PrologEpilogInserter.cpp revision 845012e6d31799c7fbd1193fa1af8ee2d12e9231
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 // Early exit if no callee saved registers are modified! 276 if (CSI.empty()) 277 return; 278 279 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo(); 280 MachineBasicBlock::iterator I; 281 282 if (! ShrinkWrapThisFunction) { 283 // Spill using target interface. 284 I = EntryBlock->begin(); 285 if (!TII.spillCalleeSavedRegisters(*EntryBlock, I, CSI)) { 286 for (unsigned i = 0, e = CSI.size(); i != e; ++i) { 287 // Add the callee-saved register as live-in. 288 // It's killed at the spill. 289 EntryBlock->addLiveIn(CSI[i].getReg()); 290 291 // Insert the spill to the stack frame. 292 TII.storeRegToStackSlot(*EntryBlock, I, CSI[i].getReg(), true, 293 CSI[i].getFrameIdx(), CSI[i].getRegClass()); 294 } 295 } 296 297 // Restore using target interface. 298 for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) { 299 MachineBasicBlock* MBB = ReturnBlocks[ri]; 300 I = MBB->end(); --I; 301 302 // Skip over all terminator instructions, which are part of the return 303 // sequence. 304 MachineBasicBlock::iterator I2 = I; 305 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator()) 306 I = I2; 307 308 bool AtStart = I == MBB->begin(); 309 MachineBasicBlock::iterator BeforeI = I; 310 if (!AtStart) 311 --BeforeI; 312 313 // Restore all registers immediately before the return and any 314 // terminators that preceed it. 315 if (!TII.restoreCalleeSavedRegisters(*MBB, I, CSI)) { 316 for (unsigned i = 0, e = CSI.size(); i != e; ++i) { 317 TII.loadRegFromStackSlot(*MBB, I, CSI[i].getReg(), 318 CSI[i].getFrameIdx(), 319 CSI[i].getRegClass()); 320 assert(I != MBB->begin() && 321 "loadRegFromStackSlot didn't insert any code!"); 322 // Insert in reverse order. loadRegFromStackSlot can insert 323 // multiple instructions. 324 if (AtStart) 325 I = MBB->begin(); 326 else { 327 I = BeforeI; 328 ++I; 329 } 330 } 331 } 332 } 333 return; 334 } 335 336 // Insert spills. 337 std::vector<CalleeSavedInfo> blockCSI; 338 for (CSRegBlockMap::iterator BI = CSRSave.begin(), 339 BE = CSRSave.end(); BI != BE; ++BI) { 340 MachineBasicBlock* MBB = BI->first; 341 CSRegSet save = BI->second; 342 343 if (save.empty()) 344 continue; 345 346 blockCSI.clear(); 347 for (CSRegSet::iterator RI = save.begin(), 348 RE = save.end(); RI != RE; ++RI) { 349 blockCSI.push_back(CSI[*RI]); 350 } 351 assert(blockCSI.size() > 0 && 352 "Could not collect callee saved register info"); 353 354 I = MBB->begin(); 355 356 // When shrink wrapping, use stack slot stores/loads. 357 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) { 358 // Add the callee-saved register as live-in. 359 // It's killed at the spill. 360 MBB->addLiveIn(blockCSI[i].getReg()); 361 362 // Insert the spill to the stack frame. 363 TII.storeRegToStackSlot(*MBB, I, blockCSI[i].getReg(), 364 true, 365 blockCSI[i].getFrameIdx(), 366 blockCSI[i].getRegClass()); 367 } 368 } 369 370 for (CSRegBlockMap::iterator BI = CSRRestore.begin(), 371 BE = CSRRestore.end(); BI != BE; ++BI) { 372 MachineBasicBlock* MBB = BI->first; 373 CSRegSet restore = BI->second; 374 375 if (restore.empty()) 376 continue; 377 378 blockCSI.clear(); 379 for (CSRegSet::iterator RI = restore.begin(), 380 RE = restore.end(); RI != RE; ++RI) { 381 blockCSI.push_back(CSI[*RI]); 382 } 383 assert(blockCSI.size() > 0 && 384 "Could not find callee saved register info"); 385 386 // If MBB is empty and needs restores, insert at the _beginning_. 387 if (MBB->empty()) { 388 I = MBB->begin(); 389 } else { 390 I = MBB->end(); 391 --I; 392 393 // Skip over all terminator instructions, which are part of the 394 // return sequence. 395 if (! I->getDesc().isTerminator()) { 396 ++I; 397 } else { 398 MachineBasicBlock::iterator I2 = I; 399 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator()) 400 I = I2; 401 } 402 } 403 404 bool AtStart = I == MBB->begin(); 405 MachineBasicBlock::iterator BeforeI = I; 406 if (!AtStart) 407 --BeforeI; 408 409 // Restore all registers immediately before the return and any 410 // terminators that preceed it. 411 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) { 412 TII.loadRegFromStackSlot(*MBB, I, blockCSI[i].getReg(), 413 blockCSI[i].getFrameIdx(), 414 blockCSI[i].getRegClass()); 415 assert(I != MBB->begin() && 416 "loadRegFromStackSlot didn't insert any code!"); 417 // Insert in reverse order. loadRegFromStackSlot can insert 418 // multiple instructions. 419 if (AtStart) 420 I = MBB->begin(); 421 else { 422 I = BeforeI; 423 ++I; 424 } 425 } 426 } 427} 428 429/// AdjustStackOffset - Helper function used to adjust the stack frame offset. 430static inline void 431AdjustStackOffset(MachineFrameInfo *FFI, int FrameIdx, 432 bool StackGrowsDown, int64_t &Offset, 433 unsigned &MaxAlign) { 434 // If stack grows down, we need to add size of find the lowest address of the 435 // object. 436 if (StackGrowsDown) 437 Offset += FFI->getObjectSize(FrameIdx); 438 439 unsigned Align = FFI->getObjectAlignment(FrameIdx); 440 441 // If the alignment of this object is greater than that of the stack, then 442 // increase the stack alignment to match. 443 MaxAlign = std::max(MaxAlign, Align); 444 445 // Adjust to alignment boundary. 446 Offset = (Offset + Align - 1) / Align * Align; 447 448 if (StackGrowsDown) { 449 FFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset 450 } else { 451 FFI->setObjectOffset(FrameIdx, Offset); 452 Offset += FFI->getObjectSize(FrameIdx); 453 } 454} 455 456/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the 457/// abstract stack objects. 458/// 459void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { 460 const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo(); 461 462 bool StackGrowsDown = 463 TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown; 464 465 // Loop over all of the stack objects, assigning sequential addresses... 466 MachineFrameInfo *FFI = Fn.getFrameInfo(); 467 468 unsigned MaxAlign = FFI->getMaxAlignment(); 469 470 // Start at the beginning of the local area. 471 // The Offset is the distance from the stack top in the direction 472 // of stack growth -- so it's always nonnegative. 473 int64_t Offset = TFI.getOffsetOfLocalArea(); 474 if (StackGrowsDown) 475 Offset = -Offset; 476 assert(Offset >= 0 477 && "Local area offset should be in direction of stack growth"); 478 479 // If there are fixed sized objects that are preallocated in the local area, 480 // non-fixed objects can't be allocated right at the start of local area. 481 // We currently don't support filling in holes in between fixed sized 482 // objects, so we adjust 'Offset' to point to the end of last fixed sized 483 // preallocated object. 484 for (int i = FFI->getObjectIndexBegin(); i != 0; ++i) { 485 int64_t FixedOff; 486 if (StackGrowsDown) { 487 // The maximum distance from the stack pointer is at lower address of 488 // the object -- which is given by offset. For down growing stack 489 // the offset is negative, so we negate the offset to get the distance. 490 FixedOff = -FFI->getObjectOffset(i); 491 } else { 492 // The maximum distance from the start pointer is at the upper 493 // address of the object. 494 FixedOff = FFI->getObjectOffset(i) + FFI->getObjectSize(i); 495 } 496 if (FixedOff > Offset) Offset = FixedOff; 497 } 498 499 // First assign frame offsets to stack objects that are used to spill 500 // callee saved registers. 501 if (StackGrowsDown) { 502 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) { 503 // If stack grows down, we need to add size of find the lowest 504 // address of the object. 505 Offset += FFI->getObjectSize(i); 506 507 unsigned Align = FFI->getObjectAlignment(i); 508 // If the alignment of this object is greater than that of the stack, 509 // then increase the stack alignment to match. 510 MaxAlign = std::max(MaxAlign, Align); 511 // Adjust to alignment boundary 512 Offset = (Offset+Align-1)/Align*Align; 513 514 FFI->setObjectOffset(i, -Offset); // Set the computed offset 515 } 516 } else { 517 int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex; 518 for (int i = MaxCSFI; i >= MinCSFI ; --i) { 519 unsigned Align = FFI->getObjectAlignment(i); 520 // If the alignment of this object is greater than that of the stack, 521 // then increase the stack alignment to match. 522 MaxAlign = std::max(MaxAlign, Align); 523 // Adjust to alignment boundary 524 Offset = (Offset+Align-1)/Align*Align; 525 526 FFI->setObjectOffset(i, Offset); 527 Offset += FFI->getObjectSize(i); 528 } 529 } 530 531 // Make sure the special register scavenging spill slot is closest to the 532 // frame pointer if a frame pointer is required. 533 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); 534 if (RS && RegInfo->hasFP(Fn)) { 535 int SFI = RS->getScavengingFrameIndex(); 536 if (SFI >= 0) 537 AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign); 538 } 539 540 // Make sure that the stack protector comes before the local variables on the 541 // stack. 542 if (FFI->getStackProtectorIndex() >= 0) 543 AdjustStackOffset(FFI, FFI->getStackProtectorIndex(), StackGrowsDown, 544 Offset, MaxAlign); 545 546 // Then assign frame offsets to stack objects that are not used to spill 547 // callee saved registers. 548 for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) { 549 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) 550 continue; 551 if (RS && (int)i == RS->getScavengingFrameIndex()) 552 continue; 553 if (FFI->isDeadObjectIndex(i)) 554 continue; 555 if (FFI->getStackProtectorIndex() == (int)i) 556 continue; 557 558 AdjustStackOffset(FFI, i, StackGrowsDown, Offset, MaxAlign); 559 } 560 561 // Make sure the special register scavenging spill slot is closest to the 562 // stack pointer. 563 if (RS && !RegInfo->hasFP(Fn)) { 564 int SFI = RS->getScavengingFrameIndex(); 565 if (SFI >= 0) 566 AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign); 567 } 568 569 // Round up the size to a multiple of the alignment, but only if there are 570 // calls or alloca's in the function. This ensures that any calls to 571 // subroutines have their stack frames suitable aligned. 572 // Also do this if we need runtime alignment of the stack. In this case 573 // offsets will be relative to SP not FP; round up the stack size so this 574 // works. 575 if (!RegInfo->targetHandlesStackFrameRounding() && 576 (FFI->hasCalls() || FFI->hasVarSizedObjects() || 577 (RegInfo->needsStackRealignment(Fn) && 578 FFI->getObjectIndexEnd() != 0))) { 579 // If we have reserved argument space for call sites in the function 580 // immediately on entry to the current function, count it as part of the 581 // overall stack size. 582 if (RegInfo->hasReservedCallFrame(Fn)) 583 Offset += FFI->getMaxCallFrameSize(); 584 585 unsigned AlignMask = std::max(TFI.getStackAlignment(),MaxAlign) - 1; 586 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask); 587 } 588 589 // Update frame info to pretend that this is part of the stack... 590 FFI->setStackSize(Offset+TFI.getOffsetOfLocalArea()); 591 592 // Remember the required stack alignment in case targets need it to perform 593 // dynamic stack alignment. 594 FFI->setMaxAlignment(MaxAlign); 595} 596 597 598/// insertPrologEpilogCode - Scan the function for modified callee saved 599/// registers, insert spill code for these callee saved registers, then add 600/// prolog and epilog code to the function. 601/// 602void PEI::insertPrologEpilogCode(MachineFunction &Fn) { 603 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); 604 605 // Add prologue to the function... 606 TRI->emitPrologue(Fn); 607 608 // Add epilogue to restore the callee-save registers in each exiting block 609 for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) { 610 // If last instruction is a return instruction, add an epilogue 611 if (!I->empty() && I->back().getDesc().isReturn()) 612 TRI->emitEpilogue(Fn, *I); 613 } 614} 615 616 617/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical 618/// register references and actual offsets. 619/// 620void PEI::replaceFrameIndices(MachineFunction &Fn) { 621 if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do? 622 623 const TargetMachine &TM = Fn.getTarget(); 624 assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!"); 625 const TargetRegisterInfo &TRI = *TM.getRegisterInfo(); 626 const TargetFrameInfo *TFI = TM.getFrameInfo(); 627 bool StackGrowsDown = 628 TFI->getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown; 629 int FrameSetupOpcode = TRI.getCallFrameSetupOpcode(); 630 int FrameDestroyOpcode = TRI.getCallFrameDestroyOpcode(); 631 632 for (MachineFunction::iterator BB = Fn.begin(), 633 E = Fn.end(); BB != E; ++BB) { 634 int SPAdj = 0; // SP offset due to call frame setup / destroy. 635 if (RS) RS->enterBasicBlock(BB); 636 637 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { 638 if (I->getOpcode() == TargetInstrInfo::DECLARE) { 639 // Ignore it. 640 ++I; 641 continue; 642 } 643 644 if (I->getOpcode() == FrameSetupOpcode || 645 I->getOpcode() == FrameDestroyOpcode) { 646 // Remember how much SP has been adjusted to create the call 647 // frame. 648 int Size = I->getOperand(0).getImm(); 649 650 if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) || 651 (StackGrowsDown && I->getOpcode() == FrameDestroyOpcode)) 652 Size = -Size; 653 654 SPAdj += Size; 655 656 MachineBasicBlock::iterator PrevI = BB->end(); 657 if (I != BB->begin()) PrevI = prior(I); 658 TRI.eliminateCallFramePseudoInstr(Fn, *BB, I); 659 660 // Visit the instructions created by eliminateCallFramePseudoInstr(). 661 if (PrevI == BB->end()) 662 I = BB->begin(); // The replaced instr was the first in the block. 663 else 664 I = next(PrevI); 665 continue; 666 } 667 668 MachineInstr *MI = I; 669 bool DoIncr = true; 670 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) 671 if (MI->getOperand(i).isFI()) { 672 // Some instructions (e.g. inline asm instructions) can have 673 // multiple frame indices and/or cause eliminateFrameIndex 674 // to insert more than one instruction. We need the register 675 // scavenger to go through all of these instructions so that 676 // it can update its register information. We keep the 677 // iterator at the point before insertion so that we can 678 // revisit them in full. 679 bool AtBeginning = (I == BB->begin()); 680 if (!AtBeginning) --I; 681 682 // If this instruction has a FrameIndex operand, we need to 683 // use that target machine register info object to eliminate 684 // it. 685 686 TRI.eliminateFrameIndex(MI, SPAdj, RS); 687 688 // Reset the iterator if we were at the beginning of the BB. 689 if (AtBeginning) { 690 I = BB->begin(); 691 DoIncr = false; 692 } 693 694 MI = 0; 695 break; 696 } 697 698 if (DoIncr && I != BB->end()) ++I; 699 700 // Update register states. 701 if (RS && MI) RS->forward(MI); 702 } 703 704 assert(SPAdj == 0 && "Unbalanced call frame setup / destroy pairs?"); 705 } 706} 707 708