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 // This pass provides an optional shrink wrapping variant of prolog/epilog
18 // insertion, enabled via --shrink-wrap. See ShrinkWrapping.cpp.
20 //===----------------------------------------------------------------------===//
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/TargetRegisterInfo.h"
33 #include "llvm/Target/TargetFrameLowering.h"
34 #include "llvm/Target/TargetInstrInfo.h"
35 #include "llvm/Support/CommandLine.h"
36 #include "llvm/Support/Compiler.h"
37 #include "llvm/Support/Debug.h"
38 #include "llvm/ADT/IndexedMap.h"
39 #include "llvm/ADT/SmallSet.h"
40 #include "llvm/ADT/Statistic.h"
41 #include "llvm/ADT/STLExtras.h"
48 INITIALIZE_PASS_BEGIN(PEI, "prologepilog",
49 "Prologue/Epilogue Insertion", false, false)
50 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
51 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
52 INITIALIZE_PASS_END(PEI, "prologepilog",
53 "Prologue/Epilogue Insertion", false, false)
55 STATISTIC(NumVirtualFrameRegs, "Number of virtual frame regs encountered");
56 STATISTIC(NumScavengedRegs, "Number of frame index regs scavenged");
58 /// createPrologEpilogCodeInserter - This function returns a pass that inserts
59 /// prolog and epilog code, and eliminates abstract frame references.
61 FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); }
63 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
64 /// frame indexes with appropriate references.
66 bool PEI::runOnMachineFunction(MachineFunction &Fn) {
67 const Function* F = Fn.getFunction();
68 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
69 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
71 RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
72 FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
74 // Calculate the MaxCallFrameSize and AdjustsStack variables for the
75 // function's frame information. Also eliminates call frame pseudo
77 calculateCallsInformation(Fn);
79 // Allow the target machine to make some adjustments to the function
80 // e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
81 TFI->processFunctionBeforeCalleeSavedScan(Fn, RS);
83 // Scan the function for modified callee saved registers and insert spill code
84 // for any callee saved registers that are modified.
85 calculateCalleeSavedRegisters(Fn);
87 // Determine placement of CSR spill/restore code:
88 // - With shrink wrapping, place spills and restores to tightly
89 // enclose regions in the Machine CFG of the function where
91 // - Without shink wrapping (default), place all spills in the
92 // entry block, all restores in return blocks.
93 placeCSRSpillsAndRestores(Fn);
95 // Add the code to save and restore the callee saved registers
96 if (!F->hasFnAttr(Attribute::Naked))
97 insertCSRSpillsAndRestores(Fn);
99 // Allow the target machine to make final modifications to the function
100 // before the frame layout is finalized.
101 TFI->processFunctionBeforeFrameFinalized(Fn);
103 // Calculate actual frame offsets for all abstract stack objects...
104 calculateFrameObjectOffsets(Fn);
106 // Add prolog and epilog code to the function. This function is required
107 // to align the stack frame as necessary for any stack variables or
108 // called functions. Because of this, calculateCalleeSavedRegisters()
109 // must be called before this function in order to set the AdjustsStack
110 // and MaxCallFrameSize variables.
111 if (!F->hasFnAttr(Attribute::Naked))
112 insertPrologEpilogCode(Fn);
114 // Replace all MO_FrameIndex operands with physical register references
115 // and actual offsets.
117 replaceFrameIndices(Fn);
119 // If register scavenging is needed, as we've enabled doing it as a
120 // post-pass, scavenge the virtual registers that frame index elimiation
122 if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging)
123 scavengeFrameVirtualRegs(Fn);
131 void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
132 AU.setPreservesCFG();
133 if (ShrinkWrapping || ShrinkWrapFunc != "") {
134 AU.addRequired<MachineLoopInfo>();
135 AU.addRequired<MachineDominatorTree>();
137 AU.addPreserved<MachineLoopInfo>();
138 AU.addPreserved<MachineDominatorTree>();
139 MachineFunctionPass::getAnalysisUsage(AU);
143 /// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack
144 /// variables for the function's frame information and eliminate call frame
145 /// pseudo instructions.
146 void PEI::calculateCallsInformation(MachineFunction &Fn) {
147 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
148 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
149 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
150 MachineFrameInfo *MFI = Fn.getFrameInfo();
152 unsigned MaxCallFrameSize = 0;
153 bool AdjustsStack = MFI->adjustsStack();
155 // Get the function call frame set-up and tear-down instruction opcode
156 int FrameSetupOpcode = TII.getCallFrameSetupOpcode();
157 int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
159 // Early exit for targets which have no call frame setup/destroy pseudo
161 if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
164 std::vector<MachineBasicBlock::iterator> FrameSDOps;
165 for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
166 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
167 if (I->getOpcode() == FrameSetupOpcode ||
168 I->getOpcode() == FrameDestroyOpcode) {
169 assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
170 " instructions should have a single immediate argument!");
171 unsigned Size = I->getOperand(0).getImm();
172 if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
174 FrameSDOps.push_back(I);
175 } else if (I->isInlineAsm()) {
176 // Some inline asm's need a stack frame, as indicated by operand 1.
177 unsigned ExtraInfo = I->getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
178 if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
182 MFI->setAdjustsStack(AdjustsStack);
183 MFI->setMaxCallFrameSize(MaxCallFrameSize);
185 for (std::vector<MachineBasicBlock::iterator>::iterator
186 i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) {
187 MachineBasicBlock::iterator I = *i;
189 // If call frames are not being included as part of the stack frame, and
190 // the target doesn't indicate otherwise, remove the call frame pseudos
191 // here. The sub/add sp instruction pairs are still inserted, but we don't
192 // need to track the SP adjustment for frame index elimination.
193 if (TFI->canSimplifyCallFramePseudos(Fn))
194 RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
199 /// calculateCalleeSavedRegisters - Scan the function for modified callee saved
201 void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) {
202 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
203 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
204 MachineFrameInfo *MFI = Fn.getFrameInfo();
206 // Get the callee saved register list...
207 const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn);
209 // These are used to keep track the callee-save area. Initialize them.
210 MinCSFrameIndex = INT_MAX;
213 // Early exit for targets which have no callee saved registers.
214 if (CSRegs == 0 || CSRegs[0] == 0)
217 // In Naked functions we aren't going to save any registers.
218 if (Fn.getFunction()->hasFnAttr(Attribute::Naked))
221 std::vector<CalleeSavedInfo> CSI;
222 for (unsigned i = 0; CSRegs[i]; ++i) {
223 unsigned Reg = CSRegs[i];
224 if (Fn.getRegInfo().isPhysRegUsed(Reg)) {
225 // If the reg is modified, save it!
226 CSI.push_back(CalleeSavedInfo(Reg));
228 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
229 *AliasSet; ++AliasSet) { // Check alias registers too.
230 if (Fn.getRegInfo().isPhysRegUsed(*AliasSet)) {
231 CSI.push_back(CalleeSavedInfo(Reg));
239 return; // Early exit if no callee saved registers are modified!
241 unsigned NumFixedSpillSlots;
242 const TargetFrameLowering::SpillSlot *FixedSpillSlots =
243 TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
245 // Now that we know which registers need to be saved and restored, allocate
246 // stack slots for them.
247 for (std::vector<CalleeSavedInfo>::iterator
248 I = CSI.begin(), E = CSI.end(); I != E; ++I) {
249 unsigned Reg = I->getReg();
250 const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
253 if (RegInfo->hasReservedSpillSlot(Fn, Reg, FrameIdx)) {
254 I->setFrameIdx(FrameIdx);
258 // Check to see if this physreg must be spilled to a particular stack slot
260 const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots;
261 while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
262 FixedSlot->Reg != Reg)
265 if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
266 // Nope, just spill it anywhere convenient.
267 unsigned Align = RC->getAlignment();
268 unsigned StackAlign = TFI->getStackAlignment();
270 // We may not be able to satisfy the desired alignment specification of
271 // the TargetRegisterClass if the stack alignment is smaller. Use the
273 Align = std::min(Align, StackAlign);
274 FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
275 if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
276 if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
278 // Spill it to the stack where we must.
279 FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true);
282 I->setFrameIdx(FrameIdx);
285 MFI->setCalleeSavedInfo(CSI);
288 /// insertCSRSpillsAndRestores - Insert spill and restore code for
289 /// callee saved registers used in the function, handling shrink wrapping.
291 void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
292 // Get callee saved register information.
293 MachineFrameInfo *MFI = Fn.getFrameInfo();
294 const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
296 MFI->setCalleeSavedInfoValid(true);
298 // Early exit if no callee saved registers are modified!
302 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
303 const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
304 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
305 MachineBasicBlock::iterator I;
307 if (! ShrinkWrapThisFunction) {
308 // Spill using target interface.
309 I = EntryBlock->begin();
310 if (!TFI->spillCalleeSavedRegisters(*EntryBlock, I, CSI, TRI)) {
311 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
312 // Add the callee-saved register as live-in.
313 // It's killed at the spill.
314 EntryBlock->addLiveIn(CSI[i].getReg());
316 // Insert the spill to the stack frame.
317 unsigned Reg = CSI[i].getReg();
318 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
319 TII.storeRegToStackSlot(*EntryBlock, I, Reg, true,
320 CSI[i].getFrameIdx(), RC, TRI);
324 // Restore using target interface.
325 for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) {
326 MachineBasicBlock* MBB = ReturnBlocks[ri];
329 // Skip over all terminator instructions, which are part of the return
331 MachineBasicBlock::iterator I2 = I;
332 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
335 bool AtStart = I == MBB->begin();
336 MachineBasicBlock::iterator BeforeI = I;
340 // Restore all registers immediately before the return and any
341 // terminators that precede it.
342 if (!TFI->restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) {
343 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
344 unsigned Reg = CSI[i].getReg();
345 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
346 TII.loadRegFromStackSlot(*MBB, I, Reg,
347 CSI[i].getFrameIdx(),
349 assert(I != MBB->begin() &&
350 "loadRegFromStackSlot didn't insert any code!");
351 // Insert in reverse order. loadRegFromStackSlot can insert
352 // multiple instructions.
366 std::vector<CalleeSavedInfo> blockCSI;
367 for (CSRegBlockMap::iterator BI = CSRSave.begin(),
368 BE = CSRSave.end(); BI != BE; ++BI) {
369 MachineBasicBlock* MBB = BI->first;
370 CSRegSet save = BI->second;
376 for (CSRegSet::iterator RI = save.begin(),
377 RE = save.end(); RI != RE; ++RI) {
378 blockCSI.push_back(CSI[*RI]);
380 assert(blockCSI.size() > 0 &&
381 "Could not collect callee saved register info");
385 // When shrink wrapping, use stack slot stores/loads.
386 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
387 // Add the callee-saved register as live-in.
388 // It's killed at the spill.
389 MBB->addLiveIn(blockCSI[i].getReg());
391 // Insert the spill to the stack frame.
392 unsigned Reg = blockCSI[i].getReg();
393 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
394 TII.storeRegToStackSlot(*MBB, I, Reg,
396 blockCSI[i].getFrameIdx(),
401 for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
402 BE = CSRRestore.end(); BI != BE; ++BI) {
403 MachineBasicBlock* MBB = BI->first;
404 CSRegSet restore = BI->second;
410 for (CSRegSet::iterator RI = restore.begin(),
411 RE = restore.end(); RI != RE; ++RI) {
412 blockCSI.push_back(CSI[*RI]);
414 assert(blockCSI.size() > 0 &&
415 "Could not find callee saved register info");
417 // If MBB is empty and needs restores, insert at the _beginning_.
424 // Skip over all terminator instructions, which are part of the
426 if (! I->getDesc().isTerminator()) {
429 MachineBasicBlock::iterator I2 = I;
430 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
435 bool AtStart = I == MBB->begin();
436 MachineBasicBlock::iterator BeforeI = I;
440 // Restore all registers immediately before the return and any
441 // terminators that precede it.
442 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
443 unsigned Reg = blockCSI[i].getReg();
444 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
445 TII.loadRegFromStackSlot(*MBB, I, Reg,
446 blockCSI[i].getFrameIdx(),
448 assert(I != MBB->begin() &&
449 "loadRegFromStackSlot didn't insert any code!");
450 // Insert in reverse order. loadRegFromStackSlot can insert
451 // multiple instructions.
462 /// AdjustStackOffset - Helper function used to adjust the stack frame offset.
464 AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
465 bool StackGrowsDown, int64_t &Offset,
466 unsigned &MaxAlign) {
467 // If the stack grows down, add the object size to find the lowest address.
469 Offset += MFI->getObjectSize(FrameIdx);
471 unsigned Align = MFI->getObjectAlignment(FrameIdx);
473 // If the alignment of this object is greater than that of the stack, then
474 // increase the stack alignment to match.
475 MaxAlign = std::max(MaxAlign, Align);
477 // Adjust to alignment boundary.
478 Offset = (Offset + Align - 1) / Align * Align;
480 if (StackGrowsDown) {
481 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n");
482 MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
484 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n");
485 MFI->setObjectOffset(FrameIdx, Offset);
486 Offset += MFI->getObjectSize(FrameIdx);
490 /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
491 /// abstract stack objects.
493 void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
494 const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
496 bool StackGrowsDown =
497 TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
499 // Loop over all of the stack objects, assigning sequential addresses...
500 MachineFrameInfo *MFI = Fn.getFrameInfo();
502 // Start at the beginning of the local area.
503 // The Offset is the distance from the stack top in the direction
504 // of stack growth -- so it's always nonnegative.
505 int LocalAreaOffset = TFI.getOffsetOfLocalArea();
507 LocalAreaOffset = -LocalAreaOffset;
508 assert(LocalAreaOffset >= 0
509 && "Local area offset should be in direction of stack growth");
510 int64_t Offset = LocalAreaOffset;
512 // If there are fixed sized objects that are preallocated in the local area,
513 // non-fixed objects can't be allocated right at the start of local area.
514 // We currently don't support filling in holes in between fixed sized
515 // objects, so we adjust 'Offset' to point to the end of last fixed sized
516 // preallocated object.
517 for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
519 if (StackGrowsDown) {
520 // The maximum distance from the stack pointer is at lower address of
521 // the object -- which is given by offset. For down growing stack
522 // the offset is negative, so we negate the offset to get the distance.
523 FixedOff = -MFI->getObjectOffset(i);
525 // The maximum distance from the start pointer is at the upper
526 // address of the object.
527 FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
529 if (FixedOff > Offset) Offset = FixedOff;
532 // First assign frame offsets to stack objects that are used to spill
533 // callee saved registers.
534 if (StackGrowsDown) {
535 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
536 // If the stack grows down, we need to add the size to find the lowest
537 // address of the object.
538 Offset += MFI->getObjectSize(i);
540 unsigned Align = MFI->getObjectAlignment(i);
541 // Adjust to alignment boundary
542 Offset = (Offset+Align-1)/Align*Align;
544 MFI->setObjectOffset(i, -Offset); // Set the computed offset
547 int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
548 for (int i = MaxCSFI; i >= MinCSFI ; --i) {
549 unsigned Align = MFI->getObjectAlignment(i);
550 // Adjust to alignment boundary
551 Offset = (Offset+Align-1)/Align*Align;
553 MFI->setObjectOffset(i, Offset);
554 Offset += MFI->getObjectSize(i);
558 unsigned MaxAlign = MFI->getMaxAlignment();
560 // Make sure the special register scavenging spill slot is closest to the
561 // frame pointer if a frame pointer is required.
562 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
563 if (RS && TFI.hasFP(Fn) && RegInfo->useFPForScavengingIndex(Fn) &&
564 !RegInfo->needsStackRealignment(Fn)) {
565 int SFI = RS->getScavengingFrameIndex();
567 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
570 // FIXME: Once this is working, then enable flag will change to a target
571 // check for whether the frame is large enough to want to use virtual
572 // frame index registers. Functions which don't want/need this optimization
573 // will continue to use the existing code path.
574 if (MFI->getUseLocalStackAllocationBlock()) {
575 unsigned Align = MFI->getLocalFrameMaxAlign();
577 // Adjust to alignment boundary.
578 Offset = (Offset + Align - 1) / Align * Align;
580 DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
582 // Resolve offsets for objects in the local block.
583 for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
584 std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
585 int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
586 DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
588 MFI->setObjectOffset(Entry.first, FIOffset);
590 // Allocate the local block
591 Offset += MFI->getLocalFrameSize();
593 MaxAlign = std::max(Align, MaxAlign);
596 // Make sure that the stack protector comes before the local variables on the
598 SmallSet<int, 16> LargeStackObjs;
599 if (MFI->getStackProtectorIndex() >= 0) {
600 AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
603 // Assign large stack objects first.
604 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
605 if (MFI->isObjectPreAllocated(i) &&
606 MFI->getUseLocalStackAllocationBlock())
608 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
610 if (RS && (int)i == RS->getScavengingFrameIndex())
612 if (MFI->isDeadObjectIndex(i))
614 if (MFI->getStackProtectorIndex() == (int)i)
616 if (!MFI->MayNeedStackProtector(i))
619 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
620 LargeStackObjs.insert(i);
624 // Then assign frame offsets to stack objects that are not used to spill
625 // callee saved registers.
626 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
627 if (MFI->isObjectPreAllocated(i) &&
628 MFI->getUseLocalStackAllocationBlock())
630 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
632 if (RS && (int)i == RS->getScavengingFrameIndex())
634 if (MFI->isDeadObjectIndex(i))
636 if (MFI->getStackProtectorIndex() == (int)i)
638 if (LargeStackObjs.count(i))
641 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
644 // Make sure the special register scavenging spill slot is closest to the
646 if (RS && (!TFI.hasFP(Fn) || RegInfo->needsStackRealignment(Fn) ||
647 !RegInfo->useFPForScavengingIndex(Fn))) {
648 int SFI = RS->getScavengingFrameIndex();
650 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
653 if (!TFI.targetHandlesStackFrameRounding()) {
654 // If we have reserved argument space for call sites in the function
655 // immediately on entry to the current function, count it as part of the
656 // overall stack size.
657 if (MFI->adjustsStack() && TFI.hasReservedCallFrame(Fn))
658 Offset += MFI->getMaxCallFrameSize();
660 // Round up the size to a multiple of the alignment. If the function has
661 // any calls or alloca's, align to the target's StackAlignment value to
662 // ensure that the callee's frame or the alloca data is suitably aligned;
663 // otherwise, for leaf functions, align to the TransientStackAlignment
666 if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
667 (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
668 StackAlign = TFI.getStackAlignment();
670 StackAlign = TFI.getTransientStackAlignment();
672 // If the frame pointer is eliminated, all frame offsets will be relative to
673 // SP not FP. Align to MaxAlign so this works.
674 StackAlign = std::max(StackAlign, MaxAlign);
675 unsigned AlignMask = StackAlign - 1;
676 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
679 // Update frame info to pretend that this is part of the stack...
680 MFI->setStackSize(Offset - LocalAreaOffset);
683 /// insertPrologEpilogCode - Scan the function for modified callee saved
684 /// registers, insert spill code for these callee saved registers, then add
685 /// prolog and epilog code to the function.
687 void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
688 const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
690 // Add prologue to the function...
691 TFI.emitPrologue(Fn);
693 // Add epilogue to restore the callee-save registers in each exiting block
694 for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
695 // If last instruction is a return instruction, add an epilogue
696 if (!I->empty() && I->back().getDesc().isReturn())
697 TFI.emitEpilogue(Fn, *I);
701 /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
702 /// register references and actual offsets.
704 void PEI::replaceFrameIndices(MachineFunction &Fn) {
705 if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
707 const TargetMachine &TM = Fn.getTarget();
708 assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
709 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
710 const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
711 const TargetFrameLowering *TFI = TM.getFrameLowering();
712 bool StackGrowsDown =
713 TFI->getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
714 int FrameSetupOpcode = TII.getCallFrameSetupOpcode();
715 int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
717 for (MachineFunction::iterator BB = Fn.begin(),
718 E = Fn.end(); BB != E; ++BB) {
720 int SPAdjCount = 0; // frame setup / destroy count.
722 int SPAdj = 0; // SP offset due to call frame setup / destroy.
723 if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
725 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
727 if (I->getOpcode() == FrameSetupOpcode ||
728 I->getOpcode() == FrameDestroyOpcode) {
730 // Track whether we see even pairs of them
731 SPAdjCount += I->getOpcode() == FrameSetupOpcode ? 1 : -1;
733 // Remember how much SP has been adjusted to create the call
735 int Size = I->getOperand(0).getImm();
737 if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
738 (StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
743 MachineBasicBlock::iterator PrevI = BB->end();
744 if (I != BB->begin()) PrevI = prior(I);
745 TRI.eliminateCallFramePseudoInstr(Fn, *BB, I);
747 // Visit the instructions created by eliminateCallFramePseudoInstr().
748 if (PrevI == BB->end())
749 I = BB->begin(); // The replaced instr was the first in the block.
751 I = llvm::next(PrevI);
755 MachineInstr *MI = I;
757 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
758 if (MI->getOperand(i).isFI()) {
759 // Some instructions (e.g. inline asm instructions) can have
760 // multiple frame indices and/or cause eliminateFrameIndex
761 // to insert more than one instruction. We need the register
762 // scavenger to go through all of these instructions so that
763 // it can update its register information. We keep the
764 // iterator at the point before insertion so that we can
765 // revisit them in full.
766 bool AtBeginning = (I == BB->begin());
767 if (!AtBeginning) --I;
769 // If this instruction has a FrameIndex operand, we need to
770 // use that target machine register info object to eliminate
772 TRI.eliminateFrameIndex(MI, SPAdj,
773 FrameIndexVirtualScavenging ? NULL : RS);
775 // Reset the iterator if we were at the beginning of the BB.
785 if (DoIncr && I != BB->end()) ++I;
787 // Update register states.
788 if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
791 // If we have evenly matched pairs of frame setup / destroy instructions,
792 // make sure the adjustments come out to zero. If we don't have matched
793 // pairs, we can't be sure the missing bit isn't in another basic block
794 // due to a custom inserter playing tricks, so just asserting SPAdj==0
795 // isn't sufficient. See tMOVCC on Thumb1, for example.
796 assert((SPAdjCount || SPAdj == 0) &&
797 "Unbalanced call frame setup / destroy pairs?");
801 /// scavengeFrameVirtualRegs - Replace all frame index virtual registers
802 /// with physical registers. Use the register scavenger to find an
803 /// appropriate register to use.
804 void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
805 // Run through the instructions and find any virtual registers.
806 for (MachineFunction::iterator BB = Fn.begin(),
807 E = Fn.end(); BB != E; ++BB) {
808 RS->enterBasicBlock(BB);
810 unsigned VirtReg = 0;
811 unsigned ScratchReg = 0;
814 // The instruction stream may change in the loop, so check BB->end()
816 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
817 MachineInstr *MI = I;
818 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
819 if (MI->getOperand(i).isReg()) {
820 MachineOperand &MO = MI->getOperand(i);
821 unsigned Reg = MO.getReg();
824 if (!TargetRegisterInfo::isVirtualRegister(Reg))
827 ++NumVirtualFrameRegs;
829 // Have we already allocated a scratch register for this virtual?
830 if (Reg != VirtReg) {
831 // When we first encounter a new virtual register, it
832 // must be a definition.
833 assert(MI->getOperand(i).isDef() &&
834 "frame index virtual missing def!");
835 // Scavenge a new scratch register
837 const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
838 ScratchReg = RS->scavengeRegister(RC, I, SPAdj);
841 // Replace this reference to the virtual register with the
843 assert (ScratchReg && "Missing scratch register!");
844 MI->getOperand(i).setReg(ScratchReg);