1//===-- AsmPrinterInlineAsm.cpp - AsmPrinter Inline Asm Handling ----------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the inline assembler pieces of the AsmPrinter class.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/ADT/SmallString.h"
14#include "llvm/ADT/SmallVector.h"
15#include "llvm/ADT/StringExtras.h"
16#include "llvm/ADT/Twine.h"
17#include "llvm/CodeGen/AsmPrinter.h"
18#include "llvm/CodeGen/MachineBasicBlock.h"
19#include "llvm/CodeGen/MachineFunction.h"
20#include "llvm/CodeGen/MachineModuleInfo.h"
21#include "llvm/CodeGen/TargetRegisterInfo.h"
22#include "llvm/CodeGen/TargetSubtargetInfo.h"
23#include "llvm/IR/Constants.h"
24#include "llvm/IR/DataLayout.h"
25#include "llvm/IR/DiagnosticInfo.h"
26#include "llvm/IR/InlineAsm.h"
27#include "llvm/IR/LLVMContext.h"
28#include "llvm/IR/Module.h"
29#include "llvm/MC/MCAsmInfo.h"
30#include "llvm/MC/MCInstrInfo.h"
31#include "llvm/MC/MCParser/MCAsmLexer.h"
32#include "llvm/MC/MCParser/MCTargetAsmParser.h"
33#include "llvm/MC/MCStreamer.h"
34#include "llvm/MC/MCSymbol.h"
35#include "llvm/MC/TargetRegistry.h"
36#include "llvm/Support/ErrorHandling.h"
37#include "llvm/Support/MemoryBuffer.h"
38#include "llvm/Support/SourceMgr.h"
39#include "llvm/Support/raw_ostream.h"
40#include "llvm/Target/TargetMachine.h"
41using namespace llvm;
42
43#define DEBUG_TYPE "asm-printer"
44
45unsigned AsmPrinter::addInlineAsmDiagBuffer(StringRef AsmStr,
46                                            const MDNode *LocMDNode) const {
47  MCContext &Context = MMI->getContext();
48  Context.initInlineSourceManager();
49  SourceMgr &SrcMgr = *Context.getInlineSourceManager();
50  std::vector<const MDNode *> &LocInfos = Context.getLocInfos();
51
52  std::unique_ptr<MemoryBuffer> Buffer;
53  // The inline asm source manager will outlive AsmStr, so make a copy of the
54  // string for SourceMgr to own.
55  Buffer = MemoryBuffer::getMemBufferCopy(AsmStr, "<inline asm>");
56
57  // Tell SrcMgr about this buffer, it takes ownership of the buffer.
58  unsigned BufNum = SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
59
60  // Store LocMDNode in DiagInfo, using BufNum as an identifier.
61  if (LocMDNode) {
62    LocInfos.resize(BufNum);
63    LocInfos[BufNum - 1] = LocMDNode;
64  }
65
66  return BufNum;
67}
68
69
70/// EmitInlineAsm - Emit a blob of inline asm to the output streamer.
71void AsmPrinter::emitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
72                               const MCTargetOptions &MCOptions,
73                               const MDNode *LocMDNode,
74                               InlineAsm::AsmDialect Dialect) const {
75  assert(!Str.empty() && "Can't emit empty inline asm block");
76
77  // Remember if the buffer is nul terminated or not so we can avoid a copy.
78  bool isNullTerminated = Str.back() == 0;
79  if (isNullTerminated)
80    Str = Str.substr(0, Str.size()-1);
81
82  // If the output streamer does not have mature MC support or the integrated
83  // assembler has been disabled or not required, just emit the blob textually.
84  // Otherwise parse the asm and emit it via MC support.
85  // This is useful in case the asm parser doesn't handle something but the
86  // system assembler does.
87  const MCAsmInfo *MCAI = TM.getMCAsmInfo();
88  assert(MCAI && "No MCAsmInfo");
89  if (!MCAI->useIntegratedAssembler() &&
90      !MCAI->parseInlineAsmUsingAsmParser() &&
91      !OutStreamer->isIntegratedAssemblerRequired()) {
92    emitInlineAsmStart();
93    OutStreamer->emitRawText(Str);
94    emitInlineAsmEnd(STI, nullptr);
95    return;
96  }
97
98  unsigned BufNum = addInlineAsmDiagBuffer(Str, LocMDNode);
99  SourceMgr &SrcMgr = *MMI->getContext().getInlineSourceManager();
100  SrcMgr.setIncludeDirs(MCOptions.IASSearchPaths);
101
102  std::unique_ptr<MCAsmParser> Parser(
103      createMCAsmParser(SrcMgr, OutContext, *OutStreamer, *MAI, BufNum));
104
105  // Do not use assembler-level information for parsing inline assembly.
106  OutStreamer->setUseAssemblerInfoForParsing(false);
107
108  // We create a new MCInstrInfo here since we might be at the module level
109  // and not have a MachineFunction to initialize the TargetInstrInfo from and
110  // we only need MCInstrInfo for asm parsing. We create one unconditionally
111  // because it's not subtarget dependent.
112  std::unique_ptr<MCInstrInfo> MII(TM.getTarget().createMCInstrInfo());
113  assert(MII && "Failed to create instruction info");
114  std::unique_ptr<MCTargetAsmParser> TAP(TM.getTarget().createMCAsmParser(
115      STI, *Parser, *MII, MCOptions));
116  if (!TAP)
117    report_fatal_error("Inline asm not supported by this streamer because"
118                       " we don't have an asm parser for this target\n");
119  Parser->setAssemblerDialect(Dialect);
120  Parser->setTargetParser(*TAP);
121  // Enable lexing Masm binary and hex integer literals in intel inline
122  // assembly.
123  if (Dialect == InlineAsm::AD_Intel)
124    Parser->getLexer().setLexMasmIntegers(true);
125
126  emitInlineAsmStart();
127  // Don't implicitly switch to the text section before the asm.
128  (void)Parser->Run(/*NoInitialTextSection*/ true,
129                    /*NoFinalize*/ true);
130  emitInlineAsmEnd(STI, &TAP->getSTI());
131}
132
133static void EmitInlineAsmStr(const char *AsmStr, const MachineInstr *MI,
134                             MachineModuleInfo *MMI, const MCAsmInfo *MAI,
135                             AsmPrinter *AP, uint64_t LocCookie,
136                             raw_ostream &OS) {
137  bool InputIsIntelDialect = MI->getInlineAsmDialect() == InlineAsm::AD_Intel;
138
139  if (InputIsIntelDialect) {
140    // Switch to the inline assembly variant.
141    OS << "\t.intel_syntax\n\t";
142  }
143
144  int CurVariant = -1; // The number of the {.|.|.} region we are in.
145  const char *LastEmitted = AsmStr; // One past the last character emitted.
146  unsigned NumOperands = MI->getNumOperands();
147
148  int AsmPrinterVariant;
149  if (InputIsIntelDialect)
150    AsmPrinterVariant = 1; // X86MCAsmInfo.cpp's AsmWriterFlavorTy::Intel.
151  else
152    AsmPrinterVariant = MMI->getTarget().unqualifiedInlineAsmVariant();
153
154  // FIXME: Should this happen for `asm inteldialect` as well?
155  if (!InputIsIntelDialect && MAI->getEmitGNUAsmStartIndentationMarker())
156    OS << '\t';
157
158  while (*LastEmitted) {
159    switch (*LastEmitted) {
160    default: {
161      // Not a special case, emit the string section literally.
162      const char *LiteralEnd = LastEmitted+1;
163      while (*LiteralEnd && *LiteralEnd != '{' && *LiteralEnd != '|' &&
164             *LiteralEnd != '}' && *LiteralEnd != '$' && *LiteralEnd != '\n')
165        ++LiteralEnd;
166      if (CurVariant == -1 || CurVariant == AsmPrinterVariant)
167        OS.write(LastEmitted, LiteralEnd - LastEmitted);
168      LastEmitted = LiteralEnd;
169      break;
170    }
171    case '\n':
172      ++LastEmitted;   // Consume newline character.
173      OS << '\n';      // Indent code with newline.
174      break;
175    case '$': {
176      ++LastEmitted;   // Consume '$' character.
177      bool Done = true;
178
179      // Handle escapes.
180      switch (*LastEmitted) {
181      default: Done = false; break;
182      case '$':     // $$ -> $
183        if (!InputIsIntelDialect)
184          if (CurVariant == -1 || CurVariant == AsmPrinterVariant)
185            OS << '$';
186        ++LastEmitted;  // Consume second '$' character.
187        break;
188      case '(':        // $( -> same as GCC's { character.
189        ++LastEmitted; // Consume '(' character.
190        if (CurVariant != -1)
191          report_fatal_error("Nested variants found in inline asm string: '" +
192                             Twine(AsmStr) + "'");
193        CurVariant = 0; // We're in the first variant now.
194        break;
195      case '|':
196        ++LastEmitted; // Consume '|' character.
197        if (CurVariant == -1)
198          OS << '|'; // This is gcc's behavior for | outside a variant.
199        else
200          ++CurVariant; // We're in the next variant.
201        break;
202      case ')':        // $) -> same as GCC's } char.
203        ++LastEmitted; // Consume ')' character.
204        if (CurVariant == -1)
205          OS << '}'; // This is gcc's behavior for } outside a variant.
206        else
207          CurVariant = -1;
208        break;
209      }
210      if (Done) break;
211
212      bool HasCurlyBraces = false;
213      if (*LastEmitted == '{') {     // ${variable}
214        ++LastEmitted;               // Consume '{' character.
215        HasCurlyBraces = true;
216      }
217
218      // If we have ${:foo}, then this is not a real operand reference, it is a
219      // "magic" string reference, just like in .td files.  Arrange to call
220      // PrintSpecial.
221      if (HasCurlyBraces && *LastEmitted == ':') {
222        ++LastEmitted;
223        const char *StrStart = LastEmitted;
224        const char *StrEnd = strchr(StrStart, '}');
225        if (!StrEnd)
226          report_fatal_error("Unterminated ${:foo} operand in inline asm"
227                             " string: '" + Twine(AsmStr) + "'");
228        if (CurVariant == -1 || CurVariant == AsmPrinterVariant)
229          AP->PrintSpecial(MI, OS, StringRef(StrStart, StrEnd - StrStart));
230        LastEmitted = StrEnd+1;
231        break;
232      }
233
234      const char *IDStart = LastEmitted;
235      const char *IDEnd = IDStart;
236      while (isDigit(*IDEnd))
237        ++IDEnd;
238
239      unsigned Val;
240      if (StringRef(IDStart, IDEnd-IDStart).getAsInteger(10, Val))
241        report_fatal_error("Bad $ operand number in inline asm string: '" +
242                           Twine(AsmStr) + "'");
243      LastEmitted = IDEnd;
244
245      if (Val >= NumOperands - 1)
246        report_fatal_error("Invalid $ operand number in inline asm string: '" +
247                           Twine(AsmStr) + "'");
248
249      char Modifier[2] = { 0, 0 };
250
251      if (HasCurlyBraces) {
252        // If we have curly braces, check for a modifier character.  This
253        // supports syntax like ${0:u}, which correspond to "%u0" in GCC asm.
254        if (*LastEmitted == ':') {
255          ++LastEmitted;    // Consume ':' character.
256          if (*LastEmitted == 0)
257            report_fatal_error("Bad ${:} expression in inline asm string: '" +
258                               Twine(AsmStr) + "'");
259
260          Modifier[0] = *LastEmitted;
261          ++LastEmitted;    // Consume modifier character.
262        }
263
264        if (*LastEmitted != '}')
265          report_fatal_error("Bad ${} expression in inline asm string: '" +
266                             Twine(AsmStr) + "'");
267        ++LastEmitted;    // Consume '}' character.
268      }
269
270      // Okay, we finally have a value number.  Ask the target to print this
271      // operand!
272      if (CurVariant == -1 || CurVariant == AsmPrinterVariant) {
273        unsigned OpNo = InlineAsm::MIOp_FirstOperand;
274
275        bool Error = false;
276
277        // Scan to find the machine operand number for the operand.
278        for (; Val; --Val) {
279          if (OpNo >= MI->getNumOperands())
280            break;
281          const InlineAsm::Flag F(MI->getOperand(OpNo).getImm());
282          OpNo += F.getNumOperandRegisters() + 1;
283        }
284
285        // We may have a location metadata attached to the end of the
286        // instruction, and at no point should see metadata at any
287        // other point while processing. It's an error if so.
288        if (OpNo >= MI->getNumOperands() || MI->getOperand(OpNo).isMetadata()) {
289          Error = true;
290        } else {
291          const InlineAsm::Flag F(MI->getOperand(OpNo).getImm());
292          ++OpNo; // Skip over the ID number.
293
294          // FIXME: Shouldn't arch-independent output template handling go into
295          // PrintAsmOperand?
296          // Labels are target independent.
297          if (MI->getOperand(OpNo).isBlockAddress()) {
298            const BlockAddress *BA = MI->getOperand(OpNo).getBlockAddress();
299            MCSymbol *Sym = AP->GetBlockAddressSymbol(BA);
300            Sym->print(OS, AP->MAI);
301            MMI->getContext().registerInlineAsmLabel(Sym);
302          } else if (MI->getOperand(OpNo).isMBB()) {
303            const MCSymbol *Sym = MI->getOperand(OpNo).getMBB()->getSymbol();
304            Sym->print(OS, AP->MAI);
305          } else if (F.isMemKind()) {
306            Error = AP->PrintAsmMemoryOperand(
307                MI, OpNo, Modifier[0] ? Modifier : nullptr, OS);
308          } else {
309            Error = AP->PrintAsmOperand(MI, OpNo,
310                                        Modifier[0] ? Modifier : nullptr, OS);
311          }
312        }
313        if (Error) {
314          std::string msg;
315          raw_string_ostream Msg(msg);
316          Msg << "invalid operand in inline asm: '" << AsmStr << "'";
317          MMI->getModule()->getContext().emitError(LocCookie, Msg.str());
318        }
319      }
320      break;
321    }
322    }
323  }
324  if (InputIsIntelDialect)
325    OS << "\n\t.att_syntax";
326  OS << '\n' << (char)0;  // null terminate string.
327}
328
329/// This method formats and emits the specified machine instruction that is an
330/// inline asm.
331void AsmPrinter::emitInlineAsm(const MachineInstr *MI) const {
332  assert(MI->isInlineAsm() && "printInlineAsm only works on inline asms");
333
334  // Disassemble the AsmStr, printing out the literal pieces, the operands, etc.
335  const char *AsmStr = MI->getOperand(0).getSymbolName();
336
337  // If this asmstr is empty, just print the #APP/#NOAPP markers.
338  // These are useful to see where empty asm's wound up.
339  if (AsmStr[0] == 0) {
340    OutStreamer->emitRawComment(MAI->getInlineAsmStart());
341    OutStreamer->emitRawComment(MAI->getInlineAsmEnd());
342    return;
343  }
344
345  // Emit the #APP start marker.  This has to happen even if verbose-asm isn't
346  // enabled, so we use emitRawComment.
347  OutStreamer->emitRawComment(MAI->getInlineAsmStart());
348
349  // Get the !srcloc metadata node if we have it, and decode the loc cookie from
350  // it.
351  uint64_t LocCookie = 0;
352  const MDNode *LocMD = nullptr;
353  for (const MachineOperand &MO : llvm::reverse(MI->operands())) {
354    if (MO.isMetadata() && (LocMD = MO.getMetadata()) &&
355        LocMD->getNumOperands() != 0) {
356      if (const ConstantInt *CI =
357              mdconst::dyn_extract<ConstantInt>(LocMD->getOperand(0))) {
358        LocCookie = CI->getZExtValue();
359        break;
360      }
361    }
362  }
363
364  // Emit the inline asm to a temporary string so we can emit it through
365  // EmitInlineAsm.
366  SmallString<256> StringData;
367  raw_svector_ostream OS(StringData);
368
369  AsmPrinter *AP = const_cast<AsmPrinter*>(this);
370  EmitInlineAsmStr(AsmStr, MI, MMI, MAI, AP, LocCookie, OS);
371
372  // Emit warnings if we use reserved registers on the clobber list, as
373  // that might lead to undefined behaviour.
374  SmallVector<Register, 8> RestrRegs;
375  const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
376  // Start with the first operand descriptor, and iterate over them.
377  for (unsigned I = InlineAsm::MIOp_FirstOperand, NumOps = MI->getNumOperands();
378       I < NumOps; ++I) {
379    const MachineOperand &MO = MI->getOperand(I);
380    if (!MO.isImm())
381      continue;
382    const InlineAsm::Flag F(MO.getImm());
383    if (F.isClobberKind()) {
384      Register Reg = MI->getOperand(I + 1).getReg();
385      if (!TRI->isAsmClobberable(*MF, Reg))
386        RestrRegs.push_back(Reg);
387    }
388    // Skip to one before the next operand descriptor, if it exists.
389    I += F.getNumOperandRegisters();
390  }
391
392  if (!RestrRegs.empty()) {
393    std::string Msg = "inline asm clobber list contains reserved registers: ";
394    ListSeparator LS;
395    for (const Register RR : RestrRegs) {
396      Msg += LS;
397      Msg += TRI->getRegAsmName(RR);
398    }
399    const char *Note =
400        "Reserved registers on the clobber list may not be "
401        "preserved across the asm statement, and clobbering them may "
402        "lead to undefined behaviour.";
403    MMI->getModule()->getContext().diagnose(DiagnosticInfoInlineAsm(
404        LocCookie, Msg, DiagnosticSeverity::DS_Warning));
405    MMI->getModule()->getContext().diagnose(
406        DiagnosticInfoInlineAsm(LocCookie, Note, DiagnosticSeverity::DS_Note));
407
408    for (const Register RR : RestrRegs) {
409      if (std::optional<std::string> reason =
410              TRI->explainReservedReg(*MF, RR)) {
411        MMI->getModule()->getContext().diagnose(DiagnosticInfoInlineAsm(
412            LocCookie, *reason, DiagnosticSeverity::DS_Note));
413      }
414    }
415  }
416
417  emitInlineAsm(OS.str(), getSubtargetInfo(), TM.Options.MCOptions, LocMD,
418                MI->getInlineAsmDialect());
419
420  // Emit the #NOAPP end marker.  This has to happen even if verbose-asm isn't
421  // enabled, so we use emitRawComment.
422  OutStreamer->emitRawComment(MAI->getInlineAsmEnd());
423}
424
425/// PrintSpecial - Print information related to the specified machine instr
426/// that is independent of the operand, and may be independent of the instr
427/// itself.  This can be useful for portably encoding the comment character
428/// or other bits of target-specific knowledge into the asmstrings.  The
429/// syntax used is ${:comment}.  Targets can override this to add support
430/// for their own strange codes.
431void AsmPrinter::PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
432                              StringRef Code) const {
433  if (Code == "private") {
434    const DataLayout &DL = MF->getDataLayout();
435    OS << DL.getPrivateGlobalPrefix();
436  } else if (Code == "comment") {
437    OS << MAI->getCommentString();
438  } else if (Code == "uid") {
439    // Comparing the address of MI isn't sufficient, because machineinstrs may
440    // be allocated to the same address across functions.
441
442    // If this is a new LastFn instruction, bump the counter.
443    if (LastMI != MI || LastFn != getFunctionNumber()) {
444      ++Counter;
445      LastMI = MI;
446      LastFn = getFunctionNumber();
447    }
448    OS << Counter;
449  } else {
450    std::string msg;
451    raw_string_ostream Msg(msg);
452    Msg << "Unknown special formatter '" << Code
453         << "' for machine instr: " << *MI;
454    report_fatal_error(Twine(Msg.str()));
455  }
456}
457
458void AsmPrinter::PrintSymbolOperand(const MachineOperand &MO, raw_ostream &OS) {
459  assert(MO.isGlobal() && "caller should check MO.isGlobal");
460  getSymbolPreferLocal(*MO.getGlobal())->print(OS, MAI);
461  printOffset(MO.getOffset(), OS);
462}
463
464/// PrintAsmOperand - Print the specified operand of MI, an INLINEASM
465/// instruction, using the specified assembler variant.  Targets should
466/// override this to format as appropriate for machine specific ExtraCodes
467/// or when the arch-independent handling would be too complex otherwise.
468bool AsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
469                                 const char *ExtraCode, raw_ostream &O) {
470  // Does this asm operand have a single letter operand modifier?
471  if (ExtraCode && ExtraCode[0]) {
472    if (ExtraCode[1] != 0) return true; // Unknown modifier.
473
474    // https://gcc.gnu.org/onlinedocs/gccint/Output-Template.html
475    const MachineOperand &MO = MI->getOperand(OpNo);
476    switch (ExtraCode[0]) {
477    default:
478      return true;  // Unknown modifier.
479    case 'a': // Print as memory address.
480      if (MO.isReg()) {
481        PrintAsmMemoryOperand(MI, OpNo, nullptr, O);
482        return false;
483      }
484      [[fallthrough]]; // GCC allows '%a' to behave like '%c' with immediates.
485    case 'c': // Substitute immediate value without immediate syntax
486      if (MO.isImm()) {
487        O << MO.getImm();
488        return false;
489      }
490      if (MO.isGlobal()) {
491        PrintSymbolOperand(MO, O);
492        return false;
493      }
494      return true;
495    case 'n':  // Negate the immediate constant.
496      if (!MO.isImm())
497        return true;
498      O << -MO.getImm();
499      return false;
500    case 's':  // The GCC deprecated s modifier
501      if (!MO.isImm())
502        return true;
503      O << ((32 - MO.getImm()) & 31);
504      return false;
505    }
506  }
507  return true;
508}
509
510bool AsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
511                                       const char *ExtraCode, raw_ostream &O) {
512  // Target doesn't support this yet!
513  return true;
514}
515
516void AsmPrinter::emitInlineAsmStart() const {}
517
518void AsmPrinter::emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
519                                  const MCSubtargetInfo *EndInfo) const {}
520