llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp

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