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1 //===-- llvm/CodeGen/AsmPrinter.h - AsmPrinter Framework --------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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
12 // all asm writers.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #ifndef LLVM_CODEGEN_ASMPRINTER_H
17 #define LLVM_CODEGEN_ASMPRINTER_H
18 
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"
26 
27 namespace llvm {
28 class AsmPrinterHandler;
29 class BlockAddress;
30 class ByteStreamer;
31 class GCStrategy;
32 class Constant;
33 class ConstantArray;
34 class DIE;
35 class DIEAbbrev;
36 class GCMetadataPrinter;
37 class GlobalIndirectSymbol;
38 class GlobalValue;
39 class GlobalVariable;
40 class MachineBasicBlock;
41 class MachineFunction;
42 class MachineInstr;
43 class MachineLocation;
44 class MachineLoopInfo;
45 class MachineLoop;
46 class MachineConstantPoolValue;
47 class MachineJumpTableInfo;
48 class MachineModuleInfo;
49 class MCAsmInfo;
50 class MCCFIInstruction;
51 class MCContext;
52 class MCExpr;
53 class MCInst;
54 class MCSection;
55 class MCStreamer;
56 class MCSubtargetInfo;
57 class MCSymbol;
58 class MCTargetOptions;
59 class MDNode;
60 class DwarfDebug;
61 class Mangler;
62 class TargetLoweringObjectFile;
63 class DataLayout;
64 class TargetMachine;
65 
66 /// This class is intended to be used as a driving class for all asm writers.
67 class AsmPrinter : public MachineFunctionPass {
68 public:
69   /// Target machine description.
70   ///
71   TargetMachine &TM;
72 
73   /// Target Asm Printer information.
74   ///
75   const MCAsmInfo *MAI;
76 
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;
80 
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;
85 
86   /// The current machine function.
87   const MachineFunction *MF;
88 
89   /// This is a pointer to the current MachineModuleInfo.
90   MachineModuleInfo *MMI;
91 
92   /// Name-mangler for global names.
93   ///
94   Mangler *Mang;
95 
96   /// The symbol for the current function. This is recalculated at the beginning
97   /// of each call to runOnMachineFunction().
98   ///
99   MCSymbol *CurrentFnSym;
100 
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;
105 
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;
110 
111 private:
112   MCSymbol *CurrentFnBegin;
113   MCSymbol *CurrentFnEnd;
114   MCSymbol *CurExceptionSym;
115 
116   // The garbage collection metadata printer table.
117   void *GCMetadataPrinters; // Really a DenseMap.
118 
119   /// Emit comments in assembly output if this is true.
120   ///
121   bool VerboseAsm;
122   static char ID;
123 
124   /// If VerboseAsm is set, a pointer to the loop info for this function.
125   MachineLoopInfo *LI;
126 
127   struct HandlerInfo {
128     AsmPrinterHandler *Handler;
129     const char *TimerName, *TimerGroupName;
HandlerInfoHandlerInfo130     HandlerInfo(AsmPrinterHandler *Handler, const char *TimerName,
131                 const char *TimerGroupName)
132         : Handler(Handler), TimerName(TimerName),
133           TimerGroupName(TimerGroupName) {}
134   };
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;
138 
139   /// If the target supports dwarf debug info, this pointer is non-null.
140   DwarfDebug *DD;
141 
142 protected:
143   explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
144 
145 public:
146   ~AsmPrinter() override;
147 
getDwarfDebug()148   DwarfDebug *getDwarfDebug() { return DD; }
getDwarfDebug()149   DwarfDebug *getDwarfDebug() const { return DD; }
150 
151   bool isPositionIndependent() const;
152 
153   /// Return true if assembly output should contain comments.
154   ///
isVerbose()155   bool isVerbose() const { return VerboseAsm; }
156 
157   /// Return a unique ID for the current function.
158   ///
159   unsigned getFunctionNumber() const;
160 
getFunctionBegin()161   MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
getFunctionEnd()162   MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
163   MCSymbol *getCurExceptionSym();
164 
165   /// Return information about object file lowering.
166   const TargetLoweringObjectFile &getObjFileLowering() const;
167 
168   /// Return information about data layout.
169   const DataLayout &getDataLayout() const;
170 
171   /// Return the pointer size from the TargetMachine
172   unsigned getPointerSize() const;
173 
174   /// Return information about subtarget.
175   const MCSubtargetInfo &getSubtargetInfo() const;
176 
177   void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
178 
179   /// Return the target triple string.
180   StringRef getTargetTriple() const;
181 
182   /// Return the current section we are emitting to.
183   const MCSection *getCurrentSection() const;
184 
185   void getNameWithPrefix(SmallVectorImpl<char> &Name,
186                          const GlobalValue *GV) const;
187 
188   MCSymbol *getSymbol(const GlobalValue *GV) const;
189 
190   //===------------------------------------------------------------------===//
191   // MachineFunctionPass Implementation.
192   //===------------------------------------------------------------------===//
193 
194   /// Record analysis usage.
195   ///
196   void getAnalysisUsage(AnalysisUsage &AU) const override;
197 
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;
201 
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;
205 
206   /// Emit the specified function out to the OutStreamer.
runOnMachineFunction(MachineFunction & MF)207   bool runOnMachineFunction(MachineFunction &MF) override {
208     SetupMachineFunction(MF);
209     EmitFunctionBody();
210     return false;
211   }
212 
213   //===------------------------------------------------------------------===//
214   // Coarse grained IR lowering routines.
215   //===------------------------------------------------------------------===//
216 
217   /// This should be called when a new MachineFunction is being processed from
218   /// runOnMachineFunction.
219   void SetupMachineFunction(MachineFunction &MF);
220 
221   /// This method emits the body and trailer for a function.
222   void EmitFunctionBody();
223 
224   void emitCFIInstruction(const MachineInstr &MI);
225 
226   void emitFrameAlloc(const MachineInstr &MI);
227 
228   enum CFIMoveType { CFI_M_None, CFI_M_EH, CFI_M_Debug };
229   CFIMoveType needsCFIMoves();
230 
231   bool needsSEHMoves();
232 
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.
236   ///
237   virtual void EmitConstantPool();
238 
239   /// Print assembly representations of the jump tables used by the current
240   /// function to the current output stream.
241   ///
242   virtual void EmitJumpTableInfo();
243 
244   /// Emit the specified global variable to the .s file.
245   virtual void EmitGlobalVariable(const GlobalVariable *GV);
246 
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);
250 
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
255   /// correctness.
256   ///
257   void EmitAlignment(unsigned NumBits, const GlobalObject *GO = nullptr) const;
258 
259   /// Lower the specified LLVM Constant to an MCExpr.
260   virtual const MCExpr *lowerConstant(const Constant *CV);
261 
262   /// \brief Print a general LLVM constant to the .s file.
263   void EmitGlobalConstant(const DataLayout &DL, const Constant *CV);
264 
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);
274 
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();
279 
280   //===------------------------------------------------------------------===//
281   // Overridable Hooks
282   //===------------------------------------------------------------------===//
283 
284   // Targets can, or in the case of EmitInstruction, must implement these to
285   // customize output.
286 
287   /// This virtual method can be overridden by targets that want to emit
288   /// something at the start of their file.
EmitStartOfAsmFile(Module &)289   virtual void EmitStartOfAsmFile(Module &) {}
290 
291   /// This virtual method can be overridden by targets that want to emit
292   /// something at the end of their file.
EmitEndOfAsmFile(Module &)293   virtual void EmitEndOfAsmFile(Module &) {}
294 
295   /// Targets can override this to emit stuff before the first basic block in
296   /// the function.
EmitFunctionBodyStart()297   virtual void EmitFunctionBodyStart() {}
298 
299   /// Targets can override this to emit stuff after the last basic block in the
300   /// function.
EmitFunctionBodyEnd()301   virtual void EmitFunctionBodyEnd() {}
302 
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
306   /// if appropriate.
307   virtual void EmitBasicBlockStart(const MachineBasicBlock &MBB) const;
308 
309   /// Targets can override this to emit stuff at the end of a basic block.
EmitBasicBlockEnd(const MachineBasicBlock & MBB)310   virtual void EmitBasicBlockEnd(const MachineBasicBlock &MBB) {}
311 
312   /// Targets should implement this to emit instructions.
EmitInstruction(const MachineInstr *)313   virtual void EmitInstruction(const MachineInstr *) {
314     llvm_unreachable("EmitInstruction not implemented");
315   }
316 
317   /// Return the symbol for the specified constant pool entry.
318   virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
319 
320   virtual void EmitFunctionEntryLabel();
321 
322   virtual void EmitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
323 
324   /// Targets can override this to change how global constants that are part of
325   /// a C++ static/global constructor list are emitted.
EmitXXStructor(const DataLayout & DL,const Constant * CV)326   virtual void EmitXXStructor(const DataLayout &DL, const Constant *CV) {
327     EmitGlobalConstant(DL, CV);
328   }
329 
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
332   /// fall-through.
333   virtual bool
334   isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
335 
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;
339 
340   //===------------------------------------------------------------------===//
341   // Symbol Lowering Routines.
342   //===------------------------------------------------------------------===//
343 public:
344   MCSymbol *createTempSymbol(const Twine &Name) const;
345 
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;
350 
351   /// Return the MCSymbol for the specified ExternalSymbol.
352   MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
353 
354   /// Return the symbol for the specified jump table entry.
355   MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
356 
357   /// Return the symbol for the specified jump table .set
358   /// FIXME: privatize to AsmPrinter.
359   MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
360 
361   /// Return the MCSymbol used to satisfy BlockAddress uses of the specified
362   /// basic block.
363   MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
364   MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
365 
366   //===------------------------------------------------------------------===//
367   // Emission Helper Routines.
368   //===------------------------------------------------------------------===//
369 public:
370   /// This is just convenient handler for printing offsets.
371   void printOffset(int64_t Offset, raw_ostream &OS) const;
372 
373   /// Emit a byte directive and value.
374   ///
375   void EmitInt8(int Value) const;
376 
377   /// Emit a short directive and value.
378   ///
379   void EmitInt16(int Value) const;
380 
381   /// Emit a long directive and value.
382   ///
383   void EmitInt32(int Value) const;
384 
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;
390 
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;
396 
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);
402   }
403 
404   //===------------------------------------------------------------------===//
405   // Dwarf Emission Helper Routines
406   //===------------------------------------------------------------------===//
407 
408   /// Emit the specified signed leb128 value.
409   void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
410 
411   /// Emit the specified unsigned leb128 value.
412   void EmitULEB128(uint64_t Value, const char *Desc = nullptr,
413                    unsigned PadTo = 0) const;
414 
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;
419 
420   /// Return the size of the encoding in bytes.
421   unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
422 
423   /// Emit reference to a ttype global with a specified encoding.
424   void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const;
425 
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;
431 
432   /// Emit the 4-byte offset of a string from the start of its section.
433   ///
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;
438 
439   /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
getISAEncoding()440   virtual unsigned getISAEncoding() { return 0; }
441 
442   /// EmitDwarfRegOp - Emit a dwarf register operation.
443   virtual void EmitDwarfRegOp(ByteStreamer &BS,
444                               const MachineLocation &MLoc) const;
445 
446   //===------------------------------------------------------------------===//
447   // Dwarf Lowering Routines
448   //===------------------------------------------------------------------===//
449 
450   /// \brief Emit frame instruction to describe the layout of the frame.
451   void emitCFIInstruction(const MCCFIInstruction &Inst) const;
452 
453   /// \brief Emit Dwarf abbreviation table.
emitDwarfAbbrevs(const T & Abbrevs)454   template <typename T> void emitDwarfAbbrevs(const T &Abbrevs) const {
455     // For each abbreviation.
456     for (const auto &Abbrev : Abbrevs)
457       emitDwarfAbbrev(*Abbrev);
458 
459     // Mark end of abbreviations.
460     EmitULEB128(0, "EOM(3)");
461   }
462 
463   void emitDwarfAbbrev(const DIEAbbrev &Abbrev) const;
464 
465   /// \brief Recursively emit Dwarf DIE tree.
466   void emitDwarfDIE(const DIE &Die) const;
467 
468   //===------------------------------------------------------------------===//
469   // Inline Asm Support
470   //===------------------------------------------------------------------===//
471 public:
472   // These are hooks that targets can override to implement inline asm
473   // support.  These should probably be moved out of AsmPrinter someday.
474 
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
480   /// strange codes.
481   virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
482                             const char *Code) const;
483 
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,
489                                raw_ostream &OS);
490 
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
494   /// erroneous.
495   virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
496                                      unsigned AsmVariant, const char *ExtraCode,
497                                      raw_ostream &OS);
498 
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;
502 
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;
511 
512 private:
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;
518 
519   /// This method emits the header for the current function.
520   virtual void EmitFunctionHeader();
521 
522   /// Emit a blob of inline asm to the output streamer.
523   void
524   EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
525                 const MCTargetOptions &MCOptions,
526                 const MDNode *LocMDNode = nullptr,
527                 InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
528 
529   /// This method formats and emits the specified machine instruction that is an
530   /// inline asm.
531   void EmitInlineAsm(const MachineInstr *MI) const;
532 
533   //===------------------------------------------------------------------===//
534   // Internal Implementation Details
535   //===------------------------------------------------------------------===//
536 
537   /// This emits visibility information about symbol, if this is suported by the
538   /// target.
539   void EmitVisibility(MCSymbol *Sym, unsigned Visibility,
540                       bool IsDefinition = true) const;
541 
542   void EmitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
543 
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,
550                           bool isCtor);
551   GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &C);
552   /// Emit GlobalAlias or GlobalIFunc.
553   void emitGlobalIndirectSymbol(Module &M,
554                                 const GlobalIndirectSymbol& GIS);
555 };
556 }
557 
558 #endif
559