1 //===-- Thumb1FrameLowering.cpp - Thumb1 Frame Information ----------------===//
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 Thumb1 implementation of TargetFrameLowering class.
12 //===----------------------------------------------------------------------===//
14 #include "Thumb1FrameLowering.h"
15 #include "ARMMachineFunctionInfo.h"
16 #include "llvm/CodeGen/MachineFrameInfo.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/CodeGen/MachineInstrBuilder.h"
19 #include "llvm/CodeGen/MachineRegisterInfo.h"
23 bool Thumb1FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const{
24 const MachineFrameInfo *FFI = MF.getFrameInfo();
25 unsigned CFSize = FFI->getMaxCallFrameSize();
26 // It's not always a good idea to include the call frame as part of the
27 // stack frame. ARM (especially Thumb) has small immediate offset to
28 // address the stack frame. So a large call frame can cause poor codegen
29 // and may even makes it impossible to scavenge a register.
30 if (CFSize >= ((1 << 8) - 1) * 4 / 2) // Half of imm8 * 4
33 return !MF.getFrameInfo()->hasVarSizedObjects();
37 emitSPUpdate(MachineBasicBlock &MBB,
38 MachineBasicBlock::iterator &MBBI,
39 const TargetInstrInfo &TII, DebugLoc dl,
40 const Thumb1RegisterInfo &MRI,
41 int NumBytes, unsigned MIFlags = MachineInstr::NoFlags) {
42 emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes, TII,
47 void Thumb1FrameLowering::
48 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
49 MachineBasicBlock::iterator I) const {
50 const Thumb1InstrInfo &TII =
51 *static_cast<const Thumb1InstrInfo*>(MF.getTarget().getInstrInfo());
52 const Thumb1RegisterInfo *RegInfo =
53 static_cast<const Thumb1RegisterInfo*>(MF.getTarget().getRegisterInfo());
54 if (!hasReservedCallFrame(MF)) {
55 // If we have alloca, convert as follows:
56 // ADJCALLSTACKDOWN -> sub, sp, sp, amount
57 // ADJCALLSTACKUP -> add, sp, sp, amount
58 MachineInstr *Old = I;
59 DebugLoc dl = Old->getDebugLoc();
60 unsigned Amount = Old->getOperand(0).getImm();
62 // We need to keep the stack aligned properly. To do this, we round the
63 // amount of space needed for the outgoing arguments up to the next
64 // alignment boundary.
65 unsigned Align = getStackAlignment();
66 Amount = (Amount+Align-1)/Align*Align;
68 // Replace the pseudo instruction with a new instruction...
69 unsigned Opc = Old->getOpcode();
70 if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) {
71 emitSPUpdate(MBB, I, TII, dl, *RegInfo, -Amount);
73 assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP);
74 emitSPUpdate(MBB, I, TII, dl, *RegInfo, Amount);
81 void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const {
82 MachineBasicBlock &MBB = MF.front();
83 MachineBasicBlock::iterator MBBI = MBB.begin();
84 MachineFrameInfo *MFI = MF.getFrameInfo();
85 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
86 const Thumb1RegisterInfo *RegInfo =
87 static_cast<const Thumb1RegisterInfo*>(MF.getTarget().getRegisterInfo());
88 const Thumb1InstrInfo &TII =
89 *static_cast<const Thumb1InstrInfo*>(MF.getTarget().getInstrInfo());
91 unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize();
92 unsigned NumBytes = MFI->getStackSize();
93 const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
94 DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
95 unsigned FramePtr = RegInfo->getFrameRegister(MF);
96 unsigned BasePtr = RegInfo->getBaseRegister();
98 // Thumb add/sub sp, imm8 instructions implicitly multiply the offset by 4.
99 NumBytes = (NumBytes + 3) & ~3;
100 MFI->setStackSize(NumBytes);
102 // Determine the sizes of each callee-save spill areas and record which frame
103 // belongs to which callee-save spill areas.
104 unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
105 int FramePtrSpillFI = 0;
108 emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -ArgRegsSaveSize,
109 MachineInstr::FrameSetup);
111 if (!AFI->hasStackFrame()) {
113 emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes,
114 MachineInstr::FrameSetup);
118 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
119 unsigned Reg = CSI[i].getReg();
120 int FI = CSI[i].getFrameIdx();
128 FramePtrSpillFI = FI;
129 AFI->addGPRCalleeSavedArea1Frame(FI);
137 FramePtrSpillFI = FI;
138 if (STI.isTargetIOS()) {
139 AFI->addGPRCalleeSavedArea2Frame(FI);
142 AFI->addGPRCalleeSavedArea1Frame(FI);
147 AFI->addDPRCalleeSavedAreaFrame(FI);
152 if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPUSH) {
154 if (MBBI != MBB.end())
155 dl = MBBI->getDebugLoc();
158 // Determine starting offsets of spill areas.
159 unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize);
160 unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
161 unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
162 bool HasFP = hasFP(MF);
164 AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) +
166 AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
167 AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
168 AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
169 NumBytes = DPRCSOffset;
171 // Adjust FP so it point to the stack slot that contains the previous FP.
173 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr)
174 .addFrameIndex(FramePtrSpillFI).addImm(0)
175 .setMIFlags(MachineInstr::FrameSetup));
177 // If offset is > 508 then sp cannot be adjusted in a single instruction,
178 // try restoring from fp instead.
179 AFI->setShouldRestoreSPFromFP(true);
183 // Insert it after all the callee-save spills.
184 emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes,
185 MachineInstr::FrameSetup);
187 if (STI.isTargetELF() && HasFP)
188 MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() -
189 AFI->getFramePtrSpillOffset());
191 AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
192 AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
193 AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
195 // Thumb1 does not currently support dynamic stack realignment. Report a
196 // fatal error rather then silently generate bad code.
197 if (RegInfo->needsStackRealignment(MF))
198 report_fatal_error("Dynamic stack realignment not supported for thumb1.");
200 // If we need a base pointer, set it up here. It's whatever the value
201 // of the stack pointer is at this point. Any variable size objects
202 // will be allocated after this, so we can still use the base pointer
203 // to reference locals.
204 if (RegInfo->hasBasePointer(MF))
205 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), BasePtr)
208 // If the frame has variable sized objects then the epilogue must restore
209 // the sp from fp. We can assume there's an FP here since hasFP already
210 // checks for hasVarSizedObjects.
211 if (MFI->hasVarSizedObjects())
212 AFI->setShouldRestoreSPFromFP(true);
215 static bool isCalleeSavedRegister(unsigned Reg, const uint16_t *CSRegs) {
216 for (unsigned i = 0; CSRegs[i]; ++i)
217 if (Reg == CSRegs[i])
222 static bool isCSRestore(MachineInstr *MI, const uint16_t *CSRegs) {
223 if (MI->getOpcode() == ARM::tLDRspi &&
224 MI->getOperand(1).isFI() &&
225 isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs))
227 else if (MI->getOpcode() == ARM::tPOP) {
228 // The first two operands are predicates. The last two are
229 // imp-def and imp-use of SP. Check everything in between.
230 for (int i = 2, e = MI->getNumOperands() - 2; i != e; ++i)
231 if (!isCalleeSavedRegister(MI->getOperand(i).getReg(), CSRegs))
238 void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF,
239 MachineBasicBlock &MBB) const {
240 MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
241 assert((MBBI->getOpcode() == ARM::tBX_RET ||
242 MBBI->getOpcode() == ARM::tPOP_RET) &&
243 "Can only insert epilog into returning blocks");
244 DebugLoc dl = MBBI->getDebugLoc();
245 MachineFrameInfo *MFI = MF.getFrameInfo();
246 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
247 const Thumb1RegisterInfo *RegInfo =
248 static_cast<const Thumb1RegisterInfo*>(MF.getTarget().getRegisterInfo());
249 const Thumb1InstrInfo &TII =
250 *static_cast<const Thumb1InstrInfo*>(MF.getTarget().getInstrInfo());
252 unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize();
253 int NumBytes = (int)MFI->getStackSize();
254 const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs();
255 unsigned FramePtr = RegInfo->getFrameRegister(MF);
257 if (!AFI->hasStackFrame()) {
259 emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes);
261 // Unwind MBBI to point to first LDR / VLDRD.
262 if (MBBI != MBB.begin()) {
265 while (MBBI != MBB.begin() && isCSRestore(MBBI, CSRegs));
266 if (!isCSRestore(MBBI, CSRegs))
270 // Move SP to start of FP callee save spill area.
271 NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
272 AFI->getGPRCalleeSavedArea2Size() +
273 AFI->getDPRCalleeSavedAreaSize());
275 if (AFI->shouldRestoreSPFromFP()) {
276 NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
277 // Reset SP based on frame pointer only if the stack frame extends beyond
278 // frame pointer stack slot, the target is ELF and the function has FP, or
279 // the target uses var sized objects.
281 assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
282 "No scratch register to restore SP from FP!");
283 emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
285 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
289 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
293 if (MBBI->getOpcode() == ARM::tBX_RET &&
294 &MBB.front() != MBBI &&
295 prior(MBBI)->getOpcode() == ARM::tPOP) {
296 MachineBasicBlock::iterator PMBBI = prior(MBBI);
297 emitSPUpdate(MBB, PMBBI, TII, dl, *RegInfo, NumBytes);
299 emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes);
303 if (ArgRegsSaveSize) {
304 // Unlike T2 and ARM mode, the T1 pop instruction cannot restore
305 // to LR, and we can't pop the value directly to the PC since
306 // we need to update the SP after popping the value. Therefore, we
307 // pop the old LR into R3 as a temporary.
309 // Move back past the callee-saved register restoration
310 while (MBBI != MBB.end() && isCSRestore(MBBI, CSRegs))
312 // Epilogue for vararg functions: pop LR to R3 and branch off it.
313 AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
314 .addReg(ARM::R3, RegState::Define);
316 emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize);
318 MachineInstrBuilder MIB =
319 BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX_RET_vararg))
320 .addReg(ARM::R3, RegState::Kill);
322 MIB.copyImplicitOps(&*MBBI);
323 // erase the old tBX_RET instruction
328 bool Thumb1FrameLowering::
329 spillCalleeSavedRegisters(MachineBasicBlock &MBB,
330 MachineBasicBlock::iterator MI,
331 const std::vector<CalleeSavedInfo> &CSI,
332 const TargetRegisterInfo *TRI) const {
337 MachineFunction &MF = *MBB.getParent();
338 const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
340 if (MI != MBB.end()) DL = MI->getDebugLoc();
342 MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(ARM::tPUSH));
344 for (unsigned i = CSI.size(); i != 0; --i) {
345 unsigned Reg = CSI[i-1].getReg();
348 // Add the callee-saved register as live-in unless it's LR and
349 // @llvm.returnaddress is called. If LR is returned for @llvm.returnaddress
350 // then it's already added to the function and entry block live-in sets.
351 if (Reg == ARM::LR) {
352 MachineFunction &MF = *MBB.getParent();
353 if (MF.getFrameInfo()->isReturnAddressTaken() &&
354 MF.getRegInfo().isLiveIn(Reg))
361 MIB.addReg(Reg, getKillRegState(isKill));
363 MIB.setMIFlags(MachineInstr::FrameSetup);
367 bool Thumb1FrameLowering::
368 restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
369 MachineBasicBlock::iterator MI,
370 const std::vector<CalleeSavedInfo> &CSI,
371 const TargetRegisterInfo *TRI) const {
375 MachineFunction &MF = *MBB.getParent();
376 ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
377 const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
379 bool isVarArg = AFI->getArgRegsSaveSize() > 0;
380 DebugLoc DL = MI->getDebugLoc();
381 MachineInstrBuilder MIB = BuildMI(MF, DL, TII.get(ARM::tPOP));
384 bool NumRegs = false;
385 for (unsigned i = CSI.size(); i != 0; --i) {
386 unsigned Reg = CSI[i-1].getReg();
387 if (Reg == ARM::LR) {
388 // Special epilogue for vararg functions. See emitEpilogue
392 (*MIB).setDesc(TII.get(ARM::tPOP_RET));
393 MIB.copyImplicitOps(&*MI);
396 MIB.addReg(Reg, getDefRegState(true));
400 // It's illegal to emit pop instruction without operands.
402 MBB.insert(MI, &*MIB);
404 MF.DeleteMachineInstr(MIB);