1 //===-- cc1as_main.cpp - Clang Assembler  ---------------------------------===//
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 is the entry point to the clang -cc1as functionality, which implements
10 // the direct interface to the LLVM MC based assembler.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/Basic/Diagnostic.h"
15 #include "clang/Basic/DiagnosticOptions.h"
16 #include "clang/Driver/DriverDiagnostic.h"
17 #include "clang/Driver/Options.h"
18 #include "clang/Frontend/FrontendDiagnostic.h"
19 #include "clang/Frontend/TextDiagnosticPrinter.h"
20 #include "clang/Frontend/Utils.h"
21 #include "llvm/ADT/STLExtras.h"
22 #include "llvm/ADT/StringSwitch.h"
23 #include "llvm/ADT/Triple.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/MC/MCAsmBackend.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCCodeEmitter.h"
28 #include "llvm/MC/MCContext.h"
29 #include "llvm/MC/MCInstrInfo.h"
30 #include "llvm/MC/MCObjectFileInfo.h"
31 #include "llvm/MC/MCObjectWriter.h"
32 #include "llvm/MC/MCParser/MCAsmParser.h"
33 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
34 #include "llvm/MC/MCRegisterInfo.h"
35 #include "llvm/MC/MCSectionMachO.h"
36 #include "llvm/MC/MCStreamer.h"
37 #include "llvm/MC/MCSubtargetInfo.h"
38 #include "llvm/MC/MCTargetOptions.h"
39 #include "llvm/Option/Arg.h"
40 #include "llvm/Option/ArgList.h"
41 #include "llvm/Option/OptTable.h"
42 #include "llvm/Support/CommandLine.h"
43 #include "llvm/Support/ErrorHandling.h"
44 #include "llvm/Support/FileSystem.h"
45 #include "llvm/Support/FormattedStream.h"
46 #include "llvm/Support/Host.h"
47 #include "llvm/Support/MemoryBuffer.h"
48 #include "llvm/Support/Path.h"
49 #include "llvm/Support/Process.h"
50 #include "llvm/Support/Signals.h"
51 #include "llvm/Support/SourceMgr.h"
52 #include "llvm/Support/TargetRegistry.h"
53 #include "llvm/Support/TargetSelect.h"
54 #include "llvm/Support/Timer.h"
55 #include "llvm/Support/raw_ostream.h"
56 #include <memory>
57 #include <system_error>
58 using namespace clang;
59 using namespace clang::driver;
60 using namespace clang::driver::options;
61 using namespace llvm;
62 using namespace llvm::opt;
63 
64 namespace {
65 
66 /// Helper class for representing a single invocation of the assembler.
67 struct AssemblerInvocation {
68   /// @name Target Options
69   /// @{
70 
71   /// The name of the target triple to assemble for.
72   std::string Triple;
73 
74   /// If given, the name of the target CPU to determine which instructions
75   /// are legal.
76   std::string CPU;
77 
78   /// The list of target specific features to enable or disable -- this should
79   /// be a list of strings starting with '+' or '-'.
80   std::vector<std::string> Features;
81 
82   /// The list of symbol definitions.
83   std::vector<std::string> SymbolDefs;
84 
85   /// @}
86   /// @name Language Options
87   /// @{
88 
89   std::vector<std::string> IncludePaths;
90   unsigned NoInitialTextSection : 1;
91   unsigned SaveTemporaryLabels : 1;
92   unsigned GenDwarfForAssembly : 1;
93   unsigned RelaxELFRelocations : 1;
94   unsigned Dwarf64 : 1;
95   unsigned DwarfVersion;
96   std::string DwarfDebugFlags;
97   std::string DwarfDebugProducer;
98   std::string DebugCompilationDir;
99   std::map<const std::string, const std::string> DebugPrefixMap;
100   llvm::DebugCompressionType CompressDebugSections =
101       llvm::DebugCompressionType::None;
102   std::string MainFileName;
103   std::string SplitDwarfOutput;
104 
105   /// @}
106   /// @name Frontend Options
107   /// @{
108 
109   std::string InputFile;
110   std::vector<std::string> LLVMArgs;
111   std::string OutputPath;
112   enum FileType {
113     FT_Asm,  ///< Assembly (.s) output, transliterate mode.
114     FT_Null, ///< No output, for timing purposes.
115     FT_Obj   ///< Object file output.
116   };
117   FileType OutputType;
118   unsigned ShowHelp : 1;
119   unsigned ShowVersion : 1;
120 
121   /// @}
122   /// @name Transliterate Options
123   /// @{
124 
125   unsigned OutputAsmVariant;
126   unsigned ShowEncoding : 1;
127   unsigned ShowInst : 1;
128 
129   /// @}
130   /// @name Assembler Options
131   /// @{
132 
133   unsigned RelaxAll : 1;
134   unsigned NoExecStack : 1;
135   unsigned FatalWarnings : 1;
136   unsigned NoWarn : 1;
137   unsigned IncrementalLinkerCompatible : 1;
138   unsigned EmbedBitcode : 1;
139 
140   /// The name of the relocation model to use.
141   std::string RelocationModel;
142 
143   /// The ABI targeted by the backend. Specified using -target-abi. Empty
144   /// otherwise.
145   std::string TargetABI;
146 
147   /// @}
148 
149 public:
150   AssemblerInvocation() {
151     Triple = "";
152     NoInitialTextSection = 0;
153     InputFile = "-";
154     OutputPath = "-";
155     OutputType = FT_Asm;
156     OutputAsmVariant = 0;
157     ShowInst = 0;
158     ShowEncoding = 0;
159     RelaxAll = 0;
160     NoExecStack = 0;
161     FatalWarnings = 0;
162     NoWarn = 0;
163     IncrementalLinkerCompatible = 0;
164     Dwarf64 = 0;
165     DwarfVersion = 0;
166     EmbedBitcode = 0;
167   }
168 
169   static bool CreateFromArgs(AssemblerInvocation &Res,
170                              ArrayRef<const char *> Argv,
171                              DiagnosticsEngine &Diags);
172 };
173 
174 }
175 
176 bool AssemblerInvocation::CreateFromArgs(AssemblerInvocation &Opts,
177                                          ArrayRef<const char *> Argv,
178                                          DiagnosticsEngine &Diags) {
179   bool Success = true;
180 
181   // Parse the arguments.
182   const OptTable &OptTbl = getDriverOptTable();
183 
184   const unsigned IncludedFlagsBitmask = options::CC1AsOption;
185   unsigned MissingArgIndex, MissingArgCount;
186   InputArgList Args = OptTbl.ParseArgs(Argv, MissingArgIndex, MissingArgCount,
187                                        IncludedFlagsBitmask);
188 
189   // Check for missing argument error.
190   if (MissingArgCount) {
191     Diags.Report(diag::err_drv_missing_argument)
192         << Args.getArgString(MissingArgIndex) << MissingArgCount;
193     Success = false;
194   }
195 
196   // Issue errors on unknown arguments.
197   for (const Arg *A : Args.filtered(OPT_UNKNOWN)) {
198     auto ArgString = A->getAsString(Args);
199     std::string Nearest;
200     if (OptTbl.findNearest(ArgString, Nearest, IncludedFlagsBitmask) > 1)
201       Diags.Report(diag::err_drv_unknown_argument) << ArgString;
202     else
203       Diags.Report(diag::err_drv_unknown_argument_with_suggestion)
204           << ArgString << Nearest;
205     Success = false;
206   }
207 
208   // Construct the invocation.
209 
210   // Target Options
211   Opts.Triple = llvm::Triple::normalize(Args.getLastArgValue(OPT_triple));
212   Opts.CPU = std::string(Args.getLastArgValue(OPT_target_cpu));
213   Opts.Features = Args.getAllArgValues(OPT_target_feature);
214 
215   // Use the default target triple if unspecified.
216   if (Opts.Triple.empty())
217     Opts.Triple = llvm::sys::getDefaultTargetTriple();
218 
219   // Language Options
220   Opts.IncludePaths = Args.getAllArgValues(OPT_I);
221   Opts.NoInitialTextSection = Args.hasArg(OPT_n);
222   Opts.SaveTemporaryLabels = Args.hasArg(OPT_msave_temp_labels);
223   // Any DebugInfoKind implies GenDwarfForAssembly.
224   Opts.GenDwarfForAssembly = Args.hasArg(OPT_debug_info_kind_EQ);
225 
226   if (const Arg *A = Args.getLastArg(OPT_compress_debug_sections_EQ)) {
227     Opts.CompressDebugSections =
228         llvm::StringSwitch<llvm::DebugCompressionType>(A->getValue())
229             .Case("none", llvm::DebugCompressionType::None)
230             .Case("zlib", llvm::DebugCompressionType::Z)
231             .Case("zlib-gnu", llvm::DebugCompressionType::GNU)
232             .Default(llvm::DebugCompressionType::None);
233   }
234 
235   Opts.RelaxELFRelocations = Args.hasArg(OPT_mrelax_relocations);
236   if (auto *DwarfFormatArg = Args.getLastArg(OPT_gdwarf64, OPT_gdwarf32))
237     Opts.Dwarf64 = DwarfFormatArg->getOption().matches(OPT_gdwarf64);
238   Opts.DwarfVersion = getLastArgIntValue(Args, OPT_dwarf_version_EQ, 2, Diags);
239   Opts.DwarfDebugFlags =
240       std::string(Args.getLastArgValue(OPT_dwarf_debug_flags));
241   Opts.DwarfDebugProducer =
242       std::string(Args.getLastArgValue(OPT_dwarf_debug_producer));
243   Opts.DebugCompilationDir =
244       std::string(Args.getLastArgValue(OPT_fdebug_compilation_dir));
245   Opts.MainFileName = std::string(Args.getLastArgValue(OPT_main_file_name));
246 
247   for (const auto &Arg : Args.getAllArgValues(OPT_fdebug_prefix_map_EQ)) {
248     auto Split = StringRef(Arg).split('=');
249     Opts.DebugPrefixMap.insert(
250         {std::string(Split.first), std::string(Split.second)});
251   }
252 
253   // Frontend Options
254   if (Args.hasArg(OPT_INPUT)) {
255     bool First = true;
256     for (const Arg *A : Args.filtered(OPT_INPUT)) {
257       if (First) {
258         Opts.InputFile = A->getValue();
259         First = false;
260       } else {
261         Diags.Report(diag::err_drv_unknown_argument) << A->getAsString(Args);
262         Success = false;
263       }
264     }
265   }
266   Opts.LLVMArgs = Args.getAllArgValues(OPT_mllvm);
267   Opts.OutputPath = std::string(Args.getLastArgValue(OPT_o));
268   Opts.SplitDwarfOutput =
269       std::string(Args.getLastArgValue(OPT_split_dwarf_output));
270   if (Arg *A = Args.getLastArg(OPT_filetype)) {
271     StringRef Name = A->getValue();
272     unsigned OutputType = StringSwitch<unsigned>(Name)
273       .Case("asm", FT_Asm)
274       .Case("null", FT_Null)
275       .Case("obj", FT_Obj)
276       .Default(~0U);
277     if (OutputType == ~0U) {
278       Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << Name;
279       Success = false;
280     } else
281       Opts.OutputType = FileType(OutputType);
282   }
283   Opts.ShowHelp = Args.hasArg(OPT_help);
284   Opts.ShowVersion = Args.hasArg(OPT_version);
285 
286   // Transliterate Options
287   Opts.OutputAsmVariant =
288       getLastArgIntValue(Args, OPT_output_asm_variant, 0, Diags);
289   Opts.ShowEncoding = Args.hasArg(OPT_show_encoding);
290   Opts.ShowInst = Args.hasArg(OPT_show_inst);
291 
292   // Assemble Options
293   Opts.RelaxAll = Args.hasArg(OPT_mrelax_all);
294   Opts.NoExecStack = Args.hasArg(OPT_mno_exec_stack);
295   Opts.FatalWarnings = Args.hasArg(OPT_massembler_fatal_warnings);
296   Opts.NoWarn = Args.hasArg(OPT_massembler_no_warn);
297   Opts.RelocationModel =
298       std::string(Args.getLastArgValue(OPT_mrelocation_model, "pic"));
299   Opts.TargetABI = std::string(Args.getLastArgValue(OPT_target_abi));
300   Opts.IncrementalLinkerCompatible =
301       Args.hasArg(OPT_mincremental_linker_compatible);
302   Opts.SymbolDefs = Args.getAllArgValues(OPT_defsym);
303 
304   // EmbedBitcode Option. If -fembed-bitcode is enabled, set the flag.
305   // EmbedBitcode behaves the same for all embed options for assembly files.
306   if (auto *A = Args.getLastArg(OPT_fembed_bitcode_EQ)) {
307     Opts.EmbedBitcode = llvm::StringSwitch<unsigned>(A->getValue())
308                             .Case("all", 1)
309                             .Case("bitcode", 1)
310                             .Case("marker", 1)
311                             .Default(0);
312   }
313 
314   return Success;
315 }
316 
317 static std::unique_ptr<raw_fd_ostream>
318 getOutputStream(StringRef Path, DiagnosticsEngine &Diags, bool Binary) {
319   // Make sure that the Out file gets unlinked from the disk if we get a
320   // SIGINT.
321   if (Path != "-")
322     sys::RemoveFileOnSignal(Path);
323 
324   std::error_code EC;
325   auto Out = std::make_unique<raw_fd_ostream>(
326       Path, EC, (Binary ? sys::fs::OF_None : sys::fs::OF_Text));
327   if (EC) {
328     Diags.Report(diag::err_fe_unable_to_open_output) << Path << EC.message();
329     return nullptr;
330   }
331 
332   return Out;
333 }
334 
335 static bool ExecuteAssembler(AssemblerInvocation &Opts,
336                              DiagnosticsEngine &Diags) {
337   // Get the target specific parser.
338   std::string Error;
339   const Target *TheTarget = TargetRegistry::lookupTarget(Opts.Triple, Error);
340   if (!TheTarget)
341     return Diags.Report(diag::err_target_unknown_triple) << Opts.Triple;
342 
343   ErrorOr<std::unique_ptr<MemoryBuffer>> Buffer =
344       MemoryBuffer::getFileOrSTDIN(Opts.InputFile);
345 
346   if (std::error_code EC = Buffer.getError()) {
347     Error = EC.message();
348     return Diags.Report(diag::err_fe_error_reading) << Opts.InputFile;
349   }
350 
351   SourceMgr SrcMgr;
352 
353   // Tell SrcMgr about this buffer, which is what the parser will pick up.
354   unsigned BufferIndex = SrcMgr.AddNewSourceBuffer(std::move(*Buffer), SMLoc());
355 
356   // Record the location of the include directories so that the lexer can find
357   // it later.
358   SrcMgr.setIncludeDirs(Opts.IncludePaths);
359 
360   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(Opts.Triple));
361   assert(MRI && "Unable to create target register info!");
362 
363   MCTargetOptions MCOptions;
364   std::unique_ptr<MCAsmInfo> MAI(
365       TheTarget->createMCAsmInfo(*MRI, Opts.Triple, MCOptions));
366   assert(MAI && "Unable to create target asm info!");
367 
368   // Ensure MCAsmInfo initialization occurs before any use, otherwise sections
369   // may be created with a combination of default and explicit settings.
370   MAI->setCompressDebugSections(Opts.CompressDebugSections);
371 
372   MAI->setRelaxELFRelocations(Opts.RelaxELFRelocations);
373 
374   bool IsBinary = Opts.OutputType == AssemblerInvocation::FT_Obj;
375   if (Opts.OutputPath.empty())
376     Opts.OutputPath = "-";
377   std::unique_ptr<raw_fd_ostream> FDOS =
378       getOutputStream(Opts.OutputPath, Diags, IsBinary);
379   if (!FDOS)
380     return true;
381   std::unique_ptr<raw_fd_ostream> DwoOS;
382   if (!Opts.SplitDwarfOutput.empty())
383     DwoOS = getOutputStream(Opts.SplitDwarfOutput, Diags, IsBinary);
384 
385   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and
386   // MCObjectFileInfo needs a MCContext reference in order to initialize itself.
387   std::unique_ptr<MCObjectFileInfo> MOFI(new MCObjectFileInfo());
388 
389   MCContext Ctx(MAI.get(), MRI.get(), MOFI.get(), &SrcMgr, &MCOptions);
390 
391   bool PIC = false;
392   if (Opts.RelocationModel == "static") {
393     PIC = false;
394   } else if (Opts.RelocationModel == "pic") {
395     PIC = true;
396   } else {
397     assert(Opts.RelocationModel == "dynamic-no-pic" &&
398            "Invalid PIC model!");
399     PIC = false;
400   }
401 
402   MOFI->InitMCObjectFileInfo(Triple(Opts.Triple), PIC, Ctx);
403   if (Opts.SaveTemporaryLabels)
404     Ctx.setAllowTemporaryLabels(false);
405   if (Opts.GenDwarfForAssembly)
406     Ctx.setGenDwarfForAssembly(true);
407   if (!Opts.DwarfDebugFlags.empty())
408     Ctx.setDwarfDebugFlags(StringRef(Opts.DwarfDebugFlags));
409   if (!Opts.DwarfDebugProducer.empty())
410     Ctx.setDwarfDebugProducer(StringRef(Opts.DwarfDebugProducer));
411   if (!Opts.DebugCompilationDir.empty())
412     Ctx.setCompilationDir(Opts.DebugCompilationDir);
413   else {
414     // If no compilation dir is set, try to use the current directory.
415     SmallString<128> CWD;
416     if (!sys::fs::current_path(CWD))
417       Ctx.setCompilationDir(CWD);
418   }
419   if (!Opts.DebugPrefixMap.empty())
420     for (const auto &KV : Opts.DebugPrefixMap)
421       Ctx.addDebugPrefixMapEntry(KV.first, KV.second);
422   if (!Opts.MainFileName.empty())
423     Ctx.setMainFileName(StringRef(Opts.MainFileName));
424   Ctx.setDwarfFormat(Opts.Dwarf64 ? dwarf::DWARF64 : dwarf::DWARF32);
425   Ctx.setDwarfVersion(Opts.DwarfVersion);
426   if (Opts.GenDwarfForAssembly)
427     Ctx.setGenDwarfRootFile(Opts.InputFile,
428                             SrcMgr.getMemoryBuffer(BufferIndex)->getBuffer());
429 
430   // Build up the feature string from the target feature list.
431   std::string FS = llvm::join(Opts.Features, ",");
432 
433   std::unique_ptr<MCStreamer> Str;
434 
435   std::unique_ptr<MCInstrInfo> MCII(TheTarget->createMCInstrInfo());
436   assert(MCII && "Unable to create instruction info!");
437 
438   std::unique_ptr<MCSubtargetInfo> STI(
439       TheTarget->createMCSubtargetInfo(Opts.Triple, Opts.CPU, FS));
440   assert(STI && "Unable to create subtarget info!");
441 
442   raw_pwrite_stream *Out = FDOS.get();
443   std::unique_ptr<buffer_ostream> BOS;
444 
445   MCOptions.MCNoWarn = Opts.NoWarn;
446   MCOptions.MCFatalWarnings = Opts.FatalWarnings;
447   MCOptions.ABIName = Opts.TargetABI;
448 
449   // FIXME: There is a bit of code duplication with addPassesToEmitFile.
450   if (Opts.OutputType == AssemblerInvocation::FT_Asm) {
451     MCInstPrinter *IP = TheTarget->createMCInstPrinter(
452         llvm::Triple(Opts.Triple), Opts.OutputAsmVariant, *MAI, *MCII, *MRI);
453 
454     std::unique_ptr<MCCodeEmitter> CE;
455     if (Opts.ShowEncoding)
456       CE.reset(TheTarget->createMCCodeEmitter(*MCII, *MRI, Ctx));
457     std::unique_ptr<MCAsmBackend> MAB(
458         TheTarget->createMCAsmBackend(*STI, *MRI, MCOptions));
459 
460     auto FOut = std::make_unique<formatted_raw_ostream>(*Out);
461     Str.reset(TheTarget->createAsmStreamer(
462         Ctx, std::move(FOut), /*asmverbose*/ true,
463         /*useDwarfDirectory*/ true, IP, std::move(CE), std::move(MAB),
464         Opts.ShowInst));
465   } else if (Opts.OutputType == AssemblerInvocation::FT_Null) {
466     Str.reset(createNullStreamer(Ctx));
467   } else {
468     assert(Opts.OutputType == AssemblerInvocation::FT_Obj &&
469            "Invalid file type!");
470     if (!FDOS->supportsSeeking()) {
471       BOS = std::make_unique<buffer_ostream>(*FDOS);
472       Out = BOS.get();
473     }
474 
475     std::unique_ptr<MCCodeEmitter> CE(
476         TheTarget->createMCCodeEmitter(*MCII, *MRI, Ctx));
477     std::unique_ptr<MCAsmBackend> MAB(
478         TheTarget->createMCAsmBackend(*STI, *MRI, MCOptions));
479     assert(MAB && "Unable to create asm backend!");
480 
481     std::unique_ptr<MCObjectWriter> OW =
482         DwoOS ? MAB->createDwoObjectWriter(*Out, *DwoOS)
483               : MAB->createObjectWriter(*Out);
484 
485     Triple T(Opts.Triple);
486     Str.reset(TheTarget->createMCObjectStreamer(
487         T, Ctx, std::move(MAB), std::move(OW), std::move(CE), *STI,
488         Opts.RelaxAll, Opts.IncrementalLinkerCompatible,
489         /*DWARFMustBeAtTheEnd*/ true));
490     Str.get()->InitSections(Opts.NoExecStack);
491   }
492 
493   // When -fembed-bitcode is passed to clang_as, a 1-byte marker
494   // is emitted in __LLVM,__asm section if the object file is MachO format.
495   if (Opts.EmbedBitcode && Ctx.getObjectFileInfo()->getObjectFileType() ==
496                                MCObjectFileInfo::IsMachO) {
497     MCSection *AsmLabel = Ctx.getMachOSection(
498         "__LLVM", "__asm", MachO::S_REGULAR, 4, SectionKind::getReadOnly());
499     Str.get()->SwitchSection(AsmLabel);
500     Str.get()->emitZeros(1);
501   }
502 
503   // Assembly to object compilation should leverage assembly info.
504   Str->setUseAssemblerInfoForParsing(true);
505 
506   bool Failed = false;
507 
508   std::unique_ptr<MCAsmParser> Parser(
509       createMCAsmParser(SrcMgr, Ctx, *Str.get(), *MAI));
510 
511   // FIXME: init MCTargetOptions from sanitizer flags here.
512   std::unique_ptr<MCTargetAsmParser> TAP(
513       TheTarget->createMCAsmParser(*STI, *Parser, *MCII, MCOptions));
514   if (!TAP)
515     Failed = Diags.Report(diag::err_target_unknown_triple) << Opts.Triple;
516 
517   // Set values for symbols, if any.
518   for (auto &S : Opts.SymbolDefs) {
519     auto Pair = StringRef(S).split('=');
520     auto Sym = Pair.first;
521     auto Val = Pair.second;
522     int64_t Value;
523     // We have already error checked this in the driver.
524     Val.getAsInteger(0, Value);
525     Ctx.setSymbolValue(Parser->getStreamer(), Sym, Value);
526   }
527 
528   if (!Failed) {
529     Parser->setTargetParser(*TAP.get());
530     Failed = Parser->Run(Opts.NoInitialTextSection);
531   }
532 
533   // Parser has a reference to the output stream (Str), so close Parser first.
534   Parser.reset();
535   Str.reset();
536   // Close the output stream early.
537   BOS.reset();
538   FDOS.reset();
539 
540   // Delete output file if there were errors.
541   if (Failed) {
542     if (Opts.OutputPath != "-")
543       sys::fs::remove(Opts.OutputPath);
544     if (!Opts.SplitDwarfOutput.empty() && Opts.SplitDwarfOutput != "-")
545       sys::fs::remove(Opts.SplitDwarfOutput);
546   }
547 
548   return Failed;
549 }
550 
551 static void LLVMErrorHandler(void *UserData, const std::string &Message,
552                              bool GenCrashDiag) {
553   DiagnosticsEngine &Diags = *static_cast<DiagnosticsEngine*>(UserData);
554 
555   Diags.Report(diag::err_fe_error_backend) << Message;
556 
557   // We cannot recover from llvm errors.
558   sys::Process::Exit(1);
559 }
560 
561 int cc1as_main(ArrayRef<const char *> Argv, const char *Argv0, void *MainAddr) {
562   // Initialize targets and assembly printers/parsers.
563   InitializeAllTargetInfos();
564   InitializeAllTargetMCs();
565   InitializeAllAsmParsers();
566 
567   // Construct our diagnostic client.
568   IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
569   TextDiagnosticPrinter *DiagClient
570     = new TextDiagnosticPrinter(errs(), &*DiagOpts);
571   DiagClient->setPrefix("clang -cc1as");
572   IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
573   DiagnosticsEngine Diags(DiagID, &*DiagOpts, DiagClient);
574 
575   // Set an error handler, so that any LLVM backend diagnostics go through our
576   // error handler.
577   ScopedFatalErrorHandler FatalErrorHandler
578     (LLVMErrorHandler, static_cast<void*>(&Diags));
579 
580   // Parse the arguments.
581   AssemblerInvocation Asm;
582   if (!AssemblerInvocation::CreateFromArgs(Asm, Argv, Diags))
583     return 1;
584 
585   if (Asm.ShowHelp) {
586     getDriverOptTable().PrintHelp(
587         llvm::outs(), "clang -cc1as [options] file...",
588         "Clang Integrated Assembler",
589         /*Include=*/driver::options::CC1AsOption, /*Exclude=*/0,
590         /*ShowAllAliases=*/false);
591     return 0;
592   }
593 
594   // Honor -version.
595   //
596   // FIXME: Use a better -version message?
597   if (Asm.ShowVersion) {
598     llvm::cl::PrintVersionMessage();
599     return 0;
600   }
601 
602   // Honor -mllvm.
603   //
604   // FIXME: Remove this, one day.
605   if (!Asm.LLVMArgs.empty()) {
606     unsigned NumArgs = Asm.LLVMArgs.size();
607     auto Args = std::make_unique<const char*[]>(NumArgs + 2);
608     Args[0] = "clang (LLVM option parsing)";
609     for (unsigned i = 0; i != NumArgs; ++i)
610       Args[i + 1] = Asm.LLVMArgs[i].c_str();
611     Args[NumArgs + 1] = nullptr;
612     llvm::cl::ParseCommandLineOptions(NumArgs + 1, Args.get());
613   }
614 
615   // Execute the invocation, unless there were parsing errors.
616   bool Failed = Diags.hasErrorOccurred() || ExecuteAssembler(Asm, Diags);
617 
618   // If any timers were active but haven't been destroyed yet, print their
619   // results now.
620   TimerGroup::printAll(errs());
621   TimerGroup::clearAll();
622 
623   return !!Failed;
624 }
625