2> SFIs; 891 RS->getScavengingFrameIndices(SFIs); 892 for (SmallVectorImpl<int>::iterator I = SFIs.begin(), 893 IE = SFIs.end(); I != IE; ++I) 894 AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign, Skew); 895 } 896 897 // FIXME: Once this is working, then enable flag will change to a target 898 // check for whether the frame is large enough to want to use virtual 899 // frame index registers. Functions which don't want/need this optimization 900 // will continue to use the existing code path. 901 if (MFI.getUseLocalStackAllocationBlock()) { 902 unsigned Align = MFI.getLocalFrameMaxAlign().value(); 903 904 // Adjust to alignment boundary. 905 Offset = alignTo(Offset, Align, Skew); 906 907 LLVM_DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n"); 908 909 // Resolve offsets for objects in the local block. 910 for (unsigned i = 0, e = MFI.getLocalFrameObjectCount(); i != e; ++i) { 911 std::pair<int, int64_t> Entry = MFI.getLocalFrameObjectMap(i); 912 int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second; 913 LLVM_DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" << FIOffset 914 << "]\n"); 915 MFI.setObjectOffset(Entry.first, FIOffset); 916 } 917 // Allocate the local block 918 Offset += MFI.getLocalFrameSize(); 919 920 MaxAlign = std::max(Align, MaxAlign); 921 } 922 923 // Retrieve the Exception Handler registration node. 924 int EHRegNodeFrameIndex = std::numeric_limits<int>::max(); 925 if (const WinEHFuncInfo *FuncInfo = MF.getWinEHFuncInfo()) 926 EHRegNodeFrameIndex = FuncInfo->EHRegNodeFrameIndex; 927 928 // Make sure that the stack protector comes before the local variables on the 929 // stack. 930 SmallSet<int, 16> ProtectedObjs; 931 if (MFI.hasStackProtectorIndex()) { 932 int StackProtectorFI = MFI.getStackProtectorIndex(); 933 StackObjSet LargeArrayObjs; 934 StackObjSet SmallArrayObjs; 935 StackObjSet AddrOfObjs; 936 937 // If we need a stack protector, we need to make sure that 938 // LocalStackSlotPass didn't already allocate a slot for it. 939 // If we are told to use the LocalStackAllocationBlock, the stack protector 940 // is expected to be already pre-allocated. 941 if (!MFI.getUseLocalStackAllocationBlock()) 942 AdjustStackOffset(MFI, StackProtectorFI, StackGrowsDown, Offset, MaxAlign, 943 Skew); 944 else if (!MFI.isObjectPreAllocated(MFI.getStackProtectorIndex())) 945 llvm_unreachable( 946 "Stack protector not pre-allocated by LocalStackSlotPass."); 947 948 // Assign large stack objects first. 949 for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) { 950 if (MFI.isObjectPreAllocated(i) && MFI.getUseLocalStackAllocationBlock()) 951 continue; 952 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) 953 continue; 954 if (RS && RS->isScavengingFrameIndex((int)i)) 955 continue; 956 if (MFI.isDeadObjectIndex(i)) 957 continue; 958 if (StackProtectorFI == (int)i || EHRegNodeFrameIndex == (int)i) 959 continue; 960 if (MFI.getStackID(i) != 961 TargetStackID::Default) // Only allocate objects on the default stack. 962 continue; 963 964 switch (MFI.getObjectSSPLayout(i)) { 965 case MachineFrameInfo::SSPLK_None: 966 continue; 967 case MachineFrameInfo::SSPLK_SmallArray: 968 SmallArrayObjs.insert(i); 969 continue; 970 case MachineFrameInfo::SSPLK_AddrOf: 971 AddrOfObjs.insert(i); 972 continue; 973 case MachineFrameInfo::SSPLK_LargeArray: 974 LargeArrayObjs.insert(i); 975 continue; 976 } 977 llvm_unreachable("Unexpected SSPLayoutKind."); 978 } 979 980 // We expect **all** the protected stack objects to be pre-allocated by 981 // LocalStackSlotPass. If it turns out that PEI still has to allocate some 982 // of them, we may end up messing up the expected order of the objects. 983 if (MFI.getUseLocalStackAllocationBlock() && 984 !(LargeArrayObjs.empty() && SmallArrayObjs.empty() && 985 AddrOfObjs.empty())) 986 llvm_unreachable("Found protected stack objects not pre-allocated by " 987 "LocalStackSlotPass."); 988 989 AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown, 990 Offset, MaxAlign, Skew); 991 AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown, 992 Offset, MaxAlign, Skew); 993 AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown, 994 Offset, MaxAlign, Skew); 995 } 996 997 SmallVector<int, 8> ObjectsToAllocate; 998 999 // Then prepare to assign frame offsets to stack objects that are not used to 1000 // spill callee saved registers. 1001 for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) { 1002 if (MFI.isObjectPreAllocated(i) && MFI.getUseLocalStackAllocationBlock()) 1003 continue; 1004 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) 1005 continue; 1006 if (RS && RS->isScavengingFrameIndex((int)i)) 1007 continue; 1008 if (MFI.isDeadObjectIndex(i)) 1009 continue; 1010 if (MFI.getStackProtectorIndex() == (int)i || EHRegNodeFrameIndex == (int)i) 1011 continue; 1012 if (ProtectedObjs.count(i)) 1013 continue; 1014 if (MFI.getStackID(i) != 1015 TargetStackID::Default) // Only allocate objects on the default stack. 1016 continue; 1017 1018 // Add the objects that we need to allocate to our working set. 1019 ObjectsToAllocate.push_back(i); 1020 } 1021 1022 // Allocate the EH registration node first if one is present. 1023 if (EHRegNodeFrameIndex != std::numeric_limits<int>::max()) 1024 AdjustStackOffset(MFI, EHRegNodeFrameIndex, StackGrowsDown, Offset, 1025 MaxAlign, Skew); 1026 1027 // Give the targets a chance to order the objects the way they like it. 1028 if (MF.getTarget().getOptLevel() != CodeGenOpt::None && 1029 MF.getTarget().Options.StackSymbolOrdering) 1030 TFI.orderFrameObjects(MF, ObjectsToAllocate); 1031 1032 // Keep track of which bytes in the fixed and callee-save range are used so we 1033 // can use the holes when allocating later stack objects. Only do this if 1034 // stack protector isn't being used and the target requests it and we're 1035 // optimizing. 1036 BitVector StackBytesFree; 1037 if (!ObjectsToAllocate.empty() && 1038 MF.getTarget().getOptLevel() != CodeGenOpt::None && 1039 MFI.getStackProtectorIndex() < 0 && TFI.enableStackSlotScavenging(MF)) 1040 computeFreeStackSlots(MFI, StackGrowsDown, MinCSFrameIndex, MaxCSFrameIndex, 1041 FixedCSEnd, StackBytesFree); 1042 1043 // Now walk the objects and actually assign base offsets to them. 1044 for (auto &Object : ObjectsToAllocate) 1045 if (!scavengeStackSlot(MFI, Object, StackGrowsDown, MaxAlign, 1046 StackBytesFree)) 1047 AdjustStackOffset(MFI, Object, StackGrowsDown, Offset, MaxAlign, Skew); 1048 1049 // Make sure the special register scavenging spill slot is closest to the 1050 // stack pointer. 1051 if (RS && !EarlyScavengingSlots) { 1052 SmallVector<int, 2> SFIs; 1053 RS->getScavengingFrameIndices(SFIs); 1054 for (SmallVectorImpl<int>::iterator I = SFIs.begin(), 1055 IE = SFIs.end(); I != IE; ++I) 1056 AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign, Skew); 1057 } 1058 1059 if (!TFI.targetHandlesStackFrameRounding()) { 1060 // If we have reserved argument space for call sites in the function 1061 // immediately on entry to the current function, count it as part of the 1062 // overall stack size. 1063 if (MFI.adjustsStack() && TFI.hasReservedCallFrame(MF)) 1064 Offset += MFI.getMaxCallFrameSize(); 1065 1066 // Round up the size to a multiple of the alignment. If the function has 1067 // any calls or alloca's, align to the target's StackAlignment value to 1068 // ensure that the callee's frame or the alloca data is suitably aligned; 1069 // otherwise, for leaf functions, align to the TransientStackAlignment 1070 // value. 1071 unsigned StackAlign; 1072 if (MFI.adjustsStack() || MFI.hasVarSizedObjects() || 1073 (RegInfo->needsStackRealignment(MF) && MFI.getObjectIndexEnd() != 0)) 1074 StackAlign = TFI.getStackAlignment(); 1075 else 1076 StackAlign = TFI.getTransientStackAlignment(); 1077 1078 // If the frame pointer is eliminated, all frame offsets will be relative to 1079 // SP not FP. Align to MaxAlign so this works. 1080 StackAlign = std::max(StackAlign, MaxAlign); 1081 Offset = alignTo(Offset, StackAlign, Skew); 1082 } 1083 1084 // Update frame info to pretend that this is part of the stack... 1085 int64_t StackSize = Offset - LocalAreaOffset; 1086 MFI.setStackSize(StackSize); 1087 NumBytesStackSpace += StackSize; 1088 } 1089 1090 /// insertPrologEpilogCode - Scan the function for modified callee saved 1091 /// registers, insert spill code for these callee saved registers, then add 1092 /// prolog and epilog code to the function. 1093 void PEI::insertPrologEpilogCode(MachineFunction &MF) { 1094 const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering(); 1095 1096 // Add prologue to the function... 1097 for (MachineBasicBlock *SaveBlock : SaveBlocks) 1098 TFI.emitPrologue(MF, *SaveBlock); 1099 1100 // Add epilogue to restore the callee-save registers in each exiting block. 1101 for (MachineBasicBlock *RestoreBlock : RestoreBlocks) 1102 TFI.emitEpilogue(MF, *RestoreBlock); 1103 1104 for (MachineBasicBlock *SaveBlock : SaveBlocks) 1105 TFI.inlineStackProbe(MF, *SaveBlock); 1106 1107 // Emit additional code that is required to support segmented stacks, if 1108 // we've been asked for it. This, when linked with a runtime with support 1109 // for segmented stacks (libgcc is one), will result in allocating stack 1110 // space in small chunks instead of one large contiguous block. 1111 if (MF.shouldSplitStack()) { 1112 for (MachineBasicBlock *SaveBlock : SaveBlocks) 1113 TFI.adjustForSegmentedStacks(MF, *SaveBlock); 1114 // Record that there are split-stack functions, so we will emit a 1115 // special section to tell the linker. 1116 MF.getMMI().setHasSplitStack(true); 1117 } else 1118 MF.getMMI().setHasNosplitStack(true); 1119 1120 // Emit additional code that is required to explicitly handle the stack in 1121 // HiPE native code (if needed) when loaded in the Erlang/OTP runtime. The 1122 // approach is rather similar to that of Segmented Stacks, but it uses a 1123 // different conditional check and another BIF for allocating more stack 1124 // space. 1125 if (MF.getFunction().getCallingConv() == CallingConv::HiPE) 1126 for (MachineBasicBlock *SaveBlock : SaveBlocks) 1127 TFI.adjustForHiPEPrologue(MF, *SaveBlock); 1128 } 1129 1130 /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical 1131 /// register references and actual offsets. 1132 void PEI::replaceFrameIndices(MachineFunction &MF) { 1133 const auto &ST = MF.getSubtarget(); 1134 const TargetFrameLowering &TFI = *ST.getFrameLowering(); 1135 if (!TFI.needsFrameIndexResolution(MF)) 1136 return; 1137 1138 const TargetRegisterInfo *TRI = ST.getRegisterInfo(); 1139 1140 // Allow the target to determine this after knowing the frame size. 1141 FrameIndexEliminationScavenging = (RS && !FrameIndexVirtualScavenging) || 1142 TRI->requiresFrameIndexReplacementScavenging(MF); 1143 1144 // Store SPAdj at exit of a basic block. 1145 SmallVector<int, 8> SPState; 1146 SPState.resize(MF.getNumBlockIDs()); 1147 df_iterator_default_set<MachineBasicBlock*> Reachable; 1148 1149 // Iterate over the reachable blocks in DFS order. 1150 for (auto DFI = df_ext_begin(&MF, Reachable), DFE = df_ext_end(&MF, Reachable); 1151 DFI != DFE; ++DFI) { 1152 int SPAdj = 0; 1153 // Check the exit state of the DFS stack predecessor. 1154 if (DFI.getPathLength() >= 2) { 1155 MachineBasicBlock *StackPred = DFI.getPath(DFI.getPathLength() - 2); 1156 assert(Reachable.count(StackPred) && 1157 "DFS stack predecessor is already visited.\n"); 1158 SPAdj = SPState[StackPred->getNumber()]; 1159 } 1160 MachineBasicBlock *BB = *DFI; 1161 replaceFrameIndices(BB, MF, SPAdj); 1162 SPState[BB->getNumber()] = SPAdj; 1163 } 1164 1165 // Handle the unreachable blocks. 1166 for (auto &BB : MF) { 1167 if (Reachable.count(&BB)) 1168 // Already handled in DFS traversal. 1169 continue; 1170 int SPAdj = 0; 1171 replaceFrameIndices(&BB, MF, SPAdj); 1172 } 1173 } 1174 1175 void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &MF, 1176 int &SPAdj) { 1177 assert(MF.getSubtarget().getRegisterInfo() && 1178 "getRegisterInfo() must be implemented!"); 1179 const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); 1180 const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo(); 1181 const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering(); 1182 1183 if (RS && FrameIndexEliminationScavenging) 1184 RS->enterBasicBlock(*BB); 1185 1186 bool InsideCallSequence = false; 1187 1188 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { 1189 if (TII.isFrameInstr(*I)) { 1190 InsideCallSequence = TII.isFrameSetup(*I); 1191 SPAdj += TII.getSPAdjust(*I); 1192 I = TFI->eliminateCallFramePseudoInstr(MF, *BB, I); 1193 continue; 1194 } 1195 1196 MachineInstr &MI = *I; 1197 bool DoIncr = true; 1198 bool DidFinishLoop = true; 1199 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 1200 if (!MI.getOperand(i).isFI()) 1201 continue; 1202 1203 // Frame indices in debug values are encoded in a target independent 1204 // way with simply the frame index and offset rather than any 1205 // target-specific addressing mode. 1206 if (MI.isDebugValue()) { 1207 assert(i == 0 && "Frame indices can only appear as the first " 1208 "operand of a DBG_VALUE machine instruction"); 1209 unsigned Reg; 1210 unsigned FrameIdx = MI.getOperand(0).getIndex(); 1211 unsigned Size = MF.getFrameInfo().getObjectSize(FrameIdx); 1212 1213 int64_t Offset = 1214 TFI->getFrameIndexReference(MF, FrameIdx, Reg); 1215 MI.getOperand(0).ChangeToRegister(Reg, false /*isDef*/); 1216 MI.getOperand(0).setIsDebug(); 1217 1218 const DIExpression *DIExpr = MI.getDebugExpression(); 1219 1220 // If we have a direct DBG_VALUE, and its location expression isn't 1221 // currently complex, then adding an offset will morph it into a 1222 // complex location that is interpreted as being a memory address. 1223 // This changes a pointer-valued variable to dereference that pointer, 1224 // which is incorrect. Fix by adding DW_OP_stack_value. 1225 unsigned PrependFlags = DIExpression::ApplyOffset; 1226 if (!MI.isIndirectDebugValue() && !DIExpr->isComplex()) 1227 PrependFlags |= DIExpression::StackValue; 1228 1229 // If we have DBG_VALUE that is indirect and has a Implicit location 1230 // expression need to insert a deref before prepending a Memory 1231 // location expression. Also after doing this we change the DBG_VALUE 1232 // to be direct. 1233 if (MI.isIndirectDebugValue() && DIExpr->isImplicit()) { 1234 SmallVector<uint64_t, 2> Ops = {dwarf::DW_OP_deref_size, Size}; 1235 bool WithStackValue = true; 1236 DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, WithStackValue); 1237 // Make the DBG_VALUE direct. 1238 MI.getOperand(1).ChangeToRegister(0, false); 1239 } 1240 DIExpr = DIExpression::prepend(DIExpr, PrependFlags, Offset); 1241 MI.getOperand(3).setMetadata(DIExpr); 1242 continue; 1243 } 1244 1245 // TODO: This code should be commoned with the code for 1246 // PATCHPOINT. There's no good reason for the difference in 1247 // implementation other than historical accident. The only 1248 // remaining difference is the unconditional use of the stack 1249 // pointer as the base register. 1250 if (MI.getOpcode() == TargetOpcode::STATEPOINT) { 1251 assert((!MI.isDebugValue() || i == 0) && 1252 "Frame indicies can only appear as the first operand of a " 1253 "DBG_VALUE machine instruction"); 1254 unsigned Reg; 1255 MachineOperand &Offset = MI.getOperand(i + 1); 1256 int refOffset = TFI->getFrameIndexReferencePreferSP( 1257 MF, MI.getOperand(i).getIndex(), Reg, /*IgnoreSPUpdates*/ false); 1258 Offset.setImm(Offset.getImm() + refOffset + SPAdj); 1259 MI.getOperand(i).ChangeToRegister(Reg, false /*isDef*/); 1260 continue; 1261 } 1262 1263 // Some instructions (e.g. inline asm instructions) can have 1264 // multiple frame indices and/or cause eliminateFrameIndex 1265 // to insert more than one instruction. We need the register 1266 // scavenger to go through all of these instructions so that 1267 // it can update its register information. We keep the 1268 // iterator at the point before insertion so that we can 1269 // revisit them in full. 1270 bool AtBeginning = (I == BB->begin()); 1271 if (!AtBeginning) --I; 1272 1273 // If this instruction has a FrameIndex operand, we need to 1274 // use that target machine register info object to eliminate 1275 // it. 1276 TRI.eliminateFrameIndex(MI, SPAdj, i, 1277 FrameIndexEliminationScavenging ? RS : nullptr); 1278 1279 // Reset the iterator if we were at the beginning of the BB. 1280 if (AtBeginning) { 1281 I = BB->begin(); 1282 DoIncr = false; 1283 } 1284 1285 DidFinishLoop = false; 1286 break; 1287 } 1288 1289 // If we are looking at a call sequence, we need to keep track of 1290 // the SP adjustment made by each instruction in the sequence. 1291 // This includes both the frame setup/destroy pseudos (handled above), 1292 // as well as other instructions that have side effects w.r.t the SP. 1293 // Note that this must come after eliminateFrameIndex, because 1294 // if I itself referred to a frame index, we shouldn't count its own 1295 // adjustment. 1296 if (DidFinishLoop && InsideCallSequence) 1297 SPAdj += TII.getSPAdjust(MI); 1298 1299 if (DoIncr && I != BB->end()) ++I; 1300 1301 // Update register states. 1302 if (RS && FrameIndexEliminationScavenging && DidFinishLoop) 1303 RS->forward(MI); 1304 } 1305 } 1306