/// 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 Is64BitTarget, bool Is64BitStackPtr, bool UseLEA,
- const TargetInstrInfo &TII, const TargetRegisterInfo &TRI) {
+void X86FrameLowering::emitSPUpdate(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator &MBBI,
+ unsigned StackPtr, int64_t NumBytes,
+ bool Is64BitTarget, bool Is64BitStackPtr,
+ bool UseLEA, const TargetInstrInfo &TII,
+ const TargetRegisterInfo &TRI) {
bool isSub = NumBytes < 0;
uint64_t Offset = isSub ? -NumBytes : NumBytes;
unsigned Opc;
}
}
-/// 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) {
+int X86FrameLowering::mergeSPUpdates(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator &MBBI,
+ unsigned StackPtr,
+ bool doMergeWithPrevious) {
if ((doMergeWithPrevious && MBBI == MBB.begin()) ||
(!doMergeWithPrevious && MBBI == MBB.end()))
return 0;
void X86FrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
- assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
const Function *Fn = MF.getFunction();
}
}
+bool X86FrameLowering::canUseLEAForSPInEpilogue(
+ const MachineFunction &MF) const {
+ // We can't use LEA instructions for adjusting the stack pointer if this is a
+ // leaf function in the Win64 ABI. Only ADD instructions may be used to
+ // deallocate the stack.
+ // This means that we can use LEA for SP in two situations:
+ // 1. We *aren't* using the Win64 ABI which means we are free to use LEA.
+ // 2. We *have* a frame pointer which means we are permitted to use LEA.
+ return !MF.getTarget().getMCAsmInfo()->usesWindowsCFI() || hasFP(MF);
+}
+
+/// Check whether or not the terminators of \p MBB needs to read EFLAGS.
+static bool terminatorsNeedFlagsAsInput(const MachineBasicBlock &MBB) {
+ for (const MachineInstr &MI : MBB.terminators()) {
+ bool BreakNext = false;
+ for (const MachineOperand &MO : MI.operands()) {
+ if (!MO.isReg())
+ continue;
+ unsigned Reg = MO.getReg();
+ if (Reg != X86::EFLAGS)
+ continue;
+
+ // This terminator needs an eflag that is not defined
+ // by a previous terminator.
+ if (!MO.isDef())
+ return true;
+ BreakNext = true;
+ }
+ if (BreakNext)
+ break;
+ }
+ return false;
+}
+
void X86FrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
const X86Subtarget &STI = MF.getSubtarget<X86Subtarget>();
const X86RegisterInfo *RegInfo = STI.getRegisterInfo();
const TargetInstrInfo &TII = *STI.getInstrInfo();
- MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
- assert(MBBI != MBB.end() && "Returning block has no instructions");
- unsigned RetOpcode = MBBI->getOpcode();
- DebugLoc DL = MBBI->getDebugLoc();
+ MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
+ DebugLoc DL;
+ if (MBBI != MBB.end())
+ DL = MBBI->getDebugLoc();
bool Is64Bit = STI.is64Bit();
// standard x86_64 and NaCl use 64-bit frame/stack pointers, x32 - 32-bit.
const bool Uses64BitFramePtr = STI.isTarget64BitLP64() || STI.isTargetNaCl64();
- bool HasFP = hasFP(MF);
const bool Is64BitILP32 = STI.isTarget64BitILP32();
unsigned SlotSize = RegInfo->getSlotSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
bool IsWinEH = MF.getTarget().getMCAsmInfo()->usesWindowsCFI();
bool NeedsWinEH = IsWinEH && MF.getFunction()->needsUnwindTableEntry();
- bool UseLEAForSP = false;
-
- // We can't use LEA instructions for adjusting the stack pointer if this is a
- // leaf function in the Win64 ABI. Only ADD instructions may be used to
- // deallocate the stack.
- if (STI.useLeaForSP()) {
- if (!IsWinEH) {
- // We *aren't* using the Win64 ABI which means we are free to use LEA.
- UseLEAForSP = true;
- } else if (HasFP) {
- // We *have* a frame pointer which means we are permitted to use LEA.
- UseLEAForSP = true;
- }
- }
-
- switch (RetOpcode) {
- default:
- llvm_unreachable("Can only insert epilogue into returning blocks");
- case X86::RETQ:
- case X86::RETL:
- case X86::RETIL:
- case X86::RETIQ:
- 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
- }
+ bool UseLEAForSP = canUseLEAForSPInEpilogue(MF);
+ // If we can use LEA for SP but we shouldn't, check that none
+ // of the terminators uses the eflags. Otherwise we will insert
+ // a ADD that will redefine the eflags and break the condition.
+ // Alternatively, we could move the ADD, but this may not be possible
+ // and is an optimization anyway.
+ if (UseLEAForSP && !MF.getSubtarget<X86Subtarget>().useLeaForSP())
+ UseLEAForSP = terminatorsNeedFlagsAsInput(MBB);
+ // If that assert breaks, that means we do not do the right thing
+ // in canUseAsEpilogue.
+ assert((UseLEAForSP || !terminatorsNeedFlagsAsInput(MBB)) &&
+ "We shouldn't have allowed this insertion point");
// Get the number of bytes to allocate from the FrameInfo.
uint64_t StackSize = MFI->getStackSize();
}
MachineBasicBlock::iterator FirstCSPop = MBBI;
- DL = MBBI->getDebugLoc();
+ if (MBBI != MBB.end())
+ DL = MBBI->getDebugLoc();
// If there is an ADD32ri or SUB32ri of ESP immediately before this
// instruction, merge the two instructions.
if (NeedsWinEH)
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_Epilogue));
- // 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(Uses64BitFramePtr ? 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, Uses64BitFramePtr,
- UseLEAForSP, TII, *RegInfo);
- }
-
- // Jump to label or value in register.
- bool IsWin64 = STI.isTargetWin64();
- if (RetOpcode == X86::TCRETURNdi || RetOpcode == X86::TCRETURNdi64) {
- unsigned Op = (RetOpcode == X86::TCRETURNdi)
- ? X86::TAILJMPd
- : (IsWin64 ? X86::TAILJMPd64_REX : X86::TAILJMPd64);
- MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII.get(Op));
- 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) {
- unsigned Op = (RetOpcode == X86::TCRETURNmi)
- ? X86::TAILJMPm
- : (IsWin64 ? X86::TAILJMPm64_REX : X86::TAILJMPm64);
- MachineInstrBuilder MIB = BuildMI(MBB, MBBI, DL, TII.get(Op));
- for (unsigned i = 0; i != 5; ++i)
- MIB.addOperand(MBBI->getOperand(i));
- } else if (RetOpcode == X86::TCRETURNri64) {
- BuildMI(MBB, MBBI, DL,
- TII.get(IsWin64 ? X86::TAILJMPr64_REX : X86::TAILJMPr64))
- .addReg(JumpTarget.getReg(), RegState::Kill);
- } else {
- BuildMI(MBB, MBBI, DL, TII.get(X86::TAILJMPr)).
- addReg(JumpTarget.getReg(), RegState::Kill);
- }
-
- MachineInstr *NewMI = std::prev(MBBI);
- NewMI->copyImplicitOps(MF, MBBI);
-
- // Delete the pseudo instruction TCRETURN.
- MBB.erase(MBBI);
- } else if ((RetOpcode == X86::RETQ || RetOpcode == X86::RETL ||
- RetOpcode == X86::RETIQ || RetOpcode == X86::RETIL) &&
- (X86FI->getTCReturnAddrDelta() < 0)) {
- // Add the return addr area delta back since we are not tail calling.
- int delta = -1*X86FI->getTCReturnAddrDelta();
- MBBI = MBB.getLastNonDebugInstr();
+ // Add the return addr area delta back since we are not tail calling.
+ int Offset = -1 * X86FI->getTCReturnAddrDelta();
+ assert(Offset >= 0 && "TCDelta should never be positive");
+ if (Offset) {
+ MBBI = MBB.getFirstTerminator();
// Check for possible merge with preceding ADD instruction.
- delta += mergeSPUpdates(MBB, MBBI, StackPtr, true);
- emitSPUpdate(MBB, MBBI, StackPtr, delta, Is64Bit, Uses64BitFramePtr,
+ Offset += mergeSPUpdates(MBB, MBBI, StackPtr, true);
+ emitSPUpdate(MBB, MBBI, StackPtr, Offset, Is64Bit, Uses64BitFramePtr,
UseLEAForSP, TII, *RegInfo);
}
}
void X86FrameLowering::adjustForSegmentedStacks(
MachineFunction &MF, MachineBasicBlock &PrologueMBB) const {
- assert(&PrologueMBB == &MF.front() &&
- "Shrink-wrapping is not implemented yet");
MachineFrameInfo *MFI = MF.getFrameInfo();
const X86Subtarget &STI = MF.getSubtarget<X86Subtarget>();
const TargetInstrInfo &TII = *STI.getInstrInfo();
// 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) {
- assert(&PrologueMBB == &MF.front() &&
- "Shrink-wrapping is not implemented yet");
MachineBasicBlock *stackCheckMBB = MF.CreateMachineBasicBlock();
MachineBasicBlock *incStackMBB = MF.CreateMachineBasicBlock();
const X86RegisterInfo &RegInfo = *STI.getRegisterInfo();
unsigned StackPtr = RegInfo.getStackRegister();
bool reserveCallFrame = hasReservedCallFrame(MF);
- int Opcode = I->getOpcode();
+ unsigned Opcode = I->getOpcode();
bool isDestroy = Opcode == TII.getCallFrameDestroyOpcode();
bool IsLP64 = STI.isTarget64BitLP64();
DebugLoc DL = I->getDebugLoc();
}
}
+bool X86FrameLowering::canUseAsEpilogue(const MachineBasicBlock &MBB) const {
+ assert(MBB.getParent() && "Block is not attached to a function!");
+
+ if (canUseLEAForSPInEpilogue(*MBB.getParent()))
+ return true;
+
+ // If we cannot use LEA to adjust SP, we may need to use ADD, which
+ // clobbers the EFLAGS. Check that none of the terminators reads the
+ // EFLAGS, and if one uses it, conservatively assume this is not
+ // safe to insert the epilogue here.
+ return !terminatorsNeedFlagsAsInput(MBB);
+}
projects / oota-llvm.git / blobdiff