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llvm-6502/lib/Target/ARM/ARMFrameLowering.cpp
Tim Northover de70176f5f Segmented stacks: omit __morestack call when there's no frame. 
Patch by Florian Zeitz

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209436 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-22 13:03:43 +00:00

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//===-- 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 "ARMConstantPoolValue.h"
#include "ARMMachineFunctionInfo.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/CallingConv.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCContext.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetOptions.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 isCSRestore(MachineInstr *MI,
const ARMBaseInstrInfo &TII,
const MCPhysReg *CSRegs) {
// Integer spill area is handled with "pop".
if (isPopOpcode(MI->getOpcode())) {
// 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 emitRegPlusImmediate(bool isARM, MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI, DebugLoc dl,
const ARMBaseInstrInfo &TII, unsigned DestReg,
unsigned SrcReg, int NumBytes,
unsigned MIFlags = MachineInstr::NoFlags,
ARMCC::CondCodes Pred = ARMCC::AL,
unsigned PredReg = 0) {
if (isARM)
emitARMRegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes,
Pred, PredReg, TII, MIFlags);
else
emitT2RegPlusImmediate(MBB, MBBI, dl, DestReg, SrcReg, NumBytes,
Pred, PredReg, TII, MIFlags);
}
static void emitSPUpdate(bool isARM, MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI, DebugLoc dl,
const ARMBaseInstrInfo &TII, int NumBytes,
unsigned MIFlags = MachineInstr::NoFlags,
ARMCC::CondCodes Pred = ARMCC::AL,
unsigned PredReg = 0) {
emitRegPlusImmediate(isARM, MBB, MBBI, dl, TII, ARM::SP, ARM::SP, NumBytes,
MIFlags, Pred, PredReg);
}
static int sizeOfSPAdjustment(const MachineInstr *MI) {
assert(MI->getOpcode() == ARM::VSTMDDB_UPD);
int count = 0;
// ARM and Thumb2 push/pop insts have explicit "sp, sp" operands (+
// pred) so the list starts at 4.
for (int i = MI->getNumOperands() - 1; i >= 4; --i)
count += 8;
return count;
}
static bool WindowsRequiresStackProbe(const MachineFunction &MF,
size_t StackSizeInBytes) {
const MachineFrameInfo *MFI = MF.getFrameInfo();
if (MFI->getStackProtectorIndex() > 0)
return StackSizeInBytes >= 4080;
return StackSizeInBytes >= 4096;
}
void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front();
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
MachineModuleInfo &MMI = MF.getMMI();
MCContext &Context = MMI.getContext();
const TargetMachine &TM = MF.getTarget();
const MCRegisterInfo *MRI = Context.getRegisterInfo();
const ARMBaseRegisterInfo *RegInfo =
static_cast<const ARMBaseRegisterInfo*>(TM.getRegisterInfo());
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(TM.getInstrInfo());
assert(!AFI->isThumb1OnlyFunction() &&
"This emitPrologue does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
unsigned Align = TM.getFrameLowering()->getStackAlignment();
unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align);
unsigned NumBytes = MFI->getStackSize();
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
int CFAOffset = 0;
// 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;
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction()->getCallingConv() == CallingConv::GHC)
return;
// Allocate the vararg register save area.
if (ArgRegsSaveSize) {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -ArgRegsSaveSize,
MachineInstr::FrameSetup);
CFAOffset -= ArgRegsSaveSize;
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
if (!AFI->hasStackFrame() &&
(!STI.isTargetWindows() || !WindowsRequiresStackProbe(MF, NumBytes))) {
if (NumBytes - ArgRegsSaveSize != 0) {
emitSPUpdate(isARM, MBB, MBBI, dl, TII, -(NumBytes - ArgRegsSaveSize),
MachineInstr::FrameSetup);
CFAOffset -= NumBytes - ArgRegsSaveSize;
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
return;
}
// Determine spill area sizes.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
int FI = CSI[i].getFrameIdx();
switch (Reg) {
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
case ARM::R12:
if (STI.isTargetMachO()) {
GPRCS2Size += 4;
break;
}
// fallthrough
case ARM::R0:
case ARM::R1:
case ARM::R2:
case ARM::R3:
case ARM::R4:
case ARM::R5:
case ARM::R6:
case ARM::R7:
case ARM::LR:
if (Reg == FramePtr)
FramePtrSpillFI = 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())
DPRCSSize += 8;
}
}
// Move past area 1.
MachineBasicBlock::iterator LastPush = MBB.end(), GPRCS1Push, GPRCS2Push,
DPRCSPush;
if (GPRCS1Size > 0)
GPRCS1Push = LastPush = MBBI++;
// Determine starting offsets of spill areas.
bool HasFP = hasFP(MF);
unsigned DPRCSOffset = NumBytes - (ArgRegsSaveSize + GPRCS1Size
+ GPRCS2Size + DPRCSSize);
unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
int FramePtrOffsetInPush = 0;
if (HasFP) {
FramePtrOffsetInPush = MFI->getObjectOffset(FramePtrSpillFI)
+ GPRCS1Size + ArgRegsSaveSize;
AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) +
NumBytes);
}
AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
// Move past area 2.
if (GPRCS2Size > 0)
GPRCS2Push = LastPush = MBBI++;
// Move past area 3.
if (DPRCSSize > 0) {
DPRCSPush = MBBI;
// Since vpush register list cannot have gaps, there may be multiple vpush
// instructions in the prologue.
while (MBBI->getOpcode() == ARM::VSTMDDB_UPD)
LastPush = 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 (STI.isTargetWindows() && WindowsRequiresStackProbe(MF, NumBytes)) {
uint32_t NumWords = NumBytes >> 2;
if (NumWords < 65536)
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), ARM::R4)
.addImm(NumWords)
.setMIFlags(MachineInstr::FrameSetup));
else
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R4)
.addImm(NumWords)
.setMIFlags(MachineInstr::FrameSetup);
switch (TM.getCodeModel()) {
case CodeModel::Small:
case CodeModel::Medium:
case CodeModel::Default:
case CodeModel::Kernel:
BuildMI(MBB, MBBI, dl, TII.get(ARM::tBL))
.addImm((unsigned)ARMCC::AL).addReg(0)
.addExternalSymbol("__chkstk")
.addReg(ARM::R4, RegState::Implicit)
.setMIFlags(MachineInstr::FrameSetup);
break;
case CodeModel::Large:
case CodeModel::JITDefault:
BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi32imm), ARM::R12)
.addExternalSymbol("__chkstk")
.setMIFlags(MachineInstr::FrameSetup);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tBLXr))
.addImm((unsigned)ARMCC::AL).addReg(0)
.addReg(ARM::R12, RegState::Kill)
.addReg(ARM::R4, RegState::Implicit)
.setMIFlags(MachineInstr::FrameSetup);
break;
}
AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr),
ARM::SP)
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::R4, RegState::Kill)
.setMIFlags(MachineInstr::FrameSetup)));
NumBytes = 0;
}
unsigned adjustedGPRCS1Size = GPRCS1Size;
if (NumBytes) {
// Adjust SP after all the callee-save spills.
if (tryFoldSPUpdateIntoPushPop(STI, MF, LastPush, NumBytes)) {
if (LastPush == GPRCS1Push) {
FramePtrOffsetInPush += NumBytes;
adjustedGPRCS1Size += NumBytes;
NumBytes = 0;
}
} else
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 (adjustedGPRCS1Size > 0) {
CFAOffset -= adjustedGPRCS1Size;
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
MachineBasicBlock::iterator Pos = ++GPRCS1Push;
BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
for (const auto &Entry : CSI) {
unsigned Reg = Entry.getReg();
int FI = Entry.getFrameIdx();
switch (Reg) {
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
case ARM::R12:
if (STI.isTargetMachO())
break;
// fallthrough
case ARM::R0:
case ARM::R1:
case ARM::R2:
case ARM::R3:
case ARM::R4:
case ARM::R5:
case ARM::R6:
case ARM::R7:
case ARM::LR:
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(Reg, true), MFI->getObjectOffset(FI)));
BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
break;
}
}
}
// 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 in area one and the adjustment needs to take place just after
// that push.
if (HasFP) {
emitRegPlusImmediate(!AFI->isThumbFunction(), MBB, GPRCS1Push, dl, TII,
FramePtr, ARM::SP, FramePtrOffsetInPush,
MachineInstr::FrameSetup);
if (FramePtrOffsetInPush) {
CFAOffset += FramePtrOffsetInPush;
unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfa(
nullptr, MRI->getDwarfRegNum(FramePtr, true), CFAOffset));
BuildMI(MBB, GPRCS1Push, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
} else {
unsigned CFIIndex =
MMI.addFrameInst(MCCFIInstruction::createDefCfaRegister(
nullptr, MRI->getDwarfRegNum(FramePtr, true)));
BuildMI(MBB, GPRCS1Push, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
}
if (GPRCS2Size > 0) {
MachineBasicBlock::iterator Pos = ++GPRCS2Push;
if (!HasFP) {
CFAOffset -= GPRCS2Size;
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
for (const auto &Entry : CSI) {
unsigned Reg = Entry.getReg();
int FI = Entry.getFrameIdx();
switch (Reg) {
case ARM::R8:
case ARM::R9:
case ARM::R10:
case ARM::R11:
case ARM::R12:
if (STI.isTargetMachO()) {
unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
unsigned Offset = MFI->getObjectOffset(FI);
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
BuildMI(MBB, Pos, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
break;
}
}
}
if (DPRCSSize > 0) {
// Since vpush register list cannot have gaps, there may be multiple vpush
// instructions in the prologue.
do {
MachineBasicBlock::iterator Push = DPRCSPush++;
if (!HasFP) {
CFAOffset -= sizeOfSPAdjustment(Push);
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
BuildMI(MBB, DPRCSPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
} while (DPRCSPush->getOpcode() == ARM::VSTMDDB_UPD);
for (const auto &Entry : CSI) {
unsigned Reg = Entry.getReg();
int FI = Entry.getFrameIdx();
if ((Reg >= ARM::D0 && Reg <= ARM::D31) &&
(Reg < ARM::D8 || Reg >= ARM::D8 + AFI->getNumAlignedDPRCS2Regs())) {
unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
unsigned Offset = MFI->getObjectOffset(FI);
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(nullptr, DwarfReg, Offset));
BuildMI(MBB, DPRCSPush, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
}
}
if (NumBytes) {
if (!HasFP) {
CFAOffset -= NumBytes;
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
}
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 Align = MF.getTarget().getFrameLowering()->getStackAlignment();
unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align);
int NumBytes = (int)MFI->getStackSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
// All calls are tail calls in GHC calling conv, and functions have no
// prologue/epilogue.
if (MF.getFunction()->getCallingConv() == CallingConv::GHC)
return;
if (!AFI->hasStackFrame()) {
if (NumBytes - ArgRegsSaveSize != 0)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes - ArgRegsSaveSize);
} else {
// Unwind MBBI to point to first LDR / VLDRD.
const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF);
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 -= (ArgRegsSaveSize +
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 &&
!tryFoldSPUpdateIntoPushPop(STI, MF, MBBI, 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.isTargetMachO() ? 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 = std::prev(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 (ArgRegsSaveSize)
emitSPUpdate(isARM, MBB, MBBI, dl, TII, ArgRegsSaveSize);
}
/// 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;
// 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.isTargetMachO())) 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();
// Put any subsequent vpush instructions before this one: they will refer to
// higher register numbers so need to be pushed first in order to preserve
// monotonicity.
--MI;
}
}
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);
bool isInterrupt =
RetOpcode == ARM::SUBS_PC_LR || RetOpcode == ARM::t2SUBS_PC_LR;
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.isTargetMachO())) 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 && !isInterrupt &&
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();
// Put any subsequent vpop instructions after this one: they will refer to
// higher register numbers so need to be popped afterwards.
++MI;
}
}
/// 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::QQPRRegClass);
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::QQPRRegClass);
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::QPRRegClass);
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.
std::prev(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::QQPRRegClass);
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::QQPRRegClass);
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::QPRRegClass);
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.
std::prev(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->getArgRegsSaveSize() > 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 (auto &MBB : MF) {
for (auto &MI : MBB)
FnSize += TII.GetInstSizeInBytes(&MI);
}
return FnSize;
}
/// 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 (auto &MBB : MF) {
for (auto &MI : MBB) {
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
if (!MI.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 (MI.getOpcode() == ARM::ADDri) {
Limit = std::min(Limit, (1U << 8) - 1);
break;
}
// Otherwise check the addressing mode.
switch (MI.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()->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
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.isPhysRegUsed(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();
MachineRegisterInfo &MRI = MF.getRegInfo();
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)))
MRI.setPhysRegUsed(ARM::R4);
if (AFI->isThumb1OnlyFunction()) {
// Spill LR if Thumb1 function uses variable length argument lists.
if (AFI->getArgRegsSaveSize() > 0)
MRI.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 = MFI->estimateStackSize(MF);
if (MFI->hasVarSizedObjects() || StackSize > 508)
MRI.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))
MRI.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 MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(&MF);
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
bool Spilled = false;
if (MRI.isPhysRegUsed(Reg)) {
Spilled = true;
CanEliminateFrame = false;
}
if (!ARM::GPRRegClass.contains(Reg))
continue;
if (Spilled) {
NumGPRSpills++;
if (!STI.isTargetMachO()) {
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::R0: case ARM::R1:
case ARM::R2: case ARM::R3:
case ARM::R4: case ARM::R5:
case ARM::R6: case ARM::R7:
CS1Spilled = true;
break;
default:
break;
}
} else {
if (!STI.isTargetMachO()) {
UnspilledCS1GPRs.push_back(Reg);
continue;
}
switch (Reg) {
case ARM::R0: case ARM::R1:
case ARM::R2: case ARM::R3:
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 &&
(MFI->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) {
MRI.setPhysRegUsed(ARM::LR);
NumGPRSpills++;
SmallVectorImpl<unsigned>::iterator LRPos;
LRPos = std::find(UnspilledCS1GPRs.begin(), UnspilledCS1GPRs.end(),
(unsigned)ARM::LR);
if (LRPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(LRPos);
ForceLRSpill = false;
ExtraCSSpill = true;
}
if (hasFP(MF)) {
MRI.setPhysRegUsed(FramePtr);
auto FPPos = std::find(UnspilledCS1GPRs.begin(), UnspilledCS1GPRs.end(),
FramePtr);
if (FPPos != UnspilledCS1GPRs.end())
UnspilledCS1GPRs.erase(FPPos);
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) {
MRI.setPhysRegUsed(Reg);
if (!MRI.isReserved(Reg))
ExtraCSSpill = true;
break;
}
}
} else if (!UnspilledCS2GPRs.empty() && !AFI->isThumb1OnlyFunction()) {
unsigned Reg = UnspilledCS2GPRs.front();
MRI.setPhysRegUsed(Reg);
if (!MRI.isReserved(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 (!MRI.isReserved(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 (!MRI.isReserved(Reg)) {
Extras.push_back(Reg);
NumExtras--;
}
}
}
if (Extras.size() && NumExtras == 0) {
for (unsigned i = 0, e = Extras.size(); i != e; ++i) {
MRI.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::GPRRegClass;
RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
}
}
if (ForceLRSpill) {
MRI.setPhysRegUsed(ARM::LR);
AFI->setLRIsSpilledForFarJump(true);
}
}
void ARMFrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
if (!hasReservedCallFrame(MF)) {
// If we have alloca, convert as follows:
// ADJCALLSTACKDOWN -> sub, sp, sp, amount
// ADJCALLSTACKUP -> add, sp, sp, amount
MachineInstr *Old = I;
DebugLoc dl = Old->getDebugLoc();
unsigned Amount = Old->getOperand(0).getImm();
if (Amount != 0) {
// We need to keep the stack aligned properly. To do this, we round the
// amount of space needed for the outgoing arguments up to the next
// alignment boundary.
unsigned Align = getStackAlignment();
Amount = (Amount+Align-1)/Align*Align;
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
assert(!AFI->isThumb1OnlyFunction() &&
"This eliminateCallFramePseudoInstr does not support Thumb1!");
bool isARM = !AFI->isThumbFunction();
// Replace the pseudo instruction with a new instruction...
unsigned Opc = Old->getOpcode();
int PIdx = Old->findFirstPredOperandIdx();
ARMCC::CondCodes Pred = (PIdx == -1)
? ARMCC::AL : (ARMCC::CondCodes)Old->getOperand(PIdx).getImm();
if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) {
// Note: PredReg is operand 2 for ADJCALLSTACKDOWN.
unsigned PredReg = Old->getOperand(2).getReg();
emitSPUpdate(isARM, MBB, I, dl, TII, -Amount, MachineInstr::NoFlags,
Pred, PredReg);
} else {
// Note: PredReg is operand 3 for ADJCALLSTACKUP.
unsigned PredReg = Old->getOperand(3).getReg();
assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP);
emitSPUpdate(isARM, MBB, I, dl, TII, Amount, MachineInstr::NoFlags,
Pred, PredReg);
}
}
}
MBB.erase(I);
}
/// Get the minimum constant for ARM that is greater than or equal to the
/// argument. In ARM, constants can have any value that can be produced by
/// rotating an 8-bit value to the right by an even number of bits within a
/// 32-bit word.
static uint32_t alignToARMConstant(uint32_t Value) {
unsigned Shifted = 0;
if (Value == 0)
return 0;
while (!(Value & 0xC0000000)) {
Value = Value << 2;
Shifted += 2;
}
bool Carry = (Value & 0x00FFFFFF);
Value = ((Value & 0xFF000000) >> 24) + Carry;
if (Value & 0x0000100)
Value = Value & 0x000001FC;
if (Shifted > 24)
Value = Value >> (Shifted - 24);
else
Value = Value << (24 - Shifted);
return Value;
}
// The stack limit in the TCB is set to this many bytes above the actual
// stack limit.
static const uint64_t kSplitStackAvailable = 256;
// Adjust the function prologue to enable split stacks. This currently only
// supports android and linux.
//
// The ABI of the segmented stack prologue is a little arbitrarily chosen, but
// must be well defined in order to allow for consistent implementations of the
// __morestack helper function. The ABI is also not a normal ABI in that it
// doesn't follow the normal calling conventions because this allows the
// prologue of each function to be optimized further.
//
// Currently, the ABI looks like (when calling __morestack)
//
// * r4 holds the minimum stack size requested for this function call
// * r5 holds the stack size of the arguments to the function
// * the beginning of the function is 3 instructions after the call to
// __morestack
//
// Implementations of __morestack should use r4 to allocate a new stack, r5 to
// place the arguments on to the new stack, and the 3-instruction knowledge to
// jump directly to the body of the function when working on the new stack.
//
// An old (and possibly no longer compatible) implementation of __morestack for
// ARM can be found at [1].
//
// [1] - https://github.com/mozilla/rust/blob/86efd9/src/rt/arch/arm/morestack.S
void ARMFrameLowering::adjustForSegmentedStacks(MachineFunction &MF) const {
unsigned Opcode;
unsigned CFIIndex;
const ARMSubtarget *ST = &MF.getTarget().getSubtarget<ARMSubtarget>();
bool Thumb = ST->isThumb();
// Sadly, this currently doesn't support varargs, platforms other than
// android/linux. Note that thumb1/thumb2 are support for android/linux.
if (MF.getFunction()->isVarArg())
report_fatal_error("Segmented stacks do not support vararg functions.");
if (!ST->isTargetAndroid() && !ST->isTargetLinux())
report_fatal_error("Segmented stacks not supported on this platform.");
MachineBasicBlock &prologueMBB = MF.front();
MachineFrameInfo *MFI = MF.getFrameInfo();
MachineModuleInfo &MMI = MF.getMMI();
MCContext &Context = MMI.getContext();
const MCRegisterInfo *MRI = Context.getRegisterInfo();
const ARMBaseInstrInfo &TII =
*static_cast<const ARMBaseInstrInfo*>(MF.getTarget().getInstrInfo());
ARMFunctionInfo *ARMFI = MF.getInfo<ARMFunctionInfo>();
DebugLoc DL;
uint64_t StackSize = MFI->getStackSize();
// Do not generate a prologue for functions with a stack of size zero
if (StackSize == 0)
return;
// Use R4 and R5 as scratch registers.
// We save R4 and R5 before use and restore them before leaving the function.
unsigned ScratchReg0 = ARM::R4;
unsigned ScratchReg1 = ARM::R5;
uint64_t AlignedStackSize;
MachineBasicBlock *PrevStackMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *PostStackMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *AllocMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *GetMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *McrMBB = MF.CreateMachineBasicBlock();
for (MachineBasicBlock::livein_iterator i = prologueMBB.livein_begin(),
e = prologueMBB.livein_end();
i != e; ++i) {
AllocMBB->addLiveIn(*i);
GetMBB->addLiveIn(*i);
McrMBB->addLiveIn(*i);
PrevStackMBB->addLiveIn(*i);
PostStackMBB->addLiveIn(*i);
}
MF.push_front(PostStackMBB);
MF.push_front(AllocMBB);
MF.push_front(GetMBB);
MF.push_front(McrMBB);
MF.push_front(PrevStackMBB);
// The required stack size that is aligned to ARM constant criterion.
AlignedStackSize = alignToARMConstant(StackSize);
// When the frame size is less than 256 we just compare the stack
// boundary directly to the value of the stack pointer, per gcc.
bool CompareStackPointer = AlignedStackSize < kSplitStackAvailable;
// We will use two of the callee save registers as scratch registers so we
// need to save those registers onto the stack.
// We will use SR0 to hold stack limit and SR1 to hold the stack size
// requested and arguments for __morestack().
// SR0: Scratch Register #0
// SR1: Scratch Register #1
// push {SR0, SR1}
if (Thumb) {
AddDefaultPred(BuildMI(PrevStackMBB, DL, TII.get(ARM::tPUSH)))
.addReg(ScratchReg0).addReg(ScratchReg1);
} else {
AddDefaultPred(BuildMI(PrevStackMBB, DL, TII.get(ARM::STMDB_UPD))
.addReg(ARM::SP, RegState::Define).addReg(ARM::SP))
.addReg(ScratchReg0).addReg(ScratchReg1);
}
// Emit the relevant DWARF information about the change in stack pointer as
// well as where to find both r4 and r5 (the callee-save registers)
CFIIndex =
MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, -8));
BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(ScratchReg1, true), -4));
BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(ScratchReg0, true), -8));
BuildMI(PrevStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// mov SR1, sp
if (Thumb) {
AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::tMOVr), ScratchReg1)
.addReg(ARM::SP));
} else if (CompareStackPointer) {
AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::MOVr), ScratchReg1)
.addReg(ARM::SP)).addReg(0);
}
// sub SR1, sp, #StackSize
if (!CompareStackPointer && Thumb) {
AddDefaultPred(
AddDefaultCC(BuildMI(McrMBB, DL, TII.get(ARM::tSUBi8), ScratchReg1))
.addReg(ScratchReg1).addImm(AlignedStackSize));
} else if (!CompareStackPointer) {
AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::SUBri), ScratchReg1)
.addReg(ARM::SP).addImm(AlignedStackSize)).addReg(0);
}
if (Thumb && ST->isThumb1Only()) {
unsigned PCLabelId = ARMFI->createPICLabelUId();
ARMConstantPoolValue *NewCPV = ARMConstantPoolSymbol::Create(
MF.getFunction()->getContext(), "__STACK_LIMIT", PCLabelId, 0);
MachineConstantPool *MCP = MF.getConstantPool();
unsigned CPI = MCP->getConstantPoolIndex(NewCPV, MF.getAlignment());
// ldr SR0, [pc, offset(STACK_LIMIT)]
AddDefaultPred(BuildMI(GetMBB, DL, TII.get(ARM::tLDRpci), ScratchReg0)
.addConstantPoolIndex(CPI));
// ldr SR0, [SR0]
AddDefaultPred(BuildMI(GetMBB, DL, TII.get(ARM::tLDRi), ScratchReg0)
.addReg(ScratchReg0).addImm(0));
} else {
// Get TLS base address from the coprocessor
// mrc p15, #0, SR0, c13, c0, #3
AddDefaultPred(BuildMI(McrMBB, DL, TII.get(ARM::MRC), ScratchReg0)
.addImm(15)
.addImm(0)
.addImm(13)
.addImm(0)
.addImm(3));
// Use the last tls slot on android and a private field of the TCP on linux.
assert(ST->isTargetAndroid() || ST->isTargetLinux());
unsigned TlsOffset = ST->isTargetAndroid() ? 63 : 1;
// Get the stack limit from the right offset
// ldr SR0, [sr0, #4 * TlsOffset]
AddDefaultPred(BuildMI(GetMBB, DL, TII.get(ARM::LDRi12), ScratchReg0)
.addReg(ScratchReg0).addImm(4 * TlsOffset));
}
// Compare stack limit with stack size requested.
// cmp SR0, SR1
Opcode = Thumb ? ARM::tCMPr : ARM::CMPrr;
AddDefaultPred(BuildMI(GetMBB, DL, TII.get(Opcode))
.addReg(ScratchReg0)
.addReg(ScratchReg1));
// This jump is taken if StackLimit < SP - stack required.
Opcode = Thumb ? ARM::tBcc : ARM::Bcc;
BuildMI(GetMBB, DL, TII.get(Opcode)).addMBB(PostStackMBB)
.addImm(ARMCC::LO)
.addReg(ARM::CPSR);
// Calling __morestack(StackSize, Size of stack arguments).
// __morestack knows that the stack size requested is in SR0(r4)
// and amount size of stack arguments is in SR1(r5).
// Pass first argument for the __morestack by Scratch Register #0.
// The amount size of stack required
if (Thumb) {
AddDefaultPred(AddDefaultCC(BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8),
ScratchReg0)).addImm(AlignedStackSize));
} else {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg0)
.addImm(AlignedStackSize)).addReg(0);
}
// Pass second argument for the __morestack by Scratch Register #1.
// The amount size of stack consumed to save function arguments.
if (Thumb) {
AddDefaultPred(
AddDefaultCC(BuildMI(AllocMBB, DL, TII.get(ARM::tMOVi8), ScratchReg1))
.addImm(alignToARMConstant(ARMFI->getArgumentStackSize())));
} else {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::MOVi), ScratchReg1)
.addImm(alignToARMConstant(ARMFI->getArgumentStackSize())))
.addReg(0);
}
// push {lr} - Save return address of this function.
if (Thumb) {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tPUSH)))
.addReg(ARM::LR);
} else {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::STMDB_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP))
.addReg(ARM::LR);
}
// Emit the DWARF info about the change in stack as well as where to find the
// previous link register
CFIIndex =
MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, -12));
BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(ARM::LR, true), -12));
BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// Call __morestack().
if (Thumb) {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tBL)))
.addExternalSymbol("__morestack");
} else {
BuildMI(AllocMBB, DL, TII.get(ARM::BL))
.addExternalSymbol("__morestack");
}
// pop {lr} - Restore return address of this original function.
if (Thumb) {
if (ST->isThumb1Only()) {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tPOP)))
.addReg(ScratchReg0);
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tMOVr), ARM::LR)
.addReg(ScratchReg0));
} else {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::t2LDR_POST))
.addReg(ARM::LR, RegState::Define)
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP)
.addImm(4));
}
} else {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP))
.addReg(ARM::LR);
}
// Restore SR0 and SR1 in case of __morestack() was called.
// __morestack() will skip PostStackMBB block so we need to restore
// scratch registers from here.
// pop {SR0, SR1}
if (Thumb) {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::tPOP)))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Update the CFA offset now that we've popped
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, 0));
BuildMI(AllocMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// bx lr - Return from this function.
Opcode = Thumb ? ARM::tBX_RET : ARM::BX_RET;
AddDefaultPred(BuildMI(AllocMBB, DL, TII.get(Opcode)));
// Restore SR0 and SR1 in case of __morestack() was not called.
// pop {SR0, SR1}
if (Thumb) {
AddDefaultPred(BuildMI(PostStackMBB, DL, TII.get(ARM::tPOP)))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
} else {
AddDefaultPred(BuildMI(PostStackMBB, DL, TII.get(ARM::LDMIA_UPD))
.addReg(ARM::SP, RegState::Define)
.addReg(ARM::SP))
.addReg(ScratchReg0)
.addReg(ScratchReg1);
}
// Update the CFA offset now that we've popped
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, 0));
BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// Tell debuggers that r4 and r5 are now the same as they were in the
// previous function, that they're the "Same Value".
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createSameValue(
nullptr, MRI->getDwarfRegNum(ScratchReg0, true)));
BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
CFIIndex = MMI.addFrameInst(MCCFIInstruction::createSameValue(
nullptr, MRI->getDwarfRegNum(ScratchReg1, true)));
BuildMI(PostStackMBB, DL, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
// Organizing MBB lists
PostStackMBB->addSuccessor(&prologueMBB);
AllocMBB->addSuccessor(PostStackMBB);
GetMBB->addSuccessor(PostStackMBB);
GetMBB->addSuccessor(AllocMBB);
McrMBB->addSuccessor(GetMBB);
PrevStackMBB->addSuccessor(McrMBB);
#ifdef XDEBUG
MF.verify();
#endif
}
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