PrologEpilogInserter.cpp revision e81abfd30b7c81735e9f3d79006c2653690aa592
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#define DEBUG_TYPE "pei" 23#include "PrologEpilogInserter.h" 24#include "llvm/InlineAsm.h" 25#include "llvm/CodeGen/MachineDominators.h" 26#include "llvm/CodeGen/MachineLoopInfo.h" 27#include "llvm/CodeGen/MachineInstr.h" 28#include "llvm/CodeGen/MachineFrameInfo.h" 29#include "llvm/CodeGen/MachineRegisterInfo.h" 30#include "llvm/CodeGen/RegisterScavenging.h" 31#include "llvm/Target/TargetMachine.h" 32#include "llvm/Target/TargetOptions.h" 33#include "llvm/Target/TargetRegisterInfo.h" 34#include "llvm/Target/TargetFrameLowering.h" 35#include "llvm/Target/TargetInstrInfo.h" 36#include "llvm/Support/CommandLine.h" 37#include "llvm/Support/Compiler.h" 38#include "llvm/Support/Debug.h" 39#include "llvm/ADT/IndexedMap.h" 40#include "llvm/ADT/SmallSet.h" 41#include "llvm/ADT/Statistic.h" 42#include "llvm/ADT/STLExtras.h" 43#include <climits> 44 45using namespace llvm; 46 47char PEI::ID = 0; 48 49INITIALIZE_PASS_BEGIN(PEI, "prologepilog", 50 "Prologue/Epilogue Insertion", false, false) 51INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) 52INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) 53INITIALIZE_PASS_END(PEI, "prologepilog", 54 "Prologue/Epilogue Insertion", false, false) 55 56STATISTIC(NumVirtualFrameRegs, "Number of virtual frame regs encountered"); 57STATISTIC(NumScavengedRegs, "Number of frame index regs scavenged"); 58STATISTIC(NumBytesStackSpace, "Number of bytes used for stack in all functions"); 59 60/// createPrologEpilogCodeInserter - This function returns a pass that inserts 61/// prolog and epilog code, and eliminates abstract frame references. 62/// 63FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); } 64 65/// runOnMachineFunction - Insert prolog/epilog code and replace abstract 66/// frame indexes with appropriate references. 67/// 68bool PEI::runOnMachineFunction(MachineFunction &Fn) { 69 const Function* F = Fn.getFunction(); 70 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); 71 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering(); 72 73 RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL; 74 FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn); 75 76 // Calculate the MaxCallFrameSize and AdjustsStack variables for the 77 // function's frame information. Also eliminates call frame pseudo 78 // instructions. 79 calculateCallsInformation(Fn); 80 81 // Allow the target machine to make some adjustments to the function 82 // e.g. UsedPhysRegs before calculateCalleeSavedRegisters. 83 TFI->processFunctionBeforeCalleeSavedScan(Fn, RS); 84 85 // Scan the function for modified callee saved registers and insert spill code 86 // for any callee saved registers that are modified. 87 calculateCalleeSavedRegisters(Fn); 88 89 // Determine placement of CSR spill/restore code: 90 // - With shrink wrapping, place spills and restores to tightly 91 // enclose regions in the Machine CFG of the function where 92 // they are used. 93 // - Without shink wrapping (default), place all spills in the 94 // entry block, all restores in return blocks. 95 placeCSRSpillsAndRestores(Fn); 96 97 // Add the code to save and restore the callee saved registers 98 if (!F->hasFnAttr(Attribute::Naked)) 99 insertCSRSpillsAndRestores(Fn); 100 101 // Allow the target machine to make final modifications to the function 102 // before the frame layout is finalized. 103 TFI->processFunctionBeforeFrameFinalized(Fn); 104 105 // Calculate actual frame offsets for all abstract stack objects... 106 calculateFrameObjectOffsets(Fn); 107 108 // Add prolog and epilog code to the function. This function is required 109 // to align the stack frame as necessary for any stack variables or 110 // called functions. Because of this, calculateCalleeSavedRegisters() 111 // must be called before this function in order to set the AdjustsStack 112 // and MaxCallFrameSize variables. 113 if (!F->hasFnAttr(Attribute::Naked)) 114 insertPrologEpilogCode(Fn); 115 116 // Replace all MO_FrameIndex operands with physical register references 117 // and actual offsets. 118 // 119 replaceFrameIndices(Fn); 120 121 // If register scavenging is needed, as we've enabled doing it as a 122 // post-pass, scavenge the virtual registers that frame index elimiation 123 // inserted. 124 if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging) 125 scavengeFrameVirtualRegs(Fn); 126 127 delete RS; 128 clearAllSets(); 129 return true; 130} 131 132#if 0 133void PEI::getAnalysisUsage(AnalysisUsage &AU) const { 134 AU.setPreservesCFG(); 135 if (ShrinkWrapping || ShrinkWrapFunc != "") { 136 AU.addRequired<MachineLoopInfo>(); 137 AU.addRequired<MachineDominatorTree>(); 138 } 139 AU.addPreserved<MachineLoopInfo>(); 140 AU.addPreserved<MachineDominatorTree>(); 141 MachineFunctionPass::getAnalysisUsage(AU); 142} 143#endif 144 145/// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack 146/// variables for the function's frame information and eliminate call frame 147/// pseudo instructions. 148void PEI::calculateCallsInformation(MachineFunction &Fn) { 149 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); 150 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo(); 151 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering(); 152 MachineFrameInfo *MFI = Fn.getFrameInfo(); 153 154 unsigned MaxCallFrameSize = 0; 155 bool AdjustsStack = MFI->adjustsStack(); 156 157 // Get the function call frame set-up and tear-down instruction opcode 158 int FrameSetupOpcode = TII.getCallFrameSetupOpcode(); 159 int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode(); 160 161 // Early exit for targets which have no call frame setup/destroy pseudo 162 // instructions. 163 if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1) 164 return; 165 166 std::vector<MachineBasicBlock::iterator> FrameSDOps; 167 for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) 168 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) 169 if (I->getOpcode() == FrameSetupOpcode || 170 I->getOpcode() == FrameDestroyOpcode) { 171 assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo" 172 " instructions should have a single immediate argument!"); 173 unsigned Size = I->getOperand(0).getImm(); 174 if (Size > MaxCallFrameSize) MaxCallFrameSize = Size; 175 AdjustsStack = true; 176 FrameSDOps.push_back(I); 177 } else if (I->isInlineAsm()) { 178 // Some inline asm's need a stack frame, as indicated by operand 1. 179 unsigned ExtraInfo = I->getOperand(InlineAsm::MIOp_ExtraInfo).getImm(); 180 if (ExtraInfo & InlineAsm::Extra_IsAlignStack) 181 AdjustsStack = true; 182 } 183 184 MFI->setAdjustsStack(AdjustsStack); 185 MFI->setMaxCallFrameSize(MaxCallFrameSize); 186 187 for (std::vector<MachineBasicBlock::iterator>::iterator 188 i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) { 189 MachineBasicBlock::iterator I = *i; 190 191 // If call frames are not being included as part of the stack frame, and 192 // the target doesn't indicate otherwise, remove the call frame pseudos 193 // here. The sub/add sp instruction pairs are still inserted, but we don't 194 // need to track the SP adjustment for frame index elimination. 195 if (TFI->canSimplifyCallFramePseudos(Fn)) 196 RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I); 197 } 198} 199 200 201/// calculateCalleeSavedRegisters - Scan the function for modified callee saved 202/// registers. 203void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) { 204 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); 205 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering(); 206 MachineFrameInfo *MFI = Fn.getFrameInfo(); 207 208 // Get the callee saved register list... 209 const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn); 210 211 // These are used to keep track the callee-save area. Initialize them. 212 MinCSFrameIndex = INT_MAX; 213 MaxCSFrameIndex = 0; 214 215 // Early exit for targets which have no callee saved registers. 216 if (CSRegs == 0 || CSRegs[0] == 0) 217 return; 218 219 // In Naked functions we aren't going to save any registers. 220 if (Fn.getFunction()->hasFnAttr(Attribute::Naked)) 221 return; 222 223 std::vector<CalleeSavedInfo> CSI; 224 for (unsigned i = 0; CSRegs[i]; ++i) { 225 unsigned Reg = CSRegs[i]; 226 if (Fn.getRegInfo().isPhysRegUsed(Reg)) { 227 // If the reg is modified, save it! 228 CSI.push_back(CalleeSavedInfo(Reg)); 229 } else { 230 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg); 231 *AliasSet; ++AliasSet) { // Check alias registers too. 232 if (Fn.getRegInfo().isPhysRegUsed(*AliasSet)) { 233 CSI.push_back(CalleeSavedInfo(Reg)); 234 break; 235 } 236 } 237 } 238 } 239 240 if (CSI.empty()) 241 return; // Early exit if no callee saved registers are modified! 242 243 unsigned NumFixedSpillSlots; 244 const TargetFrameLowering::SpillSlot *FixedSpillSlots = 245 TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots); 246 247 // Now that we know which registers need to be saved and restored, allocate 248 // stack slots for them. 249 for (std::vector<CalleeSavedInfo>::iterator 250 I = CSI.begin(), E = CSI.end(); I != E; ++I) { 251 unsigned Reg = I->getReg(); 252 const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg); 253 254 int FrameIdx; 255 if (RegInfo->hasReservedSpillSlot(Fn, Reg, FrameIdx)) { 256 I->setFrameIdx(FrameIdx); 257 continue; 258 } 259 260 // Check to see if this physreg must be spilled to a particular stack slot 261 // on this target. 262 const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots; 263 while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots && 264 FixedSlot->Reg != Reg) 265 ++FixedSlot; 266 267 if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) { 268 // Nope, just spill it anywhere convenient. 269 unsigned Align = RC->getAlignment(); 270 unsigned StackAlign = TFI->getStackAlignment(); 271 272 // We may not be able to satisfy the desired alignment specification of 273 // the TargetRegisterClass if the stack alignment is smaller. Use the 274 // min. 275 Align = std::min(Align, StackAlign); 276 FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true); 277 if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx; 278 if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx; 279 } else { 280 // Spill it to the stack where we must. 281 FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true); 282 } 283 284 I->setFrameIdx(FrameIdx); 285 } 286 287 MFI->setCalleeSavedInfo(CSI); 288} 289 290/// insertCSRSpillsAndRestores - Insert spill and restore code for 291/// callee saved registers used in the function, handling shrink wrapping. 292/// 293void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) { 294 // Get callee saved register information. 295 MachineFrameInfo *MFI = Fn.getFrameInfo(); 296 const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo(); 297 298 MFI->setCalleeSavedInfoValid(true); 299 300 // Early exit if no callee saved registers are modified! 301 if (CSI.empty()) 302 return; 303 304 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo(); 305 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering(); 306 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); 307 MachineBasicBlock::iterator I; 308 309 if (! ShrinkWrapThisFunction) { 310 // Spill using target interface. 311 I = EntryBlock->begin(); 312 if (!TFI->spillCalleeSavedRegisters(*EntryBlock, I, CSI, TRI)) { 313 for (unsigned i = 0, e = CSI.size(); i != e; ++i) { 314 // Add the callee-saved register as live-in. 315 // It's killed at the spill. 316 EntryBlock->addLiveIn(CSI[i].getReg()); 317 318 // Insert the spill to the stack frame. 319 unsigned Reg = CSI[i].getReg(); 320 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg); 321 TII.storeRegToStackSlot(*EntryBlock, I, Reg, true, 322 CSI[i].getFrameIdx(), RC, TRI); 323 } 324 } 325 326 // Restore using target interface. 327 for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) { 328 MachineBasicBlock* MBB = ReturnBlocks[ri]; 329 I = MBB->end(); --I; 330 331 // Skip over all terminator instructions, which are part of the return 332 // sequence. 333 MachineBasicBlock::iterator I2 = I; 334 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator()) 335 I = I2; 336 337 bool AtStart = I == MBB->begin(); 338 MachineBasicBlock::iterator BeforeI = I; 339 if (!AtStart) 340 --BeforeI; 341 342 // Restore all registers immediately before the return and any 343 // terminators that precede it. 344 if (!TFI->restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) { 345 for (unsigned i = 0, e = CSI.size(); i != e; ++i) { 346 unsigned Reg = CSI[i].getReg(); 347 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg); 348 TII.loadRegFromStackSlot(*MBB, I, Reg, 349 CSI[i].getFrameIdx(), 350 RC, TRI); 351 assert(I != MBB->begin() && 352 "loadRegFromStackSlot didn't insert any code!"); 353 // Insert in reverse order. loadRegFromStackSlot can insert 354 // multiple instructions. 355 if (AtStart) 356 I = MBB->begin(); 357 else { 358 I = BeforeI; 359 ++I; 360 } 361 } 362 } 363 } 364 return; 365 } 366 367 // Insert spills. 368 std::vector<CalleeSavedInfo> blockCSI; 369 for (CSRegBlockMap::iterator BI = CSRSave.begin(), 370 BE = CSRSave.end(); BI != BE; ++BI) { 371 MachineBasicBlock* MBB = BI->first; 372 CSRegSet save = BI->second; 373 374 if (save.empty()) 375 continue; 376 377 blockCSI.clear(); 378 for (CSRegSet::iterator RI = save.begin(), 379 RE = save.end(); RI != RE; ++RI) { 380 blockCSI.push_back(CSI[*RI]); 381 } 382 assert(blockCSI.size() > 0 && 383 "Could not collect callee saved register info"); 384 385 I = MBB->begin(); 386 387 // When shrink wrapping, use stack slot stores/loads. 388 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) { 389 // Add the callee-saved register as live-in. 390 // It's killed at the spill. 391 MBB->addLiveIn(blockCSI[i].getReg()); 392 393 // Insert the spill to the stack frame. 394 unsigned Reg = blockCSI[i].getReg(); 395 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg); 396 TII.storeRegToStackSlot(*MBB, I, Reg, 397 true, 398 blockCSI[i].getFrameIdx(), 399 RC, TRI); 400 } 401 } 402 403 for (CSRegBlockMap::iterator BI = CSRRestore.begin(), 404 BE = CSRRestore.end(); BI != BE; ++BI) { 405 MachineBasicBlock* MBB = BI->first; 406 CSRegSet restore = BI->second; 407 408 if (restore.empty()) 409 continue; 410 411 blockCSI.clear(); 412 for (CSRegSet::iterator RI = restore.begin(), 413 RE = restore.end(); RI != RE; ++RI) { 414 blockCSI.push_back(CSI[*RI]); 415 } 416 assert(blockCSI.size() > 0 && 417 "Could not find callee saved register info"); 418 419 // If MBB is empty and needs restores, insert at the _beginning_. 420 if (MBB->empty()) { 421 I = MBB->begin(); 422 } else { 423 I = MBB->end(); 424 --I; 425 426 // Skip over all terminator instructions, which are part of the 427 // return sequence. 428 if (! I->getDesc().isTerminator()) { 429 ++I; 430 } else { 431 MachineBasicBlock::iterator I2 = I; 432 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator()) 433 I = I2; 434 } 435 } 436 437 bool AtStart = I == MBB->begin(); 438 MachineBasicBlock::iterator BeforeI = I; 439 if (!AtStart) 440 --BeforeI; 441 442 // Restore all registers immediately before the return and any 443 // terminators that precede it. 444 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) { 445 unsigned Reg = blockCSI[i].getReg(); 446 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg); 447 TII.loadRegFromStackSlot(*MBB, I, Reg, 448 blockCSI[i].getFrameIdx(), 449 RC, TRI); 450 assert(I != MBB->begin() && 451 "loadRegFromStackSlot didn't insert any code!"); 452 // Insert in reverse order. loadRegFromStackSlot can insert 453 // multiple instructions. 454 if (AtStart) 455 I = MBB->begin(); 456 else { 457 I = BeforeI; 458 ++I; 459 } 460 } 461 } 462} 463 464/// AdjustStackOffset - Helper function used to adjust the stack frame offset. 465static inline void 466AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, 467 bool StackGrowsDown, int64_t &Offset, 468 unsigned &MaxAlign) { 469 // If the stack grows down, add the object size to find the lowest address. 470 if (StackGrowsDown) 471 Offset += MFI->getObjectSize(FrameIdx); 472 473 unsigned Align = MFI->getObjectAlignment(FrameIdx); 474 475 // If the alignment of this object is greater than that of the stack, then 476 // increase the stack alignment to match. 477 MaxAlign = std::max(MaxAlign, Align); 478 479 // Adjust to alignment boundary. 480 Offset = (Offset + Align - 1) / Align * Align; 481 482 if (StackGrowsDown) { 483 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n"); 484 MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset 485 } else { 486 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n"); 487 MFI->setObjectOffset(FrameIdx, Offset); 488 Offset += MFI->getObjectSize(FrameIdx); 489 } 490} 491 492/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the 493/// abstract stack objects. 494/// 495void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { 496 const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering(); 497 498 bool StackGrowsDown = 499 TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown; 500 501 // Loop over all of the stack objects, assigning sequential addresses... 502 MachineFrameInfo *MFI = Fn.getFrameInfo(); 503 504 // Start at the beginning of the local area. 505 // The Offset is the distance from the stack top in the direction 506 // of stack growth -- so it's always nonnegative. 507 int LocalAreaOffset = TFI.getOffsetOfLocalArea(); 508 if (StackGrowsDown) 509 LocalAreaOffset = -LocalAreaOffset; 510 assert(LocalAreaOffset >= 0 511 && "Local area offset should be in direction of stack growth"); 512 int64_t Offset = LocalAreaOffset; 513 514 // If there are fixed sized objects that are preallocated in the local area, 515 // non-fixed objects can't be allocated right at the start of local area. 516 // We currently don't support filling in holes in between fixed sized 517 // objects, so we adjust 'Offset' to point to the end of last fixed sized 518 // preallocated object. 519 for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) { 520 int64_t FixedOff; 521 if (StackGrowsDown) { 522 // The maximum distance from the stack pointer is at lower address of 523 // the object -- which is given by offset. For down growing stack 524 // the offset is negative, so we negate the offset to get the distance. 525 FixedOff = -MFI->getObjectOffset(i); 526 } else { 527 // The maximum distance from the start pointer is at the upper 528 // address of the object. 529 FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i); 530 } 531 if (FixedOff > Offset) Offset = FixedOff; 532 } 533 534 // First assign frame offsets to stack objects that are used to spill 535 // callee saved registers. 536 if (StackGrowsDown) { 537 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) { 538 // If the stack grows down, we need to add the size to find the lowest 539 // address of the object. 540 Offset += MFI->getObjectSize(i); 541 542 unsigned Align = MFI->getObjectAlignment(i); 543 // Adjust to alignment boundary 544 Offset = (Offset+Align-1)/Align*Align; 545 546 MFI->setObjectOffset(i, -Offset); // Set the computed offset 547 } 548 } else { 549 int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex; 550 for (int i = MaxCSFI; i >= MinCSFI ; --i) { 551 unsigned Align = MFI->getObjectAlignment(i); 552 // Adjust to alignment boundary 553 Offset = (Offset+Align-1)/Align*Align; 554 555 MFI->setObjectOffset(i, Offset); 556 Offset += MFI->getObjectSize(i); 557 } 558 } 559 560 unsigned MaxAlign = MFI->getMaxAlignment(); 561 562 // Make sure the special register scavenging spill slot is closest to the 563 // frame pointer if a frame pointer is required. 564 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); 565 if (RS && TFI.hasFP(Fn) && RegInfo->useFPForScavengingIndex(Fn) && 566 !RegInfo->needsStackRealignment(Fn)) { 567 int SFI = RS->getScavengingFrameIndex(); 568 if (SFI >= 0) 569 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign); 570 } 571 572 // FIXME: Once this is working, then enable flag will change to a target 573 // check for whether the frame is large enough to want to use virtual 574 // frame index registers. Functions which don't want/need this optimization 575 // will continue to use the existing code path. 576 if (MFI->getUseLocalStackAllocationBlock()) { 577 unsigned Align = MFI->getLocalFrameMaxAlign(); 578 579 // Adjust to alignment boundary. 580 Offset = (Offset + Align - 1) / Align * Align; 581 582 DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n"); 583 584 // Resolve offsets for objects in the local block. 585 for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) { 586 std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i); 587 int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second; 588 DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" << 589 FIOffset << "]\n"); 590 MFI->setObjectOffset(Entry.first, FIOffset); 591 } 592 // Allocate the local block 593 Offset += MFI->getLocalFrameSize(); 594 595 MaxAlign = std::max(Align, MaxAlign); 596 } 597 598 // Make sure that the stack protector comes before the local variables on the 599 // stack. 600 SmallSet<int, 16> LargeStackObjs; 601 if (MFI->getStackProtectorIndex() >= 0) { 602 AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown, 603 Offset, MaxAlign); 604 605 // Assign large stack objects first. 606 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) { 607 if (MFI->isObjectPreAllocated(i) && 608 MFI->getUseLocalStackAllocationBlock()) 609 continue; 610 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) 611 continue; 612 if (RS && (int)i == RS->getScavengingFrameIndex()) 613 continue; 614 if (MFI->isDeadObjectIndex(i)) 615 continue; 616 if (MFI->getStackProtectorIndex() == (int)i) 617 continue; 618 if (!MFI->MayNeedStackProtector(i)) 619 continue; 620 621 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign); 622 LargeStackObjs.insert(i); 623 } 624 } 625 626 // Then assign frame offsets to stack objects that are not used to spill 627 // callee saved registers. 628 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) { 629 if (MFI->isObjectPreAllocated(i) && 630 MFI->getUseLocalStackAllocationBlock()) 631 continue; 632 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex) 633 continue; 634 if (RS && (int)i == RS->getScavengingFrameIndex()) 635 continue; 636 if (MFI->isDeadObjectIndex(i)) 637 continue; 638 if (MFI->getStackProtectorIndex() == (int)i) 639 continue; 640 if (LargeStackObjs.count(i)) 641 continue; 642 643 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign); 644 } 645 646 // Make sure the special register scavenging spill slot is closest to the 647 // stack pointer. 648 if (RS && (!TFI.hasFP(Fn) || RegInfo->needsStackRealignment(Fn) || 649 !RegInfo->useFPForScavengingIndex(Fn))) { 650 int SFI = RS->getScavengingFrameIndex(); 651 if (SFI >= 0) 652 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign); 653 } 654 655 if (!TFI.targetHandlesStackFrameRounding()) { 656 // If we have reserved argument space for call sites in the function 657 // immediately on entry to the current function, count it as part of the 658 // overall stack size. 659 if (MFI->adjustsStack() && TFI.hasReservedCallFrame(Fn)) 660 Offset += MFI->getMaxCallFrameSize(); 661 662 // Round up the size to a multiple of the alignment. If the function has 663 // any calls or alloca's, align to the target's StackAlignment value to 664 // ensure that the callee's frame or the alloca data is suitably aligned; 665 // otherwise, for leaf functions, align to the TransientStackAlignment 666 // value. 667 unsigned StackAlign; 668 if (MFI->adjustsStack() || MFI->hasVarSizedObjects() || 669 (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0)) 670 StackAlign = TFI.getStackAlignment(); 671 else 672 StackAlign = TFI.getTransientStackAlignment(); 673 674 // If the frame pointer is eliminated, all frame offsets will be relative to 675 // SP not FP. Align to MaxAlign so this works. 676 StackAlign = std::max(StackAlign, MaxAlign); 677 unsigned AlignMask = StackAlign - 1; 678 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask); 679 } 680 681 // Update frame info to pretend that this is part of the stack... 682 int64_t StackSize = Offset - LocalAreaOffset; 683 MFI->setStackSize(StackSize); 684 NumBytesStackSpace += StackSize; 685} 686 687/// insertPrologEpilogCode - Scan the function for modified callee saved 688/// registers, insert spill code for these callee saved registers, then add 689/// prolog and epilog code to the function. 690/// 691void PEI::insertPrologEpilogCode(MachineFunction &Fn) { 692 const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering(); 693 694 // Add prologue to the function... 695 TFI.emitPrologue(Fn); 696 697 // Add epilogue to restore the callee-save registers in each exiting block 698 for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) { 699 // If last instruction is a return instruction, add an epilogue 700 if (!I->empty() && I->back().getDesc().isReturn()) 701 TFI.emitEpilogue(Fn, *I); 702 } 703 704 // Emit additional code that is required to support segmented stacks, if 705 // we've been asked for it. This, when linked with a runtime with support 706 // for segmented stacks (libgcc is one), will result in allocating stack 707 // space in small chunks instead of one large contiguous block. 708 if (EnableSegmentedStacks) 709 TFI.adjustForSegmentedStacks(Fn); 710} 711 712/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical 713/// register references and actual offsets. 714/// 715void PEI::replaceFrameIndices(MachineFunction &Fn) { 716 if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do? 717 718 const TargetMachine &TM = Fn.getTarget(); 719 assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!"); 720 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo(); 721 const TargetRegisterInfo &TRI = *TM.getRegisterInfo(); 722 const TargetFrameLowering *TFI = TM.getFrameLowering(); 723 bool StackGrowsDown = 724 TFI->getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown; 725 int FrameSetupOpcode = TII.getCallFrameSetupOpcode(); 726 int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode(); 727 728 for (MachineFunction::iterator BB = Fn.begin(), 729 E = Fn.end(); BB != E; ++BB) { 730#ifndef NDEBUG 731 int SPAdjCount = 0; // frame setup / destroy count. 732#endif 733 int SPAdj = 0; // SP offset due to call frame setup / destroy. 734 if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB); 735 736 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { 737 738 if (I->getOpcode() == FrameSetupOpcode || 739 I->getOpcode() == FrameDestroyOpcode) { 740#ifndef NDEBUG 741 // Track whether we see even pairs of them 742 SPAdjCount += I->getOpcode() == FrameSetupOpcode ? 1 : -1; 743#endif 744 // Remember how much SP has been adjusted to create the call 745 // frame. 746 int Size = I->getOperand(0).getImm(); 747 748 if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) || 749 (StackGrowsDown && I->getOpcode() == FrameDestroyOpcode)) 750 Size = -Size; 751 752 SPAdj += Size; 753 754 MachineBasicBlock::iterator PrevI = BB->end(); 755 if (I != BB->begin()) PrevI = prior(I); 756 TRI.eliminateCallFramePseudoInstr(Fn, *BB, I); 757 758 // Visit the instructions created by eliminateCallFramePseudoInstr(). 759 if (PrevI == BB->end()) 760 I = BB->begin(); // The replaced instr was the first in the block. 761 else 762 I = llvm::next(PrevI); 763 continue; 764 } 765 766 MachineInstr *MI = I; 767 bool DoIncr = true; 768 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) 769 if (MI->getOperand(i).isFI()) { 770 // Some instructions (e.g. inline asm instructions) can have 771 // multiple frame indices and/or cause eliminateFrameIndex 772 // to insert more than one instruction. We need the register 773 // scavenger to go through all of these instructions so that 774 // it can update its register information. We keep the 775 // iterator at the point before insertion so that we can 776 // revisit them in full. 777 bool AtBeginning = (I == BB->begin()); 778 if (!AtBeginning) --I; 779 780 // If this instruction has a FrameIndex operand, we need to 781 // use that target machine register info object to eliminate 782 // it. 783 TRI.eliminateFrameIndex(MI, SPAdj, 784 FrameIndexVirtualScavenging ? NULL : RS); 785 786 // Reset the iterator if we were at the beginning of the BB. 787 if (AtBeginning) { 788 I = BB->begin(); 789 DoIncr = false; 790 } 791 792 MI = 0; 793 break; 794 } 795 796 if (DoIncr && I != BB->end()) ++I; 797 798 // Update register states. 799 if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI); 800 } 801 802 // If we have evenly matched pairs of frame setup / destroy instructions, 803 // make sure the adjustments come out to zero. If we don't have matched 804 // pairs, we can't be sure the missing bit isn't in another basic block 805 // due to a custom inserter playing tricks, so just asserting SPAdj==0 806 // isn't sufficient. See tMOVCC on Thumb1, for example. 807 assert((SPAdjCount || SPAdj == 0) && 808 "Unbalanced call frame setup / destroy pairs?"); 809 } 810} 811 812/// scavengeFrameVirtualRegs - Replace all frame index virtual registers 813/// with physical registers. Use the register scavenger to find an 814/// appropriate register to use. 815void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) { 816 // Run through the instructions and find any virtual registers. 817 for (MachineFunction::iterator BB = Fn.begin(), 818 E = Fn.end(); BB != E; ++BB) { 819 RS->enterBasicBlock(BB); 820 821 unsigned VirtReg = 0; 822 unsigned ScratchReg = 0; 823 int SPAdj = 0; 824 825 // The instruction stream may change in the loop, so check BB->end() 826 // directly. 827 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { 828 MachineInstr *MI = I; 829 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 830 if (MI->getOperand(i).isReg()) { 831 MachineOperand &MO = MI->getOperand(i); 832 unsigned Reg = MO.getReg(); 833 if (Reg == 0) 834 continue; 835 if (!TargetRegisterInfo::isVirtualRegister(Reg)) 836 continue; 837 838 ++NumVirtualFrameRegs; 839 840 // Have we already allocated a scratch register for this virtual? 841 if (Reg != VirtReg) { 842 // When we first encounter a new virtual register, it 843 // must be a definition. 844 assert(MI->getOperand(i).isDef() && 845 "frame index virtual missing def!"); 846 // Scavenge a new scratch register 847 VirtReg = Reg; 848 const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg); 849 ScratchReg = RS->scavengeRegister(RC, I, SPAdj); 850 ++NumScavengedRegs; 851 } 852 // Replace this reference to the virtual register with the 853 // scratch register. 854 assert (ScratchReg && "Missing scratch register!"); 855 MI->getOperand(i).setReg(ScratchReg); 856 857 } 858 } 859 RS->forward(I); 860 ++I; 861 } 862 } 863} 864