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