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 /// Name-mangler for global names.
96 /// The symbol for the current function. This is recalculated at the beginning
97 /// of each call to runOnMachineFunction().
99 MCSymbol *CurrentFnSym;
101 /// The symbol used to represent the start of the current function for the
102 /// purpose of calculating its size (e.g. using the .size directive). By
103 /// default, this is equal to CurrentFnSym.
104 MCSymbol *CurrentFnSymForSize;
106 /// Map global GOT equivalent MCSymbols to GlobalVariables and keep track of
107 /// its number of uses by other globals.
108 typedef std::pair<const GlobalVariable *, unsigned> GOTEquivUsePair;
109 MapVector<const MCSymbol *, GOTEquivUsePair> GlobalGOTEquivs;
112 MCSymbol *CurrentFnBegin;
113 MCSymbol *CurrentFnEnd;
114 MCSymbol *CurExceptionSym;
116 // The garbage collection metadata printer table.
117 void *GCMetadataPrinters; // Really a DenseMap.
119 /// Emit comments in assembly output if this is true.
124 /// If VerboseAsm is set, a pointer to the loop info for this function.
128 AsmPrinterHandler *Handler;
129 const char *TimerName, *TimerGroupName;
130 HandlerInfo(AsmPrinterHandler *Handler, const char *TimerName,
131 const char *TimerGroupName)
132 : Handler(Handler), TimerName(TimerName),
133 TimerGroupName(TimerGroupName) {}
135 /// A vector of all debug/EH info emitters we should use. This vector
136 /// maintains ownership of the emitters.
137 SmallVector<HandlerInfo, 1> Handlers;
139 /// If the target supports dwarf debug info, this pointer is non-null.
143 explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
146 ~AsmPrinter() override;
148 DwarfDebug *getDwarfDebug() { return DD; }
149 DwarfDebug *getDwarfDebug() const { return DD; }
151 bool isPositionIndependent() const;
153 /// Return true if assembly output should contain comments.
155 bool isVerbose() const { return VerboseAsm; }
157 /// Return a unique ID for the current function.
159 unsigned getFunctionNumber() const;
161 MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
162 MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
163 MCSymbol *getCurExceptionSym();
165 /// Return information about object file lowering.
166 const TargetLoweringObjectFile &getObjFileLowering() const;
168 /// Return information about data layout.
169 const DataLayout &getDataLayout() const;
171 /// Return the pointer size from the TargetMachine
172 unsigned getPointerSize() const;
174 /// Return information about subtarget.
175 const MCSubtargetInfo &getSubtargetInfo() const;
177 void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
179 /// Return the target triple string.
180 StringRef getTargetTriple() const;
182 /// Return the current section we are emitting to.
183 const MCSection *getCurrentSection() const;
185 void getNameWithPrefix(SmallVectorImpl<char> &Name,
186 const GlobalValue *GV) const;
188 MCSymbol *getSymbol(const GlobalValue *GV) const;
190 //===------------------------------------------------------------------===//
191 // MachineFunctionPass Implementation.
192 //===------------------------------------------------------------------===//
194 /// Record analysis usage.
196 void getAnalysisUsage(AnalysisUsage &AU) const override;
198 /// Set up the AsmPrinter when we are working on a new module. If your pass
199 /// overrides this, it must make sure to explicitly call this implementation.
200 bool doInitialization(Module &M) override;
202 /// Shut down the asmprinter. If you override this in your pass, you must make
203 /// sure to call it explicitly.
204 bool doFinalization(Module &M) override;
206 /// Emit the specified function out to the OutStreamer.
207 bool runOnMachineFunction(MachineFunction &MF) override {
208 SetupMachineFunction(MF);
213 //===------------------------------------------------------------------===//
214 // Coarse grained IR lowering routines.
215 //===------------------------------------------------------------------===//
217 /// This should be called when a new MachineFunction is being processed from
218 /// runOnMachineFunction.
219 void SetupMachineFunction(MachineFunction &MF);
221 /// This method emits the body and trailer for a function.
222 void EmitFunctionBody();
224 void emitCFIInstruction(const MachineInstr &MI);
226 void emitFrameAlloc(const MachineInstr &MI);
228 enum CFIMoveType { CFI_M_None, CFI_M_EH, CFI_M_Debug };
229 CFIMoveType needsCFIMoves();
231 bool needsSEHMoves();
233 /// Print to the current output stream assembly representations of the
234 /// constants in the constant pool MCP. This is used to print out constants
235 /// which have been "spilled to memory" by the code generator.
237 virtual void EmitConstantPool();
239 /// Print assembly representations of the jump tables used by the current
240 /// function to the current output stream.
242 virtual void EmitJumpTableInfo();
244 /// Emit the specified global variable to the .s file.
245 virtual void EmitGlobalVariable(const GlobalVariable *GV);
247 /// Check to see if the specified global is a special global used by LLVM. If
248 /// so, emit it and return true, otherwise do nothing and return false.
249 bool EmitSpecialLLVMGlobal(const GlobalVariable *GV);
251 /// Emit an alignment directive to the specified power of two boundary. For
252 /// example, if you pass in 3 here, you will get an 8 byte alignment. If a
253 /// global value is specified, and if that global has an explicit alignment
254 /// requested, it will override the alignment request if required for
257 void EmitAlignment(unsigned NumBits, const GlobalObject *GO = nullptr) const;
259 /// Lower the specified LLVM Constant to an MCExpr.
260 virtual const MCExpr *lowerConstant(const Constant *CV);
262 /// \brief Print a general LLVM constant to the .s file.
263 void EmitGlobalConstant(const DataLayout &DL, const Constant *CV);
265 /// \brief Unnamed constant global variables solely contaning a pointer to
266 /// another globals variable act like a global variable "proxy", or GOT
267 /// equivalents, i.e., it's only used to hold the address of the latter. One
268 /// optimization is to replace accesses to these proxies by using the GOT
269 /// entry for the final global instead. Hence, we select GOT equivalent
270 /// candidates among all the module global variables, avoid emitting them
271 /// unnecessarily and finally replace references to them by pc relative
272 /// accesses to GOT entries.
273 void computeGlobalGOTEquivs(Module &M);
275 /// \brief Constant expressions using GOT equivalent globals may not be
276 /// eligible for PC relative GOT entry conversion, in such cases we need to
277 /// emit the proxies we previously omitted in EmitGlobalVariable.
278 void emitGlobalGOTEquivs();
280 //===------------------------------------------------------------------===//
282 //===------------------------------------------------------------------===//
284 // Targets can, or in the case of EmitInstruction, must implement these to
287 /// This virtual method can be overridden by targets that want to emit
288 /// something at the start of their file.
289 virtual void EmitStartOfAsmFile(Module &) {}
291 /// This virtual method can be overridden by targets that want to emit
292 /// something at the end of their file.
293 virtual void EmitEndOfAsmFile(Module &) {}
295 /// Targets can override this to emit stuff before the first basic block in
297 virtual void EmitFunctionBodyStart() {}
299 /// Targets can override this to emit stuff after the last basic block in the
301 virtual void EmitFunctionBodyEnd() {}
303 /// Targets can override this to emit stuff at the start of a basic block.
304 /// By default, this method prints the label for the specified
305 /// MachineBasicBlock, an alignment (if present) and a comment describing it
307 virtual void EmitBasicBlockStart(const MachineBasicBlock &MBB) const;
309 /// Targets can override this to emit stuff at the end of a basic block.
310 virtual void EmitBasicBlockEnd(const MachineBasicBlock &MBB) {}
312 /// Targets should implement this to emit instructions.
313 virtual void EmitInstruction(const MachineInstr *) {
314 llvm_unreachable("EmitInstruction not implemented");
317 /// Return the symbol for the specified constant pool entry.
318 virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
320 virtual void EmitFunctionEntryLabel();
322 virtual void EmitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
324 /// Targets can override this to change how global constants that are part of
325 /// a C++ static/global constructor list are emitted.
326 virtual void EmitXXStructor(const DataLayout &DL, const Constant *CV) {
327 EmitGlobalConstant(DL, CV);
330 /// Return true if the basic block has exactly one predecessor and the control
331 /// transfer mechanism between the predecessor and this block is a
334 isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
336 /// Targets can override this to customize the output of IMPLICIT_DEF
337 /// instructions in verbose mode.
338 virtual void emitImplicitDef(const MachineInstr *MI) const;
340 //===------------------------------------------------------------------===//
341 // Symbol Lowering Routines.
342 //===------------------------------------------------------------------===//
344 MCSymbol *createTempSymbol(const Twine &Name) const;
346 /// Return the MCSymbol for a private symbol with global value name as its
347 /// base, with the specified suffix.
348 MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
349 StringRef Suffix) const;
351 /// Return the MCSymbol for the specified ExternalSymbol.
352 MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
354 /// Return the symbol for the specified jump table entry.
355 MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
357 /// Return the symbol for the specified jump table .set
358 /// FIXME: privatize to AsmPrinter.
359 MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
361 /// Return the MCSymbol used to satisfy BlockAddress uses of the specified
363 MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
364 MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
366 //===------------------------------------------------------------------===//
367 // Emission Helper Routines.
368 //===------------------------------------------------------------------===//
370 /// This is just convenient handler for printing offsets.
371 void printOffset(int64_t Offset, raw_ostream &OS) const;
373 /// Emit a byte directive and value.
375 void EmitInt8(int Value) const;
377 /// Emit a short directive and value.
379 void EmitInt16(int Value) const;
381 /// Emit a long directive and value.
383 void EmitInt32(int Value) const;
385 /// Emit something like ".long Hi-Lo" where the size in bytes of the directive
386 /// is specified by Size and Hi/Lo specify the labels. This implicitly uses
387 /// .set if it is available.
388 void EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
389 unsigned Size) const;
391 /// Emit something like ".long Label+Offset" where the size in bytes of the
392 /// directive is specified by Size and Label specifies the label. This
393 /// implicitly uses .set if it is available.
394 void EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
395 unsigned Size, bool IsSectionRelative = false) const;
397 /// Emit something like ".long Label" where the size in bytes of the directive
398 /// is specified by Size and Label specifies the label.
399 void EmitLabelReference(const MCSymbol *Label, unsigned Size,
400 bool IsSectionRelative = false) const {
401 EmitLabelPlusOffset(Label, 0, Size, IsSectionRelative);
404 //===------------------------------------------------------------------===//
405 // Dwarf Emission Helper Routines
406 //===------------------------------------------------------------------===//
408 /// Emit the specified signed leb128 value.
409 void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
411 /// Emit the specified unsigned leb128 value.
412 void EmitULEB128(uint64_t Value, const char *Desc = nullptr,
413 unsigned PadTo = 0) const;
415 /// Emit a .byte 42 directive that corresponds to an encoding. If verbose
416 /// assembly output is enabled, we output comments describing the encoding.
417 /// Desc is a string saying what the encoding is specifying (e.g. "LSDA").
418 void EmitEncodingByte(unsigned Val, const char *Desc = nullptr) const;
420 /// Return the size of the encoding in bytes.
421 unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
423 /// Emit reference to a ttype global with a specified encoding.
424 void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const;
426 /// Emit a reference to a symbol for use in dwarf. Different object formats
427 /// represent this in different ways. Some use a relocation others encode
428 /// the label offset in its section.
429 void emitDwarfSymbolReference(const MCSymbol *Label,
430 bool ForceOffset = false) const;
432 /// Emit the 4-byte offset of a string from the start of its section.
434 /// When possible, emit a DwarfStringPool section offset without any
435 /// relocations, and without using the symbol. Otherwise, defers to \a
436 /// emitDwarfSymbolReference().
437 void emitDwarfStringOffset(DwarfStringPoolEntryRef S) const;
439 /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
440 virtual unsigned getISAEncoding() { return 0; }
442 /// EmitDwarfRegOp - Emit a dwarf register operation.
443 virtual void EmitDwarfRegOp(ByteStreamer &BS,
444 const MachineLocation &MLoc) const;
446 //===------------------------------------------------------------------===//
447 // Dwarf Lowering Routines
448 //===------------------------------------------------------------------===//
450 /// \brief Emit frame instruction to describe the layout of the frame.
451 void emitCFIInstruction(const MCCFIInstruction &Inst) const;
453 /// \brief Emit Dwarf abbreviation table.
454 template <typename T> void emitDwarfAbbrevs(const T &Abbrevs) const {
455 // For each abbreviation.
456 for (const auto &Abbrev : Abbrevs)
457 emitDwarfAbbrev(*Abbrev);
459 // Mark end of abbreviations.
460 EmitULEB128(0, "EOM(3)");
463 void emitDwarfAbbrev(const DIEAbbrev &Abbrev) const;
465 /// \brief Recursively emit Dwarf DIE tree.
466 void emitDwarfDIE(const DIE &Die) const;
468 //===------------------------------------------------------------------===//
469 // Inline Asm Support
470 //===------------------------------------------------------------------===//
472 // These are hooks that targets can override to implement inline asm
473 // support. These should probably be moved out of AsmPrinter someday.
475 /// Print information related to the specified machine instr that is
476 /// independent of the operand, and may be independent of the instr itself.
477 /// This can be useful for portably encoding the comment character or other
478 /// bits of target-specific knowledge into the asmstrings. The syntax used is
479 /// ${:comment}. Targets can override this to add support for their own
481 virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
482 const char *Code) const;
484 /// Print the specified operand of MI, an INLINEASM instruction, using the
485 /// specified assembler variant. Targets should override this to format as
486 /// appropriate. This method can return true if the operand is erroneous.
487 virtual bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
488 unsigned AsmVariant, const char *ExtraCode,
491 /// Print the specified operand of MI, an INLINEASM instruction, using the
492 /// specified assembler variant as an address. Targets should override this to
493 /// format as appropriate. This method can return true if the operand is
495 virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
496 unsigned AsmVariant, const char *ExtraCode,
499 /// Let the target do anything it needs to do before emitting inlineasm.
500 /// \p StartInfo - the subtarget info before parsing inline asm
501 virtual void emitInlineAsmStart() const;
503 /// Let the target do anything it needs to do after emitting inlineasm.
504 /// This callback can be used restore the original mode in case the
505 /// inlineasm contains directives to switch modes.
506 /// \p StartInfo - the original subtarget info before inline asm
507 /// \p EndInfo - the final subtarget info after parsing the inline asm,
508 /// or NULL if the value is unknown.
509 virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
510 const MCSubtargetInfo *EndInfo) const;
513 /// Private state for PrintSpecial()
514 // Assign a unique ID to this machine instruction.
515 mutable const MachineInstr *LastMI;
516 mutable unsigned LastFn;
517 mutable unsigned Counter;
519 /// This method emits the header for the current function.
520 virtual void EmitFunctionHeader();
522 /// Emit a blob of inline asm to the output streamer.
524 EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
525 const MCTargetOptions &MCOptions,
526 const MDNode *LocMDNode = nullptr,
527 InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
529 /// This method formats and emits the specified machine instruction that is an
531 void EmitInlineAsm(const MachineInstr *MI) const;
533 //===------------------------------------------------------------------===//
534 // Internal Implementation Details
535 //===------------------------------------------------------------------===//
537 /// This emits visibility information about symbol, if this is suported by the
539 void EmitVisibility(MCSymbol *Sym, unsigned Visibility,
540 bool IsDefinition = true) const;
542 void EmitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
544 void EmitJumpTableEntry(const MachineJumpTableInfo *MJTI,
545 const MachineBasicBlock *MBB, unsigned uid) const;
546 void EmitLLVMUsedList(const ConstantArray *InitList);
547 /// Emit llvm.ident metadata in an '.ident' directive.
548 void EmitModuleIdents(Module &M);
549 void EmitXXStructorList(const DataLayout &DL, const Constant *List,
551 GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &C);
552 /// Emit GlobalAlias or GlobalIFunc.
553 void emitGlobalIndirectSymbol(Module &M,
554 const GlobalIndirectSymbol& GIS);