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//===- llvm/CodeGen/AsmPrinter.h - AsmPrinter Framework ---------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file contains a class to be used as the base class for target specific
// asm writers. This class primarily handles common functionality used by
// all asm writers.
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/DwarfStringPoolEntry.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/SourceMgr.h"
#include <cstdint>
#include <memory>
#include <utility>
#include <vector>
namespace llvm {
class AsmPrinterHandler;
class BasicBlock;
class BlockAddress;
class Constant;
class ConstantArray;
class DataLayout;
class DIE;
class DIEAbbrev;
class DwarfDebug;
class GCMetadataPrinter;
class GCStrategy;
class GlobalIndirectSymbol;
class GlobalObject;
class GlobalValue;
class GlobalVariable;
class MachineBasicBlock;
class MachineConstantPoolValue;
class MachineDominatorTree;
class MachineFunction;
class MachineInstr;
class MachineJumpTableInfo;
class MachineLoopInfo;
class MachineModuleInfo;
class MachineOptimizationRemarkEmitter;
class MCAsmInfo;
class MCCFIInstruction;
struct MCCodePaddingContext;
class MCContext;
class MCExpr;
class MCInst;
class MCSection;
class MCStreamer;
class MCSubtargetInfo;
class MCSymbol;
class MCTargetOptions;
class MDNode;
class Module;
class raw_ostream;
class StackMaps;
class TargetLoweringObjectFile;
class TargetMachine;
/// This class is intended to be used as a driving class for all asm writers.
class AsmPrinter : public MachineFunctionPass {
/// Target machine description.
TargetMachine &TM;
/// Target Asm Printer information.
const MCAsmInfo *MAI;
/// This is the context for the output file that we are streaming. This owns
/// all of the global MC-related objects for the generated translation unit.
MCContext &OutContext;
/// This is the MCStreamer object for the file we are generating. This
/// contains the transient state for the current translation unit that we are
/// generating (such as the current section etc).
std::unique_ptr<MCStreamer> OutStreamer;
/// The current machine function.
MachineFunction *MF = nullptr;
/// This is a pointer to the current MachineModuleInfo.
MachineModuleInfo *MMI = nullptr;
/// This is a pointer to the current MachineLoopInfo.
MachineDominatorTree *MDT = nullptr;
/// This is a pointer to the current MachineLoopInfo.
MachineLoopInfo *MLI = nullptr;
/// Optimization remark emitter.
MachineOptimizationRemarkEmitter *ORE;
/// The symbol for the current function. This is recalculated at the beginning
/// of each call to runOnMachineFunction().
MCSymbol *CurrentFnSym = nullptr;
/// The symbol used to represent the start of the current function for the
/// purpose of calculating its size (e.g. using the .size directive). By
/// default, this is equal to CurrentFnSym.
MCSymbol *CurrentFnSymForSize = nullptr;
/// Map global GOT equivalent MCSymbols to GlobalVariables and keep track of
/// its number of uses by other globals.
using GOTEquivUsePair = std::pair<const GlobalVariable *, unsigned>;
MapVector<const MCSymbol *, GOTEquivUsePair> GlobalGOTEquivs;
MCSymbol *CurrentFnBegin = nullptr;
MCSymbol *CurrentFnEnd = nullptr;
MCSymbol *CurExceptionSym = nullptr;
// The garbage collection metadata printer table.
void *GCMetadataPrinters = nullptr; // Really a DenseMap.
/// Emit comments in assembly output if this is true.
bool VerboseAsm;
static char ID;
/// Protected struct HandlerInfo and Handlers permit target extended
/// AsmPrinter adds their own handlers.
struct HandlerInfo {
AsmPrinterHandler *Handler;
const char *TimerName;
const char *TimerDescription;
const char *TimerGroupName;
const char *TimerGroupDescription;
HandlerInfo(AsmPrinterHandler *Handler, const char *TimerName,
const char *TimerDescription, const char *TimerGroupName,
const char *TimerGroupDescription)
: Handler(Handler), TimerName(TimerName),
TimerDescription(TimerDescription), TimerGroupName(TimerGroupName),
TimerGroupDescription(TimerGroupDescription) {}
/// A vector of all debug/EH info emitters we should use. This vector
/// maintains ownership of the emitters.
SmallVector<HandlerInfo, 1> Handlers;
struct SrcMgrDiagInfo {
SourceMgr SrcMgr;
std::vector<const MDNode *> LocInfos;
LLVMContext::InlineAsmDiagHandlerTy DiagHandler;
void *DiagContext;
/// If generated on the fly this own the instance.
std::unique_ptr<MachineDominatorTree> OwnedMDT;
/// If generated on the fly this own the instance.
std::unique_ptr<MachineLoopInfo> OwnedMLI;
/// Structure for generating diagnostics for inline assembly. Only initialised
/// when necessary.
mutable std::unique_ptr<SrcMgrDiagInfo> DiagInfo;
/// If the target supports dwarf debug info, this pointer is non-null.
DwarfDebug *DD = nullptr;
/// If the current module uses dwarf CFI annotations strictly for debugging.
bool isCFIMoveForDebugging = false;
explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
~AsmPrinter() override;
DwarfDebug *getDwarfDebug() { return DD; }
DwarfDebug *getDwarfDebug() const { return DD; }
uint16_t getDwarfVersion() const;
void setDwarfVersion(uint16_t Version);
bool isPositionIndependent() const;
/// Return true if assembly output should contain comments.
bool isVerbose() const { return VerboseAsm; }
/// Return a unique ID for the current function.
unsigned getFunctionNumber() const;
/// Return symbol for the function pseudo stack if the stack frame is not a
/// register based.
virtual const MCSymbol *getFunctionFrameSymbol() const { return nullptr; }
MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
MCSymbol *getCurExceptionSym();
/// Return information about object file lowering.
const TargetLoweringObjectFile &getObjFileLowering() const;
/// Return information about data layout.
const DataLayout &getDataLayout() const;
/// Return the pointer size from the TargetMachine
unsigned getPointerSize() const;
/// Return information about subtarget.
const MCSubtargetInfo &getSubtargetInfo() const;
void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
/// Emits inital debug location directive.
void emitInitialRawDwarfLocDirective(const MachineFunction &MF);
/// Return the current section we are emitting to.
const MCSection *getCurrentSection() const;
void getNameWithPrefix(SmallVectorImpl<char> &Name,
const GlobalValue *GV) const;
MCSymbol *getSymbol(const GlobalValue *GV) const;
// XRay instrumentation implementation.
// This describes the kind of sled we're storing in the XRay table.
enum class SledKind : uint8_t {
// The table will contain these structs that point to the sled, the function
// containing the sled, and what kind of sled (and whether they should always
// be instrumented). We also use a version identifier that the runtime can use
// to decide what to do with the sled, depending on the version of the sled.
struct XRayFunctionEntry {
const MCSymbol *Sled;
const MCSymbol *Function;
SledKind Kind;
bool AlwaysInstrument;
const class Function *Fn;
uint8_t Version;
void emit(int, MCStreamer *, const MCSymbol *) const;
// All the sleds to be emitted.
SmallVector<XRayFunctionEntry, 4> Sleds;
// A unique ID used for ELF sections associated with a particular function.
unsigned XRayFnUniqueID = 0;
// Helper function to record a given XRay sled.
void recordSled(MCSymbol *Sled, const MachineInstr &MI, SledKind Kind,
uint8_t Version = 0);
/// Emit a table with all XRay instrumentation points.
void emitXRayTable();
// MachineFunctionPass Implementation.
/// Record analysis usage.
void getAnalysisUsage(AnalysisUsage &AU) const override;
/// Set up the AsmPrinter when we are working on a new module. If your pass
/// overrides this, it must make sure to explicitly call this implementation.
bool doInitialization(Module &M) override;
/// Shut down the asmprinter. If you override this in your pass, you must make
/// sure to call it explicitly.
bool doFinalization(Module &M) override;
/// Emit the specified function out to the OutStreamer.
bool runOnMachineFunction(MachineFunction &MF) override {
return false;
// Coarse grained IR lowering routines.
/// This should be called when a new MachineFunction is being processed from
/// runOnMachineFunction.
void SetupMachineFunction(MachineFunction &MF);
/// This method emits the body and trailer for a function.
void EmitFunctionBody();
void emitCFIInstruction(const MachineInstr &MI);
void emitFrameAlloc(const MachineInstr &MI);
void emitStackSizeSection(const MachineFunction &MF);
void emitRemarksSection(Module &M);
enum CFIMoveType { CFI_M_None, CFI_M_EH, CFI_M_Debug };
CFIMoveType needsCFIMoves() const;
/// Returns false if needsCFIMoves() == CFI_M_EH for any function
/// in the module.
bool needsOnlyDebugCFIMoves() const { return isCFIMoveForDebugging; }
bool needsSEHMoves();
/// Print to the current output stream assembly representations of the
/// constants in the constant pool MCP. This is used to print out constants
/// which have been "spilled to memory" by the code generator.
virtual void EmitConstantPool();
/// Print assembly representations of the jump tables used by the current
/// function to the current output stream.
virtual void EmitJumpTableInfo();
/// Emit the specified global variable to the .s file.
virtual void EmitGlobalVariable(const GlobalVariable *GV);
/// Check to see if the specified global is a special global used by LLVM. If
/// so, emit it and return true, otherwise do nothing and return false.
bool EmitSpecialLLVMGlobal(const GlobalVariable *GV);
/// Emit an alignment directive to the specified power of two boundary. For
/// example, if you pass in 3 here, you will get an 8 byte alignment. If a
/// global value is specified, and if that global has an explicit alignment
/// requested, it will override the alignment request if required for
/// correctness.
void EmitAlignment(unsigned NumBits, const GlobalObject *GV = nullptr) const;
/// Lower the specified LLVM Constant to an MCExpr.
virtual const MCExpr *lowerConstant(const Constant *CV);
/// Print a general LLVM constant to the .s file.
void EmitGlobalConstant(const DataLayout &DL, const Constant *CV);
/// Unnamed constant global variables solely contaning a pointer to
/// another globals variable act like a global variable "proxy", or GOT
/// equivalents, i.e., it's only used to hold the address of the latter. One
/// optimization is to replace accesses to these proxies by using the GOT
/// entry for the final global instead. Hence, we select GOT equivalent
/// candidates among all the module global variables, avoid emitting them
/// unnecessarily and finally replace references to them by pc relative
/// accesses to GOT entries.
void computeGlobalGOTEquivs(Module &M);
/// Constant expressions using GOT equivalent globals may not be
/// eligible for PC relative GOT entry conversion, in such cases we need to
/// emit the proxies we previously omitted in EmitGlobalVariable.
void emitGlobalGOTEquivs();
/// Emit the stack maps.
void emitStackMaps(StackMaps &SM);
// Overridable Hooks
// Targets can, or in the case of EmitInstruction, must implement these to
// customize output.
/// This virtual method can be overridden by targets that want to emit
/// something at the start of their file.
virtual void EmitStartOfAsmFile(Module &) {}
/// This virtual method can be overridden by targets that want to emit
/// something at the end of their file.
virtual void EmitEndOfAsmFile(Module &) {}
/// Targets can override this to emit stuff before the first basic block in
/// the function.
virtual void EmitFunctionBodyStart() {}
/// Targets can override this to emit stuff after the last basic block in the
/// function.
virtual void EmitFunctionBodyEnd() {}
/// Targets can override this to emit stuff at the start of a basic block.
/// By default, this method prints the label for the specified
/// MachineBasicBlock, an alignment (if present) and a comment describing it
/// if appropriate.
virtual void EmitBasicBlockStart(const MachineBasicBlock &MBB) const;
/// Targets can override this to emit stuff at the end of a basic block.
virtual void EmitBasicBlockEnd(const MachineBasicBlock &MBB);
/// Targets should implement this to emit instructions.
virtual void EmitInstruction(const MachineInstr *) {
llvm_unreachable("EmitInstruction not implemented");
/// Return the symbol for the specified constant pool entry.
virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
virtual void EmitFunctionEntryLabel();
virtual void EmitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
/// Targets can override this to change how global constants that are part of
/// a C++ static/global constructor list are emitted.
virtual void EmitXXStructor(const DataLayout &DL, const Constant *CV) {
EmitGlobalConstant(DL, CV);
/// Return true if the basic block has exactly one predecessor and the control
/// transfer mechanism between the predecessor and this block is a
/// fall-through.
virtual bool
isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
/// Targets can override this to customize the output of IMPLICIT_DEF
/// instructions in verbose mode.
virtual void emitImplicitDef(const MachineInstr *MI) const;
// Symbol Lowering Routines.
MCSymbol *createTempSymbol(const Twine &Name) const;
/// Return the MCSymbol for a private symbol with global value name as its
/// base, with the specified suffix.
MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
StringRef Suffix) const;
/// Return the MCSymbol for the specified ExternalSymbol.
MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
/// Return the symbol for the specified jump table entry.
MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
/// Return the symbol for the specified jump table .set
/// FIXME: privatize to AsmPrinter.
MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
/// Return the MCSymbol used to satisfy BlockAddress uses of the specified
/// basic block.
MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
// Emission Helper Routines.
/// This is just convenient handler for printing offsets.
void printOffset(int64_t Offset, raw_ostream &OS) const;
/// Emit a byte directive and value.
void emitInt8(int Value) const;
/// Emit a short directive and value.
void emitInt16(int Value) const;
/// Emit a long directive and value.
void emitInt32(int Value) const;
/// Emit a long long directive and value.
void emitInt64(uint64_t Value) const;
/// Emit something like ".long Hi-Lo" where the size in bytes of the directive
/// is specified by Size and Hi/Lo specify the labels. This implicitly uses
/// .set if it is available.
void EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
unsigned Size) const;
/// Emit something like ".uleb128 Hi-Lo".
void EmitLabelDifferenceAsULEB128(const MCSymbol *Hi,
const MCSymbol *Lo) const;
/// Emit something like ".long Label+Offset" where the size in bytes of the
/// directive is specified by Size and Label specifies the label. This
/// implicitly uses .set if it is available.
void EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
unsigned Size, bool IsSectionRelative = false) const;
/// Emit something like ".long Label" where the size in bytes of the directive
/// is specified by Size and Label specifies the label.
void EmitLabelReference(const MCSymbol *Label, unsigned Size,
bool IsSectionRelative = false) const {
EmitLabelPlusOffset(Label, 0, Size, IsSectionRelative);
/// Emit something like ".long Label + Offset".
void EmitDwarfOffset(const MCSymbol *Label, uint64_t Offset) const;
// Dwarf Emission Helper Routines
/// Emit the specified signed leb128 value.
void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
/// Emit the specified unsigned leb128 value.
void EmitULEB128(uint64_t Value, const char *Desc = nullptr, unsigned PadTo = 0) const;
/// Emit a .byte 42 directive that corresponds to an encoding. If verbose
/// assembly output is enabled, we output comments describing the encoding.
/// Desc is a string saying what the encoding is specifying (e.g. "LSDA").
void EmitEncodingByte(unsigned Val, const char *Desc = nullptr) const;
/// Return the size of the encoding in bytes.
unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
/// Emit reference to a ttype global with a specified encoding.
void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const;
/// Emit a reference to a symbol for use in dwarf. Different object formats
/// represent this in different ways. Some use a relocation others encode
/// the label offset in its section.
void emitDwarfSymbolReference(const MCSymbol *Label,
bool ForceOffset = false) const;
/// Emit the 4-byte offset of a string from the start of its section.
/// When possible, emit a DwarfStringPool section offset without any
/// relocations, and without using the symbol. Otherwise, defers to \a
/// emitDwarfSymbolReference().
void emitDwarfStringOffset(DwarfStringPoolEntry S) const;
/// Emit the 4-byte offset of a string from the start of its section.
void emitDwarfStringOffset(DwarfStringPoolEntryRef S) const {
/// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
virtual unsigned getISAEncoding() { return 0; }
/// Emit the directive and value for debug thread local expression
/// \p Value - The value to emit.
/// \p Size - The size of the integer (in bytes) to emit.
virtual void EmitDebugValue(const MCExpr *Value, unsigned Size) const;
// Dwarf Lowering Routines
/// Emit frame instruction to describe the layout of the frame.
void emitCFIInstruction(const MCCFIInstruction &Inst) const;
/// Emit Dwarf abbreviation table.
template <typename T> void emitDwarfAbbrevs(const T &Abbrevs) const {
// For each abbreviation.
for (const auto &Abbrev : Abbrevs)
// Mark end of abbreviations.
EmitULEB128(0, "EOM(3)");
void emitDwarfAbbrev(const DIEAbbrev &Abbrev) const;
/// Recursively emit Dwarf DIE tree.
void emitDwarfDIE(const DIE &Die) const;
// Inline Asm Support
// These are hooks that targets can override to implement inline asm
// support. These should probably be moved out of AsmPrinter someday.
/// Print information related to the specified machine instr that is
/// independent of the operand, and may be independent of the instr itself.
/// This can be useful for portably encoding the comment character or other
/// bits of target-specific knowledge into the asmstrings. The syntax used is
/// ${:comment}. Targets can override this to add support for their own
/// strange codes.
virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
const char *Code) const;
/// Print the specified operand of MI, an INLINEASM instruction, using the
/// specified assembler variant. Targets should override this to format as
/// appropriate. This method can return true if the operand is erroneous.
virtual bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
const char *ExtraCode, raw_ostream &OS);
/// Print the specified operand of MI, an INLINEASM instruction, using the
/// specified assembler variant as an address. Targets should override this to
/// format as appropriate. This method can return true if the operand is
/// erroneous.
virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
const char *ExtraCode, raw_ostream &OS);
/// Let the target do anything it needs to do before emitting inlineasm.
/// \p StartInfo - the subtarget info before parsing inline asm
virtual void emitInlineAsmStart() const;
/// Let the target do anything it needs to do after emitting inlineasm.
/// This callback can be used restore the original mode in case the
/// inlineasm contains directives to switch modes.
/// \p StartInfo - the original subtarget info before inline asm
/// \p EndInfo - the final subtarget info after parsing the inline asm,
/// or NULL if the value is unknown.
virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
const MCSubtargetInfo *EndInfo) const;
/// Private state for PrintSpecial()
// Assign a unique ID to this machine instruction.
mutable const MachineInstr *LastMI = nullptr;
mutable unsigned LastFn = 0;
mutable unsigned Counter = ~0U;
/// This method emits the header for the current function.
virtual void EmitFunctionHeader();
/// Emit a blob of inline asm to the output streamer.
EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
const MCTargetOptions &MCOptions,
const MDNode *LocMDNode = nullptr,
InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
/// This method formats and emits the specified machine instruction that is an
/// inline asm.
void EmitInlineAsm(const MachineInstr *MI) const;
/// Add inline assembly info to the diagnostics machinery, so we can
/// emit file and position info. Returns SrcMgr memory buffer position.
unsigned addInlineAsmDiagBuffer(StringRef AsmStr,
const MDNode *LocMDNode) const;
// Internal Implementation Details
/// This emits visibility information about symbol, if this is supported by
/// the target.
void EmitVisibility(MCSymbol *Sym, unsigned Visibility,
bool IsDefinition = true) const;
void EmitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
void EmitJumpTableEntry(const MachineJumpTableInfo *MJTI,
const MachineBasicBlock *MBB, unsigned uid) const;
void EmitLLVMUsedList(const ConstantArray *InitList);
/// Emit llvm.ident metadata in an '.ident' directive.
void EmitModuleIdents(Module &M);
/// Emit bytes for llvm.commandline metadata.
void EmitModuleCommandLines(Module &M);
void EmitXXStructorList(const DataLayout &DL, const Constant *List,
bool isCtor);
GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &S);
/// Emit GlobalAlias or GlobalIFunc.
void emitGlobalIndirectSymbol(Module &M, const GlobalIndirectSymbol &GIS);
void setupCodePaddingContext(const MachineBasicBlock &MBB,
MCCodePaddingContext &Context) const;
} // end namespace llvm