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This patch aims to provide correct dwarf unwind information in function epilogue for X86. It consists of two parts. The first part inserts CFI instructions that set appropriate cfa offset and cfa register in emitEpilogue() in X86FrameLowering. This part is X86 specific. The second part is platform independent and ensures that: * CFI instructions do not affect code generation (they are not counted as instructions when tail duplicating or tail merging) * Unwind information remains correct when a function is modified by different passes. This is done in a late pass by analyzing information about cfa offset and cfa register in BBs and inserting additional CFI directives where necessary. Added CFIInstrInserter pass: * analyzes each basic block to determine cfa offset and register are valid at its entry and exit * verifies that outgoing cfa offset and register of predecessor blocks match incoming values of their successors * inserts additional CFI directives at basic block beginning to correct the rule for calculating CFA Having CFI instructions in function epilogue can cause incorrect CFA calculation rule for some basic blocks. This can happen if, due to basic block reordering, or the existence of multiple epilogue blocks, some of the blocks have wrong cfa offset and register values set by the epilogue block above them. CFIInstrInserter is currently run only on X86, but can be used by any target that implements support for adding CFI instructions in epilogue. Patch by Violeta Vukobrat. Differential Revision: https://reviews.llvm.org/D42848 llvm-svn: 330706
222 lines
9.6 KiB
C++
222 lines
9.6 KiB
C++
//===-- X86TargetFrameLowering.h - Define frame lowering for X86 -*- C++ -*-==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This class implements X86-specific bits of TargetFrameLowering class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_TARGET_X86_X86FRAMELOWERING_H
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#define LLVM_LIB_TARGET_X86_X86FRAMELOWERING_H
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#include "llvm/CodeGen/TargetFrameLowering.h"
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namespace llvm {
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class MachineInstrBuilder;
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class MCCFIInstruction;
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class X86InstrInfo;
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class X86Subtarget;
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class X86RegisterInfo;
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class X86FrameLowering : public TargetFrameLowering {
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public:
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X86FrameLowering(const X86Subtarget &STI, unsigned StackAlignOverride);
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// Cached subtarget predicates.
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const X86Subtarget &STI;
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const X86InstrInfo &TII;
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const X86RegisterInfo *TRI;
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unsigned SlotSize;
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/// Is64Bit implies that x86_64 instructions are available.
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bool Is64Bit;
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bool IsLP64;
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/// True if the 64-bit frame or stack pointer should be used. True for most
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/// 64-bit targets with the exception of x32. If this is false, 32-bit
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/// instruction operands should be used to manipulate StackPtr and FramePtr.
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bool Uses64BitFramePtr;
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unsigned StackPtr;
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/// Emit target stack probe code. This is required for all
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/// large stack allocations on Windows. The caller is required to materialize
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/// the number of bytes to probe in RAX/EAX.
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void emitStackProbe(MachineFunction &MF, MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI, const DebugLoc &DL,
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bool InProlog) const;
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/// Replace a StackProbe inline-stub with the actual probe code inline.
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void inlineStackProbe(MachineFunction &MF,
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MachineBasicBlock &PrologMBB) const override;
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void emitCalleeSavedFrameMoves(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL) const;
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/// emitProlog/emitEpilog - These methods insert prolog and epilog code into
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/// the function.
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void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
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void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
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void adjustForSegmentedStacks(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const override;
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void adjustForHiPEPrologue(MachineFunction &MF,
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MachineBasicBlock &PrologueMBB) const override;
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void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
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RegScavenger *RS = nullptr) const override;
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bool
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assignCalleeSavedSpillSlots(MachineFunction &MF,
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const TargetRegisterInfo *TRI,
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std::vector<CalleeSavedInfo> &CSI) const override;
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bool spillCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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const std::vector<CalleeSavedInfo> &CSI,
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const TargetRegisterInfo *TRI) const override;
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bool restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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std::vector<CalleeSavedInfo> &CSI,
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const TargetRegisterInfo *TRI) const override;
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bool hasFP(const MachineFunction &MF) const override;
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bool hasReservedCallFrame(const MachineFunction &MF) const override;
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bool canSimplifyCallFramePseudos(const MachineFunction &MF) const override;
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bool needsFrameIndexResolution(const MachineFunction &MF) const override;
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int getFrameIndexReference(const MachineFunction &MF, int FI,
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unsigned &FrameReg) const override;
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int getFrameIndexReferenceSP(const MachineFunction &MF,
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int FI, unsigned &SPReg, int Adjustment) const;
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int getFrameIndexReferencePreferSP(const MachineFunction &MF, int FI,
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unsigned &FrameReg,
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bool IgnoreSPUpdates) const override;
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MachineBasicBlock::iterator
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eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI) const override;
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unsigned getWinEHParentFrameOffset(const MachineFunction &MF) const override;
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void processFunctionBeforeFrameFinalized(MachineFunction &MF,
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RegScavenger *RS) const override;
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/// Check the instruction before/after the passed instruction. If
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/// it is an ADD/SUB/LEA instruction it is deleted argument and the
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/// stack adjustment is returned as a positive value for ADD/LEA and
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/// a negative for SUB.
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int mergeSPUpdates(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
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bool doMergeWithPrevious) const;
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/// Emit a series of instructions to increment / decrement the stack
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/// pointer by a constant value.
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void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
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const DebugLoc &DL, int64_t NumBytes, bool InEpilogue) const;
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/// Check that LEA can be used on SP in an epilogue sequence for \p MF.
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bool canUseLEAForSPInEpilogue(const MachineFunction &MF) const;
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/// Check whether or not the given \p MBB can be used as a prologue
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/// for the target.
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/// The prologue will be inserted first in this basic block.
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/// This method is used by the shrink-wrapping pass to decide if
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/// \p MBB will be correctly handled by the target.
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/// As soon as the target enable shrink-wrapping without overriding
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/// this method, we assume that each basic block is a valid
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/// prologue.
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bool canUseAsPrologue(const MachineBasicBlock &MBB) const override;
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/// Check whether or not the given \p MBB can be used as a epilogue
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/// for the target.
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/// The epilogue will be inserted before the first terminator of that block.
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/// This method is used by the shrink-wrapping pass to decide if
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/// \p MBB will be correctly handled by the target.
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bool canUseAsEpilogue(const MachineBasicBlock &MBB) const override;
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/// Returns true if the target will correctly handle shrink wrapping.
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bool enableShrinkWrapping(const MachineFunction &MF) const override;
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/// Order the symbols in the local stack.
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/// We want to place the local stack objects in some sort of sensible order.
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/// The heuristic we use is to try and pack them according to static number
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/// of uses and size in order to minimize code size.
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void orderFrameObjects(const MachineFunction &MF,
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SmallVectorImpl<int> &ObjectsToAllocate) const override;
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/// Wraps up getting a CFI index and building a MachineInstr for it.
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void BuildCFI(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL, const MCCFIInstruction &CFIInst) const;
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/// Sets up EBP and optionally ESI based on the incoming EBP value. Only
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/// needed for 32-bit. Used in funclet prologues and at catchret destinations.
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MachineBasicBlock::iterator
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restoreWin32EHStackPointers(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL, bool RestoreSP = false) const;
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int getInitialCFAOffset(const MachineFunction &MF) const override;
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unsigned getInitialCFARegister(const MachineFunction &MF) const override;
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private:
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uint64_t calculateMaxStackAlign(const MachineFunction &MF) const;
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/// Emit target stack probe as a call to a helper function
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void emitStackProbeCall(MachineFunction &MF, MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI, const DebugLoc &DL,
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bool InProlog) const;
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/// Emit target stack probe as an inline sequence.
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void emitStackProbeInline(MachineFunction &MF, MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL, bool InProlog) const;
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/// Emit a stub to later inline the target stack probe.
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void emitStackProbeInlineStub(MachineFunction &MF, MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL, bool InProlog) const;
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/// Aligns the stack pointer by ANDing it with -MaxAlign.
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void BuildStackAlignAND(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI, const DebugLoc &DL,
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unsigned Reg, uint64_t MaxAlign) const;
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/// Make small positive stack adjustments using POPs.
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bool adjustStackWithPops(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI, const DebugLoc &DL,
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int Offset) const;
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/// Adjusts the stack pointer using LEA, SUB, or ADD.
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MachineInstrBuilder BuildStackAdjustment(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL, int64_t Offset,
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bool InEpilogue) const;
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unsigned getPSPSlotOffsetFromSP(const MachineFunction &MF) const;
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unsigned getWinEHFuncletFrameSize(const MachineFunction &MF) const;
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/// Materialize the catchret target MBB in RAX.
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void emitCatchRetReturnValue(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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MachineInstr *CatchRet) const;
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};
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} // End llvm namespace
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#endif
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