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| Current File : //usr/src/contrib/llvm/lib/Target/ARM/ARMFrameLowering.cpp |
//===-- ARMFrameLowering.cpp - ARM 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 ARM implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "ARMFrameLowering.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
static cl::opt<bool>
SpillAlignedNEONRegs("align-neon-spills", cl::Hidden, cl::init(true),
cl::desc("Align ARM NEON spills in prolog and epilog"));
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs);
/// hasFP - Return true if the specified function should have a dedicated frame
/// pointer register. This is true if the function has variable sized allocas
/// or if frame pointer elimination is disabled.
bool ARMFrameLowering::hasFP(const MachineFunction &MF) const {
const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
// iOS requires FP not to be clobbered for backtracing purpose.
if (STI.isTargetIOS())
return true;
const MachineFrameInfo *MFI = MF.getFrameInfo();
// Always eliminate non-leaf frame pointers.
return ((MF.getTarget().Options.DisableFramePointerElim(MF) &&
MFI->hasCalls()) ||
RegInfo->needsStackRealignment(MF) ||
MFI->hasVarSizedObjects() ||
MFI->isFrameAddressTaken());
}
/// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
/// not required, we reserve argument space for call sites in the function
/// immediately on entry to the current function. This eliminates the need for
/// add/sub sp brackets around call sites. Returns true if the call frame is
/// included as part of the stack frame.
bool ARMFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
const MachineFrameInfo *FFI = MF.getFrameInfo();
unsigned CFSize = FFI->getMaxCallFrameSize();
// It's not always a good idea to include the call frame as part of the
// stack frame. ARM (especially Thumb) has small immediate offset to
// address the stack frame. So a large call frame can cause poor codegen
// and may even makes it impossible to scavenge a register.
if (CFSize >= ((1 << 12) - 1) / 2) // Half of imm12
return false;
return !MF.getFrameInfo()->hasVarSizedObjects();
}
/// canSimplifyCallFramePseudos - If there is a reserved call frame, the
/// call frame pseudos can be simplified. Unlike most targets, having a FP
/// is not sufficient here since we still may reference some objects via SP
/// even when FP is available in Thumb2 mode.
bool
ARMFrameLowering::canSimplifyCallFramePseudos(const MachineFunction &MF) const {
return hasReservedCallFrame(MF) || MF.getFrameInfo()->hasVarSizedObjects();
}
static bool isCalleeSavedRegister(unsigned Reg, const uint16_t *CSRegs) {
for (unsigned i = 0; CSRegs[i]; ++i)
if (Reg == CSRegs[i])
return true;
return false;
}
static bool isCSRestore(MachineInstr *MI,
const ARMBaseInstrInfo &TII,
const uint16_t *CSRegs) {
// Integer spill area is handled with "pop".
if (MI->getOpcode() == ARM::LDMIA_RET ||
MI->getOpcode() == ARM::t2LDMIA_RET ||
MI->getOpcode() == ARM::LDMIA_UPD ||
MI->getOpcode() == ARM::t2LDMIA_UPD ||
MI->getOpcode() == ARM::VLDMDIA_UPD) {
// The first two operands are predicates. The last two are
// imp-def and imp-use of SP. Check everything in between.
for (int i = 5, e = MI->getNumOperands(); i != e; ++i)
if (!isCalleeSavedRegister(MI->getOperand(i).getReg(), CSRegs))
return false;
return true;
}
if ((MI->getOpcode() == ARM::LDR_POST_IMM ||
MI->getOpcode() == ARM::LDR_POST_REG ||
MI->getOpcode() == ARM::t2LDR_POST) &&
isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs) &&
MI->getOperand(1).getReg() == ARM::SP)
return true;
return false;
}
static void
emitSPUpdate(bool isARM,
MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
DebugLoc dl, const ARMBaseInstrInfo &TII,
int NumBytes, unsigned MIFlags = MachineInstr::NoFlags) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
ARMCC::AL, 0, TII, MIFlags);
else
emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
ARMCC::AL, 0, TII, MIFlags);
}
void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front();
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
assert(!AFI->isThumb1OnlyFunction() &&
"This emitPrologue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize();
unsigned NumBytes = MFI->getStackSize();
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
// Determine the sizes of each callee-save spill areas and record which frame
// belongs to which callee-save spill areas.
unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
int FramePtrSpillFI = 0;
int D8SpillFI = 0;
// Allocate the vararg register save area. This is not counted in NumBytes.
if (VARegSaveSize)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -VARegSaveSize,
MachineInstr::FrameSetup);
if (!AFI->hasStackFrame()) {
if (NumBytes != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
return;
}
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
int FI = CSI[i].getFrameIdx();
switch (Reg) {
case ARM::R4:
case ARM::R5:
case ARM::R6:
case ARM::R7:
case ARM::LR:
if (Reg == FramePtr)
FramePtrSpillFI = FI;
AFI->addGPRCalleeSavedArea1Frame(FI);
GPRCS1Size += 4;
break;
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
if (Reg == FramePtr)
FramePtrSpillFI = FI;
if (STI.isTargetIOS()) {
AFI->addGPRCalleeSavedArea2Frame(FI);
GPRCS2Size += 4;
} else {
AFI->addGPRCalleeSavedArea1Frame(FI);
GPRCS1Size += 4;
}
break;
default:
// This is a DPR. Exclude the aligned DPRCS2 spills.
if (Reg == ARM::D8)
D8SpillFI = FI;
if (Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs()) {
AFI->addDPRCalleeSavedAreaFrame(FI);
DPRCSSize += 8;
}
}
}
// Move past area 1.
if (GPRCS1Size > 0) MBBI++;
// Set FP to point to the stack slot that contains the previous FP.
// For iOS, FP is R7, which has now been stored in spill area 1.
// Otherwise, if this is not iOS, all the callee-saved registers go
// into spill area 1, including the FP in R11. In either case, it is
// now safe to emit this assignment.
bool HasFP = hasFP(MF);
if (HasFP) {
unsigned ADDriOpc = !AFI->isThumbFunction() ? ARM::ADDri : ARM::t2ADDri;
MachineInstrBuilder MIB =
BuildMI(MBB, MBBI, dl, TII.get(ADDriOpc), FramePtr)
.addFrameIndex(FramePtrSpillFI).addImm(0)
.setMIFlag(MachineInstr::FrameSetup);
AddDefaultCC(AddDefaultPred(MIB));
}
// Move past area 2.
if (GPRCS2Size > 0) MBBI++;
// Determine starting offsets of spill areas.
unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize);
unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
if (HasFP)
AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) +
NumBytes);
AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
// Move past area 3.
if (DPRCSSize > 0) {
MBBI++;
// Since vpush register list cannot have gaps, there may be multiple vpush
// instructions in the prologue.
while (MBBI->getOpcode() == ARM::VSTMDDB_UPD)
MBBI++;
}
// Move past the aligned DPRCS2 area.
if (AFI->getNumAlignedDPRCS2Regs() > 0) {
MBBI = skipAlignedDPRCS2Spills(MBBI, AFI->getNumAlignedDPRCS2Regs());
// The code inserted by emitAlignedDPRCS2Spills realigns the stack, and
// leaves the stack pointer pointing to the DPRCS2 area.
//
// Adjust NumBytes to represent the stack slots below the DPRCS2 area.
NumBytes += MFI->getObjectOffset(D8SpillFI);
} else
NumBytes = DPRCSOffset;
if (NumBytes) {
// Adjust SP after all the callee-save spills.
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes,
MachineInstr::FrameSetup);
if (HasFP && isARM)
// Restore from fp only in ARM mode: e.g. sub sp, r7, #24
// Note it's not safe to do this in Thumb2 mode because it would have
// taken two instructions:
// mov sp, r7
// sub sp, #24
// If an interrupt is taken between the two instructions, then sp is in
// an inconsistent state (pointing to the middle of callee-saved area).
// The interrupt handler can end up clobbering the registers.
AFI->setShouldRestoreSPFromFP(true);
}
if (STI.isTargetELF() && hasFP(MF))
MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() -
AFI->getFramePtrSpillOffset());
AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
// If we need dynamic stack realignment, do it here. Be paranoid and make
// sure if we also have VLAs, we have a base pointer for frame access.
// If aligned NEON registers were spilled, the stack has already been
// realigned.
if (!AFI->getNumAlignedDPRCS2Regs() && RegInfo->needsStackRealignment(MF)) {
unsigned MaxAlign = MFI->getMaxAlignment();
assert (!AFI->isThumb1OnlyFunction());
if (!AFI->isThumbFunction()) {
// Emit bic sp, sp, MaxAlign
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
TII.get(ARM::BICri), ARM::SP)
.addReg(ARM::SP, RegState::Kill)
.addImm(MaxAlign-1)));
} else {
// We cannot use sp as source/dest register here, thus we're emitting the
// following sequence:
// mov r4, sp
// bic r4, r4, MaxAlign
// mov sp, r4
// FIXME: It will be better just to find spare register here.
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::R4)
.addReg(ARM::SP, RegState::Kill));
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
TII.get(ARM::t2BICri), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(MaxAlign-1)));
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP)
.addReg(ARM::R4, RegState::Kill));
}
AFI->setShouldRestoreSPFromFP(true);
}
// If we need a base pointer, set it up here. It's whatever the value
// of the stack pointer is at this point. Any variable size objects
// will be allocated after this, so we can still use the base pointer
// to reference locals.
// FIXME: Clarify FrameSetup flags here.
if (RegInfo->hasBasePointer(MF)) {
if (isARM)
BuildMI(MBB, MBBI, dl,
TII.get(ARM::MOVr), RegInfo->getBaseRegister())
.addReg(ARM::SP)
.addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
else
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
RegInfo->getBaseRegister())
.addReg(ARM::SP));
}
// If the frame has variable sized objects then the epilogue must restore
// the sp from fp. We can assume there's an FP here since hasFP already
// checks for hasVarSizedObjects.
if (MFI->hasVarSizedObjects())
AFI->setShouldRestoreSPFromFP(true);
}
void ARMFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
assert(MBBI->isReturn() && "Can only insert epilog into returning blocks");
unsigned RetOpcode = MBBI->getOpcode();
DebugLoc dl = MBBI->getDebugLoc();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
assert(!AFI->isThumb1OnlyFunction() &&
"This emitEpilogue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize();
int NumBytes = (int)MFI->getStackSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
if (!AFI->hasStackFrame()) {
if (NumBytes != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);
} else {
// Unwind MBBI to point to first LDR / VLDRD.
const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs();
if (MBBI != MBB.begin()) {
do
--MBBI;
while (MBBI != MBB.begin() && isCSRestore(MBBI, TII, CSRegs));
if (!isCSRestore(MBBI, TII, CSRegs))
++MBBI;
}
// Move SP to start of FP callee save spill area.
NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
AFI->getGPRCalleeSavedArea2Size() +
AFI->getDPRCalleeSavedAreaSize());
// Reset SP based on frame pointer only if the stack frame extends beyond
// frame pointer stack slot or target is ELF and the function has FP.
if (AFI->shouldRestoreSPFromFP()) {
NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
if (NumBytes) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, FramePtr, -NumBytes,
ARMCC::AL, 0, TII);
else {
// It's not possible to restore SP from FP in a single instruction.
// For iOS, this looks like:
// mov sp, r7
// sub sp, #24
// This is bad, if an interrupt is taken after the mov, sp is in an
// inconsistent state.
// Use the first callee-saved register as a scratch register.
assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
"No scratch register to restore SP from FP!");
emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
ARMCC::AL, 0, TII);
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
ARM::SP)
.addReg(ARM::R4));
}
} else {
// Thumb2 or ARM.
if (isARM)
BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), ARM::SP)
.addReg(FramePtr).addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
else
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),
ARM::SP)
.addReg(FramePtr));
}
} else if (NumBytes)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);
// Increment past our save areas.
if (AFI->getDPRCalleeSavedAreaSize()) {
MBBI++;
// Since vpop register list cannot have gaps, there may be multiple vpop
// instructions in the epilogue.
while (MBBI->getOpcode() == ARM::VLDMDIA_UPD)
MBBI++;
}
if (AFI->getGPRCalleeSavedArea2Size()) MBBI++;
if (AFI->getGPRCalleeSavedArea1Size()) MBBI++;
}
if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNri) {
// Tail call return: adjust the stack pointer and jump to callee.
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &JumpTarget = MBBI->getOperand(0);
// Jump to label or value in register.
if (RetOpcode == ARM::TCRETURNdi) {
unsigned TCOpcode = STI.isThumb() ?
(STI.isTargetIOS() ? ARM::tTAILJMPd : ARM::tTAILJMPdND) :
ARM::TAILJMPd;
MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(TCOpcode));
if (JumpTarget.isGlobal())
MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
JumpTarget.getTargetFlags());
else {
assert(JumpTarget.isSymbol());
MIB.addExternalSymbol(JumpTarget.getSymbolName(),
JumpTarget.getTargetFlags());
}
// Add the default predicate in Thumb mode.
if (STI.isThumb()) MIB.addImm(ARMCC::AL).addReg(0);
} else if (RetOpcode == ARM::TCRETURNri) {
BuildMI(MBB, MBBI, dl,
TII.get(STI.isThumb() ? ARM::tTAILJMPr : ARM::TAILJMPr)).
addReg(JumpTarget.getReg(), RegState::Kill);
}
MachineInstr *NewMI = prior(MBBI);
for (unsigned i = 1, e = MBBI->getNumOperands(); i != e; ++i)
NewMI->addOperand(MBBI->getOperand(i));
// Delete the pseudo instruction TCRETURN.
MBB.erase(MBBI);
MBBI = NewMI;
}
if (VARegSaveSize)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, VARegSaveSize);
}
/// getFrameIndexReference - Provide a base+offset reference to an FI slot for
/// debug info. It's the same as what we use for resolving the code-gen
/// references for now. FIXME: This can go wrong when references are
/// SP-relative and simple call frames aren't used.
int
ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
unsigned &FrameReg) const {
return ResolveFrameIndexReference(MF, FI, FrameReg, 0);
}
int
ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
int FI, unsigned &FrameReg,
int SPAdj) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
int Offset = MFI->getObjectOffset(FI) + MFI->getStackSize();
int FPOffset = Offset - AFI->getFramePtrSpillOffset();
bool isFixed = MFI->isFixedObjectIndex(FI);
FrameReg = ARM::SP;
Offset += SPAdj;
if (AFI->isGPRCalleeSavedArea1Frame(FI))
return Offset - AFI->getGPRCalleeSavedArea1Offset();
else if (AFI->isGPRCalleeSavedArea2Frame(FI))
return Offset - AFI->getGPRCalleeSavedArea2Offset();
else if (AFI->isDPRCalleeSavedAreaFrame(FI))
return Offset - AFI->getDPRCalleeSavedAreaOffset();
// SP can move around if there are allocas. We may also lose track of SP
// when emergency spilling inside a non-reserved call frame setup.
bool hasMovingSP = !hasReservedCallFrame(MF);
// When dynamically realigning the stack, use the frame pointer for
// parameters, and the stack/base pointer for locals.
if (RegInfo->needsStackRealignment(MF)) {
assert (hasFP(MF) && "dynamic stack realignment without a FP!");
if (isFixed) {
FrameReg = RegInfo->getFrameRegister(MF);
Offset = FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) &&
"VLAs and dynamic stack alignment, but missing base pointer!");
FrameReg = RegInfo->getBaseRegister();
}
return Offset;
}
// If there is a frame pointer, use it when we can.
if (hasFP(MF) && AFI->hasStackFrame()) {
// Use frame pointer to reference fixed objects. Use it for locals if
// there are VLAs (and thus the SP isn't reliable as a base).
if (isFixed || (hasMovingSP && !RegInfo->hasBasePointer(MF))) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
} else if (hasMovingSP) {
assert(RegInfo->hasBasePointer(MF) && "missing base pointer!");
if (AFI->isThumb2Function()) {
// Try to use the frame pointer if we can, else use the base pointer
// since it's available. This is handy for the emergency spill slot, in
// particular.
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
} else if (AFI->isThumb2Function()) {
// Use add <rd>, sp, #<imm8>
// ldr <rd>, [sp, #<imm8>]
// if at all possible to save space.
if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020)
return Offset;
// In Thumb2 mode, the negative offset is very limited. Try to avoid
// out of range references. ldr <rt>,[<rn>, #-<imm8>]
if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
} else if (Offset > (FPOffset < 0 ? -FPOffset : FPOffset)) {
// Otherwise, use SP or FP, whichever is closer to the stack slot.
FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset;
}
}
// Use the base pointer if we have one.
if (RegInfo->hasBasePointer(MF))
FrameReg = RegInfo->getBaseRegister();
return Offset;
}
int ARMFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
int FI) const {
unsigned FrameReg;
return getFrameIndexReference(MF, FI, FrameReg);
}
void ARMFrameLowering::emitPushInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
unsigned StmOpc, unsigned StrOpc,
bool NoGap,
bool(*Func)(unsigned, bool),
unsigned NumAlignedDPRCS2Regs,
unsigned MIFlags) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
DebugLoc DL;
if (MI != MBB.end()) DL = MI->getDebugLoc();
SmallVector<std::pair<unsigned,bool>, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
for (; i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (!(Func)(Reg, STI.isTargetIOS())) continue;
// D-registers in the aligned area DPRCS2 are NOT spilled here.
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
continue;
// Add the callee-saved register as live-in unless it's LR and
// @llvm.returnaddress is called. If LR is returned for
// @llvm.returnaddress then it's already added to the function and
// entry block live-in sets.
bool isKill = true;
if (Reg == ARM::LR) {
if (MF.getFrameInfo()->isReturnAddressTaken() &&
MF.getRegInfo().isLiveIn(Reg))
isKill = false;
}
if (isKill)
MBB.addLiveIn(Reg);
// If NoGap is true, push consecutive registers and then leave the rest
// for other instructions. e.g.
// vpush {d8, d10, d11} -> vpush {d8}, vpush {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
Regs.push_back(std::make_pair(Reg, isKill));
}
if (Regs.empty())
continue;
if (Regs.size() > 1 || StrOpc== 0) {
MachineInstrBuilder MIB =
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(StmOpc), ARM::SP)
.addReg(ARM::SP).setMIFlags(MIFlags));
for (unsigned i = 0, e = Regs.size(); i < e; ++i)
MIB.addReg(Regs[i].first, getKillRegState(Regs[i].second));
} else if (Regs.size() == 1) {
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(StrOpc),
ARM::SP)
.addReg(Regs[0].first, getKillRegState(Regs[0].second))
.addReg(ARM::SP).setMIFlags(MIFlags)
.addImm(-4);
AddDefaultPred(MIB);
}
Regs.clear();
}
}
void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
unsigned LdmOpc, unsigned LdrOpc,
bool isVarArg, bool NoGap,
bool(*Func)(unsigned, bool),
unsigned NumAlignedDPRCS2Regs) const {
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI->getDebugLoc();
unsigned RetOpcode = MI->getOpcode();
bool isTailCall = (RetOpcode == ARM::TCRETURNdi ||
RetOpcode == ARM::TCRETURNri);
SmallVector<unsigned, 4> Regs;
unsigned i = CSI.size();
while (i != 0) {
unsigned LastReg = 0;
bool DeleteRet = false;
for (; i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (!(Func)(Reg, STI.isTargetIOS())) continue;
// The aligned reloads from area DPRCS2 are not inserted here.
if (Reg >= ARM::D8 && Reg < ARM::D8 + NumAlignedDPRCS2Regs)
continue;
if (Reg == ARM::LR && !isTailCall && !isVarArg && STI.hasV5TOps()) {
Reg = ARM::PC;
LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
// Fold the return instruction into the LDM.
DeleteRet = true;
}
// If NoGap is true, pop consecutive registers and then leave the rest
// for other instructions. e.g.
// vpop {d8, d10, d11} -> vpop {d8}, vpop {d10, d11}
if (NoGap && LastReg && LastReg != Reg-1)
break;
LastReg = Reg;
Regs.push_back(Reg);
}
if (Regs.empty())
continue;
if (Regs.size() > 1 || LdrOpc == 0) {
MachineInstrBuilder MIB =
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(LdmOpc), ARM::SP)
.addReg(ARM::SP));
for (unsigned i = 0, e = Regs.size(); i < e; ++i)
MIB.addReg(Regs[i], getDefRegState(true));
if (DeleteRet) {
MIB->copyImplicitOps(&*MI);
MI->eraseFromParent();
}
MI = MIB;
} else if (Regs.size() == 1) {
// If we adjusted the reg to PC from LR above, switch it back here. We
// only do that for LDM.
if (Regs[0] == ARM::PC)
Regs[0] = ARM::LR;
MachineInstrBuilder MIB =
BuildMI(MBB, MI, DL, TII.get(LdrOpc), Regs[0])
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP);
// ARM mode needs an extra reg0 here due to addrmode2. Will go away once
// that refactoring is complete (eventually).
if (LdrOpc == ARM::LDR_POST_REG || LdrOpc == ARM::LDR_POST_IMM) {
MIB.addReg(0);
MIB.addImm(ARM_AM::getAM2Opc(ARM_AM::add, 4, ARM_AM::no_shift));
} else
MIB.addImm(4);
AddDefaultPred(MIB);
}
Regs.clear();
}
}
/// Emit aligned spill instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. Also insert stack realignment code and leave the stack
/// pointer pointing to the d8 spill slot.
static void emitAlignedDPRCS2Spills(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI->getDebugLoc();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
MachineFrameInfo &MFI = *MF.getFrameInfo();
// Mark the D-register spill slots as properly aligned. Since MFI computes
// stack slot layout backwards, this can actually mean that the d-reg stack
// slot offsets can be wrong. The offset for d8 will always be correct.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned DNum = CSI[i].getReg() - ARM::D8;
if (DNum >= 8)
continue;
int FI = CSI[i].getFrameIdx();
// The even-numbered registers will be 16-byte aligned, the odd-numbered
// registers will be 8-byte aligned.
MFI.setObjectAlignment(FI, DNum % 2 ? 8 : 16);
// The stack slot for D8 needs to be maximally aligned because this is
// actually the point where we align the stack pointer. MachineFrameInfo
// computes all offsets relative to the incoming stack pointer which is a
// bit weird when realigning the stack. Any extra padding for this
// over-alignment is not realized because the code inserted below adjusts
// the stack pointer by numregs * 8 before aligning the stack pointer.
if (DNum == 0)
MFI.setObjectAlignment(FI, MFI.getMaxAlignment());
}
// Move the stack pointer to the d8 spill slot, and align it at the same
// time. Leave the stack slot address in the scratch register r4.
//
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
//
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
AFI->setShouldRestoreSPFromFP(true);
// sub r4, sp, #numregs * 8
// The immediate is <= 64, so it doesn't need any special encoding.
unsigned Opc = isThumb ? ARM::t2SUBri : ARM::SUBri;
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addReg(ARM::SP)
.addImm(8 * NumAlignedDPRCS2Regs)));
// bic r4, r4, #align-1
Opc = isThumb ? ARM::t2BICri : ARM::BICri;
unsigned MaxAlign = MF.getFrameInfo()->getMaxAlignment();
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addReg(ARM::R4, RegState::Kill)
.addImm(MaxAlign - 1)));
// mov sp, r4
// The stack pointer must be adjusted before spilling anything, otherwise
// the stack slots could be clobbered by an interrupt handler.
// Leave r4 live, it is used below.
Opc = isThumb ? ARM::tMOVr : ARM::MOVr;
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(Opc), ARM::SP)
.addReg(ARM::R4);
MIB = AddDefaultPred(MIB);
if (!isThumb)
AddDefaultCC(MIB);
// Now spill NumAlignedDPRCS2Regs registers starting from d8.
// r4 holds the stack slot address.
unsigned NextReg = ARM::D8;
// 16-byte aligned vst1.64 with 4 d-regs and address writeback.
// The writeback is only needed when emitting two vst1.64 instructions.
if (NumAlignedDPRCS2Regs >= 6) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
ARM::QQPRRegisterClass);
MBB.addLiveIn(SupReg);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Qwb_fixed),
ARM::R4)
.addReg(ARM::R4, RegState::Kill).addImm(16)
.addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vst1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
ARM::QQPRRegisterClass);
MBB.addLiveIn(SupReg);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1d64Q))
.addReg(ARM::R4).addImm(16).addReg(NextReg)
.addReg(SupReg, RegState::ImplicitKill));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vst1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
ARM::QPRRegisterClass);
MBB.addLiveIn(SupReg);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VST1q64))
.addReg(ARM::R4).addImm(16).addReg(SupReg));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vstr.64 for the odd last register.
if (NumAlignedDPRCS2Regs) {
MBB.addLiveIn(NextReg);
// vstr.64 uses addrmode5 which has an offset scale of 4.
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VSTRD))
.addReg(NextReg)
.addReg(ARM::R4).addImm((NextReg-R4BaseReg)*2));
}
// The last spill instruction inserted should kill the scratch register r4.
llvm::prior(MI)->addRegisterKilled(ARM::R4, TRI);
}
/// Skip past the code inserted by emitAlignedDPRCS2Spills, and return an
/// iterator to the following instruction.
static MachineBasicBlock::iterator
skipAlignedDPRCS2Spills(MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs) {
// sub r4, sp, #numregs * 8
// bic r4, r4, #align - 1
// mov sp, r4
++MI; ++MI; ++MI;
assert(MI->mayStore() && "Expecting spill instruction");
// These switches all fall through.
switch(NumAlignedDPRCS2Regs) {
case 7:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
default:
++MI;
assert(MI->mayStore() && "Expecting spill instruction");
case 1:
case 2:
case 4:
assert(MI->killsRegister(ARM::R4) && "Missed kill flag");
++MI;
}
return MI;
}
/// Emit aligned reload instructions for NumAlignedDPRCS2Regs D-registers
/// starting from d8. These instructions are assumed to execute while the
/// stack is still aligned, unlike the code inserted by emitPopInst.
static void emitAlignedDPRCS2Restores(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
unsigned NumAlignedDPRCS2Regs,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) {
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL = MI->getDebugLoc();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
// Find the frame index assigned to d8.
int D8SpillFI = 0;
for (unsigned i = 0, e = CSI.size(); i != e; ++i)
if (CSI[i].getReg() == ARM::D8) {
D8SpillFI = CSI[i].getFrameIdx();
break;
}
// Materialize the address of the d8 spill slot into the scratch register r4.
// This can be fairly complicated if the stack frame is large, so just use
// the normal frame index elimination mechanism to do it. This code runs as
// the initial part of the epilog where the stack and base pointers haven't
// been changed yet.
bool isThumb = AFI->isThumbFunction();
assert(!AFI->isThumb1OnlyFunction() && "Can't realign stack for thumb1");
unsigned Opc = isThumb ? ARM::t2ADDri : ARM::ADDri;
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(Opc), ARM::R4)
.addFrameIndex(D8SpillFI).addImm(0)));
// Now restore NumAlignedDPRCS2Regs registers starting from d8.
unsigned NextReg = ARM::D8;
// 16-byte aligned vld1.64 with 4 d-regs and writeback.
if (NumAlignedDPRCS2Regs >= 6) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
ARM::QQPRRegisterClass);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Qwb_fixed), NextReg)
.addReg(ARM::R4, RegState::Define)
.addReg(ARM::R4, RegState::Kill).addImm(16)
.addReg(SupReg, RegState::ImplicitDefine));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// We won't modify r4 beyond this point. It currently points to the next
// register to be spilled.
unsigned R4BaseReg = NextReg;
// 16-byte aligned vld1.64 with 4 d-regs, no writeback.
if (NumAlignedDPRCS2Regs >= 4) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
ARM::QQPRRegisterClass);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1d64Q), NextReg)
.addReg(ARM::R4).addImm(16)
.addReg(SupReg, RegState::ImplicitDefine));
NextReg += 4;
NumAlignedDPRCS2Regs -= 4;
}
// 16-byte aligned vld1.64 with 2 d-regs.
if (NumAlignedDPRCS2Regs >= 2) {
unsigned SupReg = TRI->getMatchingSuperReg(NextReg, ARM::dsub_0,
ARM::QPRRegisterClass);
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLD1q64), SupReg)
.addReg(ARM::R4).addImm(16));
NextReg += 2;
NumAlignedDPRCS2Regs -= 2;
}
// Finally, use a vanilla vldr.64 for the remaining odd register.
if (NumAlignedDPRCS2Regs)
AddDefaultPred(BuildMI(MBB, MI, DL, TII.get(ARM::VLDRD), NextReg)
.addReg(ARM::R4).addImm(2*(NextReg-R4BaseReg)));
// Last store kills r4.
llvm::prior(MI)->addRegisterKilled(ARM::R4, TRI);
}
bool ARMFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
unsigned PushOpc = AFI->isThumbFunction() ? ARM::t2STMDB_UPD : ARM::STMDB_UPD;
unsigned PushOneOpc = AFI->isThumbFunction() ?
ARM::t2STR_PRE : ARM::STR_PRE_IMM;
unsigned FltOpc = ARM::VSTMDDB_UPD;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea1Register, 0,
MachineInstr::FrameSetup);
emitPushInst(MBB, MI, CSI, PushOpc, PushOneOpc, false, &isARMArea2Register, 0,
MachineInstr::FrameSetup);
emitPushInst(MBB, MI, CSI, FltOpc, 0, true, &isARMArea3Register,
NumAlignedDPRCS2Regs, MachineInstr::FrameSetup);
// The code above does not insert spill code for the aligned DPRCS2 registers.
// The stack realignment code will be inserted between the push instructions
// and these spills.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Spills(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
return true;
}
bool ARMFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
MachineFunction &MF = *MBB.getParent();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
bool isVarArg = AFI->getVarArgsRegSaveSize() > 0;
unsigned NumAlignedDPRCS2Regs = AFI->getNumAlignedDPRCS2Regs();
// The emitPopInst calls below do not insert reloads for the aligned DPRCS2
// registers. Do that here instead.
if (NumAlignedDPRCS2Regs)
emitAlignedDPRCS2Restores(MBB, MI, NumAlignedDPRCS2Regs, CSI, TRI);
unsigned PopOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_UPD : ARM::LDMIA_UPD;
unsigned LdrOpc = AFI->isThumbFunction() ? ARM::t2LDR_POST :ARM::LDR_POST_IMM;
unsigned FltOpc = ARM::VLDMDIA_UPD;
emitPopInst(MBB, MI, CSI, FltOpc, 0, isVarArg, true, &isARMArea3Register,
NumAlignedDPRCS2Regs);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
&isARMArea2Register, 0);
emitPopInst(MBB, MI, CSI, PopOpc, LdrOpc, isVarArg, false,
&isARMArea1Register, 0);
return true;
}
// FIXME: Make generic?
static unsigned GetFunctionSizeInBytes(const MachineFunction &MF,
const ARMBaseInstrInfo &TII) {
unsigned FnSize = 0;
for (MachineFunction::const_iterator MBBI = MF.begin(), E = MF.end();
MBBI != E; ++MBBI) {
const MachineBasicBlock &MBB = *MBBI;
for (MachineBasicBlock::const_iterator I = MBB.begin(),E = MBB.end();
I != E; ++I)
FnSize += TII.GetInstSizeInBytes(I);
}
return FnSize;
}
/// estimateStackSize - Estimate and return the size of the frame.
/// FIXME: Make generic?
static unsigned estimateStackSize(MachineFunction &MF) {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering();
const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
unsigned MaxAlign = MFI->getMaxAlignment();
int Offset = 0;
// This code is very, very similar to PEI::calculateFrameObjectOffsets().
// It really should be refactored to share code. Until then, changes
// should keep in mind that there's tight coupling between the two.
for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
int FixedOff = -MFI->getObjectOffset(i);
if (FixedOff > Offset) Offset = FixedOff;
}
for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
if (MFI->isDeadObjectIndex(i))
continue;
Offset += MFI->getObjectSize(i);
unsigned Align = MFI->getObjectAlignment(i);
// Adjust to alignment boundary
Offset = (Offset+Align-1)/Align*Align;
MaxAlign = std::max(Align, MaxAlign);
}
if (MFI->adjustsStack() && TFI->hasReservedCallFrame(MF))
Offset += MFI->getMaxCallFrameSize();
// Round up the size to a multiple of the alignment. If the function has
// any calls or alloca's, align to the target's StackAlignment value to
// ensure that the callee's frame or the alloca data is suitably aligned;
// otherwise, for leaf functions, align to the TransientStackAlignment
// value.
unsigned StackAlign;
if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
(RegInfo->needsStackRealignment(MF) && MFI->getObjectIndexEnd() != 0))
StackAlign = TFI->getStackAlignment();
else
StackAlign = TFI->getTransientStackAlignment();
// If the frame pointer is eliminated, all frame offsets will be relative to
// SP not FP. Align to MaxAlign so this works.
StackAlign = std::max(StackAlign, MaxAlign);
unsigned AlignMask = StackAlign - 1;
Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
return (unsigned)Offset;
}
/// estimateRSStackSizeLimit - Look at each instruction that references stack
/// frames and return the stack size limit beyond which some of these
/// instructions will require a scratch register during their expansion later.
// FIXME: Move to TII?
static unsigned estimateRSStackSizeLimit(MachineFunction &MF,
const TargetFrameLowering *TFI) {
const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
unsigned Limit = (1 << 12) - 1;
for (MachineFunction::iterator BB = MF.begin(),E = MF.end(); BB != E; ++BB) {
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
I != E; ++I) {
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
if (!I->getOperand(i).isFI()) continue;
// When using ADDri to get the address of a stack object, 255 is the
// largest offset guaranteed to fit in the immediate offset.
if (I->getOpcode() == ARM::ADDri) {
Limit = std::min(Limit, (1U << 8) - 1);
break;
}
// Otherwise check the addressing mode.
switch (I->getDesc().TSFlags & ARMII::AddrModeMask) {
case ARMII::AddrMode3:
case ARMII::AddrModeT2_i8:
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode5:
case ARMII::AddrModeT2_i8s4:
Limit = std::min(Limit, ((1U << 8) - 1) * 4);
break;
case ARMII::AddrModeT2_i12:
// i12 supports only positive offset so these will be converted to
// i8 opcodes. See llvm::rewriteT2FrameIndex.
if (TFI->hasFP(MF) && AFI->hasStackFrame())
Limit = std::min(Limit, (1U << 8) - 1);
break;
case ARMII::AddrMode4:
case ARMII::AddrMode6:
// Addressing modes 4 & 6 (load/store) instructions can't encode an
// immediate offset for stack references.
return 0;
default:
break;
}
break; // At most one FI per instruction
}
}
}
return Limit;
}
// In functions that realign the stack, it can be an advantage to spill the
// callee-saved vector registers after realigning the stack. The vst1 and vld1
// instructions take alignment hints that can improve performance.
//
static void checkNumAlignedDPRCS2Regs(MachineFunction &MF) {
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(0);
if (!SpillAlignedNEONRegs)
return;
// Naked functions don't spill callee-saved registers.
if (MF.getFunction()->hasFnAttr(Attribute::Naked))
return;
// We are planning to use NEON instructions vst1 / vld1.
if (!MF.getTarget().getSubtarget<ARMSubtarget>().hasNEON())
return;
// Don't bother if the default stack alignment is sufficiently high.
if (MF.getTarget().getFrameLowering()->getStackAlignment() >= 8)
return;
// Aligned spills require stack realignment.
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
if (!RegInfo->canRealignStack(MF))
return;
// We always spill contiguous d-registers starting from d8. Count how many
// needs spilling. The register allocator will almost always use the
// callee-saved registers in order, but it can happen that there are holes in
// the range. Registers above the hole will be spilled to the standard DPRCS
// area.
MachineRegisterInfo &MRI = MF.getRegInfo();
unsigned NumSpills = 0;
for (; NumSpills < 8; ++NumSpills)
if (!MRI.isPhysRegOrOverlapUsed(ARM::D8 + NumSpills))
break;
// Don't do this for just one d-register. It's not worth it.
if (NumSpills < 2)
return;
// Spill the first NumSpills D-registers after realigning the stack.
MF.getInfo<ARMFunctionInfo>()->setNumAlignedDPRCS2Regs(NumSpills);
// A scratch register is required for the vst1 / vld1 instructions.
MF.getRegInfo().setPhysRegUsed(ARM::R4);
}
void
ARMFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
RegScavenger *RS) const {
// This tells PEI to spill the FP as if it is any other callee-save register
// to take advantage the eliminateFrameIndex machinery. This also ensures it
// is spilled in the order specified by getCalleeSavedRegs() to make it easier
// to combine multiple loads / stores.
bool CanEliminateFrame = true;
bool CS1Spilled = false;
bool LRSpilled = false;
unsigned NumGPRSpills = 0;
SmallVector<unsigned, 4> UnspilledCS1GPRs;
SmallVector<unsigned, 4> UnspilledCS2GPRs;
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(MF.getTarget().getRegisterInfo());
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
MachineFrameInfo *MFI = MF.getFrameInfo();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
// Spill R4 if Thumb2 function requires stack realignment - it will be used as
// scratch register. Also spill R4 if Thumb2 function has varsized objects,
// since it's not always possible to restore sp from fp in a single
// instruction.
// FIXME: It will be better just to find spare register here.
if (AFI->isThumb2Function() &&
(MFI->hasVarSizedObjects() || RegInfo->needsStackRealignment(MF)))
MF.getRegInfo().setPhysRegUsed(ARM::R4);
if (AFI->isThumb1OnlyFunction()) {
// Spill LR if Thumb1 function uses variable length argument lists.
if (AFI->getVarArgsRegSaveSize() > 0)
MF.getRegInfo().setPhysRegUsed(ARM::LR);
// Spill R4 if Thumb1 epilogue has to restore SP from FP. We don't know
// for sure what the stack size will be, but for this, an estimate is good
// enough. If there anything changes it, it'll be a spill, which implies
// we've used all the registers and so R4 is already used, so not marking
// it here will be OK.
// FIXME: It will be better just to find spare register here.
unsigned StackSize = estimateStackSize(MF);
if (MFI->hasVarSizedObjects() || StackSize > 508)
MF.getRegInfo().setPhysRegUsed(ARM::R4);
}
// See if we can spill vector registers to aligned stack.
checkNumAlignedDPRCS2Regs(MF);
// Spill the BasePtr if it's used.
if (RegInfo->hasBasePointer(MF))
MF.getRegInfo().setPhysRegUsed(RegInfo->getBaseRegister());
// Don't spill FP if the frame can be eliminated. This is determined
// by scanning the callee-save registers to see if any is used.
const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs();
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
bool Spilled = false;
if (MF.getRegInfo().isPhysRegOrOverlapUsed(Reg)) {
Spilled = true;
CanEliminateFrame = false;
}
if (!ARM::GPRRegisterClass->contains(Reg))
continue;
if (Spilled) {
NumGPRSpills++;
if (!STI.isTargetIOS()) {
if (Reg == ARM::LR)
LRSpilled = true;
CS1Spilled = true;
continue;
}
// Keep track if LR and any of R4, R5, R6, and R7 is spilled.
switch (Reg) {
case ARM::LR:
LRSpilled = true;
// Fallthrough
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
CS1Spilled = true;
break;
default:
break;
}
} else {
if (!STI.isTargetIOS()) {
UnspilledCS1GPRs.push_back(Reg);
continue;
}
switch (Reg) {
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
case ARM::LR:
UnspilledCS1GPRs.push_back(Reg);
break;
default:
UnspilledCS2GPRs.push_back(Reg);
break;
}
}
}
bool ForceLRSpill = false;
if (!LRSpilled && AFI->isThumb1OnlyFunction()) {
unsigned FnSize = GetFunctionSizeInBytes(MF, TII);
// Force LR to be spilled if the Thumb function size is > 2048. This enables
// use of BL to implement far jump. If it turns out that it's not needed
// then the branch fix up path will undo it.
if (FnSize >= (1 << 11)) {
CanEliminateFrame = false;
ForceLRSpill = true;
}
}
// If any of the stack slot references may be out of range of an immediate
// offset, make sure a register (or a spill slot) is available for the
// register scavenger. Note that if we're indexing off the frame pointer, the
// effective stack size is 4 bytes larger since the FP points to the stack
// slot of the previous FP. Also, if we have variable sized objects in the
// function, stack slot references will often be negative, and some of
// our instructions are positive-offset only, so conservatively consider
// that case to want a spill slot (or register) as well. Similarly, if
// the function adjusts the stack pointer during execution and the
// adjustments aren't already part of our stack size estimate, our offset
// calculations may be off, so be conservative.
// FIXME: We could add logic to be more precise about negative offsets
// and which instructions will need a scratch register for them. Is it
// worth the effort and added fragility?
bool BigStack =
(RS &&
(estimateStackSize(MF) + ((hasFP(MF) && AFI->hasStackFrame()) ? 4:0) >=
estimateRSStackSizeLimit(MF, this)))
|| MFI->hasVarSizedObjects()
|| (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF));
bool ExtraCSSpill = false;
if (BigStack || !CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) {
AFI->setHasStackFrame(true);
// If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
// Spill LR as well so we can fold BX_RET to the registers restore (LDM).
if (!LRSpilled && CS1Spilled) {
MF.getRegInfo().setPhysRegUsed(ARM::LR);
NumGPRSpills++;
UnspilledCS1GPRs.erase(std::find(UnspilledCS1GPRs.begin(),
UnspilledCS1GPRs.end(), (unsigned)ARM::LR));
ForceLRSpill = false;
ExtraCSSpill = true;
}
if (hasFP(MF)) {
MF.getRegInfo().setPhysRegUsed(FramePtr);
NumGPRSpills++;
}
// If stack and double are 8-byte aligned and we are spilling an odd number
// of GPRs, spill one extra callee save GPR so we won't have to pad between
// the integer and double callee save areas.
unsigned TargetAlign = getStackAlignment();
if (TargetAlign == 8 && (NumGPRSpills & 1)) {
if (CS1Spilled && !UnspilledCS1GPRs.empty()) {
for (unsigned i = 0, e = UnspilledCS1GPRs.size(); i != e; ++i) {
unsigned Reg = UnspilledCS1GPRs[i];
// Don't spill high register if the function is thumb1
if (!AFI->isThumb1OnlyFunction() ||
isARMLowRegister(Reg) || Reg == ARM::LR) {
MF.getRegInfo().setPhysRegUsed(Reg);
if (!RegInfo->isReservedReg(MF, Reg))
ExtraCSSpill = true;
break;
}
}
} else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) {
unsigned Reg = UnspilledCS2GPRs.front();
MF.getRegInfo().setPhysRegUsed(Reg);
if (!RegInfo->isReservedReg(MF, Reg))
ExtraCSSpill = true;
}
}
// Estimate if we might need to scavenge a register at some point in order
// to materialize a stack offset. If so, either spill one additional
// callee-saved register or reserve a special spill slot to facilitate
// register scavenging. Thumb1 needs a spill slot for stack pointer
// adjustments also, even when the frame itself is small.
if (BigStack && !ExtraCSSpill) {
// If any non-reserved CS register isn't spilled, just spill one or two
// extra. That should take care of it!
unsigned NumExtras = TargetAlign / 4;
SmallVector<unsigned, 2> Extras;
while (NumExtras && !UnspilledCS1GPRs.empty()) {
unsigned Reg = UnspilledCS1GPRs.back();
UnspilledCS1GPRs.pop_back();
if (!RegInfo->isReservedReg(MF, Reg) &&
(!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg) ||
Reg == ARM::LR)) {
Extras.push_back(Reg);
NumExtras--;
}
}
// For non-Thumb1 functions, also check for hi-reg CS registers
if (!AFI->isThumb1OnlyFunction()) {
while (NumExtras && !UnspilledCS2GPRs.empty()) {
unsigned Reg = UnspilledCS2GPRs.back();
UnspilledCS2GPRs.pop_back();
if (!RegInfo->isReservedReg(MF, Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
}
if (Extras.size() && NumExtras == 0) {
for (unsigned i = 0, e = Extras.size(); i != e; ++i) {
MF.getRegInfo().setPhysRegUsed(Extras[i]);
}
} else if (!AFI->isThumb1OnlyFunction()) {
// note: Thumb1 functions spill to R12, not the stack. Reserve a slot
// closest to SP or frame pointer.
const TargetRegisterClass *RC = ARM::GPRRegisterClass;
RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
}
}
if (ForceLRSpill) {
MF.getRegInfo().setPhysRegUsed(ARM::LR);
AFI->setLRIsSpilledForFarJump(true);
}
}