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;
39 class MachineBasicBlock;
40 class MachineFunction;
42 class MachineLocation;
43 class MachineLoopInfo;
45 class MachineConstantPoolValue;
46 class MachineJumpTableInfo;
47 class MachineModuleInfo;
49 class MCCFIInstruction;
55 class MCSubtargetInfo;
57 class MCTargetOptions;
61 class TargetLoweringObjectFile;
65 /// This class is intended to be used as a driving class for all asm writers.
66 class AsmPrinter : public MachineFunctionPass {
68 /// Target machine description.
72 /// Target Asm Printer information.
76 /// This is the context for the output file that we are streaming. This owns
77 /// all of the global MC-related objects for the generated translation unit.
78 MCContext &OutContext;
80 /// This is the MCStreamer object for the file we are generating. This
81 /// contains the transient state for the current translation unit that we are
82 /// generating (such as the current section etc).
83 std::unique_ptr<MCStreamer> OutStreamer;
85 /// The current machine function.
86 const MachineFunction *MF;
88 /// This is a pointer to the current MachineModuleInfo.
89 MachineModuleInfo *MMI;
91 /// Name-mangler for global names.
95 /// The symbol for the current function. This is recalculated at the beginning
96 /// of each call to runOnMachineFunction().
98 MCSymbol *CurrentFnSym;
100 /// The symbol used to represent the start of the current function for the
101 /// purpose of calculating its size (e.g. using the .size directive). By
102 /// default, this is equal to CurrentFnSym.
103 MCSymbol *CurrentFnSymForSize;
105 /// Map global GOT equivalent MCSymbols to GlobalVariables and keep track of
106 /// its number of uses by other globals.
107 typedef std::pair<const GlobalVariable *, unsigned> GOTEquivUsePair;
108 MapVector<const MCSymbol *, GOTEquivUsePair> GlobalGOTEquivs;
111 MCSymbol *CurrentFnBegin;
112 MCSymbol *CurrentFnEnd;
113 MCSymbol *CurExceptionSym;
115 // The garbage collection metadata printer table.
116 void *GCMetadataPrinters; // Really a DenseMap.
118 /// Emit comments in assembly output if this is true.
123 /// If VerboseAsm is set, a pointer to the loop info for this function.
127 AsmPrinterHandler *Handler;
128 const char *TimerName, *TimerGroupName;
129 HandlerInfo(AsmPrinterHandler *Handler, const char *TimerName,
130 const char *TimerGroupName)
131 : Handler(Handler), TimerName(TimerName),
132 TimerGroupName(TimerGroupName) {}
134 /// A vector of all debug/EH info emitters we should use. This vector
135 /// maintains ownership of the emitters.
136 SmallVector<HandlerInfo, 1> Handlers;
138 /// If the target supports dwarf debug info, this pointer is non-null.
142 explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
145 ~AsmPrinter() override;
147 DwarfDebug *getDwarfDebug() { return DD; }
148 DwarfDebug *getDwarfDebug() const { return DD; }
150 /// Return true if assembly output should contain comments.
152 bool isVerbose() const { return VerboseAsm; }
154 /// Return a unique ID for the current function.
156 unsigned getFunctionNumber() const;
158 MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
159 MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
160 MCSymbol *getCurExceptionSym();
162 /// Return information about object file lowering.
163 const TargetLoweringObjectFile &getObjFileLowering() const;
165 /// Return information about data layout.
166 const DataLayout &getDataLayout() const;
168 /// Return the pointer size from the TargetMachine
169 unsigned getPointerSize() const;
171 /// Return information about subtarget.
172 const MCSubtargetInfo &getSubtargetInfo() const;
174 void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
176 /// Return the target triple string.
177 StringRef getTargetTriple() const;
179 /// Return the current section we are emitting to.
180 const MCSection *getCurrentSection() const;
182 void getNameWithPrefix(SmallVectorImpl<char> &Name,
183 const GlobalValue *GV) const;
185 MCSymbol *getSymbol(const GlobalValue *GV) const;
187 //===------------------------------------------------------------------===//
188 // MachineFunctionPass Implementation.
189 //===------------------------------------------------------------------===//
191 /// Record analysis usage.
193 void getAnalysisUsage(AnalysisUsage &AU) const override;
195 /// Set up the AsmPrinter when we are working on a new module. If your pass
196 /// overrides this, it must make sure to explicitly call this implementation.
197 bool doInitialization(Module &M) override;
199 /// Shut down the asmprinter. If you override this in your pass, you must make
200 /// sure to call it explicitly.
201 bool doFinalization(Module &M) override;
203 /// Emit the specified function out to the OutStreamer.
204 bool runOnMachineFunction(MachineFunction &MF) override {
205 SetupMachineFunction(MF);
210 //===------------------------------------------------------------------===//
211 // Coarse grained IR lowering routines.
212 //===------------------------------------------------------------------===//
214 /// This should be called when a new MachineFunction is being processed from
215 /// runOnMachineFunction.
216 void SetupMachineFunction(MachineFunction &MF);
218 /// This method emits the body and trailer for a function.
219 void EmitFunctionBody();
221 void emitCFIInstruction(const MachineInstr &MI);
223 void emitFrameAlloc(const MachineInstr &MI);
225 enum CFIMoveType { CFI_M_None, CFI_M_EH, CFI_M_Debug };
226 CFIMoveType needsCFIMoves();
228 bool needsSEHMoves();
230 /// Print to the current output stream assembly representations of the
231 /// constants in the constant pool MCP. This is used to print out constants
232 /// which have been "spilled to memory" by the code generator.
234 virtual void EmitConstantPool();
236 /// Print assembly representations of the jump tables used by the current
237 /// function to the current output stream.
239 void EmitJumpTableInfo();
241 /// Emit the specified global variable to the .s file.
242 virtual void EmitGlobalVariable(const GlobalVariable *GV);
244 /// Check to see if the specified global is a special global used by LLVM. If
245 /// so, emit it and return true, otherwise do nothing and return false.
246 bool EmitSpecialLLVMGlobal(const GlobalVariable *GV);
248 /// Emit an alignment directive to the specified power of two boundary. For
249 /// example, if you pass in 3 here, you will get an 8 byte alignment. If a
250 /// global value is specified, and if that global has an explicit alignment
251 /// requested, it will override the alignment request if required for
254 void EmitAlignment(unsigned NumBits, const GlobalObject *GO = nullptr) const;
256 /// Lower the specified LLVM Constant to an MCExpr.
257 const MCExpr *lowerConstant(const Constant *CV);
259 /// \brief Print a general LLVM constant to the .s file.
260 void EmitGlobalConstant(const Constant *CV);
262 /// \brief Unnamed constant global variables solely contaning a pointer to
263 /// another globals variable act like a global variable "proxy", or GOT
264 /// equivalents, i.e., it's only used to hold the address of the latter. One
265 /// optimization is to replace accesses to these proxies by using the GOT
266 /// entry for the final global instead. Hence, we select GOT equivalent
267 /// candidates among all the module global variables, avoid emitting them
268 /// unnecessarily and finally replace references to them by pc relative
269 /// accesses to GOT entries.
270 void computeGlobalGOTEquivs(Module &M);
272 /// \brief Constant expressions using GOT equivalent globals may not be
273 /// eligible for PC relative GOT entry conversion, in such cases we need to
274 /// emit the proxies we previously omitted in EmitGlobalVariable.
275 void emitGlobalGOTEquivs();
277 //===------------------------------------------------------------------===//
279 //===------------------------------------------------------------------===//
281 // Targets can, or in the case of EmitInstruction, must implement these to
284 /// This virtual method can be overridden by targets that want to emit
285 /// something at the start of their file.
286 virtual void EmitStartOfAsmFile(Module &) {}
288 /// This virtual method can be overridden by targets that want to emit
289 /// something at the end of their file.
290 virtual void EmitEndOfAsmFile(Module &) {}
292 /// Targets can override this to emit stuff before the first basic block in
294 virtual void EmitFunctionBodyStart() {}
296 /// Targets can override this to emit stuff after the last basic block in the
298 virtual void EmitFunctionBodyEnd() {}
300 /// Targets can override this to emit stuff at the start of a basic block.
301 /// By default, this method prints the label for the specified
302 /// MachineBasicBlock, an alignment (if present) and a comment describing it
304 virtual void EmitBasicBlockStart(const MachineBasicBlock &MBB) const;
306 /// Targets can override this to emit stuff at the end of a basic block.
307 virtual void EmitBasicBlockEnd(const MachineBasicBlock &MBB) {}
309 /// Targets should implement this to emit instructions.
310 virtual void EmitInstruction(const MachineInstr *) {
311 llvm_unreachable("EmitInstruction not implemented");
314 /// Return the symbol for the specified constant pool entry.
315 virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
317 virtual void EmitFunctionEntryLabel();
319 virtual void EmitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
321 /// Targets can override this to change how global constants that are part of
322 /// a C++ static/global constructor list are emitted.
323 virtual void EmitXXStructor(const Constant *CV) { EmitGlobalConstant(CV); }
325 /// Return true if the basic block has exactly one predecessor and the control
326 /// transfer mechanism between the predecessor and this block is a
329 isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
331 /// Targets can override this to customize the output of IMPLICIT_DEF
332 /// instructions in verbose mode.
333 virtual void emitImplicitDef(const MachineInstr *MI) const;
335 //===------------------------------------------------------------------===//
336 // Symbol Lowering Routines.
337 //===------------------------------------------------------------------===//
339 MCSymbol *createTempSymbol(const Twine &Name) const;
341 /// Return the MCSymbol for a private symbol with global value name as its
342 /// base, with the specified suffix.
343 MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
344 StringRef Suffix) const;
346 /// Return the MCSymbol for the specified ExternalSymbol.
347 MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
349 /// Return the symbol for the specified jump table entry.
350 MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
352 /// Return the symbol for the specified jump table .set
353 /// FIXME: privatize to AsmPrinter.
354 MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
356 /// Return the MCSymbol used to satisfy BlockAddress uses of the specified
358 MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
359 MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
361 //===------------------------------------------------------------------===//
362 // Emission Helper Routines.
363 //===------------------------------------------------------------------===//
365 /// This is just convenient handler for printing offsets.
366 void printOffset(int64_t Offset, raw_ostream &OS) const;
368 /// Emit a byte directive and value.
370 void EmitInt8(int Value) const;
372 /// Emit a short directive and value.
374 void EmitInt16(int Value) const;
376 /// Emit a long directive and value.
378 void EmitInt32(int Value) const;
380 /// Emit something like ".long Hi-Lo" where the size in bytes of the directive
381 /// is specified by Size and Hi/Lo specify the labels. This implicitly uses
382 /// .set if it is available.
383 void EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
384 unsigned Size) const;
386 /// Emit something like ".long Label+Offset" where the size in bytes of the
387 /// directive is specified by Size and Label specifies the label. This
388 /// implicitly uses .set if it is available.
389 void EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
390 unsigned Size, bool IsSectionRelative = false) const;
392 /// Emit something like ".long Label" where the size in bytes of the directive
393 /// is specified by Size and Label specifies the label.
394 void EmitLabelReference(const MCSymbol *Label, unsigned Size,
395 bool IsSectionRelative = false) const {
396 EmitLabelPlusOffset(Label, 0, Size, IsSectionRelative);
399 //===------------------------------------------------------------------===//
400 // Dwarf Emission Helper Routines
401 //===------------------------------------------------------------------===//
403 /// Emit the specified signed leb128 value.
404 void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
406 /// Emit the specified unsigned leb128 value.
407 void EmitULEB128(uint64_t Value, const char *Desc = nullptr,
408 unsigned PadTo = 0) const;
410 /// Emit a .byte 42 directive for a DW_CFA_xxx value.
411 void EmitCFAByte(unsigned Val) const;
413 /// Emit a .byte 42 directive that corresponds to an encoding. If verbose
414 /// assembly output is enabled, we output comments describing the encoding.
415 /// Desc is a string saying what the encoding is specifying (e.g. "LSDA").
416 void EmitEncodingByte(unsigned Val, const char *Desc = nullptr) const;
418 /// Return the size of the encoding in bytes.
419 unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
421 /// Emit reference to a ttype global with a specified encoding.
422 void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const;
424 /// Emit a reference to a symbol for use in dwarf. Different object formats
425 /// represent this in different ways. Some use a relocation others encode
426 /// the label offset in its section.
427 void emitDwarfSymbolReference(const MCSymbol *Label,
428 bool ForceOffset = false) const;
430 /// Emit the 4-byte offset of a string from the start of its section.
432 /// When possible, emit a DwarfStringPool section offset without any
433 /// relocations, and without using the symbol. Otherwise, defers to \a
434 /// emitDwarfSymbolReference().
435 void emitDwarfStringOffset(DwarfStringPoolEntryRef S) const;
437 /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
438 virtual unsigned getISAEncoding() { return 0; }
440 /// EmitDwarfRegOp - Emit a dwarf register operation.
441 virtual void EmitDwarfRegOp(ByteStreamer &BS,
442 const MachineLocation &MLoc) const;
444 //===------------------------------------------------------------------===//
445 // Dwarf Lowering Routines
446 //===------------------------------------------------------------------===//
448 /// \brief Emit frame instruction to describe the layout of the frame.
449 void emitCFIInstruction(const MCCFIInstruction &Inst) const;
451 /// \brief Emit Dwarf abbreviation table.
452 void emitDwarfAbbrevs(const std::vector<DIEAbbrev *>& Abbrevs) const;
454 /// \brief Recursively emit Dwarf DIE tree.
455 void emitDwarfDIE(const DIE &Die) const;
457 //===------------------------------------------------------------------===//
458 // Inline Asm Support
459 //===------------------------------------------------------------------===//
461 // These are hooks that targets can override to implement inline asm
462 // support. These should probably be moved out of AsmPrinter someday.
464 /// Print information related to the specified machine instr that is
465 /// independent of the operand, and may be independent of the instr itself.
466 /// This can be useful for portably encoding the comment character or other
467 /// bits of target-specific knowledge into the asmstrings. The syntax used is
468 /// ${:comment}. Targets can override this to add support for their own
470 virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
471 const char *Code) const;
473 /// Print the specified operand of MI, an INLINEASM instruction, using the
474 /// specified assembler variant. Targets should override this to format as
475 /// appropriate. This method can return true if the operand is erroneous.
476 virtual bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
477 unsigned AsmVariant, const char *ExtraCode,
480 /// Print the specified operand of MI, an INLINEASM instruction, using the
481 /// specified assembler variant as an address. Targets should override this to
482 /// format as appropriate. This method can return true if the operand is
484 virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
485 unsigned AsmVariant, const char *ExtraCode,
488 /// Let the target do anything it needs to do before emitting inlineasm.
489 /// \p StartInfo - the subtarget info before parsing inline asm
490 virtual void emitInlineAsmStart() const;
492 /// Let the target do anything it needs to do after emitting inlineasm.
493 /// This callback can be used restore the original mode in case the
494 /// inlineasm contains directives to switch modes.
495 /// \p StartInfo - the original subtarget info before inline asm
496 /// \p EndInfo - the final subtarget info after parsing the inline asm,
497 /// or NULL if the value is unknown.
498 virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
499 const MCSubtargetInfo *EndInfo) const;
502 /// Private state for PrintSpecial()
503 // Assign a unique ID to this machine instruction.
504 mutable const MachineInstr *LastMI;
505 mutable unsigned LastFn;
506 mutable unsigned Counter;
508 /// This method emits the header for the current function.
509 virtual void EmitFunctionHeader();
511 /// Emit a blob of inline asm to the output streamer.
513 EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
514 const MCTargetOptions &MCOptions,
515 const MDNode *LocMDNode = nullptr,
516 InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
518 /// This method formats and emits the specified machine instruction that is an
520 void EmitInlineAsm(const MachineInstr *MI) const;
522 //===------------------------------------------------------------------===//
523 // Internal Implementation Details
524 //===------------------------------------------------------------------===//
526 /// This emits visibility information about symbol, if this is suported by the
528 void EmitVisibility(MCSymbol *Sym, unsigned Visibility,
529 bool IsDefinition = true) const;
531 void EmitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
533 void EmitJumpTableEntry(const MachineJumpTableInfo *MJTI,
534 const MachineBasicBlock *MBB, unsigned uid) const;
535 void EmitLLVMUsedList(const ConstantArray *InitList);
536 /// Emit llvm.ident metadata in an '.ident' directive.
537 void EmitModuleIdents(Module &M);
538 void EmitXXStructorList(const Constant *List, bool isCtor);
539 GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &C);