1 //===- AArch64RegisterInfo.cpp - AArch64 Register 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 AArch64 implementation of the TargetRegisterInfo
13 //===----------------------------------------------------------------------===//
15 #include "AArch64RegisterInfo.h"
16 #include "AArch64FrameLowering.h"
17 #include "AArch64InstrInfo.h"
18 #include "AArch64MachineFunctionInfo.h"
19 #include "AArch64Subtarget.h"
20 #include "MCTargetDesc/AArch64AddressingModes.h"
21 #include "llvm/ADT/BitVector.h"
22 #include "llvm/ADT/Triple.h"
23 #include "llvm/CodeGen/MachineFrameInfo.h"
24 #include "llvm/CodeGen/MachineInstrBuilder.h"
25 #include "llvm/CodeGen/MachineRegisterInfo.h"
26 #include "llvm/CodeGen/RegisterScavenging.h"
27 #include "llvm/IR/Function.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/Target/TargetFrameLowering.h"
30 #include "llvm/Target/TargetOptions.h"
34 #define GET_REGINFO_TARGET_DESC
35 #include "AArch64GenRegisterInfo.inc"
37 AArch64RegisterInfo::AArch64RegisterInfo(const Triple &TT)
38 : AArch64GenRegisterInfo(AArch64::LR), TT(TT) {}
41 AArch64RegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
42 assert(MF && "Invalid MachineFunction pointer.");
43 if (MF->getFunction()->getCallingConv() == CallingConv::GHC)
44 // GHC set of callee saved regs is empty as all those regs are
45 // used for passing STG regs around
46 return CSR_AArch64_NoRegs_SaveList;
47 if (MF->getFunction()->getCallingConv() == CallingConv::AnyReg)
48 return CSR_AArch64_AllRegs_SaveList;
49 if (MF->getFunction()->getCallingConv() == CallingConv::CXX_FAST_TLS)
50 return MF->getInfo<AArch64FunctionInfo>()->isSplitCSR() ?
51 CSR_AArch64_CXX_TLS_Darwin_PE_SaveList :
52 CSR_AArch64_CXX_TLS_Darwin_SaveList;
53 if (MF->getSubtarget<AArch64Subtarget>().getTargetLowering()
54 ->supportSwiftError() &&
55 MF->getFunction()->getAttributes().hasAttrSomewhere(
56 Attribute::SwiftError))
57 return CSR_AArch64_AAPCS_SwiftError_SaveList;
58 if (MF->getFunction()->getCallingConv() == CallingConv::PreserveMost)
59 return CSR_AArch64_RT_MostRegs_SaveList;
61 return CSR_AArch64_AAPCS_SaveList;
64 const MCPhysReg *AArch64RegisterInfo::getCalleeSavedRegsViaCopy(
65 const MachineFunction *MF) const {
66 assert(MF && "Invalid MachineFunction pointer.");
67 if (MF->getFunction()->getCallingConv() == CallingConv::CXX_FAST_TLS &&
68 MF->getInfo<AArch64FunctionInfo>()->isSplitCSR())
69 return CSR_AArch64_CXX_TLS_Darwin_ViaCopy_SaveList;
74 AArch64RegisterInfo::getCallPreservedMask(const MachineFunction &MF,
75 CallingConv::ID CC) const {
76 if (CC == CallingConv::GHC)
77 // This is academic becase all GHC calls are (supposed to be) tail calls
78 return CSR_AArch64_NoRegs_RegMask;
79 if (CC == CallingConv::AnyReg)
80 return CSR_AArch64_AllRegs_RegMask;
81 if (CC == CallingConv::CXX_FAST_TLS)
82 return CSR_AArch64_CXX_TLS_Darwin_RegMask;
83 if (MF.getSubtarget<AArch64Subtarget>().getTargetLowering()
84 ->supportSwiftError() &&
85 MF.getFunction()->getAttributes().hasAttrSomewhere(Attribute::SwiftError))
86 return CSR_AArch64_AAPCS_SwiftError_RegMask;
87 if (CC == CallingConv::PreserveMost)
88 return CSR_AArch64_RT_MostRegs_RegMask;
90 return CSR_AArch64_AAPCS_RegMask;
93 const uint32_t *AArch64RegisterInfo::getTLSCallPreservedMask() const {
95 return CSR_AArch64_TLS_Darwin_RegMask;
97 assert(TT.isOSBinFormatELF() && "only expect Darwin or ELF TLS");
98 return CSR_AArch64_TLS_ELF_RegMask;
102 AArch64RegisterInfo::getThisReturnPreservedMask(const MachineFunction &MF,
103 CallingConv::ID CC) const {
104 // This should return a register mask that is the same as that returned by
105 // getCallPreservedMask but that additionally preserves the register used for
106 // the first i64 argument (which must also be the register used to return a
107 // single i64 return value)
109 // In case that the calling convention does not use the same register for
110 // both, the function should return NULL (does not currently apply)
111 assert(CC != CallingConv::GHC && "should not be GHC calling convention.");
112 return CSR_AArch64_AAPCS_ThisReturn_RegMask;
116 AArch64RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
117 const AArch64FrameLowering *TFI = getFrameLowering(MF);
119 // FIXME: avoid re-calculating this every time.
120 BitVector Reserved(getNumRegs());
121 markSuperRegs(Reserved, AArch64::WSP);
122 markSuperRegs(Reserved, AArch64::WZR);
124 if (TFI->hasFP(MF) || TT.isOSDarwin())
125 markSuperRegs(Reserved, AArch64::W29);
127 if (MF.getSubtarget<AArch64Subtarget>().isX18Reserved())
128 markSuperRegs(Reserved, AArch64::W18); // Platform register
130 if (hasBasePointer(MF))
131 markSuperRegs(Reserved, AArch64::W19);
133 assert(checkAllSuperRegsMarked(Reserved));
137 bool AArch64RegisterInfo::isReservedReg(const MachineFunction &MF,
138 unsigned Reg) const {
139 const AArch64FrameLowering *TFI = getFrameLowering(MF);
151 return MF.getSubtarget<AArch64Subtarget>().isX18Reserved();
154 return TFI->hasFP(MF) || TT.isOSDarwin();
157 return hasBasePointer(MF);
163 bool AArch64RegisterInfo::isConstantPhysReg(unsigned PhysReg) const {
164 return PhysReg == AArch64::WZR || PhysReg == AArch64::XZR;
167 const TargetRegisterClass *
168 AArch64RegisterInfo::getPointerRegClass(const MachineFunction &MF,
169 unsigned Kind) const {
170 return &AArch64::GPR64RegClass;
173 const TargetRegisterClass *
174 AArch64RegisterInfo::getCrossCopyRegClass(const TargetRegisterClass *RC) const {
175 if (RC == &AArch64::CCRRegClass)
176 return &AArch64::GPR64RegClass; // Only MSR & MRS copy NZCV.
180 unsigned AArch64RegisterInfo::getBaseRegister() const { return AArch64::X19; }
182 bool AArch64RegisterInfo::hasBasePointer(const MachineFunction &MF) const {
183 const MachineFrameInfo &MFI = MF.getFrameInfo();
185 // In the presence of variable sized objects, if the fixed stack size is
186 // large enough that referencing from the FP won't result in things being
187 // in range relatively often, we can use a base pointer to allow access
188 // from the other direction like the SP normally works.
189 // Furthermore, if both variable sized objects are present, and the
190 // stack needs to be dynamically re-aligned, the base pointer is the only
191 // reliable way to reference the locals.
192 if (MFI.hasVarSizedObjects()) {
193 if (needsStackRealignment(MF))
195 // Conservatively estimate whether the negative offset from the frame
196 // pointer will be sufficient to reach. If a function has a smallish
197 // frame, it's less likely to have lots of spills and callee saved
198 // space, so it's all more likely to be within range of the frame pointer.
199 // If it's wrong, we'll materialize the constant and still get to the
200 // object; it's just suboptimal. Negative offsets use the unscaled
201 // load/store instructions, which have a 9-bit signed immediate.
202 return MFI.getLocalFrameSize() >= 256;
209 AArch64RegisterInfo::getFrameRegister(const MachineFunction &MF) const {
210 const AArch64FrameLowering *TFI = getFrameLowering(MF);
211 return TFI->hasFP(MF) ? AArch64::FP : AArch64::SP;
214 bool AArch64RegisterInfo::requiresRegisterScavenging(
215 const MachineFunction &MF) const {
219 bool AArch64RegisterInfo::requiresVirtualBaseRegisters(
220 const MachineFunction &MF) const {
225 AArch64RegisterInfo::useFPForScavengingIndex(const MachineFunction &MF) const {
226 const MachineFrameInfo &MFI = MF.getFrameInfo();
227 // AArch64FrameLowering::resolveFrameIndexReference() can always fall back
228 // to the stack pointer, so only put the emergency spill slot next to the
229 // FP when there's no better way to access it (SP or base pointer).
230 return MFI.hasVarSizedObjects() && !hasBasePointer(MF);
233 bool AArch64RegisterInfo::requiresFrameIndexScavenging(
234 const MachineFunction &MF) const {
239 AArch64RegisterInfo::cannotEliminateFrame(const MachineFunction &MF) const {
240 const MachineFrameInfo &MFI = MF.getFrameInfo();
241 if (MF.getTarget().Options.DisableFramePointerElim(MF) && MFI.adjustsStack())
243 return MFI.hasVarSizedObjects() || MFI.isFrameAddressTaken();
246 /// needsFrameBaseReg - Returns true if the instruction's frame index
247 /// reference would be better served by a base register other than FP
248 /// or SP. Used by LocalStackFrameAllocation to determine which frame index
249 /// references it should create new base registers for.
250 bool AArch64RegisterInfo::needsFrameBaseReg(MachineInstr *MI,
251 int64_t Offset) const {
252 for (unsigned i = 0; !MI->getOperand(i).isFI(); ++i)
253 assert(i < MI->getNumOperands() &&
254 "Instr doesn't have FrameIndex operand!");
256 // It's the load/store FI references that cause issues, as it can be difficult
257 // to materialize the offset if it won't fit in the literal field. Estimate
258 // based on the size of the local frame and some conservative assumptions
259 // about the rest of the stack frame (note, this is pre-regalloc, so
260 // we don't know everything for certain yet) whether this offset is likely
261 // to be out of range of the immediate. Return true if so.
263 // We only generate virtual base registers for loads and stores, so
264 // return false for everything else.
265 if (!MI->mayLoad() && !MI->mayStore())
268 // Without a virtual base register, if the function has variable sized
269 // objects, all fixed-size local references will be via the frame pointer,
270 // Approximate the offset and see if it's legal for the instruction.
271 // Note that the incoming offset is based on the SP value at function entry,
272 // so it'll be negative.
273 MachineFunction &MF = *MI->getParent()->getParent();
274 const AArch64FrameLowering *TFI = getFrameLowering(MF);
275 MachineFrameInfo &MFI = MF.getFrameInfo();
277 // Estimate an offset from the frame pointer.
278 // Conservatively assume all GPR callee-saved registers get pushed.
279 // FP, LR, X19-X28, D8-D15. 64-bits each.
280 int64_t FPOffset = Offset - 16 * 20;
281 // Estimate an offset from the stack pointer.
282 // The incoming offset is relating to the SP at the start of the function,
283 // but when we access the local it'll be relative to the SP after local
284 // allocation, so adjust our SP-relative offset by that allocation size.
285 Offset += MFI.getLocalFrameSize();
286 // Assume that we'll have at least some spill slots allocated.
287 // FIXME: This is a total SWAG number. We should run some statistics
288 // and pick a real one.
289 Offset += 128; // 128 bytes of spill slots
291 // If there is a frame pointer, try using it.
292 // The FP is only available if there is no dynamic realignment. We
293 // don't know for sure yet whether we'll need that, so we guess based
294 // on whether there are any local variables that would trigger it.
295 if (TFI->hasFP(MF) && isFrameOffsetLegal(MI, AArch64::FP, FPOffset))
298 // If we can reference via the stack pointer or base pointer, try that.
299 // FIXME: This (and the code that resolves the references) can be improved
300 // to only disallow SP relative references in the live range of
301 // the VLA(s). In practice, it's unclear how much difference that
302 // would make, but it may be worth doing.
303 if (isFrameOffsetLegal(MI, AArch64::SP, Offset))
306 // The offset likely isn't legal; we want to allocate a virtual base register.
310 bool AArch64RegisterInfo::isFrameOffsetLegal(const MachineInstr *MI,
312 int64_t Offset) const {
313 assert(Offset <= INT_MAX && "Offset too big to fit in int.");
314 assert(MI && "Unable to get the legal offset for nil instruction.");
315 int SaveOffset = Offset;
316 return isAArch64FrameOffsetLegal(*MI, SaveOffset) & AArch64FrameOffsetIsLegal;
319 /// Insert defining instruction(s) for BaseReg to be a pointer to FrameIdx
320 /// at the beginning of the basic block.
321 void AArch64RegisterInfo::materializeFrameBaseRegister(MachineBasicBlock *MBB,
324 int64_t Offset) const {
325 MachineBasicBlock::iterator Ins = MBB->begin();
326 DebugLoc DL; // Defaults to "unknown"
327 if (Ins != MBB->end())
328 DL = Ins->getDebugLoc();
329 const MachineFunction &MF = *MBB->getParent();
330 const AArch64InstrInfo *TII =
331 MF.getSubtarget<AArch64Subtarget>().getInstrInfo();
332 const MCInstrDesc &MCID = TII->get(AArch64::ADDXri);
333 MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
334 MRI.constrainRegClass(BaseReg, TII->getRegClass(MCID, 0, this, MF));
335 unsigned Shifter = AArch64_AM::getShifterImm(AArch64_AM::LSL, 0);
337 BuildMI(*MBB, Ins, DL, MCID, BaseReg)
338 .addFrameIndex(FrameIdx)
343 void AArch64RegisterInfo::resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
344 int64_t Offset) const {
345 int Off = Offset; // ARM doesn't need the general 64-bit offsets
348 while (!MI.getOperand(i).isFI()) {
350 assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
352 const MachineFunction *MF = MI.getParent()->getParent();
353 const AArch64InstrInfo *TII =
354 MF->getSubtarget<AArch64Subtarget>().getInstrInfo();
355 bool Done = rewriteAArch64FrameIndex(MI, i, BaseReg, Off, TII);
356 assert(Done && "Unable to resolve frame index!");
360 void AArch64RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
361 int SPAdj, unsigned FIOperandNum,
362 RegScavenger *RS) const {
363 assert(SPAdj == 0 && "Unexpected");
365 MachineInstr &MI = *II;
366 MachineBasicBlock &MBB = *MI.getParent();
367 MachineFunction &MF = *MBB.getParent();
368 const AArch64InstrInfo *TII =
369 MF.getSubtarget<AArch64Subtarget>().getInstrInfo();
370 const AArch64FrameLowering *TFI = getFrameLowering(MF);
372 int FrameIndex = MI.getOperand(FIOperandNum).getIndex();
376 // Special handling of dbg_value, stackmap and patchpoint instructions.
377 if (MI.isDebugValue() || MI.getOpcode() == TargetOpcode::STACKMAP ||
378 MI.getOpcode() == TargetOpcode::PATCHPOINT) {
379 Offset = TFI->resolveFrameIndexReference(MF, FrameIndex, FrameReg,
381 Offset += MI.getOperand(FIOperandNum + 1).getImm();
382 MI.getOperand(FIOperandNum).ChangeToRegister(FrameReg, false /*isDef*/);
383 MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset);
387 // Modify MI as necessary to handle as much of 'Offset' as possible
388 Offset = TFI->resolveFrameIndexReference(MF, FrameIndex, FrameReg);
389 if (rewriteAArch64FrameIndex(MI, FIOperandNum, FrameReg, Offset, TII))
392 assert((!RS || !RS->isScavengingFrameIndex(FrameIndex)) &&
393 "Emergency spill slot is out of reach");
395 // If we get here, the immediate doesn't fit into the instruction. We folded
396 // as much as possible above. Handle the rest, providing a register that is
398 unsigned ScratchReg =
399 MF.getRegInfo().createVirtualRegister(&AArch64::GPR64RegClass);
400 emitFrameOffset(MBB, II, MI.getDebugLoc(), ScratchReg, FrameReg, Offset, TII);
401 MI.getOperand(FIOperandNum).ChangeToRegister(ScratchReg, false, false, true);
404 unsigned AArch64RegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC,
405 MachineFunction &MF) const {
406 const AArch64FrameLowering *TFI = getFrameLowering(MF);
408 switch (RC->getID()) {
411 case AArch64::GPR32RegClassID:
412 case AArch64::GPR32spRegClassID:
413 case AArch64::GPR32allRegClassID:
414 case AArch64::GPR64spRegClassID:
415 case AArch64::GPR64allRegClassID:
416 case AArch64::GPR64RegClassID:
417 case AArch64::GPR32commonRegClassID:
418 case AArch64::GPR64commonRegClassID:
419 return 32 - 1 // XZR/SP
420 - (TFI->hasFP(MF) || TT.isOSDarwin()) // FP
421 - MF.getSubtarget<AArch64Subtarget>()
422 .isX18Reserved() // X18 reserved as platform register
423 - hasBasePointer(MF); // X19
424 case AArch64::FPR8RegClassID:
425 case AArch64::FPR16RegClassID:
426 case AArch64::FPR32RegClassID:
427 case AArch64::FPR64RegClassID:
428 case AArch64::FPR128RegClassID:
431 case AArch64::DDRegClassID:
432 case AArch64::DDDRegClassID:
433 case AArch64::DDDDRegClassID:
434 case AArch64::QQRegClassID:
435 case AArch64::QQQRegClassID:
436 case AArch64::QQQQRegClassID:
439 case AArch64::FPR128_loRegClassID: