-//===- PPCRegisterInfo.cpp - PowerPC Register Information -------*- C++ -*-===//
+//===-- PPCRegisterInfo.cpp - PowerPC Register Information ----------------===//
//
// The LLVM Compiler Infrastructure
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "reginfo"
+#include "PPCRegisterInfo.h"
#include "PPC.h"
#include "PPCInstrBuilder.h"
#include "PPCMachineFunctionInfo.h"
-#include "PPCRegisterInfo.h"
#include "PPCFrameLowering.h"
#include "PPCSubtarget.h"
#include "llvm/CallingConv.h"
#define GET_REGINFO_TARGET_DESC
#include "PPCGenRegisterInfo.inc"
-// FIXME (64-bit): Eventually enable by default.
namespace llvm {
-cl::opt<bool> EnablePPC32RS("enable-ppc32-regscavenger",
+cl::opt<bool> DisablePPC32RS("disable-ppc32-regscavenger",
cl::init(false),
- cl::desc("Enable PPC32 register scavenger"),
+ cl::desc("Disable PPC32 register scavenger"),
cl::Hidden);
-cl::opt<bool> EnablePPC64RS("enable-ppc64-regscavenger",
+cl::opt<bool> DisablePPC64RS("disable-ppc64-regscavenger",
cl::init(false),
- cl::desc("Enable PPC64 register scavenger"),
+ cl::desc("Disable PPC64 register scavenger"),
cl::Hidden);
}
// FIXME (64-bit): Should be inlined.
bool
PPCRegisterInfo::requiresRegisterScavenging(const MachineFunction &) const {
- return ((EnablePPC32RS && !Subtarget.isPPC64()) ||
- (EnablePPC64RS && Subtarget.isPPC64()));
-}
-
-/// getRegisterNumbering - Given the enum value for some register, e.g.
-/// PPC::F14, return the number that it corresponds to (e.g. 14).
-unsigned PPCRegisterInfo::getRegisterNumbering(unsigned RegEnum) {
- using namespace PPC;
- switch (RegEnum) {
- case 0: return 0;
- case R0 : case X0 : case F0 : case V0 : case CR0: case CR0LT: return 0;
- case R1 : case X1 : case F1 : case V1 : case CR1: case CR0GT: return 1;
- case R2 : case X2 : case F2 : case V2 : case CR2: case CR0EQ: return 2;
- case R3 : case X3 : case F3 : case V3 : case CR3: case CR0UN: return 3;
- case R4 : case X4 : case F4 : case V4 : case CR4: case CR1LT: return 4;
- case R5 : case X5 : case F5 : case V5 : case CR5: case CR1GT: return 5;
- case R6 : case X6 : case F6 : case V6 : case CR6: case CR1EQ: return 6;
- case R7 : case X7 : case F7 : case V7 : case CR7: case CR1UN: return 7;
- case R8 : case X8 : case F8 : case V8 : case CR2LT: return 8;
- case R9 : case X9 : case F9 : case V9 : case CR2GT: return 9;
- case R10: case X10: case F10: case V10: case CR2EQ: return 10;
- case R11: case X11: case F11: case V11: case CR2UN: return 11;
- case R12: case X12: case F12: case V12: case CR3LT: return 12;
- case R13: case X13: case F13: case V13: case CR3GT: return 13;
- case R14: case X14: case F14: case V14: case CR3EQ: return 14;
- case R15: case X15: case F15: case V15: case CR3UN: return 15;
- case R16: case X16: case F16: case V16: case CR4LT: return 16;
- case R17: case X17: case F17: case V17: case CR4GT: return 17;
- case R18: case X18: case F18: case V18: case CR4EQ: return 18;
- case R19: case X19: case F19: case V19: case CR4UN: return 19;
- case R20: case X20: case F20: case V20: case CR5LT: return 20;
- case R21: case X21: case F21: case V21: case CR5GT: return 21;
- case R22: case X22: case F22: case V22: case CR5EQ: return 22;
- case R23: case X23: case F23: case V23: case CR5UN: return 23;
- case R24: case X24: case F24: case V24: case CR6LT: return 24;
- case R25: case X25: case F25: case V25: case CR6GT: return 25;
- case R26: case X26: case F26: case V26: case CR6EQ: return 26;
- case R27: case X27: case F27: case V27: case CR6UN: return 27;
- case R28: case X28: case F28: case V28: case CR7LT: return 28;
- case R29: case X29: case F29: case V29: case CR7GT: return 29;
- case R30: case X30: case F30: case V30: case CR7EQ: return 30;
- case R31: case X31: case F31: case V31: case CR7UN: return 31;
- default:
- llvm_unreachable("Unhandled reg in PPCRegisterInfo::getRegisterNumbering!");
- }
+ return ((!DisablePPC32RS && !Subtarget.isPPC64()) ||
+ (!DisablePPC64RS && Subtarget.isPPC64()));
}
PPCRegisterInfo::PPCRegisterInfo(const PPCSubtarget &ST,
ImmToIdxMap[PPC::ADDI8] = PPC::ADD8; ImmToIdxMap[PPC::STD_32] = PPC::STDX_32;
}
+bool
+PPCRegisterInfo::trackLivenessAfterRegAlloc(const MachineFunction &MF) const {
+ return requiresRegisterScavenging(MF);
+}
+
+
/// getPointerRegClass - Return the register class to use to hold pointers.
/// This is used for addressing modes.
const TargetRegisterClass *
-PPCRegisterInfo::getPointerRegClass(unsigned Kind) const {
+PPCRegisterInfo::getPointerRegClass(const MachineFunction &MF, unsigned Kind)
+ const {
if (Subtarget.isPPC64())
return &PPC::G8RCRegClass;
return &PPC::GPRCRegClass;
}
-const unsigned*
+const uint16_t*
PPCRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
- // 32-bit Darwin calling convention.
- static const unsigned Darwin32_CalleeSavedRegs[] = {
- PPC::R13, PPC::R14, PPC::R15,
- PPC::R16, PPC::R17, PPC::R18, PPC::R19,
- PPC::R20, PPC::R21, PPC::R22, PPC::R23,
- PPC::R24, PPC::R25, PPC::R26, PPC::R27,
- PPC::R28, PPC::R29, PPC::R30, PPC::R31,
-
- PPC::F14, PPC::F15, PPC::F16, PPC::F17,
- PPC::F18, PPC::F19, PPC::F20, PPC::F21,
- PPC::F22, PPC::F23, PPC::F24, PPC::F25,
- PPC::F26, PPC::F27, PPC::F28, PPC::F29,
- PPC::F30, PPC::F31,
-
- PPC::CR2, PPC::CR3, PPC::CR4,
- PPC::V20, PPC::V21, PPC::V22, PPC::V23,
- PPC::V24, PPC::V25, PPC::V26, PPC::V27,
- PPC::V28, PPC::V29, PPC::V30, PPC::V31,
-
- PPC::CR2LT, PPC::CR2GT, PPC::CR2EQ, PPC::CR2UN,
- PPC::CR3LT, PPC::CR3GT, PPC::CR3EQ, PPC::CR3UN,
- PPC::CR4LT, PPC::CR4GT, PPC::CR4EQ, PPC::CR4UN,
-
- PPC::LR, 0
- };
-
- // 32-bit SVR4 calling convention.
- static const unsigned SVR4_CalleeSavedRegs[] = {
- PPC::R14, PPC::R15,
- PPC::R16, PPC::R17, PPC::R18, PPC::R19,
- PPC::R20, PPC::R21, PPC::R22, PPC::R23,
- PPC::R24, PPC::R25, PPC::R26, PPC::R27,
- PPC::R28, PPC::R29, PPC::R30, PPC::R31,
-
- PPC::F14, PPC::F15, PPC::F16, PPC::F17,
- PPC::F18, PPC::F19, PPC::F20, PPC::F21,
- PPC::F22, PPC::F23, PPC::F24, PPC::F25,
- PPC::F26, PPC::F27, PPC::F28, PPC::F29,
- PPC::F30, PPC::F31,
-
- PPC::CR2, PPC::CR3, PPC::CR4,
-
- PPC::VRSAVE,
-
- PPC::V20, PPC::V21, PPC::V22, PPC::V23,
- PPC::V24, PPC::V25, PPC::V26, PPC::V27,
- PPC::V28, PPC::V29, PPC::V30, PPC::V31,
-
- PPC::CR2LT, PPC::CR2GT, PPC::CR2EQ, PPC::CR2UN,
- PPC::CR3LT, PPC::CR3GT, PPC::CR3EQ, PPC::CR3UN,
- PPC::CR4LT, PPC::CR4GT, PPC::CR4EQ, PPC::CR4UN,
-
- 0
- };
- // 64-bit Darwin calling convention.
- static const unsigned Darwin64_CalleeSavedRegs[] = {
- PPC::X14, PPC::X15,
- PPC::X16, PPC::X17, PPC::X18, PPC::X19,
- PPC::X20, PPC::X21, PPC::X22, PPC::X23,
- PPC::X24, PPC::X25, PPC::X26, PPC::X27,
- PPC::X28, PPC::X29, PPC::X30, PPC::X31,
-
- PPC::F14, PPC::F15, PPC::F16, PPC::F17,
- PPC::F18, PPC::F19, PPC::F20, PPC::F21,
- PPC::F22, PPC::F23, PPC::F24, PPC::F25,
- PPC::F26, PPC::F27, PPC::F28, PPC::F29,
- PPC::F30, PPC::F31,
-
- PPC::CR2, PPC::CR3, PPC::CR4,
- PPC::V20, PPC::V21, PPC::V22, PPC::V23,
- PPC::V24, PPC::V25, PPC::V26, PPC::V27,
- PPC::V28, PPC::V29, PPC::V30, PPC::V31,
-
- PPC::CR2LT, PPC::CR2GT, PPC::CR2EQ, PPC::CR2UN,
- PPC::CR3LT, PPC::CR3GT, PPC::CR3EQ, PPC::CR3UN,
- PPC::CR4LT, PPC::CR4GT, PPC::CR4EQ, PPC::CR4UN,
-
- PPC::LR8, 0
- };
-
- // 64-bit SVR4 calling convention.
- static const unsigned SVR4_64_CalleeSavedRegs[] = {
- PPC::X14, PPC::X15,
- PPC::X16, PPC::X17, PPC::X18, PPC::X19,
- PPC::X20, PPC::X21, PPC::X22, PPC::X23,
- PPC::X24, PPC::X25, PPC::X26, PPC::X27,
- PPC::X28, PPC::X29, PPC::X30, PPC::X31,
-
- PPC::F14, PPC::F15, PPC::F16, PPC::F17,
- PPC::F18, PPC::F19, PPC::F20, PPC::F21,
- PPC::F22, PPC::F23, PPC::F24, PPC::F25,
- PPC::F26, PPC::F27, PPC::F28, PPC::F29,
- PPC::F30, PPC::F31,
-
- PPC::CR2, PPC::CR3, PPC::CR4,
-
- PPC::VRSAVE,
-
- PPC::V20, PPC::V21, PPC::V22, PPC::V23,
- PPC::V24, PPC::V25, PPC::V26, PPC::V27,
- PPC::V28, PPC::V29, PPC::V30, PPC::V31,
+ if (Subtarget.isDarwinABI())
+ return Subtarget.isPPC64() ? CSR_Darwin64_SaveList :
+ CSR_Darwin32_SaveList;
- PPC::CR2LT, PPC::CR2GT, PPC::CR2EQ, PPC::CR2UN,
- PPC::CR3LT, PPC::CR3GT, PPC::CR3EQ, PPC::CR3UN,
- PPC::CR4LT, PPC::CR4GT, PPC::CR4EQ, PPC::CR4UN,
+ return Subtarget.isPPC64() ? CSR_SVR464_SaveList : CSR_SVR432_SaveList;
+}
- 0
- };
-
+const unsigned*
+PPCRegisterInfo::getCallPreservedMask(CallingConv::ID CC) const {
if (Subtarget.isDarwinABI())
- return Subtarget.isPPC64() ? Darwin64_CalleeSavedRegs :
- Darwin32_CalleeSavedRegs;
+ return Subtarget.isPPC64() ? CSR_Darwin64_RegMask :
+ CSR_Darwin32_RegMask;
- return Subtarget.isPPC64() ? SVR4_64_CalleeSavedRegs : SVR4_CalleeSavedRegs;
+ return Subtarget.isPPC64() ? CSR_SVR464_RegMask : CSR_SVR432_RegMask;
}
BitVector PPCRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
Reserved.set(PPC::R13);
Reserved.set(PPC::R31);
- if (!requiresRegisterScavenging(MF))
- Reserved.set(PPC::R0); // FIXME (64-bit): Remove
-
Reserved.set(PPC::X0);
Reserved.set(PPC::X1);
Reserved.set(PPC::X13);
if (Subtarget.isSVR4ABI()) {
Reserved.set(PPC::X2);
}
- // Reserve R2 on Darwin to hack around the problem of save/restore of CR
+ // Reserve X2 on Darwin to hack around the problem of save/restore of CR
// when the stack frame is too big to address directly; we need two regs.
// This is a hack.
if (Subtarget.isDarwinABI()) {
return Reserved;
}
+unsigned
+PPCRegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC,
+ MachineFunction &MF) const {
+ const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering();
+ const unsigned DefaultSafety = 1;
+
+ switch (RC->getID()) {
+ default:
+ return 0;
+ case PPC::G8RCRegClassID:
+ case PPC::GPRCRegClassID: {
+ unsigned FP = TFI->hasFP(MF) ? 1 : 0;
+ return 32 - FP - DefaultSafety;
+ }
+ case PPC::F8RCRegClassID:
+ case PPC::F4RCRegClassID:
+ case PPC::VRRCRegClassID:
+ return 32 - DefaultSafety;
+ case PPC::CRRCRegClassID:
+ return 8 - DefaultSafety;
+ }
+}
+
//===----------------------------------------------------------------------===//
// Stack Frame Processing methods
//===----------------------------------------------------------------------===//
void PPCRegisterInfo::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
- if (GuaranteedTailCallOpt && I->getOpcode() == PPC::ADJCALLSTACKUP) {
+ if (MF.getTarget().Options.GuaranteedTailCallOpt &&
+ I->getOpcode() == PPC::ADJCALLSTACKUP) {
// Add (actually subtract) back the amount the callee popped on return.
if (int CalleeAmt = I->getOperand(1).getImm()) {
bool is64Bit = Subtarget.isPPC64();
DebugLoc dl = MI->getDebugLoc();
if (isInt<16>(CalleeAmt)) {
- BuildMI(MBB, I, dl, TII.get(ADDIInstr), StackReg).addReg(StackReg).
- addImm(CalleeAmt);
+ BuildMI(MBB, I, dl, TII.get(ADDIInstr), StackReg)
+ .addReg(StackReg, RegState::Kill)
+ .addImm(CalleeAmt);
} else {
MachineBasicBlock::iterator MBBI = I;
BuildMI(MBB, MBBI, dl, TII.get(LISInstr), TmpReg)
BuildMI(MBB, MBBI, dl, TII.get(ORIInstr), TmpReg)
.addReg(TmpReg, RegState::Kill)
.addImm(CalleeAmt & 0xFFFF);
- BuildMI(MBB, MBBI, dl, TII.get(ADDInstr))
- .addReg(StackReg)
- .addReg(StackReg)
+ BuildMI(MBB, MBBI, dl, TII.get(ADDInstr), StackReg)
+ .addReg(StackReg, RegState::Kill)
.addReg(TmpReg);
}
}
if (requiresRegisterScavenging(MF)) // FIXME (64-bit): Use "true" part.
BuildMI(MBB, II, dl, TII.get(PPC::STDUX))
.addReg(Reg, RegState::Kill)
- .addReg(PPC::X1)
+ .addReg(PPC::X1, RegState::Define)
.addReg(MI.getOperand(1).getReg());
else
BuildMI(MBB, II, dl, TII.get(PPC::STDUX))
.addReg(PPC::X0, RegState::Kill)
- .addReg(PPC::X1)
+ .addReg(PPC::X1, RegState::Define)
.addReg(MI.getOperand(1).getReg());
if (!MI.getOperand(1).isKill())
} else {
BuildMI(MBB, II, dl, TII.get(PPC::STWUX))
.addReg(Reg, RegState::Kill)
- .addReg(PPC::R1)
+ .addReg(PPC::R1, RegState::Define)
.addReg(MI.getOperand(1).getReg());
if (!MI.getOperand(1).isKill())
unsigned FrameIndex, int SPAdj,
RegScavenger *RS) const {
// Get the instruction.
- MachineInstr &MI = *II; // ; SPILL_CR <SrcReg>, <offset>, <FI>
+ MachineInstr &MI = *II; // ; SPILL_CR <SrcReg>, <offset>
// Get the instruction's basic block.
MachineBasicBlock &MBB = *MI.getParent();
DebugLoc dl = MI.getDebugLoc();
- const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
- const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
- const TargetRegisterClass *RC = Subtarget.isPPC64() ? G8RC : GPRC;
- unsigned Reg = findScratchRegister(II, RS, RC, SPAdj);
- unsigned SrcReg = MI.getOperand(0).getReg();
+ // FIXME: Once LLVM supports creating virtual registers here, or the register
+ // scavenger can return multiple registers, stop using reserved registers
+ // here.
+ (void) SPAdj;
+ (void) RS;
+
bool LP64 = Subtarget.isPPC64();
+ unsigned Reg = Subtarget.isDarwinABI() ? (LP64 ? PPC::X2 : PPC::R2) :
+ (LP64 ? PPC::X0 : PPC::R0);
+ unsigned SrcReg = MI.getOperand(0).getReg();
// We need to store the CR in the low 4-bits of the saved value. First, issue
// an MFCRpsued to save all of the CRBits and, if needed, kill the SrcReg.
- BuildMI(MBB, II, dl, TII.get(PPC::MFCRpseud), Reg)
+ BuildMI(MBB, II, dl, TII.get(LP64 ? PPC::MFCR8pseud : PPC::MFCRpseud), Reg)
.addReg(SrcReg, getKillRegState(MI.getOperand(0).isKill()));
// If the saved register wasn't CR0, shift the bits left so that they are in
// CR0's slot.
if (SrcReg != PPC::CR0)
// rlwinm rA, rA, ShiftBits, 0, 31.
- BuildMI(MBB, II, dl, TII.get(PPC::RLWINM), Reg)
+ BuildMI(MBB, II, dl, TII.get(LP64 ? PPC::RLWINM8 : PPC::RLWINM), Reg)
.addReg(Reg, RegState::Kill)
- .addImm(PPCRegisterInfo::getRegisterNumbering(SrcReg) * 4)
+ .addImm(getPPCRegisterNumbering(SrcReg) * 4)
.addImm(0)
.addImm(31);
MBB.erase(II);
}
+void PPCRegisterInfo::lowerCRRestore(MachineBasicBlock::iterator II,
+ unsigned FrameIndex, int SPAdj,
+ RegScavenger *RS) const {
+ // Get the instruction.
+ MachineInstr &MI = *II; // ; <DestReg> = RESTORE_CR <offset>
+ // Get the instruction's basic block.
+ MachineBasicBlock &MBB = *MI.getParent();
+ DebugLoc dl = MI.getDebugLoc();
+
+ // FIXME: Once LLVM supports creating virtual registers here, or the register
+ // scavenger can return multiple registers, stop using reserved registers
+ // here.
+ (void) SPAdj;
+ (void) RS;
+
+ bool LP64 = Subtarget.isPPC64();
+ unsigned Reg = Subtarget.isDarwinABI() ? (LP64 ? PPC::X2 : PPC::R2) :
+ (LP64 ? PPC::X0 : PPC::R0);
+ unsigned DestReg = MI.getOperand(0).getReg();
+ assert(MI.definesRegister(DestReg) &&
+ "RESTORE_CR does not define its destination");
+
+ addFrameReference(BuildMI(MBB, II, dl, TII.get(LP64 ? PPC::LWZ8 : PPC::LWZ),
+ Reg), FrameIndex);
+
+ // If the reloaded register isn't CR0, shift the bits right so that they are
+ // in the right CR's slot.
+ if (DestReg != PPC::CR0) {
+ unsigned ShiftBits = getPPCRegisterNumbering(DestReg)*4;
+ // rlwinm r11, r11, 32-ShiftBits, 0, 31.
+ BuildMI(MBB, II, dl, TII.get(LP64 ? PPC::RLWINM8 : PPC::RLWINM), Reg)
+ .addReg(Reg).addImm(32-ShiftBits).addImm(0)
+ .addImm(31);
+ }
+
+ BuildMI(MBB, II, dl, TII.get(LP64 ? PPC::MTCRF8 : PPC::MTCRF), DestReg)
+ .addReg(Reg);
+
+ // Discard the pseudo instruction.
+ MBB.erase(II);
+}
+
void
PPCRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
int SPAdj, RegScavenger *RS) const {
return;
}
- // Special case for pseudo-op SPILL_CR.
- if (requiresRegisterScavenging(MF)) // FIXME (64-bit): Enable by default.
+ // Special case for pseudo-ops SPILL_CR and RESTORE_CR.
+ if (requiresRegisterScavenging(MF)) {
if (OpC == PPC::SPILL_CR) {
lowerCRSpilling(II, FrameIndex, SPAdj, RS);
return;
+ } else if (OpC == PPC::RESTORE_CR) {
+ lowerCRRestore(II, FrameIndex, SPAdj, RS);
+ return;
}
+ }
// Replace the FrameIndex with base register with GPR1 (SP) or GPR31 (FP).
+
+ bool is64Bit = Subtarget.isPPC64();
MI.getOperand(FIOperandNo).ChangeToRegister(TFI->hasFP(MF) ?
- PPC::R31 : PPC::R1,
+ (is64Bit ? PPC::X31 : PPC::R31) :
+ (is64Bit ? PPC::X1 : PPC::R1),
false);
// Figure out if the offset in the instruction is shifted right two bits. This
// clear can be encoded. This is extremely uncommon, because normally you
// only "std" to a stack slot that is at least 4-byte aligned, but it can
// happen in invalid code.
- if (isInt<16>(Offset) && (!isIXAddr || (Offset & 3) == 0)) {
+ if (OpC == PPC::DBG_VALUE || // DBG_VALUE is always Reg+Imm
+ (isInt<16>(Offset) && (!isIXAddr || (Offset & 3) == 0))) {
if (isIXAddr)
Offset >>= 2; // The actual encoded value has the low two bits zero.
MI.getOperand(OffsetOperandNo).ChangeToImmediate(Offset);
// The offset doesn't fit into a single register, scavenge one to build the
// offset in.
- // FIXME: figure out what SPAdj is doing here.
- // FIXME (64-bit): Use "findScratchRegister".
unsigned SReg;
- if (requiresRegisterScavenging(MF))
- SReg = findScratchRegister(II, RS, &PPC::GPRCRegClass, SPAdj);
- else
- SReg = PPC::R0;
+ if (requiresRegisterScavenging(MF)) {
+ const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
+ const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
+ SReg = findScratchRegister(II, RS, is64Bit ? G8RC : GPRC, SPAdj);
+ } else
+ SReg = is64Bit ? PPC::X0 : PPC::R0;
// Insert a set of rA with the full offset value before the ld, st, or add
- BuildMI(MBB, II, dl, TII.get(PPC::LIS), SReg)
+ BuildMI(MBB, II, dl, TII.get(is64Bit ? PPC::LIS8 : PPC::LIS), SReg)
.addImm(Offset >> 16);
- BuildMI(MBB, II, dl, TII.get(PPC::ORI), SReg)
+ BuildMI(MBB, II, dl, TII.get(is64Bit ? PPC::ORI8 : PPC::ORI), SReg)
.addReg(SReg, RegState::Kill)
.addImm(Offset);
unsigned StackReg = MI.getOperand(FIOperandNo).getReg();
MI.getOperand(OperandBase).ChangeToRegister(StackReg, false);
- MI.getOperand(OperandBase + 1).ChangeToRegister(SReg, false);
+ MI.getOperand(OperandBase + 1).ChangeToRegister(SReg, false, false, true);
}
unsigned PPCRegisterInfo::getFrameRegister(const MachineFunction &MF) const {