PrologEpilogInserter.cpp revision e31e4e51a9305b623eec819ceb6b71f20b259864
1//===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This pass is responsible for finalizing the functions frame layout, saving 11// callee saved registers, and for emitting prolog & epilog code for the 12// function. 13// 14// This pass must be run after register allocation. After this pass is 15// executed, it is illegal to construct MO_FrameIndex operands. 16// 17// This pass provides an optional shrink wrapping variant of prolog/epilog 18// insertion, enabled via --shrink-wrap. See ShrinkWrapping.cpp. 19// 20//===----------------------------------------------------------------------===// 21 22#include "PrologEpilogInserter.h" 23#include "llvm/CodeGen/MachineDominators.h" 24#include "llvm/CodeGen/MachineLoopInfo.h" 25#include "llvm/CodeGen/MachineInstr.h" 26#include "llvm/CodeGen/MachineFrameInfo.h" 27#include "llvm/CodeGen/MachineModuleInfo.h" 28#include "llvm/CodeGen/MachineRegisterInfo.h" 29#include "llvm/CodeGen/RegisterScavenging.h" 30#include "llvm/Target/TargetMachine.h" 31#include "llvm/Target/TargetRegisterInfo.h" 32#include "llvm/Target/TargetFrameInfo.h" 33#include "llvm/Target/TargetInstrInfo.h" 34#include "llvm/Support/Compiler.h" 35#include "llvm/ADT/STLExtras.h" 36#include <climits> 37 38using namespace llvm; 39 40char PEI::ID = 0; 41 42static RegisterPass<PEI> 43X("prologepilog", "Prologue/Epilogue Insertion"); 44 45/// createPrologEpilogCodeInserter - This function returns a pass that inserts 46/// prolog and epilog code, and eliminates abstract frame references. 47/// 48FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); } 49 50/// runOnMachineFunction - Insert prolog/epilog code and replace abstract 51/// frame indexes with appropriate references. 52/// 53bool PEI::runOnMachineFunction(MachineFunction &Fn) { 54 const Function* F = Fn.getFunction(); 55 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); 56 RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL; 57 58 // Get MachineModuleInfo so that we can track the construction of the 59 // frame. 60 if (MachineModuleInfo *MMI = getAnalysisIfAvailable<MachineModuleInfo>()) 61 Fn.getFrameInfo()->setMachineModuleInfo(MMI); 62 63 // Calculate the MaxCallFrameSize and HasCalls variables for the function's 64 // frame information. Also eliminates call frame pseudo instructions. 65 calculateCallsInformation(Fn); 66 67 // Allow the target machine to make some adjustments to the function 68 // e.g. UsedPhysRegs before calculateCalleeSavedRegisters. 69 TRI->processFunctionBeforeCalleeSavedScan(Fn, RS); 70 71 // Scan the function for modified callee saved registers and insert spill code 72 // for any callee saved registers that are modified. 73 calculateCalleeSavedRegisters(Fn); 74 75 // Determine placement of CSR spill/restore code: 76 // - with shrink wrapping, place spills and restores to tightly 77 // enclose regions in the Machine CFG of the function where 78 // they are used. Without shrink wrapping 79 // - default (no shrink wrapping), place all spills in the 80 // entry block, all restores in return blocks. 81 placeCSRSpillsAndRestores(Fn); 82 83 // Add the code to save and restore the callee saved registers 84 if (!F->hasFnAttr(Attribute::Naked)) 85 insertCSRSpillsAndRestores(Fn); 86 87 // Allow the target machine to make final modifications to the function 88 // before the frame layout is finalized. 89 TRI->processFunctionBeforeFrameFinalized(Fn); 90 91 // Calculate actual frame offsets for all abstract stack objects... 92 calculateFrameObjectOffsets(Fn); 93 94 // Add prolog and epilog code to the function. This function is required 95 // to align the stack frame as necessary for any stack variables or 96 // called functions. Because of this, calculateCalleeSavedRegisters 97 // must be called before this function in order to set the HasCalls 98 // and MaxCallFrameSize variables. 99 if (!F->hasFnAttr(Attribute::Naked)) 100 insertPrologEpilogCode(Fn); 101 102 // Replace all MO_FrameIndex operands with physical register references 103 // and actual offsets. 104 // 105 replaceFrameIndices(Fn); 106 107 delete RS; 108 clearAllSets(); 109 return true; 110} 111 112#if 0 113void PEI::getAnalysisUsage(AnalysisUsage &AU) const { 114 AU.setPreservesCFG(); 115 if (ShrinkWrapping || ShrinkWrapFunc != "") { 116 AU.addRequired<MachineLoopInfo>(); 117 AU.addRequired<MachineDominatorTree>(); 118 } 119 AU.addPreserved<MachineLoopInfo>(); 120 AU.addPreserved<MachineDominatorTree>(); 121 MachineFunctionPass::getAnalysisUsage(AU); 122} 123#endif 124 125/// calculateCallsInformation - Calculate the MaxCallFrameSize and HasCalls 126/// variables for the function's frame information and eliminate call frame 127/// pseudo instructions. 128void PEI::calculateCallsInformation(MachineFunction &Fn) { 129 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); 130 131 unsigned MaxCallFrameSize = 0; 132 bool HasCalls = false; 133 134 // Get the function call frame set-up and tear-down instruction opcode 135 int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode(); 136 int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode(); 137 138 // Early exit for targets which have no call frame setup/destroy pseudo 139 // instructions. 140 if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1) 141 return; 142 143 std::vector<MachineBasicBlock::iterator> FrameSDOps; 144 for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) 145 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) 146 if (I->getOpcode() == FrameSetupOpcode || 147 I->getOpcode() == FrameDestroyOpcode) { 148 assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo" 149 " instructions should have a single immediate argument!"); 150 unsigned Size = I->getOperand(0).getImm(); 151 if (Size > MaxCallFrameSize) MaxCallFrameSize = Size; 152 HasCalls = true; 153 FrameSDOps.push_back(I); 154 } else if (I->getOpcode() == TargetInstrInfo::INLINEASM) { 155 // An InlineAsm might be a call; assume it is to get the stack frame 156 // aligned correctly for calls. 157 HasCalls = true; 158 } 159 160 MachineFrameInfo *FFI = Fn.getFrameInfo(); 161 FFI->setHasCalls(HasCalls); 162 FFI->setMaxCallFrameSize(MaxCallFrameSize); 163 164 for (std::vector<MachineBasicBlock::iterator>::iterator 165 i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) { 166 MachineBasicBlock::iterator I = *i; 167 168 // If call frames are not being included as part of the stack frame, and 169 // there is no dynamic allocation (therefore referencing frame slots off 170 // sp), leave the pseudo ops alone. We'll eliminate them later. 171 if (RegInfo->hasReservedCallFrame(Fn) || RegInfo->hasFP(Fn)) 172 RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I); 173 } 174} 175 176 177/// calculateCalleeSavedRegisters - Scan the function for modified callee saved 178/// registers. 179void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) { 180 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); 181 const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo(); 182 MachineFrameInfo *FFI = Fn.getFrameInfo(); 183 184 // Get the callee saved register list... 185 const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn); 186 187 // These are used to keep track the callee-save area. Initialize them. 188 MinCSFrameIndex = INT_MAX; 189 MaxCSFrameIndex = 0; 190 191 // Early exit for targets which have no callee saved registers. 192 if (CSRegs == 0 || CSRegs[0] == 0) 193 return; 194 195 // Figure out which *callee saved* registers are modified by the current 196 // function, thus needing to be saved and restored in the prolog/epilog. 197 const TargetRegisterClass * const *CSRegClasses = 198 RegInfo->getCalleeSavedRegClasses(&Fn); 199 200 std::vector<CalleeSavedInfo> CSI; 201 for (unsigned i = 0; CSRegs[i]; ++i) { 202 unsigned Reg = CSRegs[i]; 203 if (Fn.getRegInfo().isPhysRegUsed(Reg)) { 204 // If the reg is modified, save it! 205 CSI.push_back(CalleeSavedInfo(Reg, CSRegClasses[i])); 206 } else { 207 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg); 208 *AliasSet; ++AliasSet) { // Check alias registers too. 209 if (Fn.getRegInfo().isPhysRegUsed(*AliasSet)) { 210 CSI.push_back(CalleeSavedInfo(Reg, CSRegClasses[i])); 211 break; 212 } 213 } 214 } 215 } 216 217 if (CSI.empty()) 218 return; // Early exit if no callee saved registers are modified! 219 220 unsigned NumFixedSpillSlots; 221 const std::pair<unsigned,int> *FixedSpillSlots = 222 TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots); 223 224 // Now that we know which registers need to be saved and restored, allocate 225 // stack slots for them. 226 for (std::vector<CalleeSavedInfo>::iterator 227 I = CSI.begin(), E = CSI.end(); I != E; ++I) { 228 unsigned Reg = I->getReg(); 229 const TargetRegisterClass *RC = I->getRegClass(); 230 231 int FrameIdx; 232 if (RegInfo->hasReservedSpillSlot(Fn, Reg, FrameIdx)) { 233 I->setFrameIdx(FrameIdx); 234 continue; 235 } 236 237 // Check to see if this physreg must be spilled to a particular stack slot 238 // on this target. 239 const std::pair<unsigned,int> *FixedSlot = FixedSpillSlots; 240 while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots && 241 FixedSlot->first != Reg) 242 ++FixedSlot; 243 244 if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) { 245 // Nope, just spill it anywhere convenient. 246 unsigned Align = RC->getAlignment(); 247 unsigned StackAlign = TFI->getStackAlignment(); 248 249 // We may not be able to satisfy the desired alignment specification of 250 // the TargetRegisterClass if the stack alignment is smaller. Use the 251 // min. 252 Align = std::min(Align, StackAlign); 253 FrameIdx = FFI->CreateStackObject(RC->getSize(), Align); 254 if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx; 255 if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx; 256 } else { 257 // Spill it to the stack where we must. 258 FrameIdx = FFI->CreateFixedObject(RC->getSize(), FixedSlot->second); 259 } 260 261 I->setFrameIdx(FrameIdx); 262 } 263 264 FFI->setCalleeSavedInfo(CSI); 265} 266 267/// insertCSRSpillsAndRestores - Insert spill and restore code for 268/// callee saved registers used in the function, handling shrink wrapping. 269/// 270void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) { 271 // Get callee saved register information. 272 MachineFrameInfo *FFI = Fn.getFrameInfo(); 273 const std::vector<CalleeSavedInfo> &CSI = FFI->getCalleeSavedInfo(); 274 275 FFI->setCalleeSavedInfoValid(true); 276 277 // Early exit if no callee saved registers are modified! 278 if (CSI.empty()) 279 return; 280 281 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo(); 282 MachineBasicBlock::iterator I; 283 284 if (! ShrinkWrapThisFunction) { 285 // Spill using target interface. 286 I = EntryBlock->begin(); 287 if (!TII.spillCalleeSavedRegisters(*EntryBlock, I, CSI)) { 288 for (unsigned i = 0, e = CSI.size(); i != e; ++i) { 289 // Add the callee-saved register as live-in. 290 // It's killed at the spill. 291 EntryBlock->addLiveIn(CSI[i].getReg()); 292 293 // Insert the spill to the stack frame. 294 TII.storeRegToStackSlot(*EntryBlock, I, CSI[i].getReg(), true, 295 CSI[i].getFrameIdx(), CSI[i].getRegClass()); 296 } 297 } 298 299 // Restore using target interface. 300 for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) { 301 MachineBasicBlock* MBB = ReturnBlocks[ri]; 302 I = MBB->end(); --I; 303 304 // Skip over all terminator instructions, which are part of the return 305 // sequence. 306 MachineBasicBlock::iterator I2 = I; 307 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator()) 308 I = I2; 309 310 bool AtStart = I == MBB->begin(); 311 MachineBasicBlock::iterator BeforeI = I; 312 if (!AtStart) 313 --BeforeI; 314 315 // Restore all registers immediately before the return and any 316 // terminators that preceed it. 317 if (!TII.restoreCalleeSavedRegisters(*MBB, I, CSI)) { 318 for (unsigned i = 0, e = CSI.size(); i != e; ++i) { 319 TII.loadRegFromStackSlot(*MBB, I, CSI[i].getReg(), 320 CSI[i].getFrameIdx(), 321 CSI[i].getRegClass()); 322 assert(I != MBB->begin() && 323 "loadRegFromStackSlot didn't insert any code!"); 324 // Insert in reverse order. loadRegFromStackSlot can insert 325 // multiple instructions. 326 if (AtStart) 327 I = MBB->begin(); 328 else { 329 I = BeforeI; 330 ++I; 331 } 332 } 333 } 334 } 335 return; 336 } 337 338 // Insert spills. 339 std::vector<CalleeSavedInfo> blockCSI; 340 for (CSRegBlockMap::iterator BI = CSRSave.begin(), 341 BE = CSRSave.end(); BI != BE; ++BI) { 342 MachineBasicBlock* MBB = BI->first; 343 CSRegSet save = BI->second; 344 345 if (save.empty()) 346 continue; 347 348 blockCSI.clear(); 349 for (CSRegSet::iterator RI = save.begin(), 350 RE = save.end(); RI != RE; ++RI) { 351 blockCSI.push_back(CSI[*RI]); 352 } 353 assert(blockCSI.size() > 0 && 354 "Could not collect callee saved register info"); 355 356 I = MBB->begin(); 357 358 // When shrink wrapping, use stack slot stores/loads. 359 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) { 360 // Add the callee-saved register as live-in. 361 // It's killed at the spill. 362 MBB->addLiveIn(blockCSI[i].getReg()); 363 364 // Insert the spill to the stack frame. 365 TII.storeRegToStackSlot(*MBB, I, blockCSI[i].getReg(), 366 true, 367 blockCSI[i].getFrameIdx(), 368 blockCSI[i].getRegClass()); 369 } 370 } 371 372 for (CSRegBlockMap::iterator BI = CSRRestore.begin(), 373 BE = CSRRestore.end(); BI != BE; ++BI) { 374 MachineBasicBlock* MBB = BI->first; 375 CSRegSet restore = BI->second; 376 377 if (restore.empty()) 378 continue; 379 380 blockCSI.clear(); 381 for (CSRegSet::iterator RI = restore.begin(), 382 RE = restore.end(); RI != RE; ++RI) { 383 blockCSI.push_back(CSI[*RI]); 384 } 385 assert(blockCSI.size() > 0 && 386 "Could not find callee saved register info"); 387 388 // If MBB is empty and needs restores, insert at the _beginning_. 389 if (MBB->empty()) { 390 I = MBB->begin(); 391 } else { 392 I = MBB->end(); 393 --I; 394 395 // Skip over all terminator instructions, which are part of the 396 // return sequence. 397 if (! I->getDesc().isTerminator()) { 398 ++I; 399 } else { 400 MachineBasicBlock::iterator I2 = I; 401 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator()) 402 I = I2; 403 } 404 } 405 406 bool AtStart = I == MBB->begin(); 407 MachineBasicBlock::iterator BeforeI = I; 408 if (!AtStart) 409 --BeforeI; 410 411 // Restore all registers immediately before the return and any 412 // terminators that preceed it. 413 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) { 414 TII.loadRegFromStackSlot(*MBB, I, blockCSI[i].getReg(), 415 blockCSI[i].getFrameIdx(), 416 blockCSI[i].getRegClass()); 417 assert(I != MBB->begin() && 418 "loadRegFromStackSlot didn't insert any code!"); 419 // Insert in reverse order. loadRegFromStackSlot can insert 420 // multiple instructions. 421 if (AtStart) 422 I = MBB->begin(); 423 else { 424 I = BeforeI; 425 ++I; 426 } 427 } 428 } 429} 430 431/// AdjustStackOffset - Helper function used to adjust the stack frame offset. 432static inline void 433AdjustStackOffset(MachineFrameInfo *FFI, int FrameIdx, 434 bool StackGrowsDown, int64_t &Offset, 435 unsigned &MaxAlign) { 436 // If stack grows down, we need to add size of find the lowest address of the 437 // object. 438 if (StackGrowsDown) 439 Offset += FFI->getObjectSize(FrameIdx); 440 441 unsigned Align = FFI->getObjectAlignment(FrameIdx); 442 443 // If the alignment of this object is greater than that of the stack, then 444 // increase the stack alignment to match. 445 MaxAlign = std::max(MaxAlign, Align); 446 447 // Adjust to alignment boundary. 448 Offset = (Offset + Align - 1) / Align * Align; 449 450 if (StackGrowsDown) { 451 FFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset 452 } else { 453 FFI->setObjectOffset(FrameIdx, Offset); 454 Offset += FFI->getObjectSize(FrameIdx); 455 } 456} 457 458/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the 459/// abstract stack objects. 460/// 461void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { 462 const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo(); 463 464 bool StackGrowsDown = 465 TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown; 466 467 // Loop over all of the stack objects, assigning sequential addresses... 468 MachineFrameInfo *FFI = Fn.getFrameInfo(); 469 470 unsigned MaxAlign = FFI->getMaxAlignment(); 471 472 // Start at the beginning of the local area. 473 // The Offset is the distance from the stack top in the direction 474 // of stack growth -- so it's always nonnegative. 475 int64_t Offset = TFI.getOffsetOfLocalArea(); 476 if (StackGrowsDown) 477 Offset = -Offset; 478 assert(Offset >= 0 479 && "Local area offset should be in direction of stack growth"); 480 481 // If there are fixed sized objects that are preallocated in the local area, 482 // non-fixed objects can't be allocated right at the start of local area. 483 // We currently don't support filling in holes in between fixed sized 484 // objects, so we adjust 'Offset' to point to the end of last fixed sized 485 // preallocated object. 486 for (int i = FFI->getObjectIndexBegin(); i != 0; ++i) { 487 int64_t FixedOff; 488 if (StackGrowsDown) { 489 // The maximum distance from the stack pointer is at lower address of 490 // the object -- which is given by offset. For down growing stack 491 // the offset is negative, so we negate the offset to get the distance. 492 FixedOff = -FFI->getObjectOffset(i); 493 } else { 494 // The maximum distance from the start pointer is at the upper 495 // address of the object. 496 FixedOff = FFI->getObjectOffset(i) + FFI->getObjectSize(i); 497 } 498 if (FixedOff > Offset) Offset = FixedOff; 499 } 500 501 // First assign frame offsets to stack objects that are used to spill 502 // callee saved registers. 503 if (StackGrowsDown) { 504 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) { 505 // If stack grows down, we need to add size of find the lowest 506 // address of the object. 507 Offset += FFI->getObjectSize(i); 508 509 unsigned Align = FFI->getObjectAlignment(i); 510 // If the alignment of this object is greater than that of the stack, 511 // then increase the stack alignment to match. 512 MaxAlign = std::max(MaxAlign, Align); 513 // Adjust to alignment boundary 514 Offset = (Offset+Align-1)/Align*Align; 515 516 FFI->setObjectOffset(i, -Offset); // Set the computed offset 517 } 518 } else { 519 int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex; 520 for (int i = MaxCSFI; i >= MinCSFI ; --i) { 521 unsigned Align = FFI->getObjectAlignment(i); 522 // If the alignment of this object is greater than that of the stack, 523 // then increase the stack alignment to match. 524 MaxAlign = std::max(MaxAlign, Align); 525 // Adjust to alignment boundary 526 Offset = (Offset+Align-1)/Align*Align; 527 528 FFI->setObjectOffset(i, Offset); 529 Offset += FFI->getObjectSize(i); 530 } 531 } 532 533 // Make sure the special register scavenging spill slot is closest to the 534 // frame pointer if a frame pointer is required. 535 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); 536 if (RS && RegInfo->hasFP(Fn)) { 537 int SFI = RS->getScavengingFrameIndex(); 538 if (SFI >= 0) 539 AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign); 540 } 541 542 // Make sure that the stack protector comes before the local variables on the 543 // stack. 544 if (FFI->getStackProtectorIndex() >= 0) 545 AdjustStackOffset(FFI, FFI->getStackProtectorIndex(), StackGrowsDown, 546 Offset, MaxAlign); 547 548 // Then assign frame offsets to stack objects that are not used to spill 549 // callee saved registers. 550 for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) { 551 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) 552 continue; 553 if (RS && (int)i == RS->getScavengingFrameIndex()) 554 continue; 555 if (FFI->isDeadObjectIndex(i)) 556 continue; 557 if (FFI->getStackProtectorIndex() == (int)i) 558 continue; 559 560 AdjustStackOffset(FFI, i, StackGrowsDown, Offset, MaxAlign); 561 } 562 563 // Make sure the special register scavenging spill slot is closest to the 564 // stack pointer. 565 if (RS && !RegInfo->hasFP(Fn)) { 566 int SFI = RS->getScavengingFrameIndex(); 567 if (SFI >= 0) 568 AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign); 569 } 570 571 // Round up the size to a multiple of the alignment, but only if there are 572 // calls or alloca's in the function. This ensures that any calls to 573 // subroutines have their stack frames suitably aligned. 574 // Also do this if we need runtime alignment of the stack. In this case 575 // offsets will be relative to SP not FP; round up the stack size so this 576 // works. 577 if (!RegInfo->targetHandlesStackFrameRounding() && 578 (FFI->hasCalls() || FFI->hasVarSizedObjects() || 579 (RegInfo->needsStackRealignment(Fn) && 580 FFI->getObjectIndexEnd() != 0))) { 581 // If we have reserved argument space for call sites in the function 582 // immediately on entry to the current function, count it as part of the 583 // overall stack size. 584 if (RegInfo->hasReservedCallFrame(Fn)) 585 Offset += FFI->getMaxCallFrameSize(); 586 587 unsigned AlignMask = std::max(TFI.getStackAlignment(), MaxAlign) - 1; 588 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask); 589 } 590 591 // Update frame info to pretend that this is part of the stack... 592 FFI->setStackSize(Offset+TFI.getOffsetOfLocalArea()); 593 594 // Remember the required stack alignment in case targets need it to perform 595 // dynamic stack alignment. 596 FFI->setMaxAlignment(MaxAlign); 597} 598 599 600/// insertPrologEpilogCode - Scan the function for modified callee saved 601/// registers, insert spill code for these callee saved registers, then add 602/// prolog and epilog code to the function. 603/// 604void PEI::insertPrologEpilogCode(MachineFunction &Fn) { 605 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); 606 607 // Add prologue to the function... 608 TRI->emitPrologue(Fn); 609 610 // Add epilogue to restore the callee-save registers in each exiting block 611 for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) { 612 // If last instruction is a return instruction, add an epilogue 613 if (!I->empty() && I->back().getDesc().isReturn()) 614 TRI->emitEpilogue(Fn, *I); 615 } 616} 617 618 619/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical 620/// register references and actual offsets. 621/// 622void PEI::replaceFrameIndices(MachineFunction &Fn) { 623 if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do? 624 625 const TargetMachine &TM = Fn.getTarget(); 626 assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!"); 627 const TargetRegisterInfo &TRI = *TM.getRegisterInfo(); 628 const TargetFrameInfo *TFI = TM.getFrameInfo(); 629 bool StackGrowsDown = 630 TFI->getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown; 631 int FrameSetupOpcode = TRI.getCallFrameSetupOpcode(); 632 int FrameDestroyOpcode = TRI.getCallFrameDestroyOpcode(); 633 634 for (MachineFunction::iterator BB = Fn.begin(), 635 E = Fn.end(); BB != E; ++BB) { 636 int SPAdj = 0; // SP offset due to call frame setup / destroy. 637 if (RS) RS->enterBasicBlock(BB); 638 639 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { 640 641 if (I->getOpcode() == FrameSetupOpcode || 642 I->getOpcode() == FrameDestroyOpcode) { 643 // Remember how much SP has been adjusted to create the call 644 // frame. 645 int Size = I->getOperand(0).getImm(); 646 647 if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) || 648 (StackGrowsDown && I->getOpcode() == FrameDestroyOpcode)) 649 Size = -Size; 650 651 SPAdj += Size; 652 653 MachineBasicBlock::iterator PrevI = BB->end(); 654 if (I != BB->begin()) PrevI = prior(I); 655 TRI.eliminateCallFramePseudoInstr(Fn, *BB, I); 656 657 // Visit the instructions created by eliminateCallFramePseudoInstr(). 658 if (PrevI == BB->end()) 659 I = BB->begin(); // The replaced instr was the first in the block. 660 else 661 I = next(PrevI); 662 continue; 663 } 664 665 MachineInstr *MI = I; 666 bool DoIncr = true; 667 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) 668 if (MI->getOperand(i).isFI()) { 669 // Some instructions (e.g. inline asm instructions) can have 670 // multiple frame indices and/or cause eliminateFrameIndex 671 // to insert more than one instruction. We need the register 672 // scavenger to go through all of these instructions so that 673 // it can update its register information. We keep the 674 // iterator at the point before insertion so that we can 675 // revisit them in full. 676 bool AtBeginning = (I == BB->begin()); 677 if (!AtBeginning) --I; 678 679 // If this instruction has a FrameIndex operand, we need to 680 // use that target machine register info object to eliminate 681 // it. 682 683 TRI.eliminateFrameIndex(MI, SPAdj, RS); 684 685 // Reset the iterator if we were at the beginning of the BB. 686 if (AtBeginning) { 687 I = BB->begin(); 688 DoIncr = false; 689 } 690 691 MI = 0; 692 break; 693 } 694 695 if (DoIncr && I != BB->end()) ++I; 696 697 // Update register states. 698 if (RS && MI) RS->forward(MI); 699 } 700 701 assert(SPAdj == 0 && "Unbalanced call frame setup / destroy pairs?"); 702 } 703} 704 705