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llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
Jakob Stoklund Olesen 4f28c1c714 Teach frame lowering to ignore debug values after the terminators. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123399 91177308-0d34-0410-b5e6-96231b3b80d8
2011-01-13 21:28:52 +00:00

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//======- Thumb1FrameLowering.cpp - Thumb1 Frame Information ---*- C++ -*-====//
//
// 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 Thumb1 implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "Thumb1FrameLowering.h"
#include "ARMBaseInstrInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
using namespace llvm;
bool Thumb1FrameLowering::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 << 8) - 1) * 4 / 2) // Half of imm8 * 4
return false;
return !MF.getFrameInfo()->hasVarSizedObjects();
}
static void emitSPUpdate(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
const TargetInstrInfo &TII, DebugLoc dl,
const Thumb1RegisterInfo &MRI,
int NumBytes) {
emitThumbRegPlusImmediate(MBB, MBBI, ARM::SP, ARM::SP, NumBytes, TII,
MRI, dl);
}
void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front();
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const Thumb1RegisterInfo *RegInfo =
static_cast<const Thumb1RegisterInfo*>(MF.getTarget().getRegisterInfo());
const Thumb1InstrInfo &TII =
*static_cast<const Thumb1InstrInfo*>(MF.getTarget().getInstrInfo());
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);
unsigned BasePtr = RegInfo->getBaseRegister();
// Thumb add/sub sp, imm8 instructions implicitly multiply the offset by 4.
NumBytes = (NumBytes + 3) & ~3;
MFI->setStackSize(NumBytes);
// 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;
if (VARegSaveSize)
emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -VARegSaveSize);
if (!AFI->hasStackFrame()) {
if (NumBytes != 0)
emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes);
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.isTargetDarwin()) {
AFI->addGPRCalleeSavedArea2Frame(FI);
GPRCS2Size += 4;
} else {
AFI->addGPRCalleeSavedArea1Frame(FI);
GPRCS1Size += 4;
}
break;
default:
AFI->addDPRCalleeSavedAreaFrame(FI);
DPRCSSize += 8;
}
}
if (MBBI != MBB.end() && MBBI->getOpcode() == ARM::tPUSH) {
++MBBI;
if (MBBI != MBB.end())
dl = MBBI->getDebugLoc();
}
// Determine starting offsets of spill areas.
unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize);
unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) + NumBytes);
AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);
NumBytes = DPRCSOffset;
// Adjust FP so it point to the stack slot that contains the previous FP.
if (hasFP(MF)) {
BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr)
.addFrameIndex(FramePtrSpillFI).addImm(0);
if (NumBytes > 7)
// If offset is > 7 then sp cannot be adjusted in a single instruction,
// try restoring from fp instead.
AFI->setShouldRestoreSPFromFP(true);
}
if (NumBytes)
// Insert it after all the callee-save spills.
emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes);
if (STI.isTargetELF() && hasFP(MF))
MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() -
AFI->getFramePtrSpillOffset());
AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
AFI->setDPRCalleeSavedAreaSize(DPRCSSize);
// 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.
if (RegInfo->hasBasePointer(MF))
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), BasePtr).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);
}
static bool isCalleeSavedRegister(unsigned Reg, const unsigned *CSRegs) {
for (unsigned i = 0; CSRegs[i]; ++i)
if (Reg == CSRegs[i])
return true;
return false;
}
static bool isCSRestore(MachineInstr *MI, const unsigned *CSRegs) {
if (MI->getOpcode() == ARM::tRestore &&
MI->getOperand(1).isFI() &&
isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs))
return true;
else if (MI->getOpcode() == ARM::tPOP) {
// The first two operands are predicates. The last two are
// imp-def and imp-use of SP. Check everything in between.
for (int i = 2, e = MI->getNumOperands() - 2; i != e; ++i)
if (!isCalleeSavedRegister(MI->getOperand(i).getReg(), CSRegs))
return false;
return true;
}
return false;
}
void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
assert((MBBI->getOpcode() == ARM::tBX_RET ||
MBBI->getOpcode() == ARM::tPOP_RET) &&
"Can only insert epilog into returning blocks");
DebugLoc dl = MBBI->getDebugLoc();
MachineFrameInfo *MFI = MF.getFrameInfo();
ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
const Thumb1RegisterInfo *RegInfo =
static_cast<const Thumb1RegisterInfo*>(MF.getTarget().getRegisterInfo());
const Thumb1InstrInfo &TII =
*static_cast<const Thumb1InstrInfo*>(MF.getTarget().getInstrInfo());
unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize();
int NumBytes = (int)MFI->getStackSize();
const unsigned *CSRegs = RegInfo->getCalleeSavedRegs();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
if (!AFI->hasStackFrame()) {
if (NumBytes != 0)
emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes);
} else {
// Unwind MBBI to point to first LDR / VLDRD.
if (MBBI != MBB.begin()) {
do
--MBBI;
while (MBBI != MBB.begin() && isCSRestore(MBBI, CSRegs));
if (!isCSRestore(MBBI, CSRegs))
++MBBI;
}
// Move SP to start of FP callee save spill area.
NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
AFI->getGPRCalleeSavedArea2Size() +
AFI->getDPRCalleeSavedAreaSize());
if (AFI->shouldRestoreSPFromFP()) {
NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
// Reset SP based on frame pointer only if the stack frame extends beyond
// frame pointer stack slot, the target is ELF and the function has FP, or
// the target uses var sized objects.
if (NumBytes) {
assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
"No scratch register to restore SP from FP!");
emitThumbRegPlusImmediate(MBB, MBBI, ARM::R4, FramePtr, -NumBytes,
TII, *RegInfo, dl);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::SP)
.addReg(ARM::R4);
} else
BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::SP)
.addReg(FramePtr);
} else {
if (MBBI->getOpcode() == ARM::tBX_RET &&
&MBB.front() != MBBI &&
prior(MBBI)->getOpcode() == ARM::tPOP) {
MachineBasicBlock::iterator PMBBI = prior(MBBI);
emitSPUpdate(MBB, PMBBI, TII, dl, *RegInfo, NumBytes);
} else
emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes);
}
}
if (VARegSaveSize) {
// Unlike T2 and ARM mode, the T1 pop instruction cannot restore
// to LR, and we can't pop the value directly to the PC since
// we need to update the SP after popping the value. Therefore, we
// pop the old LR into R3 as a temporary.
// Move back past the callee-saved register restoration
while (MBBI != MBB.end() && isCSRestore(MBBI, CSRegs))
++MBBI;
// Epilogue for vararg functions: pop LR to R3 and branch off it.
AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
.addReg(ARM::R3, RegState::Define);
emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, VARegSaveSize);
BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX_RET_vararg))
.addReg(ARM::R3, RegState::Kill);
// erase the old tBX_RET instruction
MBB.erase(MBBI);
}
}
bool Thumb1FrameLowering::
spillCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
DebugLoc DL;
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
if (MI != MBB.end()) DL = MI->getDebugLoc();
MachineInstrBuilder MIB = BuildMI(MBB, MI, DL, TII.get(ARM::tPUSH));
AddDefaultPred(MIB);
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
bool isKill = true;
// 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.
if (Reg == ARM::LR) {
MachineFunction &MF = *MBB.getParent();
if (MF.getFrameInfo()->isReturnAddressTaken() &&
MF.getRegInfo().isLiveIn(Reg))
isKill = false;
}
if (isKill)
MBB.addLiveIn(Reg);
MIB.addReg(Reg, getKillRegState(isKill));
}
return true;
}
bool Thumb1FrameLowering::
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>();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
bool isVarArg = AFI->getVarArgsRegSaveSize() > 0;
DebugLoc DL = MI->getDebugLoc();
MachineInstrBuilder MIB = BuildMI(MF, DL, TII.get(ARM::tPOP));
AddDefaultPred(MIB);
bool NumRegs = false;
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (Reg == ARM::LR) {
// Special epilogue for vararg functions. See emitEpilogue
if (isVarArg)
continue;
Reg = ARM::PC;
(*MIB).setDesc(TII.get(ARM::tPOP_RET));
MI = MBB.erase(MI);
}
MIB.addReg(Reg, getDefRegState(true));
NumRegs = true;
}
// It's illegal to emit pop instruction without operands.
if (NumRegs)
MBB.insert(MI, &*MIB);
else
MF.DeleteMachineInstr(MIB);
return true;
}
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