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/SmallVector.h"
21 #include "llvm/ADT/StringRef.h"
22 #include "llvm/ADT/Twine.h"
23 #include "llvm/CodeGen/DwarfStringPoolEntry.h"
24 #include "llvm/CodeGen/MachineFunctionPass.h"
25 #include "llvm/IR/InlineAsm.h"
26 #include "llvm/IR/LLVMContext.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/SourceMgr.h"
36 class AsmPrinterHandler;
45 class GCMetadataPrinter;
47 class GlobalIndirectSymbol;
51 class MachineBasicBlock;
52 class MachineConstantPoolValue;
53 class MachineFunction;
55 class MachineJumpTableInfo;
56 class MachineLoopInfo;
57 class MachineModuleInfo;
58 class MachineOptimizationRemarkEmitter;
60 class MCCFIInstruction;
61 struct MCCodePaddingContext;
67 class MCSubtargetInfo;
69 class MCTargetOptions;
73 class TargetLoweringObjectFile;
76 /// This class is intended to be used as a driving class for all asm writers.
77 class AsmPrinter : public MachineFunctionPass {
79 /// Target machine description.
82 /// Target Asm Printer information.
85 /// This is the context for the output file that we are streaming. This owns
86 /// all of the global MC-related objects for the generated translation unit.
87 MCContext &OutContext;
89 /// This is the MCStreamer object for the file we are generating. This
90 /// contains the transient state for the current translation unit that we are
91 /// generating (such as the current section etc).
92 std::unique_ptr<MCStreamer> OutStreamer;
94 /// The current machine function.
95 const MachineFunction *MF = nullptr;
97 /// This is a pointer to the current MachineModuleInfo.
98 MachineModuleInfo *MMI = nullptr;
100 /// Optimization remark emitter.
101 MachineOptimizationRemarkEmitter *ORE;
103 /// The symbol for the current function. This is recalculated at the beginning
104 /// of each call to runOnMachineFunction().
105 MCSymbol *CurrentFnSym = nullptr;
107 /// The symbol used to represent the start of the current function for the
108 /// purpose of calculating its size (e.g. using the .size directive). By
109 /// default, this is equal to CurrentFnSym.
110 MCSymbol *CurrentFnSymForSize = nullptr;
112 /// Map global GOT equivalent MCSymbols to GlobalVariables and keep track of
113 /// its number of uses by other globals.
114 using GOTEquivUsePair = std::pair<const GlobalVariable *, unsigned>;
115 MapVector<const MCSymbol *, GOTEquivUsePair> GlobalGOTEquivs;
117 /// Enable print [latency:throughput] in output.
118 bool EnablePrintSchedInfo = false;
121 MCSymbol *CurrentFnBegin = nullptr;
122 MCSymbol *CurrentFnEnd = nullptr;
123 MCSymbol *CurExceptionSym = nullptr;
125 // The garbage collection metadata printer table.
126 void *GCMetadataPrinters = nullptr; // Really a DenseMap.
128 /// Emit comments in assembly output if this is true.
133 /// If VerboseAsm is set, a pointer to the loop info for this function.
134 MachineLoopInfo *LI = nullptr;
137 AsmPrinterHandler *Handler;
138 const char *TimerName;
139 const char *TimerDescription;
140 const char *TimerGroupName;
141 const char *TimerGroupDescription;
143 HandlerInfo(AsmPrinterHandler *Handler, const char *TimerName,
144 const char *TimerDescription, const char *TimerGroupName,
145 const char *TimerGroupDescription)
146 : Handler(Handler), TimerName(TimerName),
147 TimerDescription(TimerDescription), TimerGroupName(TimerGroupName),
148 TimerGroupDescription(TimerGroupDescription) {}
151 /// A vector of all debug/EH info emitters we should use. This vector
152 /// maintains ownership of the emitters.
153 SmallVector<HandlerInfo, 1> Handlers;
156 struct SrcMgrDiagInfo {
158 std::vector<const MDNode *> LocInfos;
159 LLVMContext::InlineAsmDiagHandlerTy DiagHandler;
164 /// Structure for generating diagnostics for inline assembly. Only initialised
166 mutable std::unique_ptr<SrcMgrDiagInfo> DiagInfo;
168 /// If the target supports dwarf debug info, this pointer is non-null.
169 DwarfDebug *DD = nullptr;
171 /// If the current module uses dwarf CFI annotations strictly for debugging.
172 bool isCFIMoveForDebugging = false;
175 explicit AsmPrinter(TargetMachine &TM, std::unique_ptr<MCStreamer> Streamer);
178 ~AsmPrinter() override;
180 DwarfDebug *getDwarfDebug() { return DD; }
181 DwarfDebug *getDwarfDebug() const { return DD; }
183 uint16_t getDwarfVersion() const;
184 void setDwarfVersion(uint16_t Version);
186 bool isPositionIndependent() const;
188 /// Return true if assembly output should contain comments.
189 bool isVerbose() const { return VerboseAsm; }
191 /// Return a unique ID for the current function.
192 unsigned getFunctionNumber() const;
194 MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
195 MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
196 MCSymbol *getCurExceptionSym();
198 /// Return information about object file lowering.
199 const TargetLoweringObjectFile &getObjFileLowering() const;
201 /// Return information about data layout.
202 const DataLayout &getDataLayout() const;
204 /// Return the pointer size from the TargetMachine
205 unsigned getPointerSize() const;
207 /// Return information about subtarget.
208 const MCSubtargetInfo &getSubtargetInfo() const;
210 void EmitToStreamer(MCStreamer &S, const MCInst &Inst);
212 /// Return the current section we are emitting to.
213 const MCSection *getCurrentSection() const;
215 void getNameWithPrefix(SmallVectorImpl<char> &Name,
216 const GlobalValue *GV) const;
218 MCSymbol *getSymbol(const GlobalValue *GV) const;
220 //===------------------------------------------------------------------===//
221 // XRay instrumentation implementation.
222 //===------------------------------------------------------------------===//
224 // This describes the kind of sled we're storing in the XRay table.
225 enum class SledKind : uint8_t {
233 // The table will contain these structs that point to the sled, the function
234 // containing the sled, and what kind of sled (and whether they should always
235 // be instrumented). We also use a version identifier that the runtime can use
236 // to decide what to do with the sled, depending on the version of the sled.
237 struct XRayFunctionEntry {
238 const MCSymbol *Sled;
239 const MCSymbol *Function;
241 bool AlwaysInstrument;
242 const class Function *Fn;
245 void emit(int, MCStreamer *, const MCSymbol *) const;
248 // All the sleds to be emitted.
249 SmallVector<XRayFunctionEntry, 4> Sleds;
251 // A unique ID used for ELF sections associated with a particular function.
252 unsigned XRayFnUniqueID = 0;
254 // Helper function to record a given XRay sled.
255 void recordSled(MCSymbol *Sled, const MachineInstr &MI, SledKind Kind,
256 uint8_t Version = 0);
258 /// Emit a table with all XRay instrumentation points.
259 void emitXRayTable();
261 //===------------------------------------------------------------------===//
262 // MachineFunctionPass Implementation.
263 //===------------------------------------------------------------------===//
265 /// Record analysis usage.
266 void getAnalysisUsage(AnalysisUsage &AU) const override;
268 /// Set up the AsmPrinter when we are working on a new module. If your pass
269 /// overrides this, it must make sure to explicitly call this implementation.
270 bool doInitialization(Module &M) override;
272 /// Shut down the asmprinter. If you override this in your pass, you must make
273 /// sure to call it explicitly.
274 bool doFinalization(Module &M) override;
276 /// Emit the specified function out to the OutStreamer.
277 bool runOnMachineFunction(MachineFunction &MF) override {
278 SetupMachineFunction(MF);
283 //===------------------------------------------------------------------===//
284 // Coarse grained IR lowering routines.
285 //===------------------------------------------------------------------===//
287 /// This should be called when a new MachineFunction is being processed from
288 /// runOnMachineFunction.
289 void SetupMachineFunction(MachineFunction &MF);
291 /// This method emits the body and trailer for a function.
292 void EmitFunctionBody();
294 void emitCFIInstruction(const MachineInstr &MI);
296 void emitFrameAlloc(const MachineInstr &MI);
298 void emitStackSizeSection(const MachineFunction &MF);
300 enum CFIMoveType { CFI_M_None, CFI_M_EH, CFI_M_Debug };
301 CFIMoveType needsCFIMoves() const;
303 /// Returns false if needsCFIMoves() == CFI_M_EH for any function
305 bool needsOnlyDebugCFIMoves() const { return isCFIMoveForDebugging; }
307 bool needsSEHMoves();
309 /// Print to the current output stream assembly representations of the
310 /// constants in the constant pool MCP. This is used to print out constants
311 /// which have been "spilled to memory" by the code generator.
312 virtual void EmitConstantPool();
314 /// Print assembly representations of the jump tables used by the current
315 /// function to the current output stream.
316 virtual void EmitJumpTableInfo();
318 /// Emit the specified global variable to the .s file.
319 virtual void EmitGlobalVariable(const GlobalVariable *GV);
321 /// Check to see if the specified global is a special global used by LLVM. If
322 /// so, emit it and return true, otherwise do nothing and return false.
323 bool EmitSpecialLLVMGlobal(const GlobalVariable *GV);
325 /// Emit an alignment directive to the specified power of two boundary. For
326 /// example, if you pass in 3 here, you will get an 8 byte alignment. If a
327 /// global value is specified, and if that global has an explicit alignment
328 /// requested, it will override the alignment request if required for
330 void EmitAlignment(unsigned NumBits, const GlobalObject *GO = nullptr) const;
332 /// Lower the specified LLVM Constant to an MCExpr.
333 virtual const MCExpr *lowerConstant(const Constant *CV);
335 /// \brief Print a general LLVM constant to the .s file.
336 void EmitGlobalConstant(const DataLayout &DL, const Constant *CV);
338 /// \brief Unnamed constant global variables solely contaning a pointer to
339 /// another globals variable act like a global variable "proxy", or GOT
340 /// equivalents, i.e., it's only used to hold the address of the latter. One
341 /// optimization is to replace accesses to these proxies by using the GOT
342 /// entry for the final global instead. Hence, we select GOT equivalent
343 /// candidates among all the module global variables, avoid emitting them
344 /// unnecessarily and finally replace references to them by pc relative
345 /// accesses to GOT entries.
346 void computeGlobalGOTEquivs(Module &M);
348 /// \brief Constant expressions using GOT equivalent globals may not be
349 /// eligible for PC relative GOT entry conversion, in such cases we need to
350 /// emit the proxies we previously omitted in EmitGlobalVariable.
351 void emitGlobalGOTEquivs();
353 //===------------------------------------------------------------------===//
355 //===------------------------------------------------------------------===//
357 // Targets can, or in the case of EmitInstruction, must implement these to
360 /// This virtual method can be overridden by targets that want to emit
361 /// something at the start of their file.
362 virtual void EmitStartOfAsmFile(Module &) {}
364 /// This virtual method can be overridden by targets that want to emit
365 /// something at the end of their file.
366 virtual void EmitEndOfAsmFile(Module &) {}
368 /// Targets can override this to emit stuff before the first basic block in
370 virtual void EmitFunctionBodyStart() {}
372 /// Targets can override this to emit stuff after the last basic block in the
374 virtual void EmitFunctionBodyEnd() {}
376 /// Targets can override this to emit stuff at the start of a basic block.
377 /// By default, this method prints the label for the specified
378 /// MachineBasicBlock, an alignment (if present) and a comment describing it
380 virtual void EmitBasicBlockStart(const MachineBasicBlock &MBB) const;
382 /// Targets can override this to emit stuff at the end of a basic block.
383 virtual void EmitBasicBlockEnd(const MachineBasicBlock &MBB);
385 /// Targets should implement this to emit instructions.
386 virtual void EmitInstruction(const MachineInstr *) {
387 llvm_unreachable("EmitInstruction not implemented");
390 /// Return the symbol for the specified constant pool entry.
391 virtual MCSymbol *GetCPISymbol(unsigned CPID) const;
393 virtual void EmitFunctionEntryLabel();
395 virtual void EmitMachineConstantPoolValue(MachineConstantPoolValue *MCPV);
397 /// Targets can override this to change how global constants that are part of
398 /// a C++ static/global constructor list are emitted.
399 virtual void EmitXXStructor(const DataLayout &DL, const Constant *CV) {
400 EmitGlobalConstant(DL, CV);
403 /// Return true if the basic block has exactly one predecessor and the control
404 /// transfer mechanism between the predecessor and this block is a
407 isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const;
409 /// Targets can override this to customize the output of IMPLICIT_DEF
410 /// instructions in verbose mode.
411 virtual void emitImplicitDef(const MachineInstr *MI) const;
413 //===------------------------------------------------------------------===//
414 // Symbol Lowering Routines.
415 //===------------------------------------------------------------------===//
417 MCSymbol *createTempSymbol(const Twine &Name) const;
419 /// Return the MCSymbol for a private symbol with global value name as its
420 /// base, with the specified suffix.
421 MCSymbol *getSymbolWithGlobalValueBase(const GlobalValue *GV,
422 StringRef Suffix) const;
424 /// Return the MCSymbol for the specified ExternalSymbol.
425 MCSymbol *GetExternalSymbolSymbol(StringRef Sym) const;
427 /// Return the symbol for the specified jump table entry.
428 MCSymbol *GetJTISymbol(unsigned JTID, bool isLinkerPrivate = false) const;
430 /// Return the symbol for the specified jump table .set
431 /// FIXME: privatize to AsmPrinter.
432 MCSymbol *GetJTSetSymbol(unsigned UID, unsigned MBBID) const;
434 /// Return the MCSymbol used to satisfy BlockAddress uses of the specified
436 MCSymbol *GetBlockAddressSymbol(const BlockAddress *BA) const;
437 MCSymbol *GetBlockAddressSymbol(const BasicBlock *BB) const;
439 //===------------------------------------------------------------------===//
440 // Emission Helper Routines.
441 //===------------------------------------------------------------------===//
443 /// This is just convenient handler for printing offsets.
444 void printOffset(int64_t Offset, raw_ostream &OS) const;
446 /// Emit a byte directive and value.
447 void EmitInt8(int Value) const;
449 /// Emit a short directive and value.
450 void EmitInt16(int Value) const;
452 /// Emit a long directive and value.
453 void EmitInt32(int Value) const;
455 /// Emit something like ".long Hi-Lo" where the size in bytes of the directive
456 /// is specified by Size and Hi/Lo specify the labels. This implicitly uses
457 /// .set if it is available.
458 void EmitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
459 unsigned Size) const;
461 /// Emit something like ".long Label+Offset" where the size in bytes of the
462 /// directive is specified by Size and Label specifies the label. This
463 /// implicitly uses .set if it is available.
464 void EmitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
465 unsigned Size, bool IsSectionRelative = false) const;
467 /// Emit something like ".long Label" where the size in bytes of the directive
468 /// is specified by Size and Label specifies the label.
469 void EmitLabelReference(const MCSymbol *Label, unsigned Size,
470 bool IsSectionRelative = false) const {
471 EmitLabelPlusOffset(Label, 0, Size, IsSectionRelative);
474 //===------------------------------------------------------------------===//
475 // Dwarf Emission Helper Routines
476 //===------------------------------------------------------------------===//
478 /// Emit the specified signed leb128 value.
479 void EmitSLEB128(int64_t Value, const char *Desc = nullptr) const;
481 /// Emit the specified unsigned leb128 value.
482 void EmitULEB128(uint64_t Value, const char *Desc = nullptr) const;
484 /// Emit the specified unsigned leb128 value padded to a specific number
486 void EmitPaddedULEB128(uint64_t Value, unsigned PadTo,
487 const char *Desc = nullptr) const;
489 /// Emit a .byte 42 directive that corresponds to an encoding. If verbose
490 /// assembly output is enabled, we output comments describing the encoding.
491 /// Desc is a string saying what the encoding is specifying (e.g. "LSDA").
492 void EmitEncodingByte(unsigned Val, const char *Desc = nullptr) const;
494 /// Return the size of the encoding in bytes.
495 unsigned GetSizeOfEncodedValue(unsigned Encoding) const;
497 /// Emit reference to a ttype global with a specified encoding.
498 void EmitTTypeReference(const GlobalValue *GV, unsigned Encoding) const;
500 /// Emit a reference to a symbol for use in dwarf. Different object formats
501 /// represent this in different ways. Some use a relocation others encode
502 /// the label offset in its section.
503 void emitDwarfSymbolReference(const MCSymbol *Label,
504 bool ForceOffset = false) const;
506 /// Emit the 4-byte offset of a string from the start of its section.
508 /// When possible, emit a DwarfStringPool section offset without any
509 /// relocations, and without using the symbol. Otherwise, defers to \a
510 /// emitDwarfSymbolReference().
511 void emitDwarfStringOffset(DwarfStringPoolEntryRef S) const;
513 /// Get the value for DW_AT_APPLE_isa. Zero if no isa encoding specified.
514 virtual unsigned getISAEncoding() { return 0; }
516 /// Emit the directive and value for debug thread local expression
518 /// \p Value - The value to emit.
519 /// \p Size - The size of the integer (in bytes) to emit.
520 virtual void EmitDebugThreadLocal(const MCExpr *Value, unsigned Size) const;
522 //===------------------------------------------------------------------===//
523 // Dwarf Lowering Routines
524 //===------------------------------------------------------------------===//
526 /// \brief Emit frame instruction to describe the layout of the frame.
527 void emitCFIInstruction(const MCCFIInstruction &Inst) const;
529 /// \brief Emit Dwarf abbreviation table.
530 template <typename T> void emitDwarfAbbrevs(const T &Abbrevs) const {
531 // For each abbreviation.
532 for (const auto &Abbrev : Abbrevs)
533 emitDwarfAbbrev(*Abbrev);
535 // Mark end of abbreviations.
536 EmitULEB128(0, "EOM(3)");
539 void emitDwarfAbbrev(const DIEAbbrev &Abbrev) const;
541 /// \brief Recursively emit Dwarf DIE tree.
542 void emitDwarfDIE(const DIE &Die) const;
544 //===------------------------------------------------------------------===//
545 // Inline Asm Support
546 //===------------------------------------------------------------------===//
548 // These are hooks that targets can override to implement inline asm
549 // support. These should probably be moved out of AsmPrinter someday.
551 /// Print information related to the specified machine instr that is
552 /// independent of the operand, and may be independent of the instr itself.
553 /// This can be useful for portably encoding the comment character or other
554 /// bits of target-specific knowledge into the asmstrings. The syntax used is
555 /// ${:comment}. Targets can override this to add support for their own
557 virtual void PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
558 const char *Code) const;
560 /// Print the specified operand of MI, an INLINEASM instruction, using the
561 /// specified assembler variant. Targets should override this to format as
562 /// appropriate. This method can return true if the operand is erroneous.
563 virtual bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
564 unsigned AsmVariant, const char *ExtraCode,
567 /// Print the specified operand of MI, an INLINEASM instruction, using the
568 /// specified assembler variant as an address. Targets should override this to
569 /// format as appropriate. This method can return true if the operand is
571 virtual bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
572 unsigned AsmVariant, const char *ExtraCode,
575 /// Let the target do anything it needs to do before emitting inlineasm.
576 /// \p StartInfo - the subtarget info before parsing inline asm
577 virtual void emitInlineAsmStart() const;
579 /// Let the target do anything it needs to do after emitting inlineasm.
580 /// This callback can be used restore the original mode in case the
581 /// inlineasm contains directives to switch modes.
582 /// \p StartInfo - the original subtarget info before inline asm
583 /// \p EndInfo - the final subtarget info after parsing the inline asm,
584 /// or NULL if the value is unknown.
585 virtual void emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
586 const MCSubtargetInfo *EndInfo) const;
589 /// Private state for PrintSpecial()
590 // Assign a unique ID to this machine instruction.
591 mutable const MachineInstr *LastMI = nullptr;
592 mutable unsigned LastFn = 0;
593 mutable unsigned Counter = ~0U;
595 /// This method emits the header for the current function.
596 virtual void EmitFunctionHeader();
598 /// Emit a blob of inline asm to the output streamer.
600 EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
601 const MCTargetOptions &MCOptions,
602 const MDNode *LocMDNode = nullptr,
603 InlineAsm::AsmDialect AsmDialect = InlineAsm::AD_ATT) const;
605 /// This method formats and emits the specified machine instruction that is an
607 void EmitInlineAsm(const MachineInstr *MI) const;
609 //===------------------------------------------------------------------===//
610 // Internal Implementation Details
611 //===------------------------------------------------------------------===//
613 /// This emits visibility information about symbol, if this is supported by
615 void EmitVisibility(MCSymbol *Sym, unsigned Visibility,
616 bool IsDefinition = true) const;
618 void EmitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const;
620 void EmitJumpTableEntry(const MachineJumpTableInfo *MJTI,
621 const MachineBasicBlock *MBB, unsigned uid) const;
622 void EmitLLVMUsedList(const ConstantArray *InitList);
623 /// Emit llvm.ident metadata in an '.ident' directive.
624 void EmitModuleIdents(Module &M);
625 void EmitXXStructorList(const DataLayout &DL, const Constant *List,
628 GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &C);
629 /// Emit GlobalAlias or GlobalIFunc.
630 void emitGlobalIndirectSymbol(Module &M,
631 const GlobalIndirectSymbol& GIS);
632 void setupCodePaddingContext(const MachineBasicBlock &MBB,
633 MCCodePaddingContext &Context) const;
636 } // end namespace llvm
638 #endif // LLVM_CODEGEN_ASMPRINTER_H