1 //=======- ARMFrameLowering.cpp - ARM Frame Information --------*- C++ -*-====//
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 file contains the ARM implementation of TargetFrameLowering class.
12 //===----------------------------------------------------------------------===//
14 #include "ARMFrameLowering.h"
15 #include "ARMBaseInstrInfo.h"
16 #include "ARMBaseRegisterInfo.h"
17 #include "ARMMachineFunctionInfo.h"
18 #include "MCTargetDesc/ARMAddressingModes.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/CodeGen/MachineRegisterInfo.h"
23 #include "llvm/CodeGen/RegisterScavenging.h"
24 #include "llvm/Target/TargetOptions.h"
28 /// hasFP - Return true if the specified function should have a dedicated frame
29 /// pointer register. This is true if the function has variable sized allocas
30 /// or if frame pointer elimination is disabled.
31 bool ARMFrameLowering::hasFP(const MachineFunction &MF) const {
32 const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
34 // Mac OS X requires FP not to be clobbered for backtracing purpose.
35 if (STI.isTargetDarwin())
38 const MachineFrameInfo *MFI = MF.getFrameInfo();
39 // Always eliminate non-leaf frame pointers.
40 return ((MF.getTarget().Options.DisableFramePointerElim(MF) &&
42 RegInfo->needsStackRealignment(MF) ||
43 MFI->hasVarSizedObjects() ||
44 MFI->isFrameAddressTaken());
47 /// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
48 /// not required, we reserve argument space for call sites in the function
49 /// immediately on entry to the current function. This eliminates the need for
50 /// add/sub sp brackets around call sites. Returns true if the call frame is
51 /// included as part of the stack frame.
52 bool ARMFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
53 const MachineFrameInfo *FFI = MF.getFrameInfo();
54 unsigned CFSize = FFI->getMaxCallFrameSize();
55 // It's not always a good idea to include the call frame as part of the
56 // stack frame. ARM (especially Thumb) has small immediate offset to
57 // address the stack frame. So a large call frame can cause poor codegen
58 // and may even makes it impossible to scavenge a register.
59 if (CFSize >= ((1 << 12) - 1) / 2) // Half of imm12
62 return !MF.getFrameInfo()->hasVarSizedObjects();
65 /// canSimplifyCallFramePseudos - If there is a reserved call frame, the
66 /// call frame pseudos can be simplified. Unlike most targets, having a FP
67 /// is not sufficient here since we still may reference some objects via SP
68 /// even when FP is available in Thumb2 mode.
70 ARMFrameLowering::canSimplifyCallFramePseudos(const MachineFunction &MF) const {
71 return hasReservedCallFrame(MF) || MF.getFrameInfo()->hasVarSizedObjects();
74 static bool isCalleeSavedRegister(unsigned Reg, const unsigned *CSRegs) {
75 for (unsigned i = 0; CSRegs[i]; ++i)
81 static bool isCSRestore(MachineInstr *MI,
82 const ARMBaseInstrInfo &TII,
83 const unsigned *CSRegs) {
84 // Integer spill area is handled with "pop".
85 if (MI->getOpcode() == ARM::LDMIA_RET ||
86 MI->getOpcode() == ARM::t2LDMIA_RET ||
87 MI->getOpcode() == ARM::LDMIA_UPD ||
88 MI->getOpcode() == ARM::t2LDMIA_UPD ||
89 MI->getOpcode() == ARM::VLDMDIA_UPD) {
90 // The first two operands are predicates. The last two are
91 // imp-def and imp-use of SP. Check everything in between.
92 for (int i = 5, e = MI->getNumOperands(); i != e; ++i)
93 if (!isCalleeSavedRegister(MI->getOperand(i).getReg(), CSRegs))
97 if ((MI->getOpcode() == ARM::LDR_POST_IMM ||
98 MI->getOpcode() == ARM::LDR_POST_REG ||
99 MI->getOpcode() == ARM::t2LDR_POST) &&
100 isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs) &&
101 MI->getOperand(1).getReg() == ARM::SP)
108 emitSPUpdate(bool isARM,
109 MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
110 DebugLoc dl, const ARMBaseInstrInfo &TII,
111 int NumBytes, unsigned MIFlags = MachineInstr::NoFlags) {
113 emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
114 ARMCC::AL, 0, TII, MIFlags);
116 emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
117 ARMCC::AL, 0, TII, MIFlags);
120 void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
121 MachineBasicBlock &MBB = MF.front();
122 MachineBasicBlock::iterator MBBI = MBB.begin();
123 MachineFrameInfo *MFI = MF.getFrameInfo();
124 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
125 const ARMBaseRegisterInfo *RegInfo =
126 static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
127 const ARMBaseInstrInfo &TII =
128 *static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
129 assert(!AFI->isThumb1OnlyFunction() &&
130 "This emitPrologue does not support Thumb1!");
131 bool isARM = !AFI->isThumbFunction();
132 unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize();
133 unsigned NumBytes = MFI->getStackSize();
134 const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
135 DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
136 unsigned FramePtr = RegInfo->getFrameRegister(MF);
138 // Determine the sizes of each callee-save spill areas and record which frame
139 // belongs to which callee-save spill areas.
140 unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
141 int FramePtrSpillFI = 0;
143 // Allocate the vararg register save area. This is not counted in NumBytes.
145 emitSPUpdate(isARM, MBB, MBBI, dl, TII, -VARegSaveSize,
146 MachineInstr::FrameSetup);
148 if (!AFI->hasStackFrame()) {
150 emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
151 MachineInstr::FrameSetup);
155 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
156 unsigned Reg = CSI[i].getReg();
157 int FI = CSI[i].getFrameIdx();
165 FramePtrSpillFI = FI;
166 AFI->addGPRCalleeSavedArea1Frame(FI);
174 FramePtrSpillFI = FI;
175 if (STI.isTargetDarwin()) {
176 AFI->addGPRCalleeSavedArea2Frame(FI);
179 AFI->addGPRCalleeSavedArea1Frame(FI);
184 AFI->addDPRCalleeSavedAreaFrame(FI);
190 if (GPRCS1Size > 0) MBBI++;
192 // Set FP to point to the stack slot that contains the previous FP.
193 // For Darwin, FP is R7, which has now been stored in spill area 1.
194 // Otherwise, if this is not Darwin, all the callee-saved registers go
195 // into spill area 1, including the FP in R11. In either case, it is
196 // now safe to emit this assignment.
197 bool HasFP = hasFP(MF);
199 unsigned ADDriOpc = !AFI->isThumbFunction() ? ARM::ADDri : ARM::t2ADDri;
200 MachineInstrBuilder MIB =
201 BuildMI(MBB, MBBI, dl, TII.get(ADDriOpc), FramePtr)
202 .addFrameIndex(FramePtrSpillFI).addImm(0)
203 .setMIFlag(MachineInstr::FrameSetup);
204 AddDefaultCC(AddDefaultPred(MIB));
208 if (GPRCS2Size > 0) MBBI++;
210 // Determine starting offsets of spill areas.
211 unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize);
212 unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
213 unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
215 AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) +
217 AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
218 AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
219 AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
224 // Since vpush register list cannot have gaps, there may be multiple vpush
225 // instructions in the prologue.
226 while (MBBI->getOpcode() == ARM::VSTMDDB_UPD)
230 NumBytes = DPRCSOffset;
232 // Adjust SP after all the callee-save spills.
233 emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
234 MachineInstr::FrameSetup);
236 // Restore from fp only in ARM mode: e.g. sub sp, r7, #24
237 // Note it's not safe to do this in Thumb2 mode because it would have
238 // taken two instructions:
241 // If an interrupt is taken between the two instructions, then sp is in
242 // an inconsistent state (pointing to the middle of callee-saved area).
243 // The interrupt handler can end up clobbering the registers.
244 AFI->setShouldRestoreSPFromFP(true);
247 if (STI.isTargetELF() && hasFP(MF))
248 MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() -
249 AFI->getFramePtrSpillOffset());
251 AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
252 AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
253 AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
255 // If we need dynamic stack realignment, do it here. Be paranoid and make
256 // sure if we also have VLAs, we have a base pointer for frame access.
257 if (RegInfo->needsStackRealignment(MF)) {
258 unsigned MaxAlign = MFI->getMaxAlignment();
259 assert (!AFI->isThumb1OnlyFunction());
260 if (!AFI->isThumbFunction()) {
261 // Emit bic sp, sp, MaxAlign
262 AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
263 TII.get(ARM::BICri), ARM::SP)
264 .addReg(ARM::SP, RegState::Kill)
265 .addImm(MaxAlign-1)));
267 // We cannot use sp as source/dest register here, thus we're emitting the
268 // following sequence:
270 // bic r4, r4, MaxAlign
272 // FIXME: It will be better just to find spare register here.
273 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4)
274 .addReg(ARM::SP, RegState::Kill));
275 AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
276 TII.get(ARM::t2BICri), ARM::R4)
277 .addReg(ARM::R4, RegState::Kill)
278 .addImm(MaxAlign-1)));
279 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
280 .addReg(ARM::R4, RegState::Kill));
283 AFI->setShouldRestoreSPFromFP(true);
286 // If we need a base pointer, set it up here. It's whatever the value
287 // of the stack pointer is at this point. Any variable size objects
288 // will be allocated after this, so we can still use the base pointer
289 // to reference locals.
290 // FIXME: Clarify FrameSetup flags here.
291 if (RegInfo->hasBasePointer(MF)) {
293 BuildMI(MBB, MBBI, dl,
294 TII.get(ARM::MOVr), RegInfo->getBaseRegister())
296 .addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
298 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
299 RegInfo->getBaseRegister())
303 // If the frame has variable sized objects then the epilogue must restore
304 // the sp from fp. We can assume there's an FP here since hasFP already
305 // checks for hasVarSizedObjects.
306 if (MFI->hasVarSizedObjects())
307 AFI->setShouldRestoreSPFromFP(true);
310 void ARMFrameLowering::emitEpilogue(MachineFunction &MF,
311 MachineBasicBlock &MBB) const {
312 MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
313 assert(MBBI->isReturn() && "Can only insert epilog into returning blocks");
314 unsigned RetOpcode = MBBI->getOpcode();
315 DebugLoc dl = MBBI->getDebugLoc();
316 MachineFrameInfo *MFI = MF.getFrameInfo();
317 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
318 const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
319 const ARMBaseInstrInfo &TII =
320 *static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
321 assert(!AFI->isThumb1OnlyFunction() &&
322 "This emitEpilogue does not support Thumb1!");
323 bool isARM = !AFI->isThumbFunction();
325 unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize();
326 int NumBytes = (int)MFI->getStackSize();
327 unsigned FramePtr = RegInfo->getFrameRegister(MF);
329 if (!AFI->hasStackFrame()) {
331 emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);
333 // Unwind MBBI to point to first LDR / VLDRD.
334 const unsigned *CSRegs = RegInfo->getCalleeSavedRegs();
335 if (MBBI != MBB.begin()) {
338 while (MBBI != MBB.begin() && isCSRestore(MBBI, TII, CSRegs));
339 if (!isCSRestore(MBBI, TII, CSRegs))
343 // Move SP to start of FP callee save spill area.
344 NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
345 AFI->getGPRCalleeSavedArea2Size() +
346 AFI->getDPRCalleeSavedAreaSize());
348 // Reset SP based on frame pointer only if the stack frame extends beyond
349 // frame pointer stack slot or target is ELF and the function has FP.
350 if (AFI->shouldRestoreSPFromFP()) {
351 NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
354 emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, FramePtr, -NumBytes,
357 // It's not possible to restore SP from FP in a single instruction.
358 // For Darwin, this looks like:
361 // This is bad, if an interrupt is taken after the mov, sp is in an
362 // inconsistent state.
363 // Use the first callee-saved register as a scratch register.
364 assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
365 "No scratch register to restore SP from FP!");
366 emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
368 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
375 BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), ARM::SP)
376 .addReg(FramePtr).addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
378 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
383 emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);
385 // Increment past our save areas.
386 if (AFI->getDPRCalleeSavedAreaSize()) {
388 // Since vpop register list cannot have gaps, there may be multiple vpop
389 // instructions in the epilogue.
390 while (MBBI->getOpcode() == ARM::VLDMDIA_UPD)
393 if (AFI->getGPRCalleeSavedArea2Size()) MBBI++;
394 if (AFI->getGPRCalleeSavedArea1Size()) MBBI++;
397 if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNdiND ||
398 RetOpcode == ARM::TCRETURNri || RetOpcode == ARM::TCRETURNriND) {
399 // Tail call return: adjust the stack pointer and jump to callee.
400 MBBI = MBB.getLastNonDebugInstr();
401 MachineOperand &JumpTarget = MBBI->getOperand(0);
403 // Jump to label or value in register.
404 if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNdiND) {
405 unsigned TCOpcode = (RetOpcode == ARM::TCRETURNdi)
406 ? (STI.isThumb() ? ARM::tTAILJMPd : ARM::TAILJMPd)
407 : (STI.isThumb() ? ARM::tTAILJMPdND : ARM::TAILJMPdND);
408 MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(TCOpcode));
409 if (JumpTarget.isGlobal())
410 MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
411 JumpTarget.getTargetFlags());
413 assert(JumpTarget.isSymbol());
414 MIB.addExternalSymbol(JumpTarget.getSymbolName(),
415 JumpTarget.getTargetFlags());
418 // Add the default predicate in Thumb mode.
419 if (STI.isThumb()) MIB.addImm(ARMCC::AL).addReg(0);
420 } else if (RetOpcode == ARM::TCRETURNri) {
421 BuildMI(MBB, MBBI, dl,
422 TII.get(STI.isThumb() ? ARM::tTAILJMPr : ARM::TAILJMPr)).
423 addReg(JumpTarget.getReg(), RegState::Kill);
424 } else if (RetOpcode == ARM::TCRETURNriND) {
425 BuildMI(MBB, MBBI, dl,
426 TII.get(STI.isThumb() ? ARM::tTAILJMPrND : ARM::TAILJMPrND)).
427 addReg(JumpTarget.getReg(), RegState::Kill);
430 MachineInstr *NewMI = prior(MBBI);
431 for (unsigned i = 1, e = MBBI->getNumOperands(); i != e; ++i)
432 NewMI->addOperand(MBBI->getOperand(i));
434 // Delete the pseudo instruction TCRETURN.
440 emitSPUpdate(isARM, MBB, MBBI, dl, TII, VARegSaveSize);
443 /// getFrameIndexReference - Provide a base+offset reference to an FI slot for
444 /// debug info. It's the same as what we use for resolving the code-gen
445 /// references for now. FIXME: This can go wrong when references are
446 /// SP-relative and simple call frames aren't used.
448 ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
449 unsigned &FrameReg) const {
450 return ResolveFrameIndexReference(MF, FI, FrameReg, 0);
454 ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
455 int FI, unsigned &FrameReg,
457 const MachineFrameInfo *MFI = MF.getFrameInfo();
458 const ARMBaseRegisterInfo *RegInfo =
459 static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
460 const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
461 int Offset = MFI->getObjectOffset(FI) + MFI->getStackSize();
462 int FPOffset = Offset - AFI->getFramePtrSpillOffset();
463 bool isFixed = MFI->isFixedObjectIndex(FI);
467 if (AFI->isGPRCalleeSavedArea1Frame(FI))
468 return Offset - AFI->getGPRCalleeSavedArea1Offset();
469 else if (AFI->isGPRCalleeSavedArea2Frame(FI))
470 return Offset - AFI->getGPRCalleeSavedArea2Offset();
471 else if (AFI->isDPRCalleeSavedAreaFrame(FI))
472 return Offset - AFI->getDPRCalleeSavedAreaOffset();
474 // When dynamically realigning the stack, use the frame pointer for
475 // parameters, and the stack/base pointer for locals.
476 if (RegInfo->needsStackRealignment(MF)) {
477 assert (hasFP(MF) && "dynamic stack realignment without a FP!");
479 FrameReg = RegInfo->getFrameRegister(MF);
481 } else if (MFI->hasVarSizedObjects()) {
482 assert(RegInfo->hasBasePointer(MF) &&
483 "VLAs and dynamic stack alignment, but missing base pointer!");
484 FrameReg = RegInfo->getBaseRegister();
489 // If there is a frame pointer, use it when we can.
490 if (hasFP(MF) && AFI->hasStackFrame()) {
491 // Use frame pointer to reference fixed objects. Use it for locals if
492 // there are VLAs (and thus the SP isn't reliable as a base).
493 if (isFixed || (MFI->hasVarSizedObjects() &&
494 !RegInfo->hasBasePointer(MF))) {
495 FrameReg = RegInfo->getFrameRegister(MF);
497 } else if (MFI->hasVarSizedObjects()) {
498 assert(RegInfo->hasBasePointer(MF) && "missing base pointer!");
499 if (AFI->isThumb2Function()) {
500 // Try to use the frame pointer if we can, else use the base pointer
501 // since it's available. This is handy for the emergency spill slot, in
503 if (FPOffset >= -255 && FPOffset < 0) {
504 FrameReg = RegInfo->getFrameRegister(MF);
508 } else if (AFI->isThumb2Function()) {
509 // Use add <rd>, sp, #<imm8>
510 // ldr <rd>, [sp, #<imm8>]
511 // if at all possible to save space.
512 if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020)
514 // In Thumb2 mode, the negative offset is very limited. Try to avoid
515 // out of range references. ldr <rt>,[<rn>, #-<imm8>]
516 if (FPOffset >= -255 && FPOffset < 0) {
517 FrameReg = RegInfo->getFrameRegister(MF);
520 } else if (Offset > (FPOffset < 0 ? -FPOffset : FPOffset)) {
521 // Otherwise, use SP or FP, whichever is closer to the stack slot.
522 FrameReg = RegInfo->getFrameRegister(MF);
526 // Use the base pointer if we have one.
527 if (RegInfo->hasBasePointer(MF))
528 FrameReg = RegInfo->getBaseRegister();
532 int ARMFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
535 return getFrameIndexReference(MF, FI, FrameReg);
538 void ARMFrameLowering::emitPushInst(MachineBasicBlock &MBB,
539 MachineBasicBlock::iterator MI,
540 const std::vector<CalleeSavedInfo> &CSI,
541 unsigned StmOpc, unsigned StrOpc,
543 bool(*Func)(unsigned, bool),
544 unsigned MIFlags) const {
545 MachineFunction &MF = *MBB.getParent();
546 const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
549 if (MI != MBB.end()) DL = MI->getDebugLoc();
551 SmallVector<std::pair<unsigned,bool>, 4> Regs;
552 unsigned i = CSI.size();
554 unsigned LastReg = 0;
555 for (; i != 0; --i) {
556 unsigned Reg = CSI[i-1].getReg();
557 if (!(Func)(Reg, STI.isTargetDarwin())) continue;
559 // Add the callee-saved register as live-in unless it's LR and
560 // @llvm.returnaddress is called. If LR is returned for
561 // @llvm.returnaddress then it's already added to the function and
562 // entry block live-in sets.
564 if (Reg == ARM::LR) {
565 if (MF.getFrameInfo()->isReturnAddressTaken() &&
566 MF.getRegInfo().isLiveIn(Reg))
573 // If NoGap is true, push consecutive registers and then leave the rest
574 // for other instructions. e.g.
575 // vpush {d8, d10, d11} -> vpush {d8}, vpush {d10, d11}
576 if (NoGap && LastReg && LastReg != Reg-1)
579 Regs.push_back(std::make_pair(Reg, isKill));
584 if (Regs.size() > 1 || StrOpc== 0) {
585 MachineInstrBuilder MIB =
586 AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(StmOpc), ARM::SP)
587 .addReg(ARM::SP).setMIFlags(MIFlags));
588 for (unsigned i = 0, e = Regs.size(); i < e; ++i)
589 MIB.addReg(Regs[i].first, getKillRegState(Regs[i].second));
590 } else if (Regs.size() == 1) {
591 MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(StrOpc),
593 .addReg(Regs[0].first, getKillRegState(Regs[0].second))
594 .addReg(ARM::SP).setMIFlags(MIFlags)
602 void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
603 MachineBasicBlock::iterator MI,
604 const std::vector<CalleeSavedInfo> &CSI,
605 unsigned LdmOpc, unsigned LdrOpc,
606 bool isVarArg, bool NoGap,
607 bool(*Func)(unsigned, bool)) const {
608 MachineFunction &MF = *MBB.getParent();
609 const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
610 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
611 DebugLoc DL = MI->getDebugLoc();
612 unsigned RetOpcode = MI->getOpcode();
613 bool isTailCall = (RetOpcode == ARM::TCRETURNdi ||
614 RetOpcode == ARM::TCRETURNdiND ||
615 RetOpcode == ARM::TCRETURNri ||
616 RetOpcode == ARM::TCRETURNriND);
618 SmallVector<unsigned, 4> Regs;
619 unsigned i = CSI.size();
621 unsigned LastReg = 0;
622 bool DeleteRet = false;
623 for (; i != 0; --i) {
624 unsigned Reg = CSI[i-1].getReg();
625 if (!(Func)(Reg, STI.isTargetDarwin())) continue;
627 if (Reg == ARM::LR && !isTailCall && !isVarArg && STI.hasV5TOps()) {
629 LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
630 // Fold the return instruction into the LDM.
634 // If NoGap is true, pop consecutive registers and then leave the rest
635 // for other instructions. e.g.
636 // vpop {d8, d10, d11} -> vpop {d8}, vpop {d10, d11}
637 if (NoGap && LastReg && LastReg != Reg-1)
646 if (Regs.size() > 1 || LdrOpc == 0) {
647 MachineInstrBuilder MIB =
648 AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(LdmOpc), ARM::SP)
650 for (unsigned i = 0, e = Regs.size(); i < e; ++i)
651 MIB.addReg(Regs[i], getDefRegState(true));
653 MIB->copyImplicitOps(&*MI);
654 MI->eraseFromParent();
657 } else if (Regs.size() == 1) {
658 // If we adjusted the reg to PC from LR above, switch it back here. We
659 // only do that for LDM.
660 if (Regs[0] == ARM::PC)
662 MachineInstrBuilder MIB =
663 BuildMI(MBB, MI, DL, TII.get(LdrOpc), Regs[0])
664 .addReg(ARM::SP, RegState::Define)
666 // ARM mode needs an extra reg0 here due to addrmode2. Will go away once
667 // that refactoring is complete (eventually).
668 if (LdrOpc == ARM::LDR_POST_REG || LdrOpc == ARM::LDR_POST_IMM) {
670 MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::add, 4, ARM_AM::no_shift));
679 bool ARMFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
680 MachineBasicBlock::iterator MI,
681 const std::vector<CalleeSavedInfo> &CSI,
682 const TargetRegisterInfo *TRI) const {
686 MachineFunction &MF = *MBB.getParent();
687 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
689 unsigned PushOpc = AFI->isThumbFunction() ? ARM::t2STMDB_UPD : ARM::STMDB_UPD;
690 unsigned PushOneOpc = AFI->isThumbFunction() ?
691 ARM::t2STR_PRE : ARM::STR_PRE_IMM;
692 unsigned FltOpc = ARM::VSTMDDB_UPD;
693 emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea1Register,
694 MachineInstr::FrameSetup);
695 emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea2Register,
696 MachineInstr::FrameSetup);
697 emitPushInst(MBB, MI, CSI, FltOpc, 0, true, &isARMArea3Register,
698 MachineInstr::FrameSetup);
703 bool ARMFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
704 MachineBasicBlock::iterator MI,
705 const std::vector<CalleeSavedInfo> &CSI,
706 const TargetRegisterInfo *TRI) const {
710 MachineFunction &MF = *MBB.getParent();
711 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
712 bool isVarArg = AFI->getVarArgsRegSaveSize() > 0;
714 unsigned PopOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
715 unsigned LdrOpc = AFI->isThumbFunction() ? ARM::t2LDR_POST :ARM::LDR_POST_IMM;
716 unsigned FltOpc = ARM::VLDMDIA_UPD;
717 emitPopInst(MBB, MI, CSI, FltOpc, 0, isVarArg, true, &isARMArea3Register);
718 emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
719 &isARMArea2Register);
720 emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
721 &isARMArea1Register);
726 // FIXME: Make generic?
727 static unsigned GetFunctionSizeInBytes(const MachineFunction &MF,
728 const ARMBaseInstrInfo &TII) {
730 for (MachineFunction::const_iterator MBBI = MF.begin(), E = MF.end();
732 const MachineBasicBlock &MBB = *MBBI;
733 for (MachineBasicBlock::const_iterator I = MBB.begin(),E = MBB.end();
735 FnSize += TII.GetInstSizeInBytes(I);
740 /// estimateStackSize - Estimate and return the size of the frame.
741 /// FIXME: Make generic?
742 static unsigned estimateStackSize(MachineFunction &MF) {
743 const MachineFrameInfo *MFI = MF.getFrameInfo();
744 const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering();
745 const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
746 unsigned MaxAlign = MFI->getMaxAlignment();
749 // This code is very, very similar to PEI::calculateFrameObjectOffsets().
750 // It really should be refactored to share code. Until then, changes
751 // should keep in mind that there's tight coupling between the two.
753 for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
754 int FixedOff = -MFI->getObjectOffset(i);
755 if (FixedOff > Offset) Offset = FixedOff;
757 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
758 if (MFI->isDeadObjectIndex(i))
760 Offset += MFI->getObjectSize(i);
761 unsigned Align = MFI->getObjectAlignment(i);
762 // Adjust to alignment boundary
763 Offset = (Offset+Align-1)/Align*Align;
765 MaxAlign = std::max(Align, MaxAlign);
768 if (MFI->adjustsStack() && TFI->hasReservedCallFrame(MF))
769 Offset += MFI->getMaxCallFrameSize();
771 // Round up the size to a multiple of the alignment. If the function has
772 // any calls or alloca's, align to the target's StackAlignment value to
773 // ensure that the callee's frame or the alloca data is suitably aligned;
774 // otherwise, for leaf functions, align to the TransientStackAlignment
777 if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
778 (RegInfo->needsStackRealignment(MF) && MFI->getObjectIndexEnd() != 0))
779 StackAlign = TFI->getStackAlignment();
781 StackAlign = TFI->getTransientStackAlignment();
783 // If the frame pointer is eliminated, all frame offsets will be relative to
784 // SP not FP. Align to MaxAlign so this works.
785 StackAlign = std::max(StackAlign, MaxAlign);
786 unsigned AlignMask = StackAlign - 1;
787 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
789 return (unsigned)Offset;
792 /// estimateRSStackSizeLimit - Look at each instruction that references stack
793 /// frames and return the stack size limit beyond which some of these
794 /// instructions will require a scratch register during their expansion later.
795 // FIXME: Move to TII?
796 static unsigned estimateRSStackSizeLimit(MachineFunction &MF,
797 const TargetFrameLowering *TFI) {
798 const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
799 unsigned Limit = (1 << 12) - 1;
800 for (MachineFunction::iterator BB = MF.begin(),E = MF.end(); BB != E; ++BB) {
801 for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
803 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
804 if (!I->getOperand(i).isFI()) continue;
806 // When using ADDri to get the address of a stack object, 255 is the
807 // largest offset guaranteed to fit in the immediate offset.
808 if (I->getOpcode() == ARM::ADDri) {
809 Limit = std::min(Limit, (1U << 8) - 1);
813 // Otherwise check the addressing mode.
814 switch (I->getDesc().TSFlags & ARMII::AddrModeMask) {
815 case ARMII::AddrMode3:
816 case ARMII::AddrModeT2_i8:
817 Limit = std::min(Limit, (1U << 8) - 1);
819 case ARMII::AddrMode5:
820 case ARMII::AddrModeT2_i8s4:
821 Limit = std::min(Limit, ((1U << 8) - 1) * 4);
823 case ARMII::AddrModeT2_i12:
824 // i12 supports only positive offset so these will be converted to
825 // i8 opcodes. See llvm::rewriteT2FrameIndex.
826 if (TFI->hasFP(MF) && AFI->hasStackFrame())
827 Limit = std::min(Limit, (1U << 8) - 1);
829 case ARMII::AddrMode4:
830 case ARMII::AddrMode6:
831 // Addressing modes 4 & 6 (load/store) instructions can't encode an
832 // immediate offset for stack references.
837 break; // At most one FI per instruction
846 ARMFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
847 RegScavenger *RS) const {
848 // This tells PEI to spill the FP as if it is any other callee-save register
849 // to take advantage the eliminateFrameIndex machinery. This also ensures it
850 // is spilled in the order specified by getCalleeSavedRegs() to make it easier
851 // to combine multiple loads / stores.
852 bool CanEliminateFrame = true;
853 bool CS1Spilled = false;
854 bool LRSpilled = false;
855 unsigned NumGPRSpills = 0;
856 SmallVector<unsigned, 4> UnspilledCS1GPRs;
857 SmallVector<unsigned, 4> UnspilledCS2GPRs;
858 const ARMBaseRegisterInfo *RegInfo =
859 static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
860 const ARMBaseInstrInfo &TII =
861 *static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
862 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
863 MachineFrameInfo *MFI = MF.getFrameInfo();
864 unsigned FramePtr = RegInfo->getFrameRegister(MF);
866 // Spill R4 if Thumb2 function requires stack realignment - it will be used as
867 // scratch register. Also spill R4 if Thumb2 function has varsized objects,
868 // since it's not always possible to restore sp from fp in a single
870 // FIXME: It will be better just to find spare register here.
871 if (AFI->isThumb2Function() &&
872 (MFI->hasVarSizedObjects() || RegInfo->needsStackRealignment(MF)))
873 MF.getRegInfo().setPhysRegUsed(ARM::R4);
875 if (AFI->isThumb1OnlyFunction()) {
876 // Spill LR if Thumb1 function uses variable length argument lists.
877 if (AFI->getVarArgsRegSaveSize() > 0)
878 MF.getRegInfo().setPhysRegUsed(ARM::LR);
880 // Spill R4 if Thumb1 epilogue has to restore SP from FP. We don't know
881 // for sure what the stack size will be, but for this, an estimate is good
882 // enough. If there anything changes it, it'll be a spill, which implies
883 // we've used all the registers and so R4 is already used, so not marking
884 // it here will be OK.
885 // FIXME: It will be better just to find spare register here.
886 unsigned StackSize = estimateStackSize(MF);
887 if (MFI->hasVarSizedObjects() || StackSize > 508)
888 MF.getRegInfo().setPhysRegUsed(ARM::R4);
891 // Spill the BasePtr if it's used.
892 if (RegInfo->hasBasePointer(MF))
893 MF.getRegInfo().setPhysRegUsed(RegInfo->getBaseRegister());
895 // Don't spill FP if the frame can be eliminated. This is determined
896 // by scanning the callee-save registers to see if any is used.
897 const unsigned *CSRegs = RegInfo->getCalleeSavedRegs();
898 for (unsigned i = 0; CSRegs[i]; ++i) {
899 unsigned Reg = CSRegs[i];
900 bool Spilled = false;
901 if (MF.getRegInfo().isPhysRegOrOverlapUsed(Reg)) {
903 CanEliminateFrame = false;
906 if (!ARM::GPRRegisterClass->contains(Reg))
912 if (!STI.isTargetDarwin()) {
919 // Keep track if LR and any of R4, R5, R6, and R7 is spilled.
924 case ARM::R4: case ARM::R5:
925 case ARM::R6: case ARM::R7:
932 if (!STI.isTargetDarwin()) {
933 UnspilledCS1GPRs.push_back(Reg);
938 case ARM::R4: case ARM::R5:
939 case ARM::R6: case ARM::R7:
941 UnspilledCS1GPRs.push_back(Reg);
944 UnspilledCS2GPRs.push_back(Reg);
950 bool ForceLRSpill = false;
951 if (!LRSpilled && AFI->isThumb1OnlyFunction()) {
952 unsigned FnSize = GetFunctionSizeInBytes(MF, TII);
953 // Force LR to be spilled if the Thumb function size is > 2048. This enables
954 // use of BL to implement far jump. If it turns out that it's not needed
955 // then the branch fix up path will undo it.
956 if (FnSize >= (1 << 11)) {
957 CanEliminateFrame = false;
962 // If any of the stack slot references may be out of range of an immediate
963 // offset, make sure a register (or a spill slot) is available for the
964 // register scavenger. Note that if we're indexing off the frame pointer, the
965 // effective stack size is 4 bytes larger since the FP points to the stack
966 // slot of the previous FP. Also, if we have variable sized objects in the
967 // function, stack slot references will often be negative, and some of
968 // our instructions are positive-offset only, so conservatively consider
969 // that case to want a spill slot (or register) as well. Similarly, if
970 // the function adjusts the stack pointer during execution and the
971 // adjustments aren't already part of our stack size estimate, our offset
972 // calculations may be off, so be conservative.
973 // FIXME: We could add logic to be more precise about negative offsets
974 // and which instructions will need a scratch register for them. Is it
975 // worth the effort and added fragility?
978 (estimateStackSize(MF) + ((hasFP(MF) && AFI->hasStackFrame()) ? 4:0) >=
979 estimateRSStackSizeLimit(MF, this)))
980 || MFI->hasVarSizedObjects()
981 || (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF));
983 bool ExtraCSSpill = false;
984 if (BigStack || !CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) {
985 AFI->setHasStackFrame(true);
987 // If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
988 // Spill LR as well so we can fold BX_RET to the registers restore (LDM).
989 if (!LRSpilled && CS1Spilled) {
990 MF.getRegInfo().setPhysRegUsed(ARM::LR);
992 UnspilledCS1GPRs.erase(std::find(UnspilledCS1GPRs.begin(),
993 UnspilledCS1GPRs.end(), (unsigned)ARM::LR));
994 ForceLRSpill = false;
999 MF.getRegInfo().setPhysRegUsed(FramePtr);
1003 // If stack and double are 8-byte aligned and we are spilling an odd number
1004 // of GPRs, spill one extra callee save GPR so we won't have to pad between
1005 // the integer and double callee save areas.
1006 unsigned TargetAlign = getStackAlignment();
1007 if (TargetAlign == 8 && (NumGPRSpills & 1)) {
1008 if (CS1Spilled && !UnspilledCS1GPRs.empty()) {
1009 for (unsigned i = 0, e = UnspilledCS1GPRs.size(); i != e; ++i) {
1010 unsigned Reg = UnspilledCS1GPRs[i];
1011 // Don't spill high register if the function is thumb1
1012 if (!AFI->isThumb1OnlyFunction() ||
1013 isARMLowRegister(Reg) || Reg == ARM::LR) {
1014 MF.getRegInfo().setPhysRegUsed(Reg);
1015 if (!RegInfo->isReservedReg(MF, Reg))
1016 ExtraCSSpill = true;
1020 } else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) {
1021 unsigned Reg = UnspilledCS2GPRs.front();
1022 MF.getRegInfo().setPhysRegUsed(Reg);
1023 if (!RegInfo->isReservedReg(MF, Reg))
1024 ExtraCSSpill = true;
1028 // Estimate if we might need to scavenge a register at some point in order
1029 // to materialize a stack offset. If so, either spill one additional
1030 // callee-saved register or reserve a special spill slot to facilitate
1031 // register scavenging. Thumb1 needs a spill slot for stack pointer
1032 // adjustments also, even when the frame itself is small.
1033 if (BigStack && !ExtraCSSpill) {
1034 // If any non-reserved CS register isn't spilled, just spill one or two
1035 // extra. That should take care of it!
1036 unsigned NumExtras = TargetAlign / 4;
1037 SmallVector<unsigned, 2> Extras;
1038 while (NumExtras && !UnspilledCS1GPRs.empty()) {
1039 unsigned Reg = UnspilledCS1GPRs.back();
1040 UnspilledCS1GPRs.pop_back();
1041 if (!RegInfo->isReservedReg(MF, Reg) &&
1042 (!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg) ||
1044 Extras.push_back(Reg);
1048 // For non-Thumb1 functions, also check for hi-reg CS registers
1049 if (!AFI->isThumb1OnlyFunction()) {
1050 while (NumExtras && !UnspilledCS2GPRs.empty()) {
1051 unsigned Reg = UnspilledCS2GPRs.back();
1052 UnspilledCS2GPRs.pop_back();
1053 if (!RegInfo->isReservedReg(MF, Reg)) {
1054 Extras.push_back(Reg);
1059 if (Extras.size() && NumExtras == 0) {
1060 for (unsigned i = 0, e = Extras.size(); i != e; ++i) {
1061 MF.getRegInfo().setPhysRegUsed(Extras[i]);
1063 } else if (!AFI->isThumb1OnlyFunction()) {
1064 // note: Thumb1 functions spill to R12, not the stack. Reserve a slot
1065 // closest to SP or frame pointer.
1066 const TargetRegisterClass *RC = ARM::GPRRegisterClass;
1067 RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
1075 MF.getRegInfo().setPhysRegUsed(ARM::LR);
1076 AFI->setLRIsSpilledForFarJump(true);