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 information about subtarget.
169 const MCSubtargetInfo &getSubtargetInfo() const;
171 void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
173 /// Return the target triple string.
174 StringRef getTargetTriple() const;
176 /// Return the current section we are emitting to.
177 const MCSection *getCurrentSection() const;
179 void getNameWithPrefix(SmallVectorImpl<char> &Name,
180 const GlobalValue *GV) const;
182 MCSymbol *getSymbol(const GlobalValue *GV) const;
184 //===------------------------------------------------------------------===//
185 // MachineFunctionPass Implementation.
186 //===------------------------------------------------------------------===//
188 /// Record analysis usage.
190 void getAnalysisUsage(AnalysisUsage &AU) const override;
192 /// Set up the AsmPrinter when we are working on a new module. If your pass
193 /// overrides this, it must make sure to explicitly call this implementation.
194 bool doInitialization(Module &M) override;
196 /// Shut down the asmprinter. If you override this in your pass, you must make
197 /// sure to call it explicitly.
198 bool doFinalization(Module &M) override;
200 /// Emit the specified function out to the OutStreamer.
201 bool runOnMachineFunction(MachineFunction &MF) override {
202 SetupMachineFunction(MF);
207 //===------------------------------------------------------------------===//
208 // Coarse grained IR lowering routines.
209 //===------------------------------------------------------------------===//
211 /// This should be called when a new MachineFunction is being processed from
212 /// runOnMachineFunction.
213 void SetupMachineFunction(MachineFunction &MF);
215 /// This method emits the body and trailer for a function.
216 void EmitFunctionBody();
218 void emitCFIInstruction(const MachineInstr &MI);
220 void emitFrameAlloc(const MachineInstr &MI);
222 enum CFIMoveType { CFI_M_None, CFI_M_EH, CFI_M_Debug };
223 CFIMoveType needsCFIMoves();
225 bool needsSEHMoves();
227 /// Print to the current output stream assembly representations of the
228 /// constants in the constant pool MCP. This is used to print out constants
229 /// which have been "spilled to memory" by the code generator.
231 virtual void EmitConstantPool();
233 /// Print assembly representations of the jump tables used by the current
234 /// function to the current output stream.
236 void EmitJumpTableInfo();
238 /// Emit the specified global variable to the .s file.
239 virtual void EmitGlobalVariable(const GlobalVariable *GV);
241 /// Check to see if the specified global is a special global used by LLVM. If
242 /// so, emit it and return true, otherwise do nothing and return false.
243 bool EmitSpecialLLVMGlobal(const GlobalVariable *GV);
245 /// Emit an alignment directive to the specified power of two boundary. For
246 /// example, if you pass in 3 here, you will get an 8 byte alignment. If a
247 /// global value is specified, and if that global has an explicit alignment
248 /// requested, it will override the alignment request if required for
251 void EmitAlignment(unsigned NumBits, const GlobalObject *GO = nullptr) const;
253 /// Lower the specified LLVM Constant to an MCExpr.
254 const MCExpr *lowerConstant(const Constant *CV);
256 /// \brief Print a general LLVM constant to the .s file.
257 void EmitGlobalConstant(const Constant *CV);
259 /// \brief Unnamed constant global variables solely contaning a pointer to
260 /// another globals variable act like a global variable "proxy", or GOT
261 /// equivalents, i.e., it's only used to hold the address of the latter. One
262 /// optimization is to replace accesses to these proxies by using the GOT
263 /// entry for the final global instead. Hence, we select GOT equivalent
264 /// candidates among all the module global variables, avoid emitting them
265 /// unnecessarily and finally replace references to them by pc relative
266 /// accesses to GOT entries.
267 void computeGlobalGOTEquivs(Module &M);
269 /// \brief Constant expressions using GOT equivalent globals may not be
270 /// eligible for PC relative GOT entry conversion, in such cases we need to
271 /// emit the proxies we previously omitted in EmitGlobalVariable.
272 void emitGlobalGOTEquivs();
274 //===------------------------------------------------------------------===//
276 //===------------------------------------------------------------------===//
278 // Targets can, or in the case of EmitInstruction, must implement these to
281 /// This virtual method can be overridden by targets that want to emit
282 /// something at the start of their file.
283 virtual void EmitStartOfAsmFile(Module &) {}
285 /// This virtual method can be overridden by targets that want to emit
286 /// something at the end of their file.
287 virtual void EmitEndOfAsmFile(Module &) {}
289 /// Targets can override this to emit stuff before the first basic block in
291 virtual void EmitFunctionBodyStart() {}
293 /// Targets can override this to emit stuff after the last basic block in the
295 virtual void EmitFunctionBodyEnd() {}
297 /// Targets can override this to emit stuff at the start of a basic block.
298 /// By default, this method prints the label for the specified
299 /// MachineBasicBlock, an alignment (if present) and a comment describing it
301 virtual void EmitBasicBlockStart(const MachineBasicBlock &MBB) const;
303 /// Targets can override this to emit stuff at the end of a basic block.
304 virtual void EmitBasicBlockEnd(const MachineBasicBlock &MBB) {}
306 /// Targets should implement this to emit instructions.
307 virtual void EmitInstruction(const MachineInstr *) {
308 llvm_unreachable("EmitInstruction not implemented");
311 /// Return the symbol for the specified constant pool entry.
312 virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
314 virtual void EmitFunctionEntryLabel();
316 virtual void EmitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
318 /// Targets can override this to change how global constants that are part of
319 /// a C++ static/global constructor list are emitted.
320 virtual void EmitXXStructor(const Constant *CV) { EmitGlobalConstant(CV); }
322 /// Return true if the basic block has exactly one predecessor and the control
323 /// transfer mechanism between the predecessor and this block is a
326 isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
328 /// Targets can override this to customize the output of IMPLICIT_DEF
329 /// instructions in verbose mode.
330 virtual void emitImplicitDef(const MachineInstr *MI) const;
332 //===------------------------------------------------------------------===//
333 // Symbol Lowering Routines.
334 //===------------------------------------------------------------------===//
336 MCSymbol *createTempSymbol(const Twine &Name) const;
338 /// Return the MCSymbol for a private symbol with global value name as its
339 /// base, with the specified suffix.
340 MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
341 StringRef Suffix) const;
343 /// Return the MCSymbol for the specified ExternalSymbol.
344 MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
346 /// Return the symbol for the specified jump table entry.
347 MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
349 /// Return the symbol for the specified jump table .set
350 /// FIXME: privatize to AsmPrinter.
351 MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
353 /// Return the MCSymbol used to satisfy BlockAddress uses of the specified
355 MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
356 MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
358 //===------------------------------------------------------------------===//
359 // Emission Helper Routines.
360 //===------------------------------------------------------------------===//
362 /// This is just convenient handler for printing offsets.
363 void printOffset(int64_t Offset, raw_ostream &OS) const;
365 /// Emit a byte directive and value.
367 void EmitInt8(int Value) const;
369 /// Emit a short directive and value.
371 void EmitInt16(int Value) const;
373 /// Emit a long directive and value.
375 void EmitInt32(int Value) const;
377 /// Emit something like ".long Hi-Lo" where the size in bytes of the directive
378 /// is specified by Size and Hi/Lo specify the labels. This implicitly uses
379 /// .set if it is available.
380 void EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
381 unsigned Size) const;
383 /// Emit something like ".long Label+Offset" where the size in bytes of the
384 /// directive is specified by Size and Label specifies the label. This
385 /// implicitly uses .set if it is available.
386 void EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
387 unsigned Size, bool IsSectionRelative = false) const;
389 /// Emit something like ".long Label" where the size in bytes of the directive
390 /// is specified by Size and Label specifies the label.
391 void EmitLabelReference(const MCSymbol *Label, unsigned Size,
392 bool IsSectionRelative = false) const {
393 EmitLabelPlusOffset(Label, 0, Size, IsSectionRelative);
396 //===------------------------------------------------------------------===//
397 // Dwarf Emission Helper Routines
398 //===------------------------------------------------------------------===//
400 /// Emit the specified signed leb128 value.
401 void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
403 /// Emit the specified unsigned leb128 value.
404 void EmitULEB128(uint64_t Value, const char *Desc = nullptr,
405 unsigned PadTo = 0) const;
407 /// Emit a .byte 42 directive for a DW_CFA_xxx value.
408 void EmitCFAByte(unsigned Val) const;
410 /// Emit a .byte 42 directive that corresponds to an encoding. If verbose
411 /// assembly output is enabled, we output comments describing the encoding.
412 /// Desc is a string saying what the encoding is specifying (e.g. "LSDA").
413 void EmitEncodingByte(unsigned Val, const char *Desc = nullptr) const;
415 /// Return the size of the encoding in bytes.
416 unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
418 /// Emit reference to a ttype global with a specified encoding.
419 void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const;
421 /// Emit the 4-byte offset of Label from the start of its section. This can
422 /// be done with a special directive if the target supports it (e.g. cygwin)
423 /// or by emitting it as an offset from a label at the start of the section.
424 void emitSectionOffset(const MCSymbol *Label) const;
426 /// Emit the 4-byte offset of a string from the start of its section.
428 /// When possible, emit a DwarfStringPool section offset without any
429 /// relocations, and without using the symbol. Otherwise, defers to \a
430 /// emitSectionOffset().
431 void emitDwarfStringOffset(DwarfStringPoolEntryRef S) const;
433 /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
434 virtual unsigned getISAEncoding() { return 0; }
436 /// EmitDwarfRegOp - Emit a dwarf register operation.
437 virtual void EmitDwarfRegOp(ByteStreamer &BS,
438 const MachineLocation &MLoc) const;
440 //===------------------------------------------------------------------===//
441 // Dwarf Lowering Routines
442 //===------------------------------------------------------------------===//
444 /// \brief Emit frame instruction to describe the layout of the frame.
445 void emitCFIInstruction(const MCCFIInstruction &Inst) const;
447 /// \brief Emit Dwarf abbreviation table.
448 void emitDwarfAbbrevs(const std::vector<DIEAbbrev *>& Abbrevs) const;
450 /// \brief Recursively emit Dwarf DIE tree.
451 void emitDwarfDIE(const DIE &Die) const;
453 //===------------------------------------------------------------------===//
454 // Inline Asm Support
455 //===------------------------------------------------------------------===//
457 // These are hooks that targets can override to implement inline asm
458 // support. These should probably be moved out of AsmPrinter someday.
460 /// Print information related to the specified machine instr that is
461 /// independent of the operand, and may be independent of the instr itself.
462 /// This can be useful for portably encoding the comment character or other
463 /// bits of target-specific knowledge into the asmstrings. The syntax used is
464 /// ${:comment}. Targets can override this to add support for their own
466 virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
467 const char *Code) const;
469 /// Print the specified operand of MI, an INLINEASM instruction, using the
470 /// specified assembler variant. Targets should override this to format as
471 /// appropriate. This method can return true if the operand is erroneous.
472 virtual bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
473 unsigned AsmVariant, const char *ExtraCode,
476 /// Print the specified operand of MI, an INLINEASM instruction, using the
477 /// specified assembler variant as an address. Targets should override this to
478 /// format as appropriate. This method can return true if the operand is
480 virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
481 unsigned AsmVariant, const char *ExtraCode,
484 /// Let the target do anything it needs to do before emitting inlineasm.
485 /// \p StartInfo - the subtarget info before parsing inline asm
486 virtual void emitInlineAsmStart() const;
488 /// Let the target do anything it needs to do after emitting inlineasm.
489 /// This callback can be used restore the original mode in case the
490 /// inlineasm contains directives to switch modes.
491 /// \p StartInfo - the original subtarget info before inline asm
492 /// \p EndInfo - the final subtarget info after parsing the inline asm,
493 /// or NULL if the value is unknown.
494 virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
495 const MCSubtargetInfo *EndInfo) const;
498 /// Private state for PrintSpecial()
499 // Assign a unique ID to this machine instruction.
500 mutable const MachineInstr *LastMI;
501 mutable unsigned LastFn;
502 mutable unsigned Counter;
504 /// This method emits the header for the current function.
505 virtual void EmitFunctionHeader();
507 /// Emit a blob of inline asm to the output streamer.
509 EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
510 const MCTargetOptions &MCOptions,
511 const MDNode *LocMDNode = nullptr,
512 InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
514 /// This method formats and emits the specified machine instruction that is an
516 void EmitInlineAsm(const MachineInstr *MI) const;
518 //===------------------------------------------------------------------===//
519 // Internal Implementation Details
520 //===------------------------------------------------------------------===//
522 /// This emits visibility information about symbol, if this is suported by the
524 void EmitVisibility(MCSymbol *Sym, unsigned Visibility,
525 bool IsDefinition = true) const;
527 void EmitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
529 void EmitJumpTableEntry(const MachineJumpTableInfo *MJTI,
530 const MachineBasicBlock *MBB, unsigned uid) const;
531 void EmitLLVMUsedList(const ConstantArray *InitList);
532 /// Emit llvm.ident metadata in an '.ident' directive.
533 void EmitModuleIdents(Module &M);
534 void EmitXXStructorList(const Constant *List, bool isCtor);
535 GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &C);