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