//===-- X86FrameLowering.cpp - X86 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 X86 implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "X86FrameLowering.h"
#include "X86InstrBuilder.h"
#include "X86InstrInfo.h"
#include "X86MachineFunctionInfo.h"
#include "X86Subtarget.h"
#include "X86TargetMachine.h"
#include "llvm/ADT/SmallSet.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/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
// FIXME: completely move here.
extern cl::opt<bool> ForceStackAlign;
bool X86FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
return !MF.getFrameInfo()->hasVarSizedObjects();
}
/// 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 X86FrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const MachineModuleInfo &MMI = MF.getMMI();
const TargetRegisterInfo *RegInfo = TM.getRegisterInfo();
return (MF.getTarget().Options.DisableFramePointerElim(MF) ||
RegInfo->needsStackRealignment(MF) ||
MFI->hasVarSizedObjects() ||
MFI->isFrameAddressTaken() || MF.hasMSInlineAsm() ||
MF.getInfo<X86MachineFunctionInfo>()->getForceFramePointer() ||
MMI.callsUnwindInit() || MMI.callsEHReturn());
}
static unsigned getSUBriOpcode(unsigned IsLP64, int64_t Imm) {
if (IsLP64) {
if (isInt<8>(Imm))
return X86::SUB64ri8;
return X86::SUB64ri32;
} else {
if (isInt<8>(Imm))
return X86::SUB32ri8;
return X86::SUB32ri;
}
}
static unsigned getADDriOpcode(unsigned IsLP64, int64_t Imm) {
if (IsLP64) {
if (isInt<8>(Imm))
return X86::ADD64ri8;
return X86::ADD64ri32;
} else {
if (isInt<8>(Imm))
return X86::ADD32ri8;
return X86::ADD32ri;
}
}
static unsigned getLEArOpcode(unsigned IsLP64) {
return IsLP64 ? X86::LEA64r : X86::LEA32r;
}
/// findDeadCallerSavedReg - Return a caller-saved register that isn't live
/// when it reaches the "return" instruction. We can then pop a stack object
/// to this register without worry about clobbering it.
static unsigned findDeadCallerSavedReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
const TargetRegisterInfo &TRI,
bool Is64Bit) {
const MachineFunction *MF = MBB.getParent();
const Function *F = MF->getFunction();
if (!F || MF->getMMI().callsEHReturn())
return 0;
static const uint16_t CallerSavedRegs32Bit[] = {
X86::EAX, X86::EDX, X86::ECX, 0
};
static const uint16_t CallerSavedRegs64Bit[] = {
X86::RAX, X86::RDX, X86::RCX, X86::RSI, X86::RDI,
X86::R8, X86::R9, X86::R10, X86::R11, 0
};
unsigned Opc = MBBI->getOpcode();
switch (Opc) {
default: return 0;
case X86::RET:
case X86::RETI:
case X86::TCRETURNdi:
case X86::TCRETURNri:
case X86::TCRETURNmi:
case X86::TCRETURNdi64:
case X86::TCRETURNri64:
case X86::TCRETURNmi64:
case X86::EH_RETURN:
case X86::EH_RETURN64: {
SmallSet<uint16_t, 8> Uses;
for (unsigned i = 0, e = MBBI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MBBI->getOperand(i);
if (!MO.isReg() || MO.isDef())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
for (MCRegAliasIterator AI(Reg, &TRI, true); AI.isValid(); ++AI)
Uses.insert(*AI);
}
const uint16_t *CS = Is64Bit ? CallerSavedRegs64Bit : CallerSavedRegs32Bit;
for (; *CS; ++CS)
if (!Uses.count(*CS))
return *CS;
}
}
return 0;
}
/// emitSPUpdate - Emit a series of instructions to increment / decrement the
/// stack pointer by a constant value.
static
void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
unsigned StackPtr, int64_t NumBytes,
bool Is64Bit, bool IsLP64, bool UseLEA,
const TargetInstrInfo &TII, const TargetRegisterInfo &TRI) {
bool isSub = NumBytes < 0;
uint64_t Offset = isSub ? -NumBytes : NumBytes;
unsigned Opc;
if (UseLEA)
Opc = getLEArOpcode(IsLP64);
else
Opc = isSub
? getSUBriOpcode(IsLP64, Offset)
: getADDriOpcode(IsLP64, Offset);
uint64_t Chunk = (1LL << 31) - 1;
DebugLoc DL = MBB.findDebugLoc(MBBI);
while (Offset) {
uint64_t ThisVal = (Offset > Chunk) ? Chunk : Offset;
if (ThisVal == (Is64Bit ? 8 : 4)) {
// Use push / pop instead.
unsigned Reg = isSub
? (unsigned)(Is64Bit ? X86::RAX : X86::EAX)
: findDeadCallerSavedReg(MBB, MBBI, TRI, Is64Bit);
if (Reg) {
Opc = isSub
? (Is64Bit ? X86::PUSH64r : X86::PUSH32r)
: (Is64Bit ? X86::POP64r : X86::POP32r);
MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(Opc))
.addReg(Reg, getDefRegState(!isSub) | getUndefRegState(isSub));
if (isSub)
MI->setFlag(MachineInstr::FrameSetup);
Offset -= ThisVal;
continue;
}
}
MachineInstr *MI = NULL;
if (UseLEA) {
MI = addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr),
StackPtr, false, isSub ? -ThisVal : ThisVal);
} else {
MI = BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr)
.addImm(ThisVal);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
}
if (isSub)
MI->setFlag(MachineInstr::FrameSetup);
Offset -= ThisVal;
}
}
/// mergeSPUpdatesUp - Merge two stack-manipulating instructions upper iterator.
static
void mergeSPUpdatesUp(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
unsigned StackPtr, uint64_t *NumBytes = NULL) {
if (MBBI == MBB.begin()) return;
MachineBasicBlock::iterator PI = prior(MBBI);
unsigned Opc = PI->getOpcode();
if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
Opc == X86::ADD32ri || Opc == X86::ADD32ri8 ||
Opc == X86::LEA32r || Opc == X86::LEA64_32r) &&
PI->getOperand(0).getReg() == StackPtr) {
if (NumBytes)
*NumBytes += PI->getOperand(2).getImm();
MBB.erase(PI);
} else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
PI->getOperand(0).getReg() == StackPtr) {
if (NumBytes)
*NumBytes -= PI->getOperand(2).getImm();
MBB.erase(PI);
}
}
/// mergeSPUpdatesDown - Merge two stack-manipulating instructions lower iterator.
static
void mergeSPUpdatesDown(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
unsigned StackPtr, uint64_t *NumBytes = NULL) {
// FIXME: THIS ISN'T RUN!!!
return;
if (MBBI == MBB.end()) return;
MachineBasicBlock::iterator NI = llvm::next(MBBI);
if (NI == MBB.end()) return;
unsigned Opc = NI->getOpcode();
if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
Opc == X86::ADD32ri || Opc == X86::ADD32ri8) &&
NI->getOperand(0).getReg() == StackPtr) {
if (NumBytes)
*NumBytes -= NI->getOperand(2).getImm();
MBB.erase(NI);
MBBI = NI;
} else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
NI->getOperand(0).getReg() == StackPtr) {
if (NumBytes)
*NumBytes += NI->getOperand(2).getImm();
MBB.erase(NI);
MBBI = NI;
}
}
/// mergeSPUpdates - Checks the instruction before/after the passed
/// instruction. If it is an ADD/SUB/LEA instruction it is deleted argument and the
/// stack adjustment is returned as a positive value for ADD/LEA and a negative for
/// SUB.
static int mergeSPUpdates(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &MBBI,
unsigned StackPtr,
bool doMergeWithPrevious) {
if ((doMergeWithPrevious && MBBI == MBB.begin()) ||
(!doMergeWithPrevious && MBBI == MBB.end()))
return 0;
MachineBasicBlock::iterator PI = doMergeWithPrevious ? prior(MBBI) : MBBI;
MachineBasicBlock::iterator NI = doMergeWithPrevious ? 0 : llvm::next(MBBI);
unsigned Opc = PI->getOpcode();
int Offset = 0;
if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
Opc == X86::ADD32ri || Opc == X86::ADD32ri8 ||
Opc == X86::LEA32r || Opc == X86::LEA64_32r) &&
PI->getOperand(0).getReg() == StackPtr){
Offset += PI->getOperand(2).getImm();
MBB.erase(PI);
if (!doMergeWithPrevious) MBBI = NI;
} else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
PI->getOperand(0).getReg() == StackPtr) {
Offset -= PI->getOperand(2).getImm();
MBB.erase(PI);
if (!doMergeWithPrevious) MBBI = NI;
}
return Offset;
}
static bool isEAXLiveIn(MachineFunction &MF) {
for (MachineRegisterInfo::livein_iterator II = MF.getRegInfo().livein_begin(),
EE = MF.getRegInfo().livein_end(); II != EE; ++II) {
unsigned Reg = II->first;
if (Reg == X86::EAX || Reg == X86::AX ||
Reg == X86::AH || Reg == X86::AL)
return true;
}
return false;
}
void X86FrameLowering::emitCalleeSavedFrameMoves(MachineFunction &MF,
MCSymbol *Label,
unsigned FramePtr) const {
MachineFrameInfo *MFI = MF.getFrameInfo();
MachineModuleInfo &MMI = MF.getMMI();
const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
// Add callee saved registers to move list.
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
if (CSI.empty()) return;
const X86RegisterInfo *RegInfo = TM.getRegisterInfo();
bool HasFP = hasFP(MF);
// Calculate amount of bytes used for return address storing.
int stackGrowth = -RegInfo->getSlotSize();
// FIXME: This is dirty hack. The code itself is pretty mess right now.
// It should be rewritten from scratch and generalized sometimes.
// Determine maximum offset (minimum due to stack growth).
int64_t MaxOffset = 0;
for (std::vector<CalleeSavedInfo>::const_iterator
I = CSI.begin(), E = CSI.end(); I != E; ++I)
MaxOffset = std::min(MaxOffset,
MFI->getObjectOffset(I->getFrameIdx()));
// Calculate offsets.
int64_t saveAreaOffset = (HasFP ? 3 : 2) * stackGrowth;
for (std::vector<CalleeSavedInfo>::const_iterator
I = CSI.begin(), E = CSI.end(); I != E; ++I) {
int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
unsigned Reg = I->getReg();
Offset = MaxOffset - Offset + saveAreaOffset;
// Don't output a new machine move if we're re-saving the frame
// pointer. This happens when the PrologEpilogInserter has inserted an extra
// "PUSH" of the frame pointer -- the "emitPrologue" method automatically
// generates one when frame pointers are used. If we generate a "machine
// move" for this extra "PUSH", the linker will lose track of the fact that
// the frame pointer should have the value of the first "PUSH" when it's
// trying to unwind.
//
// FIXME: This looks inelegant. It's possibly correct, but it's covering up
// another bug. I.e., one where we generate a prolog like this:
//
// pushl %ebp
// movl %esp, %ebp
// pushl %ebp
// pushl %esi
// ...
//
// The immediate re-push of EBP is unnecessary. At the least, it's an
// optimization bug. EBP can be used as a scratch register in certain
// cases, but probably not when we have a frame pointer.
if (HasFP && FramePtr == Reg)
continue;
unsigned DwarfReg = MRI->getDwarfRegNum(Reg, true);
MMI.addFrameInst(MCCFIInstruction::createOffset(Label, DwarfReg, Offset));
}
}
/// getCompactUnwindRegNum - Get the compact unwind number for a given
/// register. The number corresponds to the enum lists in
/// compact_unwind_encoding.h.
static int getCompactUnwindRegNum(unsigned Reg, bool is64Bit) {
static const uint16_t CU32BitRegs[] = {
X86::EBX, X86::ECX, X86::EDX, X86::EDI, X86::ESI, X86::EBP, 0
};
static const uint16_t CU64BitRegs[] = {
X86::RBX, X86::R12, X86::R13, X86::R14, X86::R15, X86::RBP, 0
};
const uint16_t *CURegs = is64Bit ? CU64BitRegs : CU32BitRegs;
for (int Idx = 1; *CURegs; ++CURegs, ++Idx)
if (*CURegs == Reg)
return Idx;
return -1;
}
// Number of registers that can be saved in a compact unwind encoding.
#define CU_NUM_SAVED_REGS 6
/// encodeCompactUnwindRegistersWithoutFrame - Create the permutation encoding
/// used with frameless stacks. It is passed the number of registers to be saved
/// and an array of the registers saved.
static uint32_t
encodeCompactUnwindRegistersWithoutFrame(unsigned SavedRegs[CU_NUM_SAVED_REGS],
unsigned RegCount, bool Is64Bit) {
// The saved registers are numbered from 1 to 6. In order to encode the order
// in which they were saved, we re-number them according to their place in the
// register order. The re-numbering is relative to the last re-numbered
// register. E.g., if we have registers {6, 2, 4, 5} saved in that order:
//
// Orig Re-Num
// ---- ------
// 6 6
// 2 2
// 4 3
// 5 3
//
for (unsigned i = 0; i != CU_NUM_SAVED_REGS; ++i) {
int CUReg = getCompactUnwindRegNum(SavedRegs[i], Is64Bit);
if (CUReg == -1) return ~0U;
SavedRegs[i] = CUReg;
}
// Reverse the list.
std::swap(SavedRegs[0], SavedRegs[5]);
std::swap(SavedRegs[1], SavedRegs[4]);
std::swap(SavedRegs[2], SavedRegs[3]);
uint32_t RenumRegs[CU_NUM_SAVED_REGS];
for (unsigned i = CU_NUM_SAVED_REGS - RegCount; i < CU_NUM_SAVED_REGS; ++i) {
unsigned Countless = 0;
for (unsigned j = CU_NUM_SAVED_REGS - RegCount; j < i; ++j)
if (SavedRegs[j] < SavedRegs[i])
++Countless;
RenumRegs[i] = SavedRegs[i] - Countless - 1;
}
// Take the renumbered values and encode them into a 10-bit number.
uint32_t permutationEncoding = 0;
switch (RegCount) {
case 6:
permutationEncoding |= 120 * RenumRegs[0] + 24 * RenumRegs[1]
+ 6 * RenumRegs[2] + 2 * RenumRegs[3]
+ RenumRegs[4];
break;
case 5:
permutationEncoding |= 120 * RenumRegs[1] + 24 * RenumRegs[2]
+ 6 * RenumRegs[3] + 2 * RenumRegs[4]
+ RenumRegs[5];
break;
case 4:
permutationEncoding |= 60 * RenumRegs[2] + 12 * RenumRegs[3]
+ 3 * RenumRegs[4] + RenumRegs[5];
break;
case 3:
permutationEncoding |= 20 * RenumRegs[3] + 4 * RenumRegs[4]
+ RenumRegs[5];
break;
case 2:
permutationEncoding |= 5 * RenumRegs[4] + RenumRegs[5];
break;
case 1:
permutationEncoding |= RenumRegs[5];
break;
}
assert((permutationEncoding & 0x3FF) == permutationEncoding &&
"Invalid compact register encoding!");
return permutationEncoding;
}
/// encodeCompactUnwindRegistersWithFrame - Return the registers encoded for a
/// compact encoding with a frame pointer.
static uint32_t
encodeCompactUnwindRegistersWithFrame(unsigned SavedRegs[CU_NUM_SAVED_REGS],
bool Is64Bit) {
// Encode the registers in the order they were saved, 3-bits per register. The
// registers are numbered from 1 to CU_NUM_SAVED_REGS.
uint32_t RegEnc = 0;
for (int I = CU_NUM_SAVED_REGS - 1, Idx = 0; I != -1; --I) {
unsigned Reg = SavedRegs[I];
if (Reg == 0) continue;
int CURegNum = getCompactUnwindRegNum(Reg, Is64Bit);
if (CURegNum == -1) return ~0U;
// Encode the 3-bit register number in order, skipping over 3-bits for each
// register.
RegEnc |= (CURegNum & 0x7) << (Idx++ * 3);
}
assert((RegEnc & 0x3FFFF) == RegEnc && "Invalid compact register encoding!");
return RegEnc;
}
uint32_t X86FrameLowering::getCompactUnwindEncoding(MachineFunction &MF) const {
const X86RegisterInfo *RegInfo = TM.getRegisterInfo();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
unsigned StackPtr = RegInfo->getStackRegister();
bool Is64Bit = STI.is64Bit();
bool HasFP = hasFP(MF);
unsigned SavedRegs[CU_NUM_SAVED_REGS] = { 0, 0, 0, 0, 0, 0 };
unsigned SavedRegIdx = 0;
unsigned OffsetSize = (Is64Bit ? 8 : 4);
unsigned PushInstr = (Is64Bit ? X86::PUSH64r : X86::PUSH32r);
unsigned PushInstrSize = 1;
unsigned MoveInstr = (Is64Bit ? X86::MOV64rr : X86::MOV32rr);
unsigned MoveInstrSize = (Is64Bit ? 3 : 2);
unsigned SubtractInstrIdx = (Is64Bit ? 3 : 2);
unsigned StackDivide = (Is64Bit ? 8 : 4);
unsigned InstrOffset = 0;
unsigned StackAdjust = 0;
unsigned StackSize = 0;
MachineBasicBlock &MBB = MF.front(); // Prologue is in entry BB.
bool ExpectEnd = false;
for (MachineBasicBlock::iterator
MBBI = MBB.begin(), MBBE = MBB.end(); MBBI != MBBE; ++MBBI) {
MachineInstr &MI = *MBBI;
unsigned Opc = MI.getOpcode();
if (Opc == X86::PROLOG_LABEL) continue;
if (!MI.getFlag(MachineInstr::FrameSetup)) break;
// We don't exect any more prolog instructions.
if (ExpectEnd) return CU::UNWIND_MODE_DWARF;
if (Opc == PushInstr) {
// If there are too many saved registers, we cannot use compact encoding.
if (SavedRegIdx >= CU_NUM_SAVED_REGS) return CU::UNWIND_MODE_DWARF;
unsigned Reg = MI.getOperand(0).getReg();
if (Reg == (Is64Bit ? X86::RAX : X86::EAX)) {
ExpectEnd = true;
continue;
}
SavedRegs[SavedRegIdx++] = MI.getOperand(0).getReg();
StackAdjust += OffsetSize;
InstrOffset += PushInstrSize;
} else if (Opc == MoveInstr) {
unsigned SrcReg = MI.getOperand(1).getReg();
unsigned DstReg = MI.getOperand(0).getReg();
if (DstReg != FramePtr || SrcReg != StackPtr)
return CU::UNWIND_MODE_DWARF;
StackAdjust = 0;
memset(SavedRegs, 0, sizeof(SavedRegs));
SavedRegIdx = 0;
InstrOffset += MoveInstrSize;
} else if (Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
Opc == X86::SUB32ri || Opc == X86::SUB32ri8) {
if (StackSize)
// We already have a stack size.
return CU::UNWIND_MODE_DWARF;
if (!MI.getOperand(0).isReg() ||
MI.getOperand(0).getReg() != MI.getOperand(1).getReg() ||
MI.getOperand(0).getReg() != StackPtr || !MI.getOperand(2).isImm())
// We need this to be a stack adjustment pointer. Something like:
//
// %RSP<def> = SUB64ri8 %RSP, 48
return CU::UNWIND_MODE_DWARF;
StackSize = MI.getOperand(2).getImm() / StackDivide;
SubtractInstrIdx += InstrOffset;
ExpectEnd = true;
}
}
// Encode that we are using EBP/RBP as the frame pointer.
uint32_t CompactUnwindEncoding = 0;
StackAdjust /= StackDivide;
if (HasFP) {
if ((StackAdjust & 0xFF) != StackAdjust)
// Offset was too big for compact encoding.
return CU::UNWIND_MODE_DWARF;
// Get the encoding of the saved registers when we have a frame pointer.
uint32_t RegEnc = encodeCompactUnwindRegistersWithFrame(SavedRegs, Is64Bit);
if (RegEnc == ~0U) return CU::UNWIND_MODE_DWARF;
CompactUnwindEncoding |= CU::UNWIND_MODE_BP_FRAME;
CompactUnwindEncoding |= (StackAdjust & 0xFF) << 16;
CompactUnwindEncoding |= RegEnc & CU::UNWIND_BP_FRAME_REGISTERS;
} else {
++StackAdjust;
uint32_t TotalStackSize = StackAdjust + StackSize;
if ((TotalStackSize & 0xFF) == TotalStackSize) {
// Frameless stack with a small stack size.
CompactUnwindEncoding |= CU::UNWIND_MODE_STACK_IMMD;
// Encode the stack size.
CompactUnwindEncoding |= (TotalStackSize & 0xFF) << 16;
} else {
if ((StackAdjust & 0x7) != StackAdjust)
// The extra stack adjustments are too big for us to handle.
return CU::UNWIND_MODE_DWARF;
// Frameless stack with an offset too large for us to encode compactly.
CompactUnwindEncoding |= CU::UNWIND_MODE_STACK_IND;
// Encode the offset to the nnnnnn value in the 'subl $nnnnnn, ESP'
// instruction.
CompactUnwindEncoding |= (SubtractInstrIdx & 0xFF) << 16;
// Encode any extra stack stack adjustments (done via push instructions).
CompactUnwindEncoding |= (StackAdjust & 0x7) << 13;
}
// Encode the number of registers saved.
CompactUnwindEncoding |= (SavedRegIdx & 0x7) << 10;
// Get the encoding of the saved registers when we don't have a frame
// pointer.
uint32_t RegEnc =
encodeCompactUnwindRegistersWithoutFrame(SavedRegs, SavedRegIdx,
Is64Bit);
if (RegEnc == ~0U) return CU::UNWIND_MODE_DWARF;
// Encode the register encoding.
CompactUnwindEncoding |=
RegEnc & CU::UNWIND_FRAMELESS_STACK_REG_PERMUTATION;
}
return CompactUnwindEncoding;
}
/// usesTheStack - This function checks if any of the users of EFLAGS
/// copies the EFLAGS. We know that the code that lowers COPY of EFLAGS has
/// to use the stack, and if we don't adjust the stack we clobber the first
/// frame index.
/// See X86InstrInfo::copyPhysReg.
static bool usesTheStack(MachineFunction &MF) {
MachineRegisterInfo &MRI = MF.getRegInfo();
for (MachineRegisterInfo::reg_iterator ri = MRI.reg_begin(X86::EFLAGS),
re = MRI.reg_end(); ri != re; ++ri)
if (ri->isCopy())
return true;
return false;
}
/// emitPrologue - Push callee-saved registers onto the stack, which
/// automatically adjust the stack pointer. Adjust the stack pointer to allocate
/// space for local variables. Also emit labels used by the exception handler to
/// generate the exception handling frames.
void X86FrameLowering::emitPrologue(MachineFunction &MF) const {
MachineBasicBlock &MBB = MF.front(); // Prologue goes in entry BB.
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
const Function *Fn = MF.getFunction();
const X86RegisterInfo *RegInfo = TM.getRegisterInfo();
const X86InstrInfo &TII = *TM.getInstrInfo();
MachineModuleInfo &MMI = MF.getMMI();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
bool needsFrameMoves = MMI.hasDebugInfo() ||
Fn->needsUnwindTableEntry();
uint64_t MaxAlign = MFI->getMaxAlignment(); // Desired stack alignment.
uint64_t StackSize = MFI->getStackSize(); // Number of bytes to allocate.
bool HasFP = hasFP(MF);
bool Is64Bit = STI.is64Bit();
bool IsLP64 = STI.isTarget64BitLP64();
bool IsWin64 = STI.isTargetWin64();
bool UseLEA = STI.useLeaForSP();
unsigned StackAlign = getStackAlignment();
unsigned SlotSize = RegInfo->getSlotSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
unsigned StackPtr = RegInfo->getStackRegister();
unsigned BasePtr = RegInfo->getBaseRegister();
DebugLoc DL;
// If we're forcing a stack realignment we can't rely on just the frame
// info, we need to know the ABI stack alignment as well in case we
// have a call out. Otherwise just make sure we have some alignment - we'll
// go with the minimum SlotSize.
if (ForceStackAlign) {
if (MFI->hasCalls())
MaxAlign = (StackAlign > MaxAlign) ? StackAlign : MaxAlign;
else if (MaxAlign < SlotSize)
MaxAlign = SlotSize;
}
// Add RETADDR move area to callee saved frame size.
int TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
if (TailCallReturnAddrDelta < 0)
X86FI->setCalleeSavedFrameSize(
X86FI->getCalleeSavedFrameSize() - TailCallReturnAddrDelta);
// If this is x86-64 and the Red Zone is not disabled, if we are a leaf
// function, and use up to 128 bytes of stack space, don't have a frame
// pointer, calls, or dynamic alloca then we do not need to adjust the
// stack pointer (we fit in the Red Zone). We also check that we don't
// push and pop from the stack.
if (Is64Bit && !Fn->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
Attribute::NoRedZone) &&
!RegInfo->needsStackRealignment(MF) &&
!MFI->hasVarSizedObjects() && // No dynamic alloca.
!MFI->adjustsStack() && // No calls.
!IsWin64 && // Win64 has no Red Zone
!usesTheStack(MF) && // Don't push and pop.
!MF.getTarget().Options.EnableSegmentedStacks) { // Regular stack
uint64_t MinSize = X86FI->getCalleeSavedFrameSize();
if (HasFP) MinSize += SlotSize;
StackSize = std::max(MinSize, StackSize > 128 ? StackSize - 128 : 0);
MFI->setStackSize(StackSize);
}
// Insert stack pointer adjustment for later moving of return addr. Only
// applies to tail call optimized functions where the callee argument stack
// size is bigger than the callers.
if (TailCallReturnAddrDelta < 0) {
MachineInstr *MI =
BuildMI(MBB, MBBI, DL,
TII.get(getSUBriOpcode(IsLP64, -TailCallReturnAddrDelta)),
StackPtr)
.addReg(StackPtr)
.addImm(-TailCallReturnAddrDelta)
.setMIFlag(MachineInstr::FrameSetup);
MI->getOperand(3).setIsDead(); // The EFLAGS implicit def is dead.
}
// Mapping for machine moves:
//
// DST: VirtualFP AND
// SRC: VirtualFP => DW_CFA_def_cfa_offset
// ELSE => DW_CFA_def_cfa
//
// SRC: VirtualFP AND
// DST: Register => DW_CFA_def_cfa_register
//
// ELSE
// OFFSET < 0 => DW_CFA_offset_extended_sf
// REG < 64 => DW_CFA_offset + Reg
// ELSE => DW_CFA_offset_extended
uint64_t NumBytes = 0;
int stackGrowth = -SlotSize;
if (HasFP) {
// Calculate required stack adjustment.
uint64_t FrameSize = StackSize - SlotSize;
if (RegInfo->needsStackRealignment(MF)) {
// Callee-saved registers are pushed on stack before the stack
// is realigned.
FrameSize -= X86FI->getCalleeSavedFrameSize();
NumBytes = (FrameSize + MaxAlign - 1) / MaxAlign * MaxAlign;
} else {
NumBytes = FrameSize - X86FI->getCalleeSavedFrameSize();
}
// Get the offset of the stack slot for the EBP register, which is
// guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
// Update the frame offset adjustment.
MFI->setOffsetAdjustment(-NumBytes);
// Save EBP/RBP into the appropriate stack slot.
BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::PUSH64r : X86::PUSH32r))
.addReg(FramePtr, RegState::Kill)
.setMIFlag(MachineInstr::FrameSetup);
if (needsFrameMoves) {
// Mark the place where EBP/RBP was saved.
MCSymbol *FrameLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(X86::PROLOG_LABEL))
.addSym(FrameLabel);
// Define the current CFA rule to use the provided offset.
assert(StackSize);
MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(FrameLabel, 2 * stackGrowth));
// Change the rule for the FramePtr to be an "offset" rule.
unsigned DwarfFramePtr = RegInfo->getDwarfRegNum(FramePtr, true);
MMI.addFrameInst(MCCFIInstruction::createOffset(FrameLabel, DwarfFramePtr,
2 * stackGrowth));
}
// Update EBP with the new base value.
BuildMI(MBB, MBBI, DL,
TII.get(Is64Bit ? X86::MOV64rr : X86::MOV32rr), FramePtr)
.addReg(StackPtr)
.setMIFlag(MachineInstr::FrameSetup);
if (needsFrameMoves) {
// Mark effective beginning of when frame pointer becomes valid.
MCSymbol *FrameLabel = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(X86::PROLOG_LABEL))
.addSym(FrameLabel);
// Define the current CFA to use the EBP/RBP register.
unsigned DwarfFramePtr = RegInfo->getDwarfRegNum(FramePtr, true);
MMI.addFrameInst(
MCCFIInstruction::createDefCfaRegister(FrameLabel, DwarfFramePtr));
}
// Mark the FramePtr as live-in in every block except the entry.
for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
I != E; ++I)
I->addLiveIn(FramePtr);
} else {
NumBytes = StackSize - X86FI->getCalleeSavedFrameSize();
}
// Skip the callee-saved push instructions.
bool PushedRegs = false;
int StackOffset = 2 * stackGrowth;
while (MBBI != MBB.end() &&
(MBBI->getOpcode() == X86::PUSH32r ||
MBBI->getOpcode() == X86::PUSH64r)) {
PushedRegs = true;
MBBI->setFlag(MachineInstr::FrameSetup);
++MBBI;
if (!HasFP && needsFrameMoves) {
// Mark callee-saved push instruction.
MCSymbol *Label = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(X86::PROLOG_LABEL)).addSym(Label);
// Define the current CFA rule to use the provided offset.
assert(StackSize);
MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(Label, StackOffset));
StackOffset += stackGrowth;
}
}
// Realign stack after we pushed callee-saved registers (so that we'll be
// able to calculate their offsets from the frame pointer).
// NOTE: We push the registers before realigning the stack, so
// vector callee-saved (xmm) registers may be saved w/o proper
// alignment in this way. However, currently these regs are saved in
// stack slots (see X86FrameLowering::spillCalleeSavedRegisters()), so
// this shouldn't be a problem.
if (RegInfo->needsStackRealignment(MF)) {
assert(HasFP && "There should be a frame pointer if stack is realigned.");
MachineInstr *MI =
BuildMI(MBB, MBBI, DL,
TII.get(Is64Bit ? X86::AND64ri32 : X86::AND32ri), StackPtr)
.addReg(StackPtr)
.addImm(-MaxAlign)
.setMIFlag(MachineInstr::FrameSetup);
// The EFLAGS implicit def is dead.
MI->getOperand(3).setIsDead();
}
// If there is an SUB32ri of ESP immediately before this instruction, merge
// the two. This can be the case when tail call elimination is enabled and
// the callee has more arguments then the caller.
NumBytes -= mergeSPUpdates(MBB, MBBI, StackPtr, true);
// If there is an ADD32ri or SUB32ri of ESP immediately after this
// instruction, merge the two instructions.
mergeSPUpdatesDown(MBB, MBBI, StackPtr, &NumBytes);
// Adjust stack pointer: ESP -= numbytes.
// Windows and cygwin/mingw require a prologue helper routine when allocating
// more than 4K bytes on the stack. Windows uses __chkstk and cygwin/mingw
// uses __alloca. __alloca and the 32-bit version of __chkstk will probe the
// stack and adjust the stack pointer in one go. The 64-bit version of
// __chkstk is only responsible for probing the stack. The 64-bit prologue is
// responsible for adjusting the stack pointer. Touching the stack at 4K
// increments is necessary to ensure that the guard pages used by the OS
// virtual memory manager are allocated in correct sequence.
if (NumBytes >= 4096 && STI.isTargetCOFF() && !STI.isTargetEnvMacho()) {
const char *StackProbeSymbol;
bool isSPUpdateNeeded = false;
if (Is64Bit) {
if (STI.isTargetCygMing())
StackProbeSymbol = "___chkstk";
else {
StackProbeSymbol = "__chkstk";
isSPUpdateNeeded = true;
}
} else if (STI.isTargetCygMing())
StackProbeSymbol = "_alloca";
else
StackProbeSymbol = "_chkstk";
// Check whether EAX is livein for this function.
bool isEAXAlive = isEAXLiveIn(MF);
if (isEAXAlive) {
// Sanity check that EAX is not livein for this function.
// It should not be, so throw an assert.
assert(!Is64Bit && "EAX is livein in x64 case!");
// Save EAX
BuildMI(MBB, MBBI, DL, TII.get(X86::PUSH32r))
.addReg(X86::EAX, RegState::Kill)
.setMIFlag(MachineInstr::FrameSetup);
}
if (Is64Bit) {
// Handle the 64-bit Windows ABI case where we need to call __chkstk.
// Function prologue is responsible for adjusting the stack pointer.
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV64ri), X86::RAX)
.addImm(NumBytes)
.setMIFlag(MachineInstr::FrameSetup);
} else {
// Allocate NumBytes-4 bytes on stack in case of isEAXAlive.
// We'll also use 4 already allocated bytes for EAX.
BuildMI(MBB, MBBI, DL, TII.get(X86::MOV32ri), X86::EAX)
.addImm(isEAXAlive ? NumBytes - 4 : NumBytes)
.setMIFlag(MachineInstr::FrameSetup);
}
BuildMI(MBB, MBBI, DL,
TII.get(Is64Bit ? X86::W64ALLOCA : X86::CALLpcrel32))
.addExternalSymbol(StackProbeSymbol)
.addReg(StackPtr, RegState::Define | RegState::Implicit)
.addReg(X86::EFLAGS, RegState::Define | RegState::Implicit)
.setMIFlag(MachineInstr::FrameSetup);
// MSVC x64's __chkstk does not adjust %rsp itself.
// It also does not clobber %rax so we can reuse it when adjusting %rsp.
if (isSPUpdateNeeded) {
BuildMI(MBB, MBBI, DL, TII.get(X86::SUB64rr), StackPtr)
.addReg(StackPtr)
.addReg(X86::RAX)
.setMIFlag(MachineInstr::FrameSetup);
}
if (isEAXAlive) {
// Restore EAX
MachineInstr *MI = addRegOffset(BuildMI(MF, DL, TII.get(X86::MOV32rm),
X86::EAX),
StackPtr, false, NumBytes - 4);
MI->setFlag(MachineInstr::FrameSetup);
MBB.insert(MBBI, MI);
}
} else if (NumBytes)
emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, IsLP64,
UseLEA, TII, *RegInfo);
// 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)) {
// Update the frame pointer with the current stack pointer.
unsigned Opc = Is64Bit ? X86::MOV64rr : X86::MOV32rr;
BuildMI(MBB, MBBI, DL, TII.get(Opc), BasePtr)
.addReg(StackPtr)
.setMIFlag(MachineInstr::FrameSetup);
}
if (( (!HasFP && NumBytes) || PushedRegs) && needsFrameMoves) {
// Mark end of stack pointer adjustment.
MCSymbol *Label = MMI.getContext().CreateTempSymbol();
BuildMI(MBB, MBBI, DL, TII.get(X86::PROLOG_LABEL))
.addSym(Label);
if (!HasFP && NumBytes) {
// Define the current CFA rule to use the provided offset.
assert(StackSize);
MMI.addFrameInst(MCCFIInstruction::createDefCfaOffset(
Label, -StackSize + stackGrowth));
}
// Emit DWARF info specifying the offsets of the callee-saved registers.
if (PushedRegs)
emitCalleeSavedFrameMoves(MF, Label, HasFP ? FramePtr : StackPtr);
}
// Darwin 10.7 and greater has support for compact unwind encoding.
if (STI.getTargetTriple().isMacOSX() &&
!STI.getTargetTriple().isMacOSXVersionLT(10, 7))
MMI.setCompactUnwindEncoding(getCompactUnwindEncoding(MF));
}
void X86FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
const X86RegisterInfo *RegInfo = TM.getRegisterInfo();
const X86InstrInfo &TII = *TM.getInstrInfo();
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
assert(MBBI != MBB.end() && "Returning block has no instructions");
unsigned RetOpcode = MBBI->getOpcode();
DebugLoc DL = MBBI->getDebugLoc();
bool Is64Bit = STI.is64Bit();
bool IsLP64 = STI.isTarget64BitLP64();
bool UseLEA = STI.useLeaForSP();
unsigned StackAlign = getStackAlignment();
unsigned SlotSize = RegInfo->getSlotSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
unsigned StackPtr = RegInfo->getStackRegister();
switch (RetOpcode) {
default:
llvm_unreachable("Can only insert epilog into returning blocks");
case X86::RET:
case X86::RETI:
case X86::TCRETURNdi:
case X86::TCRETURNri:
case X86::TCRETURNmi:
case X86::TCRETURNdi64:
case X86::TCRETURNri64:
case X86::TCRETURNmi64:
case X86::EH_RETURN:
case X86::EH_RETURN64:
break; // These are ok
}
// Get the number of bytes to allocate from the FrameInfo.
uint64_t StackSize = MFI->getStackSize();
uint64_t MaxAlign = MFI->getMaxAlignment();
unsigned CSSize = X86FI->getCalleeSavedFrameSize();
uint64_t NumBytes = 0;
// If we're forcing a stack realignment we can't rely on just the frame
// info, we need to know the ABI stack alignment as well in case we
// have a call out. Otherwise just make sure we have some alignment - we'll
// go with the minimum.
if (ForceStackAlign) {
if (MFI->hasCalls())
MaxAlign = (StackAlign > MaxAlign) ? StackAlign : MaxAlign;
else
MaxAlign = MaxAlign ? MaxAlign : 4;
}
if (hasFP(MF)) {
// Calculate required stack adjustment.
uint64_t FrameSize = StackSize - SlotSize;
if (RegInfo->needsStackRealignment(MF)) {
// Callee-saved registers were pushed on stack before the stack
// was realigned.
FrameSize -= CSSize;
NumBytes = (FrameSize + MaxAlign - 1) / MaxAlign * MaxAlign;
} else {
NumBytes = FrameSize - CSSize;
}
// Pop EBP.
BuildMI(MBB, MBBI, DL,
TII.get(Is64Bit ? X86::POP64r : X86::POP32r), FramePtr);
} else {
NumBytes = StackSize - CSSize;
}
// Skip the callee-saved pop instructions.
while (MBBI != MBB.begin()) {
MachineBasicBlock::iterator PI = prior(MBBI);
unsigned Opc = PI->getOpcode();
if (Opc != X86::POP32r && Opc != X86::POP64r && Opc != X86::DBG_VALUE &&
!PI->isTerminator())
break;
--MBBI;
}
MachineBasicBlock::iterator FirstCSPop = MBBI;
DL = MBBI->getDebugLoc();
// If there is an ADD32ri or SUB32ri of ESP immediately before this
// instruction, merge the two instructions.
if (NumBytes || MFI->hasVarSizedObjects())
mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);
// If dynamic alloca is used, then reset esp to point to the last callee-saved
// slot before popping them off! Same applies for the case, when stack was
// realigned.
if (RegInfo->needsStackRealignment(MF) || MFI->hasVarSizedObjects()) {
if (RegInfo->needsStackRealignment(MF))
MBBI = FirstCSPop;
if (CSSize != 0) {
unsigned Opc = getLEArOpcode(IsLP64);
addRegOffset(BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr),
FramePtr, false, -CSSize);
} else {
unsigned Opc = (Is64Bit ? X86::MOV64rr : X86::MOV32rr);
BuildMI(MBB, MBBI, DL, TII.get(Opc), StackPtr)
.addReg(FramePtr);
}
} else if (NumBytes) {
// Adjust stack pointer back: ESP += numbytes.
emitSPUpdate(MBB, MBBI, StackPtr, NumBytes, Is64Bit, IsLP64, UseLEA,
TII, *RegInfo);
}
// We're returning from function via eh_return.
if (RetOpcode == X86::EH_RETURN || RetOpcode == X86::EH_RETURN64) {
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &DestAddr = MBBI->getOperand(0);
assert(DestAddr.isReg() && "Offset should be in register!");
BuildMI(MBB, MBBI, DL,
TII.get(Is64Bit ? X86::MOV64rr : X86::MOV32rr),
StackPtr).addReg(DestAddr.getReg());
} else if (RetOpcode == X86::TCRETURNri || RetOpcode == X86::TCRETURNdi ||
RetOpcode == X86::TCRETURNmi ||
RetOpcode == X86::TCRETURNri64 || RetOpcode == X86::TCRETURNdi64 ||
RetOpcode == X86::TCRETURNmi64) {
bool isMem = RetOpcode == X86::TCRETURNmi || RetOpcode == X86::TCRETURNmi64;
// Tail call return: adjust the stack pointer and jump to callee.
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &JumpTarget = MBBI->getOperand(0);
MachineOperand &StackAdjust = MBBI->getOperand(isMem ? 5 : 1);
assert(StackAdjust.isImm() && "Expecting immediate value.");
// Adjust stack pointer.
int StackAdj = StackAdjust.getImm();
int MaxTCDelta = X86FI->getTCReturnAddrDelta();
int Offset = 0;
assert(MaxTCDelta <= 0 && "MaxTCDelta should never be positive");
// Incoporate the retaddr area.
Offset = StackAdj-MaxTCDelta;
assert(Offset >= 0 && "Offset should never be negative");
if (Offset) {
// Check for possible merge with preceding ADD instruction.
Offset += mergeSPUpdates(MBB, MBBI, StackPtr, true);
emitSPUpdate(MBB, MBBI, StackPtr, Offset, Is64Bit, IsLP64,
UseLEA, TII, *RegInfo);
}
// Jump to label or value in register.
if (RetOpcode == X86::TCRETURNdi || RetOpcode == X86::TCRETURNdi64) {
MachineInstrBuilder MIB =
BuildMI(MBB, MBBI, DL, TII.get((RetOpcode == X86::TCRETURNdi)
? X86::TAILJMPd : X86::TAILJMPd64));
if (JumpTarget.isGlobal())
MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
JumpTarget.getTargetFlags());
else {
assert(JumpTarget.isSymbol());
MIB.addExternalSymbol(JumpTarget.getSymbolName(),
JumpTarget.getTargetFlags());
}
} else if (RetOpcode == X86::TCRETURNmi || RetOpcode == X86::TCRETURNmi64) {
MachineInstrBuilder MIB =
BuildMI(MBB, MBBI, DL, TII.get((RetOpcode == X86::TCRETURNmi)
? X86::TAILJMPm : X86::TAILJMPm64));
for (unsigned i = 0; i != 5; ++i)
MIB.addOperand(MBBI->getOperand(i));
} else if (RetOpcode == X86::TCRETURNri64) {
BuildMI(MBB, MBBI, DL, TII.get(X86::TAILJMPr64)).
addReg(JumpTarget.getReg(), RegState::Kill);
} else {
BuildMI(MBB, MBBI, DL, TII.get(X86::TAILJMPr)).
addReg(JumpTarget.getReg(), RegState::Kill);
}
MachineInstr *NewMI = prior(MBBI);
NewMI->copyImplicitOps(MF, MBBI);
// Delete the pseudo instruction TCRETURN.
MBB.erase(MBBI);
} else if ((RetOpcode == X86::RET || RetOpcode == X86::RETI) &&
(X86FI->getTCReturnAddrDelta() < 0)) {
// Add the return addr area delta back since we are not tail calling.
int delta = -1*X86FI->getTCReturnAddrDelta();
MBBI = MBB.getLastNonDebugInstr();
// Check for possible merge with preceding ADD instruction.
delta += mergeSPUpdates(MBB, MBBI, StackPtr, true);
emitSPUpdate(MBB, MBBI, StackPtr, delta, Is64Bit, IsLP64, UseLEA, TII,
*RegInfo);
}
}
int X86FrameLowering::getFrameIndexOffset(const MachineFunction &MF, int FI) const {
const X86RegisterInfo *RegInfo =
static_cast<const X86RegisterInfo*>(MF.getTarget().getRegisterInfo());
const MachineFrameInfo *MFI = MF.getFrameInfo();
int Offset = MFI->getObjectOffset(FI) - getOffsetOfLocalArea();
uint64_t StackSize = MFI->getStackSize();
if (RegInfo->hasBasePointer(MF)) {
assert (hasFP(MF) && "VLAs and dynamic stack realign, but no FP?!");
if (FI < 0) {
// Skip the saved EBP.
return Offset + RegInfo->getSlotSize();
} else {
assert((-(Offset + StackSize)) % MFI->getObjectAlignment(FI) == 0);
return Offset + StackSize;
}
} else if (RegInfo->needsStackRealignment(MF)) {
if (FI < 0) {
// Skip the saved EBP.
return Offset + RegInfo->getSlotSize();
} else {
assert((-(Offset + StackSize)) % MFI->getObjectAlignment(FI) == 0);
return Offset + StackSize;
}
// FIXME: Support tail calls
} else {
if (!hasFP(MF))
return Offset + StackSize;
// Skip the saved EBP.
Offset += RegInfo->getSlotSize();
// Skip the RETADDR move area
const X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
int TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
if (TailCallReturnAddrDelta < 0)
Offset -= TailCallReturnAddrDelta;
}
return Offset;
}
int X86FrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
unsigned &FrameReg) const {
const X86RegisterInfo *RegInfo =
static_cast<const X86RegisterInfo*>(MF.getTarget().getRegisterInfo());
// We can't calculate offset from frame pointer if the stack is realigned,
// so enforce usage of stack/base pointer. The base pointer is used when we
// have dynamic allocas in addition to dynamic realignment.
if (RegInfo->hasBasePointer(MF))
FrameReg = RegInfo->getBaseRegister();
else if (RegInfo->needsStackRealignment(MF))
FrameReg = RegInfo->getStackRegister();
else
FrameReg = RegInfo->getFrameRegister(MF);
return getFrameIndexOffset(MF, FI);
}
bool X86FrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
DebugLoc DL = MBB.findDebugLoc(MI);
MachineFunction &MF = *MBB.getParent();
unsigned SlotSize = STI.is64Bit() ? 8 : 4;
unsigned FPReg = TRI->getFrameRegister(MF);
unsigned CalleeFrameSize = 0;
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
// Push GPRs. It increases frame size.
unsigned Opc = STI.is64Bit() ? X86::PUSH64r : X86::PUSH32r;
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (!X86::GR64RegClass.contains(Reg) &&
!X86::GR32RegClass.contains(Reg))
continue;
// Add the callee-saved register as live-in. It's killed at the spill.
MBB.addLiveIn(Reg);
if (Reg == FPReg)
// X86RegisterInfo::emitPrologue will handle spilling of frame register.
continue;
CalleeFrameSize += SlotSize;
BuildMI(MBB, MI, DL, TII.get(Opc)).addReg(Reg, RegState::Kill)
.setMIFlag(MachineInstr::FrameSetup);
}
X86FI->setCalleeSavedFrameSize(CalleeFrameSize);
// Make XMM regs spilled. X86 does not have ability of push/pop XMM.
// It can be done by spilling XMMs to stack frame.
// Note that only Win64 ABI might spill XMMs.
for (unsigned i = CSI.size(); i != 0; --i) {
unsigned Reg = CSI[i-1].getReg();
if (X86::GR64RegClass.contains(Reg) ||
X86::GR32RegClass.contains(Reg))
continue;
// Add the callee-saved register as live-in. It's killed at the spill.
MBB.addLiveIn(Reg);
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.storeRegToStackSlot(MBB, MI, Reg, true, CSI[i-1].getFrameIdx(),
RC, TRI);
}
return true;
}
bool X86FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
if (CSI.empty())
return false;
DebugLoc DL = MBB.findDebugLoc(MI);
MachineFunction &MF = *MBB.getParent();
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
// Reload XMMs from stack frame.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
if (X86::GR64RegClass.contains(Reg) ||
X86::GR32RegClass.contains(Reg))
continue;
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.loadRegFromStackSlot(MBB, MI, Reg, CSI[i].getFrameIdx(),
RC, TRI);
}
// POP GPRs.
unsigned FPReg = TRI->getFrameRegister(MF);
unsigned Opc = STI.is64Bit() ? X86::POP64r : X86::POP32r;
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
if (!X86::GR64RegClass.contains(Reg) &&
!X86::GR32RegClass.contains(Reg))
continue;
if (Reg == FPReg)
// X86RegisterInfo::emitEpilogue will handle restoring of frame register.
continue;
BuildMI(MBB, MI, DL, TII.get(Opc), Reg);
}
return true;
}
void
X86FrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
RegScavenger *RS) const {
MachineFrameInfo *MFI = MF.getFrameInfo();
const X86RegisterInfo *RegInfo = TM.getRegisterInfo();
unsigned SlotSize = RegInfo->getSlotSize();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
int64_t TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
if (TailCallReturnAddrDelta < 0) {
// create RETURNADDR area
// arg
// arg
// RETADDR
// { ...
// RETADDR area
// ...
// }
// [EBP]
MFI->CreateFixedObject(-TailCallReturnAddrDelta,
TailCallReturnAddrDelta - SlotSize, true);
}
if (hasFP(MF)) {
assert((TailCallReturnAddrDelta <= 0) &&
"The Delta should always be zero or negative");
const TargetFrameLowering &TFI = *MF.getTarget().getFrameLowering();
// Create a frame entry for the EBP register that must be saved.
int FrameIdx = MFI->CreateFixedObject(SlotSize,
-(int)SlotSize +
TFI.getOffsetOfLocalArea() +
TailCallReturnAddrDelta,
true);
assert(FrameIdx == MFI->getObjectIndexBegin() &&
"Slot for EBP register must be last in order to be found!");
(void)FrameIdx;
}
// Spill the BasePtr if it's used.
if (RegInfo->hasBasePointer(MF))
MF.getRegInfo().setPhysRegUsed(RegInfo->getBaseRegister());
}
static bool
HasNestArgument(const MachineFunction *MF) {
const Function *F = MF->getFunction();
for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
I != E; I++) {
if (I->hasNestAttr())
return true;
}
return false;
}
/// GetScratchRegister - Get a temp register for performing work in the
/// segmented stack and the Erlang/HiPE stack prologue. Depending on platform
/// and the properties of the function either one or two registers will be
/// needed. Set primary to true for the first register, false for the second.
static unsigned
GetScratchRegister(bool Is64Bit, const MachineFunction &MF, bool Primary) {
CallingConv::ID CallingConvention = MF.getFunction()->getCallingConv();
// Erlang stuff.
if (CallingConvention == CallingConv::HiPE) {
if (Is64Bit)
return Primary ? X86::R14 : X86::R13;
else
return Primary ? X86::EBX : X86::EDI;
}
if (Is64Bit)
return Primary ? X86::R11 : X86::R12;
bool IsNested = HasNestArgument(&MF);
if (CallingConvention == CallingConv::X86_FastCall ||
CallingConvention == CallingConv::Fast) {
if (IsNested)
report_fatal_error("Segmented stacks does not support fastcall with "
"nested function.");
return Primary ? X86::EAX : X86::ECX;
}
if (IsNested)
return Primary ? X86::EDX : X86::EAX;
return Primary ? X86::ECX : X86::EAX;
}
// The stack limit in the TCB is set to this many bytes above the actual stack
// limit.
static const uint64_t kSplitStackAvailable = 256;
void
X86FrameLowering::adjustForSegmentedStacks(MachineFunction &MF) const {
MachineBasicBlock &prologueMBB = MF.front();
MachineFrameInfo *MFI = MF.getFrameInfo();
const X86InstrInfo &TII = *TM.getInstrInfo();
uint64_t StackSize;
bool Is64Bit = STI.is64Bit();
unsigned TlsReg, TlsOffset;
DebugLoc DL;
unsigned ScratchReg = GetScratchRegister(Is64Bit, MF, true);
assert(!MF.getRegInfo().isLiveIn(ScratchReg) &&
"Scratch register is live-in");
if (MF.getFunction()->isVarArg())
report_fatal_error("Segmented stacks do not support vararg functions.");
if (!STI.isTargetLinux() && !STI.isTargetDarwin() &&
!STI.isTargetWin32() && !STI.isTargetFreeBSD())
report_fatal_error("Segmented stacks not supported on this platform.");
MachineBasicBlock *allocMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *checkMBB = MF.CreateMachineBasicBlock();
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
bool IsNested = false;
// We need to know if the function has a nest argument only in 64 bit mode.
if (Is64Bit)
IsNested = HasNestArgument(&MF);
// The MOV R10, RAX needs to be in a different block, since the RET we emit in
// allocMBB needs to be last (terminating) instruction.
for (MachineBasicBlock::livein_iterator i = prologueMBB.livein_begin(),
e = prologueMBB.livein_end(); i != e; i++) {
allocMBB->addLiveIn(*i);
checkMBB->addLiveIn(*i);
}
if (IsNested)
allocMBB->addLiveIn(X86::R10);
MF.push_front(allocMBB);
MF.push_front(checkMBB);
// Eventually StackSize will be calculated by a link-time pass; which will
// also decide whether checking code needs to be injected into this particular
// prologue.
StackSize = MFI->getStackSize();
// 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 = StackSize < kSplitStackAvailable;
// Read the limit off the current stacklet off the stack_guard location.
if (Is64Bit) {
if (STI.isTargetLinux()) {
TlsReg = X86::FS;
TlsOffset = 0x70;
} else if (STI.isTargetDarwin()) {
TlsReg = X86::GS;
TlsOffset = 0x60 + 90*8; // See pthread_machdep.h. Steal TLS slot 90.
} else if (STI.isTargetFreeBSD()) {
TlsReg = X86::FS;
TlsOffset = 0x18;
} else {
report_fatal_error("Segmented stacks not supported on this platform.");
}
if (CompareStackPointer)
ScratchReg = X86::RSP;
else
BuildMI(checkMBB, DL, TII.get(X86::LEA64r), ScratchReg).addReg(X86::RSP)
.addImm(1).addReg(0).addImm(-StackSize).addReg(0);
BuildMI(checkMBB, DL, TII.get(X86::CMP64rm)).addReg(ScratchReg)
.addReg(0).addImm(1).addReg(0).addImm(TlsOffset).addReg(TlsReg);
} else {
if (STI.isTargetLinux()) {
TlsReg = X86::GS;
TlsOffset = 0x30;
} else if (STI.isTargetDarwin()) {
TlsReg = X86::GS;
TlsOffset = 0x48 + 90*4;
} else if (STI.isTargetWin32()) {
TlsReg = X86::FS;
TlsOffset = 0x14; // pvArbitrary, reserved for application use
} else if (STI.isTargetFreeBSD()) {
report_fatal_error("Segmented stacks not supported on FreeBSD i386.");
} else {
report_fatal_error("Segmented stacks not supported on this platform.");
}
if (CompareStackPointer)
ScratchReg = X86::ESP;
else
BuildMI(checkMBB, DL, TII.get(X86::LEA32r), ScratchReg).addReg(X86::ESP)
.addImm(1).addReg(0).addImm(-StackSize).addReg(0);
if (STI.isTargetLinux() || STI.isTargetWin32()) {
BuildMI(checkMBB, DL, TII.get(X86::CMP32rm)).addReg(ScratchReg)
.addReg(0).addImm(0).addReg(0).addImm(TlsOffset).addReg(TlsReg);
} else if (STI.isTargetDarwin()) {
// TlsOffset doesn't fit into a mod r/m byte so we need an extra register
unsigned ScratchReg2;
bool SaveScratch2;
if (CompareStackPointer) {
// The primary scratch register is available for holding the TLS offset
ScratchReg2 = GetScratchRegister(Is64Bit, MF, true);
SaveScratch2 = false;
} else {
// Need to use a second register to hold the TLS offset
ScratchReg2 = GetScratchRegister(Is64Bit, MF, false);
// Unfortunately, with fastcc the second scratch register may hold an arg
SaveScratch2 = MF.getRegInfo().isLiveIn(ScratchReg2);
}
// If Scratch2 is live-in then it needs to be saved
assert((!MF.getRegInfo().isLiveIn(ScratchReg2) || SaveScratch2) &&
"Scratch register is live-in and not saved");
if (SaveScratch2)
BuildMI(checkMBB, DL, TII.get(X86::PUSH32r))
.addReg(ScratchReg2, RegState::Kill);
BuildMI(checkMBB, DL, TII.get(X86::MOV32ri), ScratchReg2)
.addImm(TlsOffset);
BuildMI(checkMBB, DL, TII.get(X86::CMP32rm))
.addReg(ScratchReg)
.addReg(ScratchReg2).addImm(1).addReg(0)
.addImm(0)
.addReg(TlsReg);
if (SaveScratch2)
BuildMI(checkMBB, DL, TII.get(X86::POP32r), ScratchReg2);
}
}
// This jump is taken if SP >= (Stacklet Limit + Stack Space required).
// It jumps to normal execution of the function body.
BuildMI(checkMBB, DL, TII.get(X86::JA_4)).addMBB(&prologueMBB);
// On 32 bit we first push the arguments size and then the frame size. On 64
// bit, we pass the stack frame size in r10 and the argument size in r11.
if (Is64Bit) {
// Functions with nested arguments use R10, so it needs to be saved across
// the call to _morestack
if (IsNested)
BuildMI(allocMBB, DL, TII.get(X86::MOV64rr), X86::RAX).addReg(X86::R10);
BuildMI(allocMBB, DL, TII.get(X86::MOV64ri), X86::R10)
.addImm(StackSize);
BuildMI(allocMBB, DL, TII.get(X86::MOV64ri), X86::R11)
.addImm(X86FI->getArgumentStackSize());
MF.getRegInfo().setPhysRegUsed(X86::R10);
MF.getRegInfo().setPhysRegUsed(X86::R11);
} else {
BuildMI(allocMBB, DL, TII.get(X86::PUSHi32))
.addImm(X86FI->getArgumentStackSize());
BuildMI(allocMBB, DL, TII.get(X86::PUSHi32))
.addImm(StackSize);
}
// __morestack is in libgcc
if (Is64Bit)
BuildMI(allocMBB, DL, TII.get(X86::CALL64pcrel32))
.addExternalSymbol("__morestack");
else
BuildMI(allocMBB, DL, TII.get(X86::CALLpcrel32))
.addExternalSymbol("__morestack");
if (IsNested)
BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET_RESTORE_R10));
else
BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET));
allocMBB->addSuccessor(&prologueMBB);
checkMBB->addSuccessor(allocMBB);
checkMBB->addSuccessor(&prologueMBB);
#ifdef XDEBUG
MF.verify();
#endif
}
/// Erlang programs may need a special prologue to handle the stack size they
/// might need at runtime. That is because Erlang/OTP does not implement a C
/// stack but uses a custom implementation of hybrid stack/heap architecture.
/// (for more information see Eric Stenman's Ph.D. thesis:
/// http://publications.uu.se/uu/fulltext/nbn_se_uu_diva-2688.pdf)
///
/// CheckStack:
/// temp0 = sp - MaxStack
/// if( temp0 < SP_LIMIT(P) ) goto IncStack else goto OldStart
/// OldStart:
/// ...
/// IncStack:
/// call inc_stack # doubles the stack space
/// temp0 = sp - MaxStack
/// if( temp0 < SP_LIMIT(P) ) goto IncStack else goto OldStart
void X86FrameLowering::adjustForHiPEPrologue(MachineFunction &MF) const {
const X86InstrInfo &TII = *TM.getInstrInfo();
MachineFrameInfo *MFI = MF.getFrameInfo();
const unsigned SlotSize = TM.getRegisterInfo()->getSlotSize();
const bool Is64Bit = STI.is64Bit();
DebugLoc DL;
// HiPE-specific values
const unsigned HipeLeafWords = 24;
const unsigned CCRegisteredArgs = Is64Bit ? 6 : 5;
const unsigned Guaranteed = HipeLeafWords * SlotSize;
unsigned CallerStkArity = MF.getFunction()->arg_size() > CCRegisteredArgs ?
MF.getFunction()->arg_size() - CCRegisteredArgs : 0;
unsigned MaxStack = MFI->getStackSize() + CallerStkArity*SlotSize + SlotSize;
assert(STI.isTargetLinux() &&
"HiPE prologue is only supported on Linux operating systems.");
// Compute the largest caller's frame that is needed to fit the callees'
// frames. This 'MaxStack' is computed from:
//
// a) the fixed frame size, which is the space needed for all spilled temps,
// b) outgoing on-stack parameter areas, and
// c) the minimum stack space this function needs to make available for the
// functions it calls (a tunable ABI property).
if (MFI->hasCalls()) {
unsigned MoreStackForCalls = 0;
for (MachineFunction::iterator MBBI = MF.begin(), MBBE = MF.end();
MBBI != MBBE; ++MBBI)
for (MachineBasicBlock::iterator MI = MBBI->begin(), ME = MBBI->end();
MI != ME; ++MI) {
if (!MI->isCall())
continue;
// Get callee operand.
const MachineOperand &MO = MI->getOperand(0);
// Only take account of global function calls (no closures etc.).
if (!MO.isGlobal())
continue;
const Function *F = dyn_cast<Function>(MO.getGlobal());
if (!F)
continue;
// Do not update 'MaxStack' for primitive and built-in functions
// (encoded with names either starting with "erlang."/"bif_" or not
// having a ".", such as a simple <Module>.<Function>.<Arity>, or an
// "_", such as the BIF "suspend_0") as they are executed on another
// stack.
if (F->getName().find("erlang.") != StringRef::npos ||
F->getName().find("bif_") != StringRef::npos ||
F->getName().find_first_of("._") == StringRef::npos)
continue;
unsigned CalleeStkArity =
F->arg_size() > CCRegisteredArgs ? F->arg_size()-CCRegisteredArgs : 0;
if (HipeLeafWords - 1 > CalleeStkArity)
MoreStackForCalls = std::max(MoreStackForCalls,
(HipeLeafWords - 1 - CalleeStkArity) * SlotSize);
}
MaxStack += MoreStackForCalls;
}
// If the stack frame needed is larger than the guaranteed then runtime checks
// and calls to "inc_stack_0" BIF should be inserted in the assembly prologue.
if (MaxStack > Guaranteed) {
MachineBasicBlock &prologueMBB = MF.front();
MachineBasicBlock *stackCheckMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *incStackMBB = MF.CreateMachineBasicBlock();
for (MachineBasicBlock::livein_iterator I = prologueMBB.livein_begin(),
E = prologueMBB.livein_end(); I != E; I++) {
stackCheckMBB->addLiveIn(*I);
incStackMBB->addLiveIn(*I);
}
MF.push_front(incStackMBB);
MF.push_front(stackCheckMBB);
unsigned ScratchReg, SPReg, PReg, SPLimitOffset;
unsigned LEAop, CMPop, CALLop;
if (Is64Bit) {
SPReg = X86::RSP;
PReg = X86::RBP;
LEAop = X86::LEA64r;
CMPop = X86::CMP64rm;
CALLop = X86::CALL64pcrel32;
SPLimitOffset = 0x90;
} else {
SPReg = X86::ESP;
PReg = X86::EBP;
LEAop = X86::LEA32r;
CMPop = X86::CMP32rm;
CALLop = X86::CALLpcrel32;
SPLimitOffset = 0x4c;
}
ScratchReg = GetScratchRegister(Is64Bit, MF, true);
assert(!MF.getRegInfo().isLiveIn(ScratchReg) &&
"HiPE prologue scratch register is live-in");
// Create new MBB for StackCheck:
addRegOffset(BuildMI(stackCheckMBB, DL, TII.get(LEAop), ScratchReg),
SPReg, false, -MaxStack);
// SPLimitOffset is in a fixed heap location (pointed by BP).
addRegOffset(BuildMI(stackCheckMBB, DL, TII.get(CMPop))
.addReg(ScratchReg), PReg, false, SPLimitOffset);
BuildMI(stackCheckMBB, DL, TII.get(X86::JAE_4)).addMBB(&prologueMBB);
// Create new MBB for IncStack:
BuildMI(incStackMBB, DL, TII.get(CALLop)).
addExternalSymbol("inc_stack_0");
addRegOffset(BuildMI(incStackMBB, DL, TII.get(LEAop), ScratchReg),
SPReg, false, -MaxStack);
addRegOffset(BuildMI(incStackMBB, DL, TII.get(CMPop))
.addReg(ScratchReg), PReg, false, SPLimitOffset);
BuildMI(incStackMBB, DL, TII.get(X86::JLE_4)).addMBB(incStackMBB);
stackCheckMBB->addSuccessor(&prologueMBB, 99);
stackCheckMBB->addSuccessor(incStackMBB, 1);
incStackMBB->addSuccessor(&prologueMBB, 99);
incStackMBB->addSuccessor(incStackMBB, 1);
}
#ifdef XDEBUG
MF.verify();
#endif
}
void X86FrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const X86InstrInfo &TII = *TM.getInstrInfo();
const X86RegisterInfo &RegInfo = *TM.getRegisterInfo();
unsigned StackPtr = RegInfo.getStackRegister();
bool reseveCallFrame = hasReservedCallFrame(MF);
int Opcode = I->getOpcode();
bool isDestroy = Opcode == TII.getCallFrameDestroyOpcode();
bool IsLP64 = STI.isTarget64BitLP64();
DebugLoc DL = I->getDebugLoc();
uint64_t Amount = !reseveCallFrame ? I->getOperand(0).getImm() : 0;
uint64_t CalleeAmt = isDestroy ? I->getOperand(1).getImm() : 0;
I = MBB.erase(I);
if (!reseveCallFrame) {
// If the stack pointer can be changed after prologue, turn the
// adjcallstackup instruction into a 'sub ESP, <amt>' and the
// adjcallstackdown instruction into 'add ESP, <amt>'
// TODO: consider using push / pop instead of sub + store / add
if (Amount == 0)
return;
// 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 StackAlign = TM.getFrameLowering()->getStackAlignment();
Amount = (Amount + StackAlign - 1) / StackAlign * StackAlign;
MachineInstr *New = 0;
if (Opcode == TII.getCallFrameSetupOpcode()) {
New = BuildMI(MF, DL, TII.get(getSUBriOpcode(IsLP64, Amount)),
StackPtr)
.addReg(StackPtr)
.addImm(Amount);
} else {
assert(Opcode == TII.getCallFrameDestroyOpcode());
// Factor out the amount the callee already popped.
Amount -= CalleeAmt;
if (Amount) {
unsigned Opc = getADDriOpcode(IsLP64, Amount);
New = BuildMI(MF, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr).addImm(Amount);
}
}
if (New) {
// The EFLAGS implicit def is dead.
New->getOperand(3).setIsDead();
// Replace the pseudo instruction with a new instruction.
MBB.insert(I, New);
}
return;
}
if (Opcode == TII.getCallFrameDestroyOpcode() && CalleeAmt) {
// If we are performing frame pointer elimination and if the callee pops
// something off the stack pointer, add it back. We do this until we have
// more advanced stack pointer tracking ability.
unsigned Opc = getSUBriOpcode(IsLP64, CalleeAmt);
MachineInstr *New = BuildMI(MF, DL, TII.get(Opc), StackPtr)
.addReg(StackPtr).addImm(CalleeAmt);
// The EFLAGS implicit def is dead.
New->getOperand(3).setIsDead();
// We are not tracking the stack pointer adjustment by the callee, so make
// sure we restore the stack pointer immediately after the call, there may
// be spill code inserted between the CALL and ADJCALLSTACKUP instructions.
MachineBasicBlock::iterator B = MBB.begin();
while (I != B && !llvm::prior(I)->isCall())
--I;
MBB.insert(I, New);
}
}