//===- AArch64FrameLowering.cpp - AArch64 Frame Information ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the AArch64 implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "AArch64.h"
#include "AArch64FrameLowering.h"
#include "AArch64MachineFunctionInfo.h"
#include "AArch64InstrInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MachineLocation.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
using namespace llvm;
void AArch64FrameLowering::splitSPAdjustments(uint64_t Total,
uint64_t &Initial,
uint64_t &Residual) const {
// 0x1f0 here is a pessimistic (i.e. realistic) boundary: x-register LDP
// instructions have a 7-bit signed immediate scaled by 8, giving a reach of
// 0x1f8, but stack adjustment should always be a multiple of 16.
if (Total <= 0x1f0) {
Initial = Total;
Residual = 0;
} else {
Initial = 0x1f0;
Residual = Total - Initial;
}
}
void AArch64FrameLowering::emitPrologue(MachineFunction &MF) const {
AArch64MachineFunctionInfo *FuncInfo =
MF.getInfo<AArch64MachineFunctionInfo>();
MachineBasicBlock &MBB = MF.front();
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
MachineModuleInfo &MMI = MF.getMMI();
const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
bool NeedsFrameMoves = MMI.hasDebugInfo()
|| MF.getFunction()->needsUnwindTableEntry();
uint64_t NumInitialBytes, NumResidualBytes;
// Currently we expect the stack to be laid out by
// sub sp, sp, #initial
// stp x29, x30, [sp, #offset]
// ...
// str xxx, [sp, #offset]
// sub sp, sp, #rest (possibly via extra instructions).
if (MFI->getCalleeSavedInfo().size()) {
// If there are callee-saved registers, we want to store them efficiently as
// a block, and virtual base assignment happens too early to do it for us so
// we adjust the stack in two phases: first just for callee-saved fiddling,
// then to allocate the rest of the frame.
splitSPAdjustments(MFI->getStackSize(), NumInitialBytes, NumResidualBytes);
} else {
// If there aren't any callee-saved registers, two-phase adjustment is
// inefficient. It's more efficient to adjust with NumInitialBytes too
// because when we're in a "callee pops argument space" situation, that pop
// must be tacked onto Initial for correctness.
NumInitialBytes = MFI->getStackSize();
NumResidualBytes = 0;
}
// Tell everyone else how much adjustment we're expecting them to use. In
// particular if an adjustment is required for a tail call the epilogue could
// have a different view of things.
FuncInfo->setInitialStackAdjust(NumInitialBytes);
emitSPUpdate(MBB, MBBI, DL, TII, AArch64::X16, -NumInitialBytes,
MachineInstr::FrameSetup);
if (NeedsFrameMoves && NumInitialBytes) {
// We emit this update even if the CFA is set from a frame pointer later so
// that the CFA is valid in the interim.
MCSymbol *SPLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
.addSym(SPLabel);
MachineLocation Dst(MachineLocation::VirtualFP);
unsigned Reg = MRI->getDwarfRegNum(AArch64::XSP, true);
MMI.addFrameInst(
MCCFIInstruction::createDefCfa(SPLabel, Reg, -NumInitialBytes));
}
// Otherwise we need to set the frame pointer and/or add a second stack
// adjustment.
bool FPNeedsSetting = hasFP(MF);
for (; MBBI != MBB.end(); ++MBBI) {
// Note that this search makes strong assumptions about the operation used
// to store the frame-pointer: it must be "STP x29, x30, ...". This could
// change in future, but until then there's no point in implementing
// untestable more generic cases.
if (FPNeedsSetting && MBBI->getOpcode() == AArch64::LSPair64_STR
&& MBBI->getOperand(0).getReg() == AArch64::X29) {
int64_t X29FrameIdx = MBBI->getOperand(2).getIndex();
FuncInfo->setFramePointerOffset(MFI->getObjectOffset(X29FrameIdx));
++MBBI;
emitRegUpdate(MBB, MBBI, DL, TII, AArch64::X29, AArch64::XSP,
AArch64::X29,
NumInitialBytes + MFI->getObjectOffset(X29FrameIdx),
MachineInstr::FrameSetup);
// The offset adjustment used when emitting debugging locations relative
// to whatever frame base is set. AArch64 uses the default frame base (FP
// or SP) and this adjusts the calculations to be correct.
MFI->setOffsetAdjustment(- MFI->getObjectOffset(X29FrameIdx)
- MFI->getStackSize());
if (NeedsFrameMoves) {
MCSymbol *FPLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
.addSym(FPLabel);
unsigned Reg = MRI->getDwarfRegNum(AArch64::X29, true);
unsigned Offset = MFI->getObjectOffset(X29FrameIdx);
MMI.addFrameInst(MCCFIInstruction::createDefCfa(FPLabel, Reg, Offset));
}
FPNeedsSetting = false;
}
if (!MBBI->getFlag(MachineInstr::FrameSetup))
break;
}
assert(!FPNeedsSetting && "Frame pointer couldn't be set");
emitSPUpdate(MBB, MBBI, DL, TII, AArch64::X16, -NumResidualBytes,
MachineInstr::FrameSetup);
// Now we emit the rest of the frame setup information, if necessary: we've
// already noted the FP and initial SP moves so we're left with the prologue's
// final SP update and callee-saved register locations.
if (!NeedsFrameMoves)
return;
// Reuse the label if appropriate, so create it in this outer scope.
MCSymbol *CSLabel = 0;
// The rest of the stack adjustment
if (!hasFP(MF) && NumResidualBytes) {
CSLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
.addSym(CSLabel);
MachineLocation Dst(MachineLocation::VirtualFP);
unsigned Reg = MRI->getDwarfRegNum(AArch64::XSP, true);
unsigned Offset = NumResidualBytes + NumInitialBytes;
MMI.addFrameInst(MCCFIInstruction::createDefCfa(CSLabel, Reg, -Offset));
}
// And any callee-saved registers (it's fine to leave them to the end here,
// because the old values are still valid at this point.
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
if (CSI.size()) {
if (!CSLabel) {
CSLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
.addSym(CSLabel);
}
for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
E = CSI.end(); I != E; ++I) {
unsigned Offset = MFI->getObjectOffset(I->getFrameIdx());
unsigned Reg = MRI->getDwarfRegNum(I->getReg(), true);
MMI.addFrameInst(MCCFIInstruction::createOffset(CSLabel, Reg, Offset));
}
}
}
void
AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
AArch64MachineFunctionInfo *FuncInfo =
MF.getInfo<AArch64MachineFunctionInfo>();
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
DebugLoc DL = MBBI->getDebugLoc();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
MachineFrameInfo &MFI = *MF.getFrameInfo();
unsigned RetOpcode = MBBI->getOpcode();
// Initial and residual are named for consitency with the prologue. Note that
// in the epilogue, the residual adjustment is executed first.
uint64_t NumInitialBytes = FuncInfo->getInitialStackAdjust();
uint64_t NumResidualBytes = MFI.getStackSize() - NumInitialBytes;
uint64_t ArgumentPopSize = 0;
if (RetOpcode == AArch64::TC_RETURNdi ||
RetOpcode == AArch64::TC_RETURNxi) {
MachineOperand &JumpTarget = MBBI->getOperand(0);
MachineOperand &StackAdjust = MBBI->getOperand(1);
MachineInstrBuilder MIB;
if (RetOpcode == AArch64::TC_RETURNdi) {
MIB = BuildMI(MBB, MBBI, DL, TII.get(AArch64::TAIL_Bimm));
if (JumpTarget.isGlobal()) {
MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
JumpTarget.getTargetFlags());
} else {
assert(JumpTarget.isSymbol() && "unexpected tail call destination");
MIB.addExternalSymbol(JumpTarget.getSymbolName(),
JumpTarget.getTargetFlags());
}
} else {
assert(RetOpcode == AArch64::TC_RETURNxi && JumpTarget.isReg()
&& "Unexpected tail call");
MIB = BuildMI(MBB, MBBI, DL, TII.get(AArch64::TAIL_BRx));
MIB.addReg(JumpTarget.getReg(), RegState::Kill);
}
// Add the extra operands onto the new tail call instruction even though
// they're not used directly (so that liveness is tracked properly etc).
for (unsigned i = 2, e = MBBI->getNumOperands(); i != e; ++i)
MIB->addOperand(MBBI->getOperand(i));
// Delete the pseudo instruction TC_RETURN.
MachineInstr *NewMI = prior(MBBI);
MBB.erase(MBBI);
MBBI = NewMI;
// For a tail-call in a callee-pops-arguments environment, some or all of
// the stack may actually be in use for the call's arguments, this is
// calculated during LowerCall and consumed here...
ArgumentPopSize = StackAdjust.getImm();
} else {
// ... otherwise the amount to pop is *all* of the argument space,
// conveniently stored in the MachineFunctionInfo by
// LowerFormalArguments. This will, of course, be zero for the C calling
// convention.
ArgumentPopSize = FuncInfo->getArgumentStackToRestore();
}
assert(NumInitialBytes % 16 == 0 && NumResidualBytes % 16 == 0
&& "refusing to adjust stack by misaligned amt");
// We may need to address callee-saved registers differently, so find out the
// bound on the frame indices.
const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
int MinCSFI = 0;
int MaxCSFI = -1;
if (CSI.size()) {
MinCSFI = CSI[0].getFrameIdx();
MaxCSFI = CSI[CSI.size() - 1].getFrameIdx();
}
// The "residual" stack update comes first from this direction and guarantees
// that SP is NumInitialBytes below its value on function entry, either by a
// direct update or restoring it from the frame pointer.
if (NumInitialBytes + ArgumentPopSize != 0) {
emitSPUpdate(MBB, MBBI, DL, TII, AArch64::X16,
NumInitialBytes + ArgumentPopSize);
--MBBI;
}
// MBBI now points to the instruction just past the last callee-saved
// restoration (either RET/B if NumInitialBytes == 0, or the "ADD sp, sp"
// otherwise).
// Now we need to find out where to put the bulk of the stack adjustment
MachineBasicBlock::iterator FirstEpilogue = MBBI;
while (MBBI != MBB.begin()) {
--MBBI;
unsigned FrameOp;
for (FrameOp = 0; FrameOp < MBBI->getNumOperands(); ++FrameOp) {
if (MBBI->getOperand(FrameOp).isFI())
break;
}
// If this instruction doesn't have a frame index we've reached the end of
// the callee-save restoration.
if (FrameOp == MBBI->getNumOperands())
break;
// Likewise if it *is* a local reference, but not to a callee-saved object.
int FrameIdx = MBBI->getOperand(FrameOp).getIndex();
if (FrameIdx < MinCSFI || FrameIdx > MaxCSFI)
break;
FirstEpilogue = MBBI;
}
if (MF.getFrameInfo()->hasVarSizedObjects()) {
int64_t StaticFrameBase;
StaticFrameBase = -(NumInitialBytes + FuncInfo->getFramePointerOffset());
emitRegUpdate(MBB, FirstEpilogue, DL, TII,
AArch64::XSP, AArch64::X29, AArch64::NoRegister,
StaticFrameBase);
} else {
emitSPUpdate(MBB, FirstEpilogue, DL,TII, AArch64::X16, NumResidualBytes);
}
}
int64_t
AArch64FrameLowering::resolveFrameIndexReference(MachineFunction &MF,
int FrameIndex,
unsigned &FrameReg,
int SPAdj,
bool IsCalleeSaveOp) const {
AArch64MachineFunctionInfo *FuncInfo =
MF.getInfo<AArch64MachineFunctionInfo>();
MachineFrameInfo *MFI = MF.getFrameInfo();
int64_t TopOfFrameOffset = MFI->getObjectOffset(FrameIndex);
assert(!(IsCalleeSaveOp && FuncInfo->getInitialStackAdjust() == 0)
&& "callee-saved register in unexpected place");
// If the frame for this function is particularly large, we adjust the stack
// in two phases which means the callee-save related operations see a
// different (intermediate) stack size.
int64_t FrameRegPos;
if (IsCalleeSaveOp) {
FrameReg = AArch64::XSP;
FrameRegPos = -static_cast<int64_t>(FuncInfo->getInitialStackAdjust());
} else if (useFPForAddressing(MF)) {
// Have to use the frame pointer since we have no idea where SP is.
FrameReg = AArch64::X29;
FrameRegPos = FuncInfo->getFramePointerOffset();
} else {
FrameReg = AArch64::XSP;
FrameRegPos = -static_cast<int64_t>(MFI->getStackSize()) + SPAdj;
}
return TopOfFrameOffset - FrameRegPos;
}
void
AArch64FrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
RegScavenger *RS) const {
const AArch64RegisterInfo *RegInfo =
static_cast<const AArch64RegisterInfo *>(MF.getTarget().getRegisterInfo());
MachineFrameInfo *MFI = MF.getFrameInfo();
const AArch64InstrInfo &TII =
*static_cast<const AArch64InstrInfo *>(MF.getTarget().getInstrInfo());
if (hasFP(MF)) {
MF.getRegInfo().setPhysRegUsed(AArch64::X29);
MF.getRegInfo().setPhysRegUsed(AArch64::X30);
}
// If addressing of local variables is going to be more complicated than
// shoving a base register and an offset into the instruction then we may well
// need to scavenge registers. We should either specifically add an
// callee-save register for this purpose or allocate an extra spill slot.
bool BigStack =
MFI->estimateStackSize(MF) >= TII.estimateRSStackLimit(MF)
|| MFI->hasVarSizedObjects() // Access will be from X29: messes things up
|| (MFI->adjustsStack() && !hasReservedCallFrame(MF));
if (!BigStack)
return;
// We certainly need some slack space for the scavenger, preferably an extra
// register.
const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs();
uint16_t ExtraReg = AArch64::NoRegister;
for (unsigned i = 0; CSRegs[i]; ++i) {
if (AArch64::GPR64RegClass.contains(CSRegs[i]) &&
!MF.getRegInfo().isPhysRegUsed(CSRegs[i])) {
ExtraReg = CSRegs[i];
break;
}
}
if (ExtraReg != 0) {
MF.getRegInfo().setPhysRegUsed(ExtraReg);
} else {
assert(RS && "Expect register scavenger to be available");
// Create a stack slot for scavenging purposes. PrologEpilogInserter
// helpfully places it near either SP or FP for us to avoid
// infinitely-regression during scavenging.
const TargetRegisterClass *RC = &AArch64::GPR64RegClass;
RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
}
bool AArch64FrameLowering::determinePrologueDeath(MachineBasicBlock &MBB,
unsigned Reg) const {
// If @llvm.returnaddress is called then it will refer to X30 by some means;
// the prologue store does not kill the register.
if (Reg == AArch64::X30) {
if (MBB.getParent()->getFrameInfo()->isReturnAddressTaken()
&& MBB.getParent()->getRegInfo().isLiveIn(Reg))
return false;
}
// In all other cases, physical registers are dead after they've been saved
// but live at the beginning of the prologue block.
MBB.addLiveIn(Reg);
return true;
}
void
AArch64FrameLowering::emitFrameMemOps(bool isPrologue, MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI,
const LoadStoreMethod PossClasses[],
unsigned NumClasses) const {
DebugLoc DL = MBB.findDebugLoc(MBBI);
MachineFunction &MF = *MBB.getParent();
MachineFrameInfo &MFI = *MF.getFrameInfo();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
// A certain amount of implicit contract is present here. The actual stack
// offsets haven't been allocated officially yet, so for strictly correct code
// we rely on the fact that the elements of CSI are allocated in order
// starting at SP, purely as dictated by size and alignment. In practice since
// this function handles the only accesses to those slots it's not quite so
// important.
//
// We have also ordered the Callee-saved register list in AArch64CallingConv
// so that the above scheme puts registers in order: in particular we want
// &X30 to be &X29+8 for an ABI-correct frame record (PCS 5.2.2)
for (unsigned i = 0, e = CSI.size(); i < e; ++i) {
unsigned Reg = CSI[i].getReg();
// First we need to find out which register class the register belongs to so
// that we can use the correct load/store instrucitons.
unsigned ClassIdx;
for (ClassIdx = 0; ClassIdx < NumClasses; ++ClassIdx) {
if (PossClasses[ClassIdx].RegClass->contains(Reg))
break;
}
assert(ClassIdx != NumClasses
&& "Asked to store register in unexpected class");
const TargetRegisterClass &TheClass = *PossClasses[ClassIdx].RegClass;
// Now we need to decide whether it's possible to emit a paired instruction:
// for this we want the next register to be in the same class.
MachineInstrBuilder NewMI;
bool Pair = false;
if (i + 1 < CSI.size() && TheClass.contains(CSI[i+1].getReg())) {
Pair = true;
unsigned StLow = 0, StHigh = 0;
if (isPrologue) {
// Most of these registers will be live-in to the MBB and killed by our
// store, though there are exceptions (see determinePrologueDeath).
StLow = getKillRegState(determinePrologueDeath(MBB, CSI[i+1].getReg()));
StHigh = getKillRegState(determinePrologueDeath(MBB, CSI[i].getReg()));
} else {
StLow = RegState::Define;
StHigh = RegState::Define;
}
NewMI = BuildMI(MBB, MBBI, DL, TII.get(PossClasses[ClassIdx].PairOpcode))
.addReg(CSI[i+1].getReg(), StLow)
.addReg(CSI[i].getReg(), StHigh);
// If it's a paired op, we've consumed two registers
++i;
} else {
unsigned State;
if (isPrologue) {
State = getKillRegState(determinePrologueDeath(MBB, CSI[i].getReg()));
} else {
State = RegState::Define;
}
NewMI = BuildMI(MBB, MBBI, DL,
TII.get(PossClasses[ClassIdx].SingleOpcode))
.addReg(CSI[i].getReg(), State);
}
// Note that the FrameIdx refers to the second register in a pair: it will
// be allocated the smaller numeric address and so is the one an LDP/STP
// address must use.
int FrameIdx = CSI[i].getFrameIdx();
MachineMemOperand::MemOperandFlags Flags;
Flags = isPrologue ? MachineMemOperand::MOStore : MachineMemOperand::MOLoad;
MachineMemOperand *MMO =
MF.getMachineMemOperand(MachinePointerInfo::getFixedStack(FrameIdx),
Flags,
Pair ? TheClass.getSize() * 2 : TheClass.getSize(),
MFI.getObjectAlignment(FrameIdx));
NewMI.addFrameIndex(FrameIdx)
.addImm(0) // address-register offset
.addMemOperand(MMO);
if (isPrologue)
NewMI.setMIFlags(MachineInstr::FrameSetup);
// For aesthetic reasons, during an epilogue we want to emit complementary
// operations to the prologue, but in the opposite order. So we still
// iterate through the CalleeSavedInfo list in order, but we put the
// instructions successively earlier in the MBB.
if (!isPrologue)
--MBBI;
}
}
bool
AArch64FrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
static const LoadStoreMethod PossibleClasses[] = {
{&AArch64::GPR64RegClass, AArch64::LSPair64_STR, AArch64::LS64_STR},
{&AArch64::FPR64RegClass, AArch64::LSFPPair64_STR, AArch64::LSFP64_STR},
};
const unsigned NumClasses = llvm::array_lengthof(PossibleClasses);
emitFrameMemOps(/* isPrologue = */ true, MBB, MBBI, CSI, TRI,
PossibleClasses, NumClasses);
return true;
}
bool
AArch64FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
static const LoadStoreMethod PossibleClasses[] = {
{&AArch64::GPR64RegClass, AArch64::LSPair64_LDR, AArch64::LS64_LDR},
{&AArch64::FPR64RegClass, AArch64::LSFPPair64_LDR, AArch64::LSFP64_LDR},
};
const unsigned NumClasses = llvm::array_lengthof(PossibleClasses);
emitFrameMemOps(/* isPrologue = */ false, MBB, MBBI, CSI, TRI,
PossibleClasses, NumClasses);
return true;
}
bool
AArch64FrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const TargetRegisterInfo *RI = MF.getTarget().getRegisterInfo();
// This is a decision of ABI compliance. The AArch64 PCS gives various options
// for conformance, and even at the most stringent level more or less permits
// elimination for leaf functions because there's no loss of functionality
// (for debugging etc)..
if (MF.getTarget().Options.DisableFramePointerElim(MF) && MFI->hasCalls())
return true;
// The following are hard-limits: incorrect code will be generated if we try
// to omit the frame.
return (RI->needsStackRealignment(MF) ||
MFI->hasVarSizedObjects() ||
MFI->isFrameAddressTaken());
}
bool
AArch64FrameLowering::useFPForAddressing(const MachineFunction &MF) const {
return MF.getFrameInfo()->hasVarSizedObjects();
}
bool
AArch64FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
// Of the various reasons for having a frame pointer, it's actually only
// variable-sized objects that prevent reservation of a call frame.
return !(hasFP(MF) && MFI->hasVarSizedObjects());
}
void
AArch64FrameLowering::eliminateCallFramePseudoInstr(
MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI) const {
const AArch64InstrInfo &TII =
*static_cast<const AArch64InstrInfo *>(MF.getTarget().getInstrInfo());
DebugLoc dl = MI->getDebugLoc();
int Opcode = MI->getOpcode();
bool IsDestroy = Opcode == TII.getCallFrameDestroyOpcode();
uint64_t CalleePopAmount = IsDestroy ? MI->getOperand(1).getImm() : 0;
if (!hasReservedCallFrame(MF)) {
unsigned Align = getStackAlignment();
int64_t Amount = MI->getOperand(0).getImm();
Amount = RoundUpToAlignment(Amount, Align);
if (!IsDestroy) Amount = -Amount;
// N.b. if CalleePopAmount is valid but zero (i.e. callee would pop, but it
// doesn't have to pop anything), then the first operand will be zero too so
// this adjustment is a no-op.
if (CalleePopAmount == 0) {
// FIXME: in-function stack adjustment for calls is limited to 12-bits
// because there's no guaranteed temporary register available. Mostly call
// frames will be allocated at the start of a function so this is OK, but
// it is a limitation that needs dealing with.
assert(Amount > -0xfff && Amount < 0xfff && "call frame too large");
emitSPUpdate(MBB, MI, dl, TII, AArch64::NoRegister, Amount);
}
} else if (CalleePopAmount != 0) {
// If the calling convention demands that the callee pops arguments from the
// stack, we want to add it back if we have a reserved call frame.
assert(CalleePopAmount < 0xfff && "call frame too large");
emitSPUpdate(MBB, MI, dl, TII, AArch64::NoRegister, -CalleePopAmount);
}
MBB.erase(MI);
}