c3e6555616
This patch handles CFI with basic block sections, which unlike DebugInfo does not support ranges. The DWARF standard explicitly requires emitting separate CFI Frame Descriptor Entries for each contiguous fragment of a function. Thus, the CFI information for all callee-saved registers (possibly including the frame pointer, if necessary) have to be emitted along with redefining the Call Frame Address (CFA), viz. where the current frame starts. CFI directives are emitted in FDE’s in the object file with a low_pc, high_pc specification. So, a single FDE must point to a contiguous code region unlike debug info which has the support for ranges. This is what complicates CFI for basic block sections. Now, what happens when we start placing individual basic blocks in unique sections: * Basic block sections allow the linker to randomly reorder basic blocks in the address space such that a given basic block can become non-contiguous with the original function. * The different basic block sections can no longer share the cfi_startproc and cfi_endproc directives. So, each basic block section should emit this independently. * Each (cfi_startproc, cfi_endproc) directive will result in a new FDE that caters to that basic block section. * Now, this basic block section needs to duplicate the information from the entry block to compute the CFA as it is an independent entity. It cannot refer to the FDE of the original function and hence must duplicate all the stuff that is needed to compute the CFA on its own. * We are working on a de-duplication patch that can share common information in FDEs in a CIE (Common Information Entry) and we will present this as a follow up patch. This can significantly reduce the duplication overhead and is particularly useful when several basic block sections are created. * The CFI directives are emitted similarly for registers that are pushed onto the stack, like callee saved registers in the prologue. There are cfi directives that emit how to retrieve the value of the register at that point when the push happened. This has to be duplicated too in a basic block that is floated as a separate section. Differential Revision: https://reviews.llvm.org/D79978
261 lines
12 KiB
C++
261 lines
12 KiB
C++
//===-- X86TargetFrameLowering.h - Define frame lowering for X86 -*- C++ -*-==//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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, MaybeAlign 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
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emitCalleeSavedFrameMoves(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI) const override;
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void emitCalleeSavedFrameMoves(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL,
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bool IsPrologue) const override;
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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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ArrayRef<CalleeSavedInfo> CSI,
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const TargetRegisterInfo *TRI) const override;
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bool
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restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MI,
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MutableArrayRef<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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Register &FrameReg) const override;
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int getWin64EHFrameIndexRef(const MachineFunction &MF, int FI,
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Register &SPReg) const;
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int getFrameIndexReferenceSP(const MachineFunction &MF, int FI,
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Register &SPReg, int Adjustment) const;
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int getFrameIndexReferencePreferSP(const MachineFunction &MF, int FI,
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Register &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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void
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processFunctionBeforeFrameIndicesReplaced(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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void restoreWinEHStackPointersInParent(MachineFunction &MF) const;
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int getInitialCFAOffset(const MachineFunction &MF) const override;
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Register getInitialCFARegister(const MachineFunction &MF) const override;
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/// Return true if the function has a redzone (accessible bytes past the
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/// frame of the top of stack function) as part of it's ABI.
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bool has128ByteRedZone(const MachineFunction& MF) const;
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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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void emitStackProbeInlineWindowsCoreCLR64(MachineFunction &MF,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL,
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bool InProlog) const;
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void emitStackProbeInlineGeneric(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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void emitStackProbeInlineGenericBlock(MachineFunction &MF,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL,
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uint64_t Offset) const;
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void emitStackProbeInlineGenericLoop(MachineFunction &MF,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL,
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uint64_t Offset) const;
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/// Emit a stub to later inline the target stack probe.
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MachineInstr *emitStackProbeInlineStub(MachineFunction &MF,
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MachineBasicBlock &MBB,
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MachineBasicBlock::iterator MBBI,
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const DebugLoc &DL,
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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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