1 //===-- llvm/CodeGen/AsmPrinter.h - AsmPrinter Framework --------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains a class to be used as the base class for target specific
11 // asm writers. This class primarily handles common functionality used by
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_CODEGEN_ASMPRINTER_H
17 #define LLVM_CODEGEN_ASMPRINTER_H
19 #include "llvm/ADT/MapVector.h"
20 #include "llvm/ADT/Twine.h"
21 #include "llvm/CodeGen/MachineFunctionPass.h"
22 #include "llvm/CodeGen/DwarfStringPoolEntry.h"
23 #include "llvm/IR/InlineAsm.h"
24 #include "llvm/Support/DataTypes.h"
25 #include "llvm/Support/ErrorHandling.h"
28 class AsmPrinterHandler;
36 class GCMetadataPrinter;
37 class GlobalIndirectSymbol;
40 class MachineBasicBlock;
41 class MachineFunction;
43 class MachineLocation;
44 class MachineLoopInfo;
46 class MachineConstantPoolValue;
47 class MachineJumpTableInfo;
48 class MachineModuleInfo;
50 class MCCFIInstruction;
56 class MCSubtargetInfo;
58 class MCTargetOptions;
62 class TargetLoweringObjectFile;
66 /// This class is intended to be used as a driving class for all asm writers.
67 class AsmPrinter : public MachineFunctionPass {
69 /// Target machine description.
73 /// Target Asm Printer information.
77 /// This is the context for the output file that we are streaming. This owns
78 /// all of the global MC-related objects for the generated translation unit.
79 MCContext &OutContext;
81 /// This is the MCStreamer object for the file we are generating. This
82 /// contains the transient state for the current translation unit that we are
83 /// generating (such as the current section etc).
84 std::unique_ptr<MCStreamer> OutStreamer;
86 /// The current machine function.
87 const MachineFunction *MF;
89 /// This is a pointer to the current MachineModuleInfo.
90 MachineModuleInfo *MMI;
92 /// The symbol for the current function. This is recalculated at the beginning
93 /// of each call to runOnMachineFunction().
95 MCSymbol *CurrentFnSym;
97 /// The symbol used to represent the start of the current function for the
98 /// purpose of calculating its size (e.g. using the .size directive). By
99 /// default, this is equal to CurrentFnSym.
100 MCSymbol *CurrentFnSymForSize;
102 /// Map global GOT equivalent MCSymbols to GlobalVariables and keep track of
103 /// its number of uses by other globals.
104 typedef std::pair<const GlobalVariable *, unsigned> GOTEquivUsePair;
105 MapVector<const MCSymbol *, GOTEquivUsePair> GlobalGOTEquivs;
108 MCSymbol *CurrentFnBegin;
109 MCSymbol *CurrentFnEnd;
110 MCSymbol *CurExceptionSym;
112 // The garbage collection metadata printer table.
113 void *GCMetadataPrinters; // Really a DenseMap.
115 /// Emit comments in assembly output if this is true.
120 /// If VerboseAsm is set, a pointer to the loop info for this function.
124 AsmPrinterHandler *Handler;
125 const char *TimerName;
126 const char *TimerDescription;
127 const char *TimerGroupName;
128 const char *TimerGroupDescription;
129 HandlerInfo(AsmPrinterHandler *Handler, const char *TimerName,
130 const char *TimerDescription, const char *TimerGroupName,
131 const char *TimerGroupDescription)
132 : Handler(Handler), TimerName(TimerName),
133 TimerDescription(TimerDescription), TimerGroupName(TimerGroupName),
134 TimerGroupDescription(TimerGroupDescription) {}
136 /// A vector of all debug/EH info emitters we should use. This vector
137 /// maintains ownership of the emitters.
138 SmallVector<HandlerInfo, 1> Handlers;
140 /// If the target supports dwarf debug info, this pointer is non-null.
143 /// If the current module uses dwarf CFI annotations strictly for debugging.
144 bool isCFIMoveForDebugging;
147 explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
150 ~AsmPrinter() override;
152 DwarfDebug *getDwarfDebug() { return DD; }
153 DwarfDebug *getDwarfDebug() const { return DD; }
155 uint16_t getDwarfVersion() const;
156 void setDwarfVersion(uint16_t Version);
158 bool isPositionIndependent() const;
160 /// Return true if assembly output should contain comments.
162 bool isVerbose() const { return VerboseAsm; }
164 /// Return a unique ID for the current function.
166 unsigned getFunctionNumber() const;
168 MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
169 MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
170 MCSymbol *getCurExceptionSym();
172 /// Return information about object file lowering.
173 const TargetLoweringObjectFile &getObjFileLowering() const;
175 /// Return information about data layout.
176 const DataLayout &getDataLayout() const;
178 /// Return the pointer size from the TargetMachine
179 unsigned getPointerSize() const;
181 /// Return information about subtarget.
182 const MCSubtargetInfo &getSubtargetInfo() const;
184 void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
186 /// Return the current section we are emitting to.
187 const MCSection *getCurrentSection() const;
189 void getNameWithPrefix(SmallVectorImpl<char> &Name,
190 const GlobalValue *GV) const;
192 MCSymbol *getSymbol(const GlobalValue *GV) const;
194 //===------------------------------------------------------------------===//
195 // XRay instrumentation implementation.
196 //===------------------------------------------------------------------===//
198 // This describes the kind of sled we're storing in the XRay table.
199 enum class SledKind : uint8_t {
205 // The table will contain these structs that point to the sled, the function
206 // containing the sled, and what kind of sled (and whether they should always
208 struct XRayFunctionEntry {
209 const MCSymbol *Sled;
210 const MCSymbol *Function;
212 bool AlwaysInstrument;
213 const class Function *Fn;
215 void emit(int, MCStreamer *, const MCSymbol *) const;
218 // All the sleds to be emitted.
219 std::vector<XRayFunctionEntry> Sleds;
221 // Helper function to record a given XRay sled.
222 void recordSled(MCSymbol *Sled, const MachineInstr &MI, SledKind Kind);
224 /// Emit a table with all XRay instrumentation points.
225 void emitXRayTable();
227 //===------------------------------------------------------------------===//
228 // MachineFunctionPass Implementation.
229 //===------------------------------------------------------------------===//
231 /// Record analysis usage.
233 void getAnalysisUsage(AnalysisUsage &AU) const override;
235 /// Set up the AsmPrinter when we are working on a new module. If your pass
236 /// overrides this, it must make sure to explicitly call this implementation.
237 bool doInitialization(Module &M) override;
239 /// Shut down the asmprinter. If you override this in your pass, you must make
240 /// sure to call it explicitly.
241 bool doFinalization(Module &M) override;
243 /// Emit the specified function out to the OutStreamer.
244 bool runOnMachineFunction(MachineFunction &MF) override {
245 SetupMachineFunction(MF);
250 //===------------------------------------------------------------------===//
251 // Coarse grained IR lowering routines.
252 //===------------------------------------------------------------------===//
254 /// This should be called when a new MachineFunction is being processed from
255 /// runOnMachineFunction.
256 void SetupMachineFunction(MachineFunction &MF);
258 /// This method emits the body and trailer for a function.
259 void EmitFunctionBody();
261 void emitCFIInstruction(const MachineInstr &MI);
263 void emitFrameAlloc(const MachineInstr &MI);
265 enum CFIMoveType { CFI_M_None, CFI_M_EH, CFI_M_Debug };
266 CFIMoveType needsCFIMoves();
268 /// Returns false if needsCFIMoves() == CFI_M_EH for any function
270 bool needsOnlyDebugCFIMoves() const { return isCFIMoveForDebugging; }
272 bool needsSEHMoves();
274 /// Print to the current output stream assembly representations of the
275 /// constants in the constant pool MCP. This is used to print out constants
276 /// which have been "spilled to memory" by the code generator.
278 virtual void EmitConstantPool();
280 /// Print assembly representations of the jump tables used by the current
281 /// function to the current output stream.
283 virtual void EmitJumpTableInfo();
285 /// Emit the specified global variable to the .s file.
286 virtual void EmitGlobalVariable(const GlobalVariable *GV);
288 /// Check to see if the specified global is a special global used by LLVM. If
289 /// so, emit it and return true, otherwise do nothing and return false.
290 bool EmitSpecialLLVMGlobal(const GlobalVariable *GV);
292 /// Emit an alignment directive to the specified power of two boundary. For
293 /// example, if you pass in 3 here, you will get an 8 byte alignment. If a
294 /// global value is specified, and if that global has an explicit alignment
295 /// requested, it will override the alignment request if required for
298 void EmitAlignment(unsigned NumBits, const GlobalObject *GO = nullptr) const;
300 /// Lower the specified LLVM Constant to an MCExpr.
301 virtual const MCExpr *lowerConstant(const Constant *CV);
303 /// \brief Print a general LLVM constant to the .s file.
304 void EmitGlobalConstant(const DataLayout &DL, const Constant *CV);
306 /// \brief Unnamed constant global variables solely contaning a pointer to
307 /// another globals variable act like a global variable "proxy", or GOT
308 /// equivalents, i.e., it's only used to hold the address of the latter. One
309 /// optimization is to replace accesses to these proxies by using the GOT
310 /// entry for the final global instead. Hence, we select GOT equivalent
311 /// candidates among all the module global variables, avoid emitting them
312 /// unnecessarily and finally replace references to them by pc relative
313 /// accesses to GOT entries.
314 void computeGlobalGOTEquivs(Module &M);
316 /// \brief Constant expressions using GOT equivalent globals may not be
317 /// eligible for PC relative GOT entry conversion, in such cases we need to
318 /// emit the proxies we previously omitted in EmitGlobalVariable.
319 void emitGlobalGOTEquivs();
321 //===------------------------------------------------------------------===//
323 //===------------------------------------------------------------------===//
325 // Targets can, or in the case of EmitInstruction, must implement these to
328 /// This virtual method can be overridden by targets that want to emit
329 /// something at the start of their file.
330 virtual void EmitStartOfAsmFile(Module &) {}
332 /// This virtual method can be overridden by targets that want to emit
333 /// something at the end of their file.
334 virtual void EmitEndOfAsmFile(Module &) {}
336 /// Targets can override this to emit stuff before the first basic block in
338 virtual void EmitFunctionBodyStart() {}
340 /// Targets can override this to emit stuff after the last basic block in the
342 virtual void EmitFunctionBodyEnd() {}
344 /// Targets can override this to emit stuff at the start of a basic block.
345 /// By default, this method prints the label for the specified
346 /// MachineBasicBlock, an alignment (if present) and a comment describing it
348 virtual void EmitBasicBlockStart(const MachineBasicBlock &MBB) const;
350 /// Targets can override this to emit stuff at the end of a basic block.
351 virtual void EmitBasicBlockEnd(const MachineBasicBlock &MBB) {}
353 /// Targets should implement this to emit instructions.
354 virtual void EmitInstruction(const MachineInstr *) {
355 llvm_unreachable("EmitInstruction not implemented");
358 /// Return the symbol for the specified constant pool entry.
359 virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
361 virtual void EmitFunctionEntryLabel();
363 virtual void EmitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
365 /// Targets can override this to change how global constants that are part of
366 /// a C++ static/global constructor list are emitted.
367 virtual void EmitXXStructor(const DataLayout &DL, const Constant *CV) {
368 EmitGlobalConstant(DL, CV);
371 /// Return true if the basic block has exactly one predecessor and the control
372 /// transfer mechanism between the predecessor and this block is a
375 isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
377 /// Targets can override this to customize the output of IMPLICIT_DEF
378 /// instructions in verbose mode.
379 virtual void emitImplicitDef(const MachineInstr *MI) const;
381 //===------------------------------------------------------------------===//
382 // Symbol Lowering Routines.
383 //===------------------------------------------------------------------===//
385 MCSymbol *createTempSymbol(const Twine &Name) const;
387 /// Return the MCSymbol for a private symbol with global value name as its
388 /// base, with the specified suffix.
389 MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
390 StringRef Suffix) const;
392 /// Return the MCSymbol for the specified ExternalSymbol.
393 MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
395 /// Return the symbol for the specified jump table entry.
396 MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
398 /// Return the symbol for the specified jump table .set
399 /// FIXME: privatize to AsmPrinter.
400 MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
402 /// Return the MCSymbol used to satisfy BlockAddress uses of the specified
404 MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
405 MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
407 //===------------------------------------------------------------------===//
408 // Emission Helper Routines.
409 //===------------------------------------------------------------------===//
411 /// This is just convenient handler for printing offsets.
412 void printOffset(int64_t Offset, raw_ostream &OS) const;
414 /// Emit a byte directive and value.
416 void EmitInt8(int Value) const;
418 /// Emit a short directive and value.
420 void EmitInt16(int Value) const;
422 /// Emit a long directive and value.
424 void EmitInt32(int Value) const;
426 /// Emit something like ".long Hi-Lo" where the size in bytes of the directive
427 /// is specified by Size and Hi/Lo specify the labels. This implicitly uses
428 /// .set if it is available.
429 void EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
430 unsigned Size) const;
432 /// Emit something like ".long Label+Offset" where the size in bytes of the
433 /// directive is specified by Size and Label specifies the label. This
434 /// implicitly uses .set if it is available.
435 void EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
436 unsigned Size, bool IsSectionRelative = false) const;
438 /// Emit something like ".long Label" where the size in bytes of the directive
439 /// is specified by Size and Label specifies the label.
440 void EmitLabelReference(const MCSymbol *Label, unsigned Size,
441 bool IsSectionRelative = false) const {
442 EmitLabelPlusOffset(Label, 0, Size, IsSectionRelative);
445 //===------------------------------------------------------------------===//
446 // Dwarf Emission Helper Routines
447 //===------------------------------------------------------------------===//
449 /// Emit the specified signed leb128 value.
450 void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
452 /// Emit the specified unsigned leb128 value.
453 void EmitULEB128(uint64_t Value, const char *Desc = nullptr,
454 unsigned PadTo = 0) const;
456 /// Emit a .byte 42 directive that corresponds to an encoding. If verbose
457 /// assembly output is enabled, we output comments describing the encoding.
458 /// Desc is a string saying what the encoding is specifying (e.g. "LSDA").
459 void EmitEncodingByte(unsigned Val, const char *Desc = nullptr) const;
461 /// Return the size of the encoding in bytes.
462 unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
464 /// Emit reference to a ttype global with a specified encoding.
465 void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const;
467 /// Emit a reference to a symbol for use in dwarf. Different object formats
468 /// represent this in different ways. Some use a relocation others encode
469 /// the label offset in its section.
470 void emitDwarfSymbolReference(const MCSymbol *Label,
471 bool ForceOffset = false) const;
473 /// Emit the 4-byte offset of a string from the start of its section.
475 /// When possible, emit a DwarfStringPool section offset without any
476 /// relocations, and without using the symbol. Otherwise, defers to \a
477 /// emitDwarfSymbolReference().
478 void emitDwarfStringOffset(DwarfStringPoolEntryRef S) const;
480 /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
481 virtual unsigned getISAEncoding() { return 0; }
483 //===------------------------------------------------------------------===//
484 // Dwarf Lowering Routines
485 //===------------------------------------------------------------------===//
487 /// \brief Emit frame instruction to describe the layout of the frame.
488 void emitCFIInstruction(const MCCFIInstruction &Inst) const;
490 /// \brief Emit Dwarf abbreviation table.
491 template <typename T> void emitDwarfAbbrevs(const T &Abbrevs) const {
492 // For each abbreviation.
493 for (const auto &Abbrev : Abbrevs)
494 emitDwarfAbbrev(*Abbrev);
496 // Mark end of abbreviations.
497 EmitULEB128(0, "EOM(3)");
500 void emitDwarfAbbrev(const DIEAbbrev &Abbrev) const;
502 /// \brief Recursively emit Dwarf DIE tree.
503 void emitDwarfDIE(const DIE &Die) const;
505 //===------------------------------------------------------------------===//
506 // Inline Asm Support
507 //===------------------------------------------------------------------===//
509 // These are hooks that targets can override to implement inline asm
510 // support. These should probably be moved out of AsmPrinter someday.
512 /// Print information related to the specified machine instr that is
513 /// independent of the operand, and may be independent of the instr itself.
514 /// This can be useful for portably encoding the comment character or other
515 /// bits of target-specific knowledge into the asmstrings. The syntax used is
516 /// ${:comment}. Targets can override this to add support for their own
518 virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
519 const char *Code) const;
521 /// Print the specified operand of MI, an INLINEASM instruction, using the
522 /// specified assembler variant. Targets should override this to format as
523 /// appropriate. This method can return true if the operand is erroneous.
524 virtual bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
525 unsigned AsmVariant, const char *ExtraCode,
528 /// Print the specified operand of MI, an INLINEASM instruction, using the
529 /// specified assembler variant as an address. Targets should override this to
530 /// format as appropriate. This method can return true if the operand is
532 virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
533 unsigned AsmVariant, const char *ExtraCode,
536 /// Let the target do anything it needs to do before emitting inlineasm.
537 /// \p StartInfo - the subtarget info before parsing inline asm
538 virtual void emitInlineAsmStart() const;
540 /// Let the target do anything it needs to do after emitting inlineasm.
541 /// This callback can be used restore the original mode in case the
542 /// inlineasm contains directives to switch modes.
543 /// \p StartInfo - the original subtarget info before inline asm
544 /// \p EndInfo - the final subtarget info after parsing the inline asm,
545 /// or NULL if the value is unknown.
546 virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
547 const MCSubtargetInfo *EndInfo) const;
550 /// Private state for PrintSpecial()
551 // Assign a unique ID to this machine instruction.
552 mutable const MachineInstr *LastMI;
553 mutable unsigned LastFn;
554 mutable unsigned Counter;
556 /// This method emits the header for the current function.
557 virtual void EmitFunctionHeader();
559 /// Emit a blob of inline asm to the output streamer.
561 EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
562 const MCTargetOptions &MCOptions,
563 const MDNode *LocMDNode = nullptr,
564 InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
566 /// This method formats and emits the specified machine instruction that is an
568 void EmitInlineAsm(const MachineInstr *MI) const;
570 //===------------------------------------------------------------------===//
571 // Internal Implementation Details
572 //===------------------------------------------------------------------===//
574 /// This emits visibility information about symbol, if this is suported by the
576 void EmitVisibility(MCSymbol *Sym, unsigned Visibility,
577 bool IsDefinition = true) const;
579 void EmitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
581 void EmitJumpTableEntry(const MachineJumpTableInfo *MJTI,
582 const MachineBasicBlock *MBB, unsigned uid) const;
583 void EmitLLVMUsedList(const ConstantArray *InitList);
584 /// Emit llvm.ident metadata in an '.ident' directive.
585 void EmitModuleIdents(Module &M);
586 void EmitXXStructorList(const DataLayout &DL, const Constant *List,
588 GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &C);
589 /// Emit GlobalAlias or GlobalIFunc.
590 void emitGlobalIndirectSymbol(Module &M,
591 const GlobalIndirectSymbol& GIS);