1 //===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass is responsible for finalizing the functions frame layout, saving
11 // callee saved registers, and for emitting prolog & epilog code for the
14 // This pass must be run after register allocation. After this pass is
15 // executed, it is illegal to construct MO_FrameIndex operands.
17 //===----------------------------------------------------------------------===//
19 #define DEBUG_TYPE "pei"
20 #include "PrologEpilogInserter.h"
21 #include "llvm/ADT/IndexedMap.h"
22 #include "llvm/ADT/STLExtras.h"
23 #include "llvm/ADT/SetVector.h"
24 #include "llvm/ADT/SmallSet.h"
25 #include "llvm/ADT/Statistic.h"
26 #include "llvm/CodeGen/MachineDominators.h"
27 #include "llvm/CodeGen/MachineFrameInfo.h"
28 #include "llvm/CodeGen/MachineInstr.h"
29 #include "llvm/CodeGen/MachineLoopInfo.h"
30 #include "llvm/CodeGen/MachineModuleInfo.h"
31 #include "llvm/CodeGen/MachineRegisterInfo.h"
32 #include "llvm/CodeGen/RegisterScavenging.h"
33 #include "llvm/CodeGen/StackProtector.h"
34 #include "llvm/IR/DiagnosticInfo.h"
35 #include "llvm/IR/InlineAsm.h"
36 #include "llvm/IR/LLVMContext.h"
37 #include "llvm/Support/CommandLine.h"
38 #include "llvm/Support/Compiler.h"
39 #include "llvm/Support/Debug.h"
40 #include "llvm/Support/raw_ostream.h"
41 #include "llvm/Target/TargetFrameLowering.h"
42 #include "llvm/Target/TargetInstrInfo.h"
43 #include "llvm/Target/TargetMachine.h"
44 #include "llvm/Target/TargetRegisterInfo.h"
50 char &llvm::PrologEpilogCodeInserterID = PEI::ID;
52 static cl::opt<unsigned>
53 WarnStackSize("warn-stack-size", cl::Hidden, cl::init((unsigned)-1),
54 cl::desc("Warn for stack size bigger than the given"
57 INITIALIZE_PASS_BEGIN(PEI, "prologepilog",
58 "Prologue/Epilogue Insertion", false, false)
59 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
60 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
61 INITIALIZE_PASS_DEPENDENCY(StackProtector)
62 INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
63 INITIALIZE_PASS_END(PEI, "prologepilog",
64 "Prologue/Epilogue Insertion & Frame Finalization",
67 STATISTIC(NumScavengedRegs, "Number of frame index regs scavenged");
68 STATISTIC(NumBytesStackSpace,
69 "Number of bytes used for stack in all functions");
71 void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
73 AU.addPreserved<MachineLoopInfo>();
74 AU.addPreserved<MachineDominatorTree>();
75 AU.addRequired<StackProtector>();
76 AU.addRequired<TargetPassConfig>();
77 MachineFunctionPass::getAnalysisUsage(AU);
80 bool PEI::isReturnBlock(MachineBasicBlock* MBB) {
81 return (MBB && !MBB->empty() && MBB->back().isReturn());
84 /// Compute the set of return blocks
85 void PEI::calculateSets(MachineFunction &Fn) {
86 // Sets used to compute spill, restore placement sets.
87 const std::vector<CalleeSavedInfo> &CSI =
88 Fn.getFrameInfo()->getCalleeSavedInfo();
90 // If no CSRs used, we are done.
94 // Save refs to entry and return blocks.
95 EntryBlock = Fn.begin();
96 for (MachineFunction::iterator MBB = Fn.begin(), E = Fn.end();
98 if (isReturnBlock(MBB))
99 ReturnBlocks.push_back(MBB);
104 /// StackObjSet - A set of stack object indexes
105 typedef SmallSetVector<int, 8> StackObjSet;
107 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
108 /// frame indexes with appropriate references.
110 bool PEI::runOnMachineFunction(MachineFunction &Fn) {
111 const Function* F = Fn.getFunction();
112 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
113 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
115 assert(!Fn.getRegInfo().getNumVirtRegs() && "Regalloc must assign all vregs");
117 RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
118 FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
120 // Calculate the MaxCallFrameSize and AdjustsStack variables for the
121 // function's frame information. Also eliminates call frame pseudo
123 calculateCallsInformation(Fn);
125 // Allow the target machine to make some adjustments to the function
126 // e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
127 TFI->processFunctionBeforeCalleeSavedScan(Fn, RS);
129 // Scan the function for modified callee saved registers and insert spill code
130 // for any callee saved registers that are modified.
131 calculateCalleeSavedRegisters(Fn);
133 // Determine placement of CSR spill/restore code:
134 // place all spills in the entry block, all restores in return blocks.
137 // Add the code to save and restore the callee saved registers
138 if (!F->hasFnAttribute(Attribute::Naked))
139 insertCSRSpillsAndRestores(Fn);
141 // Allow the target machine to make final modifications to the function
142 // before the frame layout is finalized.
143 TFI->processFunctionBeforeFrameFinalized(Fn, RS);
145 // Calculate actual frame offsets for all abstract stack objects...
146 calculateFrameObjectOffsets(Fn);
148 // Add prolog and epilog code to the function. This function is required
149 // to align the stack frame as necessary for any stack variables or
150 // called functions. Because of this, calculateCalleeSavedRegisters()
151 // must be called before this function in order to set the AdjustsStack
152 // and MaxCallFrameSize variables.
153 if (!F->hasFnAttribute(Attribute::Naked))
154 insertPrologEpilogCode(Fn);
156 // Replace all MO_FrameIndex operands with physical register references
157 // and actual offsets.
159 replaceFrameIndices(Fn);
161 // If register scavenging is needed, as we've enabled doing it as a
162 // post-pass, scavenge the virtual registers that frame index elimiation
164 if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging)
165 scavengeFrameVirtualRegs(Fn);
167 // Clear any vregs created by virtual scavenging.
168 Fn.getRegInfo().clearVirtRegs();
170 // Warn on stack size when we exceeds the given limit.
171 MachineFrameInfo *MFI = Fn.getFrameInfo();
172 uint64_t StackSize = MFI->getStackSize();
173 if (WarnStackSize.getNumOccurrences() > 0 && WarnStackSize < StackSize) {
174 DiagnosticInfoStackSize DiagStackSize(*F, StackSize);
175 F->getContext().diagnose(DiagStackSize);
179 ReturnBlocks.clear();
183 /// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack
184 /// variables for the function's frame information and eliminate call frame
185 /// pseudo instructions.
186 void PEI::calculateCallsInformation(MachineFunction &Fn) {
187 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
188 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
189 MachineFrameInfo *MFI = Fn.getFrameInfo();
191 unsigned MaxCallFrameSize = 0;
192 bool AdjustsStack = MFI->adjustsStack();
194 // Get the function call frame set-up and tear-down instruction opcode
195 int FrameSetupOpcode = TII.getCallFrameSetupOpcode();
196 int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
198 // Early exit for targets which have no call frame setup/destroy pseudo
200 if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
203 std::vector<MachineBasicBlock::iterator> FrameSDOps;
204 for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
205 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
206 if (I->getOpcode() == FrameSetupOpcode ||
207 I->getOpcode() == FrameDestroyOpcode) {
208 assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
209 " instructions should have a single immediate argument!");
210 unsigned Size = I->getOperand(0).getImm();
211 if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
213 FrameSDOps.push_back(I);
214 } else if (I->isInlineAsm()) {
215 // Some inline asm's need a stack frame, as indicated by operand 1.
216 unsigned ExtraInfo = I->getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
217 if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
221 MFI->setAdjustsStack(AdjustsStack);
222 MFI->setMaxCallFrameSize(MaxCallFrameSize);
224 for (std::vector<MachineBasicBlock::iterator>::iterator
225 i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) {
226 MachineBasicBlock::iterator I = *i;
228 // If call frames are not being included as part of the stack frame, and
229 // the target doesn't indicate otherwise, remove the call frame pseudos
230 // here. The sub/add sp instruction pairs are still inserted, but we don't
231 // need to track the SP adjustment for frame index elimination.
232 if (TFI->canSimplifyCallFramePseudos(Fn))
233 TFI->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
238 /// calculateCalleeSavedRegisters - Scan the function for modified callee saved
240 void PEI::calculateCalleeSavedRegisters(MachineFunction &F) {
241 const TargetRegisterInfo *RegInfo = F.getTarget().getRegisterInfo();
242 const TargetFrameLowering *TFI = F.getTarget().getFrameLowering();
243 MachineFrameInfo *MFI = F.getFrameInfo();
245 // Get the callee saved register list...
246 const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&F);
248 // These are used to keep track the callee-save area. Initialize them.
249 MinCSFrameIndex = INT_MAX;
252 // Early exit for targets which have no callee saved registers.
253 if (CSRegs == 0 || CSRegs[0] == 0)
256 // In Naked functions we aren't going to save any registers.
257 if (F.getFunction()->hasFnAttribute(Attribute::Naked))
260 std::vector<CalleeSavedInfo> CSI;
261 for (unsigned i = 0; CSRegs[i]; ++i) {
262 unsigned Reg = CSRegs[i];
263 // Functions which call __builtin_unwind_init get all their registers saved.
264 if (F.getRegInfo().isPhysRegUsed(Reg) || F.getMMI().callsUnwindInit()) {
265 // If the reg is modified, save it!
266 CSI.push_back(CalleeSavedInfo(Reg));
271 return; // Early exit if no callee saved registers are modified!
273 unsigned NumFixedSpillSlots;
274 const TargetFrameLowering::SpillSlot *FixedSpillSlots =
275 TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
277 // Now that we know which registers need to be saved and restored, allocate
278 // stack slots for them.
279 for (std::vector<CalleeSavedInfo>::iterator
280 I = CSI.begin(), E = CSI.end(); I != E; ++I) {
281 unsigned Reg = I->getReg();
282 const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
285 if (RegInfo->hasReservedSpillSlot(F, Reg, FrameIdx)) {
286 I->setFrameIdx(FrameIdx);
290 // Check to see if this physreg must be spilled to a particular stack slot
292 const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots;
293 while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
294 FixedSlot->Reg != Reg)
297 if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
298 // Nope, just spill it anywhere convenient.
299 unsigned Align = RC->getAlignment();
300 unsigned StackAlign = TFI->getStackAlignment();
302 // We may not be able to satisfy the desired alignment specification of
303 // the TargetRegisterClass if the stack alignment is smaller. Use the
305 Align = std::min(Align, StackAlign);
306 FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
307 if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
308 if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
310 // Spill it to the stack where we must.
311 FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true);
314 I->setFrameIdx(FrameIdx);
317 MFI->setCalleeSavedInfo(CSI);
320 /// insertCSRSpillsAndRestores - Insert spill and restore code for
321 /// callee saved registers used in the function.
323 void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
324 // Get callee saved register information.
325 MachineFrameInfo *MFI = Fn.getFrameInfo();
326 const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
328 MFI->setCalleeSavedInfoValid(true);
330 // Early exit if no callee saved registers are modified!
334 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
335 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
336 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
337 MachineBasicBlock::iterator I;
339 // Spill using target interface.
340 I = EntryBlock->begin();
341 if (!TFI->spillCalleeSavedRegisters(*EntryBlock, I, CSI, TRI)) {
342 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
343 // Add the callee-saved register as live-in.
344 // It's killed at the spill.
345 EntryBlock->addLiveIn(CSI[i].getReg());
347 // Insert the spill to the stack frame.
348 unsigned Reg = CSI[i].getReg();
349 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
350 TII.storeRegToStackSlot(*EntryBlock, I, Reg, true, CSI[i].getFrameIdx(),
355 // Restore using target interface.
356 for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) {
357 MachineBasicBlock *MBB = ReturnBlocks[ri];
361 // Skip over all terminator instructions, which are part of the return
363 MachineBasicBlock::iterator I2 = I;
364 while (I2 != MBB->begin() && (--I2)->isTerminator())
367 bool AtStart = I == MBB->begin();
368 MachineBasicBlock::iterator BeforeI = I;
372 // Restore all registers immediately before the return and any
373 // terminators that precede it.
374 if (!TFI->restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) {
375 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
376 unsigned Reg = CSI[i].getReg();
377 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
378 TII.loadRegFromStackSlot(*MBB, I, Reg, CSI[i].getFrameIdx(), RC, TRI);
379 assert(I != MBB->begin() &&
380 "loadRegFromStackSlot didn't insert any code!");
381 // Insert in reverse order. loadRegFromStackSlot can insert
382 // multiple instructions.
394 /// AdjustStackOffset - Helper function used to adjust the stack frame offset.
396 AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
397 bool StackGrowsDown, int64_t &Offset,
398 unsigned &MaxAlign) {
399 // If the stack grows down, add the object size to find the lowest address.
401 Offset += MFI->getObjectSize(FrameIdx);
403 unsigned Align = MFI->getObjectAlignment(FrameIdx);
405 // If the alignment of this object is greater than that of the stack, then
406 // increase the stack alignment to match.
407 MaxAlign = std::max(MaxAlign, Align);
409 // Adjust to alignment boundary.
410 Offset = (Offset + Align - 1) / Align * Align;
412 if (StackGrowsDown) {
413 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n");
414 MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
416 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n");
417 MFI->setObjectOffset(FrameIdx, Offset);
418 Offset += MFI->getObjectSize(FrameIdx);
422 /// AssignProtectedObjSet - Helper function to assign large stack objects (i.e.,
423 /// those required to be close to the Stack Protector) to stack offsets.
425 AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
426 SmallSet<int, 16> &ProtectedObjs,
427 MachineFrameInfo *MFI, bool StackGrowsDown,
428 int64_t &Offset, unsigned &MaxAlign) {
430 for (StackObjSet::const_iterator I = UnassignedObjs.begin(),
431 E = UnassignedObjs.end(); I != E; ++I) {
433 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
434 ProtectedObjs.insert(i);
438 /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
439 /// abstract stack objects.
441 void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
442 const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
443 StackProtector *SP = &getAnalysis<StackProtector>();
445 bool StackGrowsDown =
446 TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
448 // Loop over all of the stack objects, assigning sequential addresses...
449 MachineFrameInfo *MFI = Fn.getFrameInfo();
451 // Start at the beginning of the local area.
452 // The Offset is the distance from the stack top in the direction
453 // of stack growth -- so it's always nonnegative.
454 int LocalAreaOffset = TFI.getOffsetOfLocalArea();
456 LocalAreaOffset = -LocalAreaOffset;
457 assert(LocalAreaOffset >= 0
458 && "Local area offset should be in direction of stack growth");
459 int64_t Offset = LocalAreaOffset;
461 // If there are fixed sized objects that are preallocated in the local area,
462 // non-fixed objects can't be allocated right at the start of local area.
463 // We currently don't support filling in holes in between fixed sized
464 // objects, so we adjust 'Offset' to point to the end of last fixed sized
465 // preallocated object.
466 for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
468 if (StackGrowsDown) {
469 // The maximum distance from the stack pointer is at lower address of
470 // the object -- which is given by offset. For down growing stack
471 // the offset is negative, so we negate the offset to get the distance.
472 FixedOff = -MFI->getObjectOffset(i);
474 // The maximum distance from the start pointer is at the upper
475 // address of the object.
476 FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
478 if (FixedOff > Offset) Offset = FixedOff;
481 // First assign frame offsets to stack objects that are used to spill
482 // callee saved registers.
483 if (StackGrowsDown) {
484 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
485 // If the stack grows down, we need to add the size to find the lowest
486 // address of the object.
487 Offset += MFI->getObjectSize(i);
489 unsigned Align = MFI->getObjectAlignment(i);
490 // Adjust to alignment boundary
491 Offset = (Offset+Align-1)/Align*Align;
493 MFI->setObjectOffset(i, -Offset); // Set the computed offset
496 int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
497 for (int i = MaxCSFI; i >= MinCSFI ; --i) {
498 unsigned Align = MFI->getObjectAlignment(i);
499 // Adjust to alignment boundary
500 Offset = (Offset+Align-1)/Align*Align;
502 MFI->setObjectOffset(i, Offset);
503 Offset += MFI->getObjectSize(i);
507 unsigned MaxAlign = MFI->getMaxAlignment();
509 // Make sure the special register scavenging spill slot is closest to the
510 // incoming stack pointer if a frame pointer is required and is closer
511 // to the incoming rather than the final stack pointer.
512 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
513 bool EarlyScavengingSlots = (TFI.hasFP(Fn) &&
514 TFI.isFPCloseToIncomingSP() &&
515 RegInfo->useFPForScavengingIndex(Fn) &&
516 !RegInfo->needsStackRealignment(Fn));
517 if (RS && EarlyScavengingSlots) {
518 SmallVector<int, 2> SFIs;
519 RS->getScavengingFrameIndices(SFIs);
520 for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
521 IE = SFIs.end(); I != IE; ++I)
522 AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign);
525 // FIXME: Once this is working, then enable flag will change to a target
526 // check for whether the frame is large enough to want to use virtual
527 // frame index registers. Functions which don't want/need this optimization
528 // will continue to use the existing code path.
529 if (MFI->getUseLocalStackAllocationBlock()) {
530 unsigned Align = MFI->getLocalFrameMaxAlign();
532 // Adjust to alignment boundary.
533 Offset = (Offset + Align - 1) / Align * Align;
535 DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
537 // Resolve offsets for objects in the local block.
538 for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
539 std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
540 int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
541 DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
543 MFI->setObjectOffset(Entry.first, FIOffset);
545 // Allocate the local block
546 Offset += MFI->getLocalFrameSize();
548 MaxAlign = std::max(Align, MaxAlign);
551 // Make sure that the stack protector comes before the local variables on the
553 SmallSet<int, 16> ProtectedObjs;
554 if (MFI->getStackProtectorIndex() >= 0) {
555 StackObjSet LargeArrayObjs;
556 StackObjSet SmallArrayObjs;
557 StackObjSet AddrOfObjs;
559 AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
562 // Assign large stack objects first.
563 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
564 if (MFI->isObjectPreAllocated(i) &&
565 MFI->getUseLocalStackAllocationBlock())
567 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
569 if (RS && RS->isScavengingFrameIndex((int)i))
571 if (MFI->isDeadObjectIndex(i))
573 if (MFI->getStackProtectorIndex() == (int)i)
576 switch (SP->getSSPLayout(MFI->getObjectAllocation(i))) {
577 case StackProtector::SSPLK_None:
579 case StackProtector::SSPLK_SmallArray:
580 SmallArrayObjs.insert(i);
582 case StackProtector::SSPLK_AddrOf:
583 AddrOfObjs.insert(i);
585 case StackProtector::SSPLK_LargeArray:
586 LargeArrayObjs.insert(i);
589 llvm_unreachable("Unexpected SSPLayoutKind.");
592 AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
594 AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
596 AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown,
600 // Then assign frame offsets to stack objects that are not used to spill
601 // callee saved registers.
602 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
603 if (MFI->isObjectPreAllocated(i) &&
604 MFI->getUseLocalStackAllocationBlock())
606 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
608 if (RS && RS->isScavengingFrameIndex((int)i))
610 if (MFI->isDeadObjectIndex(i))
612 if (MFI->getStackProtectorIndex() == (int)i)
614 if (ProtectedObjs.count(i))
617 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
620 // Make sure the special register scavenging spill slot is closest to the
622 if (RS && !EarlyScavengingSlots) {
623 SmallVector<int, 2> SFIs;
624 RS->getScavengingFrameIndices(SFIs);
625 for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
626 IE = SFIs.end(); I != IE; ++I)
627 AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign);
630 if (!TFI.targetHandlesStackFrameRounding()) {
631 // If we have reserved argument space for call sites in the function
632 // immediately on entry to the current function, count it as part of the
633 // overall stack size.
634 if (MFI->adjustsStack() && TFI.hasReservedCallFrame(Fn))
635 Offset += MFI->getMaxCallFrameSize();
637 // Round up the size to a multiple of the alignment. If the function has
638 // any calls or alloca's, align to the target's StackAlignment value to
639 // ensure that the callee's frame or the alloca data is suitably aligned;
640 // otherwise, for leaf functions, align to the TransientStackAlignment
643 if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
644 (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
645 StackAlign = TFI.getStackAlignment();
647 StackAlign = TFI.getTransientStackAlignment();
649 // If the frame pointer is eliminated, all frame offsets will be relative to
650 // SP not FP. Align to MaxAlign so this works.
651 StackAlign = std::max(StackAlign, MaxAlign);
652 unsigned AlignMask = StackAlign - 1;
653 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
656 // Update frame info to pretend that this is part of the stack...
657 int64_t StackSize = Offset - LocalAreaOffset;
658 MFI->setStackSize(StackSize);
659 NumBytesStackSpace += StackSize;
662 /// insertPrologEpilogCode - Scan the function for modified callee saved
663 /// registers, insert spill code for these callee saved registers, then add
664 /// prolog and epilog code to the function.
666 void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
667 const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
669 // Add prologue to the function...
670 TFI.emitPrologue(Fn);
672 // Add epilogue to restore the callee-save registers in each exiting block
673 for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
674 // If last instruction is a return instruction, add an epilogue
675 if (!I->empty() && I->back().isReturn())
676 TFI.emitEpilogue(Fn, *I);
679 // Emit additional code that is required to support segmented stacks, if
680 // we've been asked for it. This, when linked with a runtime with support
681 // for segmented stacks (libgcc is one), will result in allocating stack
682 // space in small chunks instead of one large contiguous block.
683 if (Fn.shouldSplitStack())
684 TFI.adjustForSegmentedStacks(Fn);
686 // Emit additional code that is required to explicitly handle the stack in
687 // HiPE native code (if needed) when loaded in the Erlang/OTP runtime. The
688 // approach is rather similar to that of Segmented Stacks, but it uses a
689 // different conditional check and another BIF for allocating more stack
691 if (Fn.getFunction()->getCallingConv() == CallingConv::HiPE)
692 TFI.adjustForHiPEPrologue(Fn);
695 /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
696 /// register references and actual offsets.
698 void PEI::replaceFrameIndices(MachineFunction &Fn) {
699 if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
701 // Store SPAdj at exit of a basic block.
702 SmallVector<int, 8> SPState;
703 SPState.resize(Fn.getNumBlockIDs());
704 SmallPtrSet<MachineBasicBlock*, 8> Reachable;
706 // Iterate over the reachable blocks in DFS order.
707 for (df_ext_iterator<MachineFunction*, SmallPtrSet<MachineBasicBlock*, 8> >
708 DFI = df_ext_begin(&Fn, Reachable), DFE = df_ext_end(&Fn, Reachable);
711 // Check the exit state of the DFS stack predecessor.
712 if (DFI.getPathLength() >= 2) {
713 MachineBasicBlock *StackPred = DFI.getPath(DFI.getPathLength() - 2);
714 assert(Reachable.count(StackPred) &&
715 "DFS stack predecessor is already visited.\n");
716 SPAdj = SPState[StackPred->getNumber()];
718 MachineBasicBlock *BB = *DFI;
719 replaceFrameIndices(BB, Fn, SPAdj);
720 SPState[BB->getNumber()] = SPAdj;
723 // Handle the unreachable blocks.
724 for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
725 if (Reachable.count(BB))
726 // Already handled in DFS traversal.
729 replaceFrameIndices(BB, Fn, SPAdj);
733 void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &Fn,
735 const TargetMachine &TM = Fn.getTarget();
736 assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
737 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
738 const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
739 const TargetFrameLowering *TFI = TM.getFrameLowering();
740 bool StackGrowsDown =
741 TFI->getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
742 int FrameSetupOpcode = TII.getCallFrameSetupOpcode();
743 int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
745 if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
747 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
749 if (I->getOpcode() == FrameSetupOpcode ||
750 I->getOpcode() == FrameDestroyOpcode) {
751 // Remember how much SP has been adjusted to create the call
753 int Size = I->getOperand(0).getImm();
755 if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
756 (StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
761 MachineBasicBlock::iterator PrevI = BB->end();
762 if (I != BB->begin()) PrevI = std::prev(I);
763 TFI->eliminateCallFramePseudoInstr(Fn, *BB, I);
765 // Visit the instructions created by eliminateCallFramePseudoInstr().
766 if (PrevI == BB->end())
767 I = BB->begin(); // The replaced instr was the first in the block.
769 I = std::next(PrevI);
773 MachineInstr *MI = I;
775 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
776 if (!MI->getOperand(i).isFI())
779 // Frame indicies in debug values are encoded in a target independent
780 // way with simply the frame index and offset rather than any
781 // target-specific addressing mode.
782 if (MI->isDebugValue()) {
783 assert(i == 0 && "Frame indicies can only appear as the first "
784 "operand of a DBG_VALUE machine instruction");
786 MachineOperand &Offset = MI->getOperand(1);
787 Offset.setImm(Offset.getImm() +
788 TFI->getFrameIndexReference(
789 Fn, MI->getOperand(0).getIndex(), Reg));
790 MI->getOperand(0).ChangeToRegister(Reg, false /*isDef*/);
794 // Some instructions (e.g. inline asm instructions) can have
795 // multiple frame indices and/or cause eliminateFrameIndex
796 // to insert more than one instruction. We need the register
797 // scavenger to go through all of these instructions so that
798 // it can update its register information. We keep the
799 // iterator at the point before insertion so that we can
800 // revisit them in full.
801 bool AtBeginning = (I == BB->begin());
802 if (!AtBeginning) --I;
804 // If this instruction has a FrameIndex operand, we need to
805 // use that target machine register info object to eliminate
807 TRI.eliminateFrameIndex(MI, SPAdj, i,
808 FrameIndexVirtualScavenging ? NULL : RS);
810 // Reset the iterator if we were at the beginning of the BB.
820 if (DoIncr && I != BB->end()) ++I;
822 // Update register states.
823 if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
827 /// scavengeFrameVirtualRegs - Replace all frame index virtual registers
828 /// with physical registers. Use the register scavenger to find an
829 /// appropriate register to use.
831 /// FIXME: Iterating over the instruction stream is unnecessary. We can simply
832 /// iterate over the vreg use list, which at this point only contains machine
833 /// operands for which eliminateFrameIndex need a new scratch reg.
834 void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
835 // Run through the instructions and find any virtual registers.
836 for (MachineFunction::iterator BB = Fn.begin(),
837 E = Fn.end(); BB != E; ++BB) {
838 RS->enterBasicBlock(BB);
842 // The instruction stream may change in the loop, so check BB->end()
844 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
845 // We might end up here again with a NULL iterator if we scavenged a
846 // register for which we inserted spill code for definition by what was
847 // originally the first instruction in BB.
848 if (I == MachineBasicBlock::iterator(NULL))
851 MachineInstr *MI = I;
852 MachineBasicBlock::iterator J = std::next(I);
853 MachineBasicBlock::iterator P =
854 I == BB->begin() ? MachineBasicBlock::iterator(NULL) : std::prev(I);
856 // RS should process this instruction before we might scavenge at this
857 // location. This is because we might be replacing a virtual register
858 // defined by this instruction, and if so, registers killed by this
859 // instruction are available, and defined registers are not.
862 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
863 if (MI->getOperand(i).isReg()) {
864 MachineOperand &MO = MI->getOperand(i);
865 unsigned Reg = MO.getReg();
868 if (!TargetRegisterInfo::isVirtualRegister(Reg))
871 // When we first encounter a new virtual register, it
872 // must be a definition.
873 assert(MI->getOperand(i).isDef() &&
874 "frame index virtual missing def!");
875 // Scavenge a new scratch register
876 const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
877 unsigned ScratchReg = RS->scavengeRegister(RC, J, SPAdj);
881 // Replace this reference to the virtual register with the
883 assert (ScratchReg && "Missing scratch register!");
884 Fn.getRegInfo().replaceRegWith(Reg, ScratchReg);
886 // Because this instruction was processed by the RS before this
887 // register was allocated, make sure that the RS now records the
888 // register as being used.
889 RS->setUsed(ScratchReg);
893 // If the scavenger needed to use one of its spill slots, the
894 // spill code will have been inserted in between I and J. This is a
895 // problem because we need the spill code before I: Move I to just
897 if (I != std::prev(J)) {
898 BB->splice(J, BB, I);
900 // Before we move I, we need to prepare the RS to visit I again.
901 // Specifically, RS will assert if it sees uses of registers that
902 // it believes are undefined. Because we have already processed
903 // register kills in I, when it visits I again, it will believe that
904 // those registers are undefined. To avoid this situation, unprocess
905 // the instruction I.
906 assert(RS->getCurrentPosition() == I &&
907 "The register scavenger has an unexpected position");