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/CodeGen/MachineDominators.h"
25 #include "llvm/CodeGen/MachineLoopInfo.h"
26 #include "llvm/CodeGen/MachineInstr.h"
27 #include "llvm/CodeGen/MachineFrameInfo.h"
28 #include "llvm/CodeGen/MachineRegisterInfo.h"
29 #include "llvm/CodeGen/RegisterScavenging.h"
30 #include "llvm/Target/TargetMachine.h"
31 #include "llvm/Target/TargetRegisterInfo.h"
32 #include "llvm/Target/TargetFrameInfo.h"
33 #include "llvm/Target/TargetInstrInfo.h"
34 #include "llvm/Support/CommandLine.h"
35 #include "llvm/Support/Compiler.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/ADT/IndexedMap.h"
38 #include "llvm/ADT/SmallSet.h"
39 #include "llvm/ADT/STLExtras.h"
46 INITIALIZE_PASS(PEI, "prologepilog",
47 "Prologue/Epilogue Insertion", false, false);
49 /// createPrologEpilogCodeInserter - This function returns a pass that inserts
50 /// prolog and epilog code, and eliminates abstract frame references.
52 FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); }
54 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
55 /// frame indexes with appropriate references.
57 bool PEI::runOnMachineFunction(MachineFunction &Fn) {
58 const Function* F = Fn.getFunction();
59 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
60 RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
61 FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
62 FrameConstantRegMap.clear();
64 // Calculate the MaxCallFrameSize and AdjustsStack variables for the
65 // function's frame information. Also eliminates call frame pseudo
67 calculateCallsInformation(Fn);
69 // Allow the target machine to make some adjustments to the function
70 // e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
71 TRI->processFunctionBeforeCalleeSavedScan(Fn, RS);
73 // Scan the function for modified callee saved registers and insert spill code
74 // for any callee saved registers that are modified.
75 calculateCalleeSavedRegisters(Fn);
77 // Determine placement of CSR spill/restore code:
78 // - With shrink wrapping, place spills and restores to tightly
79 // enclose regions in the Machine CFG of the function where
81 // - Without shink wrapping (default), place all spills in the
82 // entry block, all restores in return blocks.
83 placeCSRSpillsAndRestores(Fn);
85 // Add the code to save and restore the callee saved registers
86 if (!F->hasFnAttr(Attribute::Naked))
87 insertCSRSpillsAndRestores(Fn);
89 // Allow the target machine to make final modifications to the function
90 // before the frame layout is finalized.
91 TRI->processFunctionBeforeFrameFinalized(Fn);
93 // Calculate actual frame offsets for all abstract stack objects...
94 calculateFrameObjectOffsets(Fn);
96 // Add prolog and epilog code to the function. This function is required
97 // to align the stack frame as necessary for any stack variables or
98 // called functions. Because of this, calculateCalleeSavedRegisters()
99 // must be called before this function in order to set the AdjustsStack
100 // and MaxCallFrameSize variables.
101 if (!F->hasFnAttr(Attribute::Naked))
102 insertPrologEpilogCode(Fn);
104 // Replace all MO_FrameIndex operands with physical register references
105 // and actual offsets.
107 replaceFrameIndices(Fn);
109 // If register scavenging is needed, as we've enabled doing it as a
110 // post-pass, scavenge the virtual registers that frame index elimiation
112 if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging)
113 scavengeFrameVirtualRegs(Fn);
121 void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
122 AU.setPreservesCFG();
123 if (ShrinkWrapping || ShrinkWrapFunc != "") {
124 AU.addRequired<MachineLoopInfo>();
125 AU.addRequired<MachineDominatorTree>();
127 AU.addPreserved<MachineLoopInfo>();
128 AU.addPreserved<MachineDominatorTree>();
129 MachineFunctionPass::getAnalysisUsage(AU);
133 /// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack
134 /// variables for the function's frame information and eliminate call frame
135 /// pseudo instructions.
136 void PEI::calculateCallsInformation(MachineFunction &Fn) {
137 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
138 MachineFrameInfo *MFI = Fn.getFrameInfo();
140 unsigned MaxCallFrameSize = 0;
141 bool AdjustsStack = MFI->adjustsStack();
143 // Get the function call frame set-up and tear-down instruction opcode
144 int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode();
145 int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode();
147 // Early exit for targets which have no call frame setup/destroy pseudo
149 if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
152 std::vector<MachineBasicBlock::iterator> FrameSDOps;
153 for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
154 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
155 if (I->getOpcode() == FrameSetupOpcode ||
156 I->getOpcode() == FrameDestroyOpcode) {
157 assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
158 " instructions should have a single immediate argument!");
159 unsigned Size = I->getOperand(0).getImm();
160 if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
162 FrameSDOps.push_back(I);
163 } else if (I->isInlineAsm()) {
164 // Some inline asm's need a stack frame, as indicated by operand 1.
165 if (I->getOperand(1).getImm())
169 MFI->setAdjustsStack(AdjustsStack);
170 MFI->setMaxCallFrameSize(MaxCallFrameSize);
172 for (std::vector<MachineBasicBlock::iterator>::iterator
173 i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) {
174 MachineBasicBlock::iterator I = *i;
176 // If call frames are not being included as part of the stack frame, and
177 // the target doesn't indicate otherwise, remove the call frame pseudos
178 // here. The sub/add sp instruction pairs are still inserted, but we don't
179 // need to track the SP adjustment for frame index elimination.
180 if (RegInfo->canSimplifyCallFramePseudos(Fn))
181 RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
186 /// calculateCalleeSavedRegisters - Scan the function for modified callee saved
188 void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) {
189 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
190 const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo();
191 MachineFrameInfo *MFI = Fn.getFrameInfo();
193 // Get the callee saved register list...
194 const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn);
196 // These are used to keep track the callee-save area. Initialize them.
197 MinCSFrameIndex = INT_MAX;
200 // Early exit for targets which have no callee saved registers.
201 if (CSRegs == 0 || CSRegs[0] == 0)
204 // In Naked functions we aren't going to save any registers.
205 if (Fn.getFunction()->hasFnAttr(Attribute::Naked))
208 std::vector<CalleeSavedInfo> CSI;
209 for (unsigned i = 0; CSRegs[i]; ++i) {
210 unsigned Reg = CSRegs[i];
211 if (Fn.getRegInfo().isPhysRegUsed(Reg)) {
212 // If the reg is modified, save it!
213 CSI.push_back(CalleeSavedInfo(Reg));
215 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
216 *AliasSet; ++AliasSet) { // Check alias registers too.
217 if (Fn.getRegInfo().isPhysRegUsed(*AliasSet)) {
218 CSI.push_back(CalleeSavedInfo(Reg));
226 return; // Early exit if no callee saved registers are modified!
228 unsigned NumFixedSpillSlots;
229 const TargetFrameInfo::SpillSlot *FixedSpillSlots =
230 TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
232 // Now that we know which registers need to be saved and restored, allocate
233 // stack slots for them.
234 for (std::vector<CalleeSavedInfo>::iterator
235 I = CSI.begin(), E = CSI.end(); I != E; ++I) {
236 unsigned Reg = I->getReg();
237 const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
240 if (RegInfo->hasReservedSpillSlot(Fn, Reg, FrameIdx)) {
241 I->setFrameIdx(FrameIdx);
245 // Check to see if this physreg must be spilled to a particular stack slot
247 const TargetFrameInfo::SpillSlot *FixedSlot = FixedSpillSlots;
248 while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
249 FixedSlot->Reg != Reg)
252 if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
253 // Nope, just spill it anywhere convenient.
254 unsigned Align = RC->getAlignment();
255 unsigned StackAlign = TFI->getStackAlignment();
257 // We may not be able to satisfy the desired alignment specification of
258 // the TargetRegisterClass if the stack alignment is smaller. Use the
260 Align = std::min(Align, StackAlign);
261 FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
262 if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
263 if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
265 // Spill it to the stack where we must.
266 FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true);
269 I->setFrameIdx(FrameIdx);
272 MFI->setCalleeSavedInfo(CSI);
275 /// insertCSRSpillsAndRestores - Insert spill and restore code for
276 /// callee saved registers used in the function, handling shrink wrapping.
278 void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
279 // Get callee saved register information.
280 MachineFrameInfo *MFI = Fn.getFrameInfo();
281 const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
283 MFI->setCalleeSavedInfoValid(true);
285 // Early exit if no callee saved registers are modified!
289 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
290 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
291 MachineBasicBlock::iterator I;
293 if (! ShrinkWrapThisFunction) {
294 // Spill using target interface.
295 I = EntryBlock->begin();
296 if (!TII.spillCalleeSavedRegisters(*EntryBlock, I, CSI, TRI)) {
297 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
298 // Add the callee-saved register as live-in.
299 // It's killed at the spill.
300 EntryBlock->addLiveIn(CSI[i].getReg());
302 // Insert the spill to the stack frame.
303 unsigned Reg = CSI[i].getReg();
304 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
305 TII.storeRegToStackSlot(*EntryBlock, I, Reg, true,
306 CSI[i].getFrameIdx(), RC, TRI);
310 // Restore using target interface.
311 for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) {
312 MachineBasicBlock* MBB = ReturnBlocks[ri];
315 // Skip over all terminator instructions, which are part of the return
317 MachineBasicBlock::iterator I2 = I;
318 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
321 bool AtStart = I == MBB->begin();
322 MachineBasicBlock::iterator BeforeI = I;
326 // Restore all registers immediately before the return and any
327 // terminators that preceed it.
328 if (!TII.restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) {
329 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
330 unsigned Reg = CSI[i].getReg();
331 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
332 TII.loadRegFromStackSlot(*MBB, I, Reg,
333 CSI[i].getFrameIdx(),
335 assert(I != MBB->begin() &&
336 "loadRegFromStackSlot didn't insert any code!");
337 // Insert in reverse order. loadRegFromStackSlot can insert
338 // multiple instructions.
352 std::vector<CalleeSavedInfo> blockCSI;
353 for (CSRegBlockMap::iterator BI = CSRSave.begin(),
354 BE = CSRSave.end(); BI != BE; ++BI) {
355 MachineBasicBlock* MBB = BI->first;
356 CSRegSet save = BI->second;
362 for (CSRegSet::iterator RI = save.begin(),
363 RE = save.end(); RI != RE; ++RI) {
364 blockCSI.push_back(CSI[*RI]);
366 assert(blockCSI.size() > 0 &&
367 "Could not collect callee saved register info");
371 // When shrink wrapping, use stack slot stores/loads.
372 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
373 // Add the callee-saved register as live-in.
374 // It's killed at the spill.
375 MBB->addLiveIn(blockCSI[i].getReg());
377 // Insert the spill to the stack frame.
378 unsigned Reg = blockCSI[i].getReg();
379 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
380 TII.storeRegToStackSlot(*MBB, I, Reg,
382 blockCSI[i].getFrameIdx(),
387 for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
388 BE = CSRRestore.end(); BI != BE; ++BI) {
389 MachineBasicBlock* MBB = BI->first;
390 CSRegSet restore = BI->second;
396 for (CSRegSet::iterator RI = restore.begin(),
397 RE = restore.end(); RI != RE; ++RI) {
398 blockCSI.push_back(CSI[*RI]);
400 assert(blockCSI.size() > 0 &&
401 "Could not find callee saved register info");
403 // If MBB is empty and needs restores, insert at the _beginning_.
410 // Skip over all terminator instructions, which are part of the
412 if (! I->getDesc().isTerminator()) {
415 MachineBasicBlock::iterator I2 = I;
416 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
421 bool AtStart = I == MBB->begin();
422 MachineBasicBlock::iterator BeforeI = I;
426 // Restore all registers immediately before the return and any
427 // terminators that preceed it.
428 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
429 unsigned Reg = blockCSI[i].getReg();
430 const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
431 TII.loadRegFromStackSlot(*MBB, I, Reg,
432 blockCSI[i].getFrameIdx(),
434 assert(I != MBB->begin() &&
435 "loadRegFromStackSlot didn't insert any code!");
436 // Insert in reverse order. loadRegFromStackSlot can insert
437 // multiple instructions.
448 /// AdjustStackOffset - Helper function used to adjust the stack frame offset.
450 AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
451 bool StackGrowsDown, int64_t &Offset,
452 unsigned &MaxAlign) {
453 // If the stack grows down, add the object size to find the lowest address.
455 Offset += MFI->getObjectSize(FrameIdx);
457 unsigned Align = MFI->getObjectAlignment(FrameIdx);
459 // If the alignment of this object is greater than that of the stack, then
460 // increase the stack alignment to match.
461 MaxAlign = std::max(MaxAlign, Align);
463 // Adjust to alignment boundary.
464 Offset = (Offset + Align - 1) / Align * Align;
466 if (StackGrowsDown) {
467 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n");
468 MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
470 DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n");
471 MFI->setObjectOffset(FrameIdx, Offset);
472 Offset += MFI->getObjectSize(FrameIdx);
476 /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
477 /// abstract stack objects.
479 void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
480 const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
482 bool StackGrowsDown =
483 TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
485 // Loop over all of the stack objects, assigning sequential addresses...
486 MachineFrameInfo *MFI = Fn.getFrameInfo();
488 // Start at the beginning of the local area.
489 // The Offset is the distance from the stack top in the direction
490 // of stack growth -- so it's always nonnegative.
491 int LocalAreaOffset = TFI.getOffsetOfLocalArea();
493 LocalAreaOffset = -LocalAreaOffset;
494 assert(LocalAreaOffset >= 0
495 && "Local area offset should be in direction of stack growth");
496 int64_t Offset = LocalAreaOffset;
498 // If there are fixed sized objects that are preallocated in the local area,
499 // non-fixed objects can't be allocated right at the start of local area.
500 // We currently don't support filling in holes in between fixed sized
501 // objects, so we adjust 'Offset' to point to the end of last fixed sized
502 // preallocated object.
503 for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
505 if (StackGrowsDown) {
506 // The maximum distance from the stack pointer is at lower address of
507 // the object -- which is given by offset. For down growing stack
508 // the offset is negative, so we negate the offset to get the distance.
509 FixedOff = -MFI->getObjectOffset(i);
511 // The maximum distance from the start pointer is at the upper
512 // address of the object.
513 FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
515 if (FixedOff > Offset) Offset = FixedOff;
518 // First assign frame offsets to stack objects that are used to spill
519 // callee saved registers.
520 if (StackGrowsDown) {
521 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
522 // If the stack grows down, we need to add the size to find the lowest
523 // address of the object.
524 Offset += MFI->getObjectSize(i);
526 unsigned Align = MFI->getObjectAlignment(i);
527 // Adjust to alignment boundary
528 Offset = (Offset+Align-1)/Align*Align;
530 MFI->setObjectOffset(i, -Offset); // Set the computed offset
533 int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
534 for (int i = MaxCSFI; i >= MinCSFI ; --i) {
535 unsigned Align = MFI->getObjectAlignment(i);
536 // Adjust to alignment boundary
537 Offset = (Offset+Align-1)/Align*Align;
539 MFI->setObjectOffset(i, Offset);
540 Offset += MFI->getObjectSize(i);
544 unsigned MaxAlign = MFI->getMaxAlignment();
546 // Make sure the special register scavenging spill slot is closest to the
547 // frame pointer if a frame pointer is required.
548 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
549 if (RS && RegInfo->hasFP(Fn) && !RegInfo->needsStackRealignment(Fn)) {
550 int SFI = RS->getScavengingFrameIndex();
552 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
555 // FIXME: Once this is working, then enable flag will change to a target
556 // check for whether the frame is large enough to want to use virtual
557 // frame index registers. Functions which don't want/need this optimization
558 // will continue to use the existing code path.
559 if (MFI->getUseLocalStackAllocationBlock()) {
560 unsigned Align = MFI->getLocalFrameMaxAlign();
562 // Adjust to alignment boundary.
563 Offset = (Offset + Align - 1) / Align * Align;
565 DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
567 // Resolve offsets for objects in the local block.
568 for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
569 std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
570 int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
571 DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
573 MFI->setObjectOffset(Entry.first, FIOffset);
575 // Allocate the local block
576 Offset += MFI->getLocalFrameSize();
578 MaxAlign = std::max(Align, MaxAlign);
581 // Make sure that the stack protector comes before the local variables on the
583 SmallSet<int, 16> LargeStackObjs;
584 if (MFI->getStackProtectorIndex() >= 0) {
585 AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
588 // Assign large stack objects first.
589 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
590 if (MFI->isObjectPreAllocated(i) &&
591 MFI->getUseLocalStackAllocationBlock())
593 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
595 if (RS && (int)i == RS->getScavengingFrameIndex())
597 if (MFI->isDeadObjectIndex(i))
599 if (MFI->getStackProtectorIndex() == (int)i)
601 if (!MFI->MayNeedStackProtector(i))
604 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
605 LargeStackObjs.insert(i);
609 // Then assign frame offsets to stack objects that are not used to spill
610 // callee saved registers.
611 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
612 if (MFI->isObjectPreAllocated(i) &&
613 MFI->getUseLocalStackAllocationBlock())
615 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
617 if (RS && (int)i == RS->getScavengingFrameIndex())
619 if (MFI->isDeadObjectIndex(i))
621 if (MFI->getStackProtectorIndex() == (int)i)
623 if (LargeStackObjs.count(i))
626 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
629 // Make sure the special register scavenging spill slot is closest to the
631 if (RS && (!RegInfo->hasFP(Fn) || RegInfo->needsStackRealignment(Fn))) {
632 int SFI = RS->getScavengingFrameIndex();
634 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
637 if (!RegInfo->targetHandlesStackFrameRounding()) {
638 // If we have reserved argument space for call sites in the function
639 // immediately on entry to the current function, count it as part of the
640 // overall stack size.
641 if (MFI->adjustsStack() && RegInfo->hasReservedCallFrame(Fn))
642 Offset += MFI->getMaxCallFrameSize();
644 // Round up the size to a multiple of the alignment. If the function has
645 // any calls or alloca's, align to the target's StackAlignment value to
646 // ensure that the callee's frame or the alloca data is suitably aligned;
647 // otherwise, for leaf functions, align to the TransientStackAlignment
650 if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
651 (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
652 StackAlign = TFI.getStackAlignment();
654 StackAlign = TFI.getTransientStackAlignment();
656 // If the frame pointer is eliminated, all frame offsets will be relative to
657 // SP not FP. Align to MaxAlign so this works.
658 StackAlign = std::max(StackAlign, MaxAlign);
659 unsigned AlignMask = StackAlign - 1;
660 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
663 // Update frame info to pretend that this is part of the stack...
664 MFI->setStackSize(Offset - LocalAreaOffset);
667 /// insertPrologEpilogCode - Scan the function for modified callee saved
668 /// registers, insert spill code for these callee saved registers, then add
669 /// prolog and epilog code to the function.
671 void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
672 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
674 // Add prologue to the function...
675 TRI->emitPrologue(Fn);
677 // Add epilogue to restore the callee-save registers in each exiting block
678 for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
679 // If last instruction is a return instruction, add an epilogue
680 if (!I->empty() && I->back().getDesc().isReturn())
681 TRI->emitEpilogue(Fn, *I);
685 /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
686 /// register references and actual offsets.
688 void PEI::replaceFrameIndices(MachineFunction &Fn) {
689 if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
691 const TargetMachine &TM = Fn.getTarget();
692 assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
693 const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
694 const TargetFrameInfo *TFI = TM.getFrameInfo();
695 bool StackGrowsDown =
696 TFI->getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
697 int FrameSetupOpcode = TRI.getCallFrameSetupOpcode();
698 int FrameDestroyOpcode = TRI.getCallFrameDestroyOpcode();
700 for (MachineFunction::iterator BB = Fn.begin(),
701 E = Fn.end(); BB != E; ++BB) {
703 int SPAdjCount = 0; // frame setup / destroy count.
705 int SPAdj = 0; // SP offset due to call frame setup / destroy.
706 if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
708 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
710 if (I->getOpcode() == FrameSetupOpcode ||
711 I->getOpcode() == FrameDestroyOpcode) {
713 // Track whether we see even pairs of them
714 SPAdjCount += I->getOpcode() == FrameSetupOpcode ? 1 : -1;
716 // Remember how much SP has been adjusted to create the call
718 int Size = I->getOperand(0).getImm();
720 if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
721 (StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
726 MachineBasicBlock::iterator PrevI = BB->end();
727 if (I != BB->begin()) PrevI = prior(I);
728 TRI.eliminateCallFramePseudoInstr(Fn, *BB, I);
730 // Visit the instructions created by eliminateCallFramePseudoInstr().
731 if (PrevI == BB->end())
732 I = BB->begin(); // The replaced instr was the first in the block.
734 I = llvm::next(PrevI);
738 MachineInstr *MI = I;
740 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
741 if (MI->getOperand(i).isFI()) {
742 // Some instructions (e.g. inline asm instructions) can have
743 // multiple frame indices and/or cause eliminateFrameIndex
744 // to insert more than one instruction. We need the register
745 // scavenger to go through all of these instructions so that
746 // it can update its register information. We keep the
747 // iterator at the point before insertion so that we can
748 // revisit them in full.
749 bool AtBeginning = (I == BB->begin());
750 if (!AtBeginning) --I;
752 // If this instruction has a FrameIndex operand, we need to
753 // use that target machine register info object to eliminate
755 TargetRegisterInfo::FrameIndexValue Value;
757 TRI.eliminateFrameIndex(MI, SPAdj, &Value,
758 FrameIndexVirtualScavenging ? NULL : RS);
760 assert (FrameIndexVirtualScavenging &&
761 "Not scavenging, but virtual returned from "
762 "eliminateFrameIndex()!");
763 FrameConstantRegMap[VReg] = FrameConstantEntry(Value, SPAdj);
766 // Reset the iterator if we were at the beginning of the BB.
776 if (DoIncr && I != BB->end()) ++I;
778 // Update register states.
779 if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
782 // If we have evenly matched pairs of frame setup / destroy instructions,
783 // make sure the adjustments come out to zero. If we don't have matched
784 // pairs, we can't be sure the missing bit isn't in another basic block
785 // due to a custom inserter playing tricks, so just asserting SPAdj==0
786 // isn't sufficient. See tMOVCC on Thumb1, for example.
787 assert((SPAdjCount || SPAdj == 0) &&
788 "Unbalanced call frame setup / destroy pairs?");
792 /// findLastUseReg - find the killing use of the specified register within
793 /// the instruciton range. Return the operand number of the kill in Operand.
794 static MachineBasicBlock::iterator
795 findLastUseReg(MachineBasicBlock::iterator I, MachineBasicBlock::iterator ME,
797 // Scan forward to find the last use of this virtual register
798 for (++I; I != ME; ++I) {
799 MachineInstr *MI = I;
800 bool isDefInsn = false;
801 bool isKillInsn = false;
802 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
803 if (MI->getOperand(i).isReg()) {
804 unsigned OpReg = MI->getOperand(i).getReg();
805 if (OpReg == 0 || !TargetRegisterInfo::isVirtualRegister(OpReg))
808 && "overlapping use of scavenged index register!");
809 // If this is the killing use, we have a candidate.
810 if (MI->getOperand(i).isKill())
812 else if (MI->getOperand(i).isDef())
815 if (isKillInsn && !isDefInsn)
818 // If we hit the end of the basic block, there was no kill of
819 // the virtual register, which is wrong.
820 assert (0 && "scavenged index register never killed!");
824 /// scavengeFrameVirtualRegs - Replace all frame index virtual registers
825 /// with physical registers. Use the register scavenger to find an
826 /// appropriate register to use.
827 void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
828 // Run through the instructions and find any virtual registers.
829 for (MachineFunction::iterator BB = Fn.begin(),
830 E = Fn.end(); BB != E; ++BB) {
831 RS->enterBasicBlock(BB);
833 // FIXME: The logic flow in this function is still too convoluted.
834 // It needs a cleanup refactoring. Do that in preparation for tracking
835 // more than one scratch register value and using ranges to find
836 // available scratch registers.
837 unsigned CurrentVirtReg = 0;
838 unsigned CurrentScratchReg = 0;
839 bool havePrevValue = false;
840 TargetRegisterInfo::FrameIndexValue PrevValue(0,0);
841 TargetRegisterInfo::FrameIndexValue Value(0,0);
842 MachineInstr *PrevLastUseMI = NULL;
843 unsigned PrevLastUseOp = 0;
844 bool trackingCurrentValue = false;
847 // The instruction stream may change in the loop, so check BB->end()
849 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
850 MachineInstr *MI = I;
851 bool isDefInsn = false;
852 bool isKillInsn = false;
853 bool clobbersScratchReg = false;
855 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
856 if (MI->getOperand(i).isReg()) {
857 MachineOperand &MO = MI->getOperand(i);
858 unsigned Reg = MO.getReg();
861 if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
862 // If we have a previous scratch reg, check and see if anything
863 // here kills whatever value is in there.
864 if (Reg == CurrentScratchReg) {
866 // Two-address operands implicitly kill
867 if (MO.isKill() || MI->isRegTiedToDefOperand(i))
868 clobbersScratchReg = true;
871 clobbersScratchReg = true;
876 // If this is a def, remember that this insn defines the value.
877 // This lets us properly consider insns which re-use the scratch
878 // register, such as r2 = sub r2, #imm, in the middle of the
883 // Have we already allocated a scratch register for this virtual?
884 if (Reg != CurrentVirtReg) {
885 // When we first encounter a new virtual register, it
886 // must be a definition.
887 assert(MI->getOperand(i).isDef() &&
888 "frame index virtual missing def!");
889 // We can't have nested virtual register live ranges because
890 // there's only a guarantee of one scavenged register at a time.
891 assert (CurrentVirtReg == 0 &&
892 "overlapping frame index virtual registers!");
894 // If the target gave us information about what's in the register,
895 // we can use that to re-use scratch regs.
896 DenseMap<unsigned, FrameConstantEntry>::iterator Entry =
897 FrameConstantRegMap.find(Reg);
898 trackingCurrentValue = Entry != FrameConstantRegMap.end();
899 if (trackingCurrentValue) {
900 SPAdj = (*Entry).second.second;
901 Value = (*Entry).second.first;
908 // If the scratch register from the last allocation is still
909 // available, see if the value matches. If it does, just re-use it.
910 if (trackingCurrentValue && havePrevValue && PrevValue == Value) {
911 // FIXME: This assumes that the instructions in the live range
912 // for the virtual register are exclusively for the purpose
913 // of populating the value in the register. That's reasonable
914 // for these frame index registers, but it's still a very, very
915 // strong assumption. rdar://7322732. Better would be to
916 // explicitly check each instruction in the range for references
917 // to the virtual register. Only delete those insns that
918 // touch the virtual register.
920 // Find the last use of the new virtual register. Remove all
921 // instruction between here and there, and update the current
922 // instruction to reference the last use insn instead.
923 MachineBasicBlock::iterator LastUseMI =
924 findLastUseReg(I, BB->end(), Reg);
926 // Remove all instructions up 'til the last use, since they're
927 // just calculating the value we already have.
928 BB->erase(I, LastUseMI);
931 // Extend the live range of the scratch register
932 PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false);
933 RS->setUsed(CurrentScratchReg);
934 CurrentVirtReg = Reg;
936 // We deleted the instruction we were scanning the operands of.
937 // Jump back to the instruction iterator loop. Don't increment
938 // past this instruction since we updated the iterator already.
943 // Scavenge a new scratch register
944 CurrentVirtReg = Reg;
945 const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
946 CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);
949 // replace this reference to the virtual register with the
951 assert (CurrentScratchReg && "Missing scratch register!");
952 MI->getOperand(i).setReg(CurrentScratchReg);
954 if (MI->getOperand(i).isKill()) {
961 // If this is the last use of the scratch, stop tracking it. The
962 // last use will be a kill operand in an instruction that does
963 // not also define the scratch register.
964 if (isKillInsn && !isDefInsn) {
966 havePrevValue = trackingCurrentValue;
968 // Similarly, notice if instruction clobbered the value in the
969 // register we're tracking for possible later reuse. This is noted
970 // above, but enforced here since the value is still live while we
971 // process the rest of the operands of the instruction.
972 if (clobbersScratchReg) {
973 havePrevValue = false;
974 CurrentScratchReg = 0;