xref: /freebsd/contrib/llvm-project/llvm/tools/llc/llc.cpp (revision 13ec1e3155c7e9bf037b12af186351b7fa9b9450)
1 //===-- llc.cpp - Implement the LLVM Native Code Generator ----------------===//
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 llc code generator driver. It provides a convenient
10 // command-line interface for generating native assembly-language code
11 // or C code, given LLVM bitcode.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/Triple.h"
17 #include "llvm/Analysis/TargetLibraryInfo.h"
18 #include "llvm/CodeGen/CommandFlags.h"
19 #include "llvm/CodeGen/LinkAllAsmWriterComponents.h"
20 #include "llvm/CodeGen/LinkAllCodegenComponents.h"
21 #include "llvm/CodeGen/MIRParser/MIRParser.h"
22 #include "llvm/CodeGen/MachineFunctionPass.h"
23 #include "llvm/CodeGen/MachineModuleInfo.h"
24 #include "llvm/CodeGen/TargetPassConfig.h"
25 #include "llvm/CodeGen/TargetSubtargetInfo.h"
26 #include "llvm/IR/AutoUpgrade.h"
27 #include "llvm/IR/DataLayout.h"
28 #include "llvm/IR/DiagnosticInfo.h"
29 #include "llvm/IR/DiagnosticPrinter.h"
30 #include "llvm/IR/IRPrintingPasses.h"
31 #include "llvm/IR/LLVMContext.h"
32 #include "llvm/IR/LLVMRemarkStreamer.h"
33 #include "llvm/IR/LegacyPassManager.h"
34 #include "llvm/IR/Module.h"
35 #include "llvm/IR/Verifier.h"
36 #include "llvm/IRReader/IRReader.h"
37 #include "llvm/InitializePasses.h"
38 #include "llvm/MC/SubtargetFeature.h"
39 #include "llvm/Pass.h"
40 #include "llvm/Remarks/HotnessThresholdParser.h"
41 #include "llvm/Support/CommandLine.h"
42 #include "llvm/Support/Debug.h"
43 #include "llvm/Support/FileSystem.h"
44 #include "llvm/Support/FormattedStream.h"
45 #include "llvm/Support/Host.h"
46 #include "llvm/Support/InitLLVM.h"
47 #include "llvm/Support/ManagedStatic.h"
48 #include "llvm/Support/PluginLoader.h"
49 #include "llvm/Support/SourceMgr.h"
50 #include "llvm/Support/TargetRegistry.h"
51 #include "llvm/Support/TargetSelect.h"
52 #include "llvm/Support/ToolOutputFile.h"
53 #include "llvm/Support/WithColor.h"
54 #include "llvm/Target/TargetLoweringObjectFile.h"
55 #include "llvm/Target/TargetMachine.h"
56 #include "llvm/Transforms/Utils/Cloning.h"
57 #include <memory>
58 using namespace llvm;
59 
60 static codegen::RegisterCodeGenFlags CGF;
61 
62 // General options for llc.  Other pass-specific options are specified
63 // within the corresponding llc passes, and target-specific options
64 // and back-end code generation options are specified with the target machine.
65 //
66 static cl::opt<std::string>
67 InputFilename(cl::Positional, cl::desc("<input bitcode>"), cl::init("-"));
68 
69 static cl::opt<std::string>
70 InputLanguage("x", cl::desc("Input language ('ir' or 'mir')"));
71 
72 static cl::opt<std::string>
73 OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"));
74 
75 static cl::opt<std::string>
76     SplitDwarfOutputFile("split-dwarf-output",
77                          cl::desc(".dwo output filename"),
78                          cl::value_desc("filename"));
79 
80 static cl::opt<unsigned>
81 TimeCompilations("time-compilations", cl::Hidden, cl::init(1u),
82                  cl::value_desc("N"),
83                  cl::desc("Repeat compilation N times for timing"));
84 
85 static cl::opt<std::string>
86     BinutilsVersion("binutils-version", cl::Hidden,
87                     cl::desc("Produced object files can use all ELF features "
88                              "supported by this binutils version and newer."
89                              "If -no-integrated-as is specified, the generated "
90                              "assembly will consider GNU as support."
91                              "'none' means that all ELF features can be used, "
92                              "regardless of binutils support"));
93 
94 static cl::opt<bool>
95 NoIntegratedAssembler("no-integrated-as", cl::Hidden,
96                       cl::desc("Disable integrated assembler"));
97 
98 static cl::opt<bool>
99     PreserveComments("preserve-as-comments", cl::Hidden,
100                      cl::desc("Preserve Comments in outputted assembly"),
101                      cl::init(true));
102 
103 // Determine optimization level.
104 static cl::opt<char>
105 OptLevel("O",
106          cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
107                   "(default = '-O2')"),
108          cl::Prefix,
109          cl::ZeroOrMore,
110          cl::init(' '));
111 
112 static cl::opt<std::string>
113 TargetTriple("mtriple", cl::desc("Override target triple for module"));
114 
115 static cl::opt<std::string> SplitDwarfFile(
116     "split-dwarf-file",
117     cl::desc(
118         "Specify the name of the .dwo file to encode in the DWARF output"));
119 
120 static cl::opt<bool> NoVerify("disable-verify", cl::Hidden,
121                               cl::desc("Do not verify input module"));
122 
123 static cl::opt<bool> DisableSimplifyLibCalls("disable-simplify-libcalls",
124                                              cl::desc("Disable simplify-libcalls"));
125 
126 static cl::opt<bool> ShowMCEncoding("show-mc-encoding", cl::Hidden,
127                                     cl::desc("Show encoding in .s output"));
128 
129 static cl::opt<bool>
130     DwarfDirectory("dwarf-directory", cl::Hidden,
131                    cl::desc("Use .file directives with an explicit directory"),
132                    cl::init(true));
133 
134 static cl::opt<bool> AsmVerbose("asm-verbose",
135                                 cl::desc("Add comments to directives."),
136                                 cl::init(true));
137 
138 static cl::opt<bool>
139     CompileTwice("compile-twice", cl::Hidden,
140                  cl::desc("Run everything twice, re-using the same pass "
141                           "manager and verify the result is the same."),
142                  cl::init(false));
143 
144 static cl::opt<bool> DiscardValueNames(
145     "discard-value-names",
146     cl::desc("Discard names from Value (other than GlobalValue)."),
147     cl::init(false), cl::Hidden);
148 
149 static cl::list<std::string> IncludeDirs("I", cl::desc("include search path"));
150 
151 static cl::opt<bool> RemarksWithHotness(
152     "pass-remarks-with-hotness",
153     cl::desc("With PGO, include profile count in optimization remarks"),
154     cl::Hidden);
155 
156 static cl::opt<Optional<uint64_t>, false, remarks::HotnessThresholdParser>
157     RemarksHotnessThreshold(
158         "pass-remarks-hotness-threshold",
159         cl::desc("Minimum profile count required for "
160                  "an optimization remark to be output. "
161                  "Use 'auto' to apply the threshold from profile summary."),
162         cl::value_desc("N or 'auto'"), cl::init(0), cl::Hidden);
163 
164 static cl::opt<std::string>
165     RemarksFilename("pass-remarks-output",
166                     cl::desc("Output filename for pass remarks"),
167                     cl::value_desc("filename"));
168 
169 static cl::opt<std::string>
170     RemarksPasses("pass-remarks-filter",
171                   cl::desc("Only record optimization remarks from passes whose "
172                            "names match the given regular expression"),
173                   cl::value_desc("regex"));
174 
175 static cl::opt<std::string> RemarksFormat(
176     "pass-remarks-format",
177     cl::desc("The format used for serializing remarks (default: YAML)"),
178     cl::value_desc("format"), cl::init("yaml"));
179 
180 namespace {
181 static ManagedStatic<std::vector<std::string>> RunPassNames;
182 
183 struct RunPassOption {
184   void operator=(const std::string &Val) const {
185     if (Val.empty())
186       return;
187     SmallVector<StringRef, 8> PassNames;
188     StringRef(Val).split(PassNames, ',', -1, false);
189     for (auto PassName : PassNames)
190       RunPassNames->push_back(std::string(PassName));
191   }
192 };
193 }
194 
195 static RunPassOption RunPassOpt;
196 
197 static cl::opt<RunPassOption, true, cl::parser<std::string>> RunPass(
198     "run-pass",
199     cl::desc("Run compiler only for specified passes (comma separated list)"),
200     cl::value_desc("pass-name"), cl::ZeroOrMore, cl::location(RunPassOpt));
201 
202 static int compileModule(char **, LLVMContext &);
203 
204 LLVM_ATTRIBUTE_NORETURN static void reportError(Twine Msg,
205                                                 StringRef Filename = "") {
206   SmallString<256> Prefix;
207   if (!Filename.empty()) {
208     if (Filename == "-")
209       Filename = "<stdin>";
210     ("'" + Twine(Filename) + "': ").toStringRef(Prefix);
211   }
212   WithColor::error(errs(), "llc") << Prefix << Msg << "\n";
213   exit(1);
214 }
215 
216 LLVM_ATTRIBUTE_NORETURN static void reportError(Error Err, StringRef Filename) {
217   assert(Err);
218   handleAllErrors(createFileError(Filename, std::move(Err)),
219                   [&](const ErrorInfoBase &EI) { reportError(EI.message()); });
220   llvm_unreachable("reportError() should not return");
221 }
222 
223 static std::unique_ptr<ToolOutputFile> GetOutputStream(const char *TargetName,
224                                                        Triple::OSType OS,
225                                                        const char *ProgName) {
226   // If we don't yet have an output filename, make one.
227   if (OutputFilename.empty()) {
228     if (InputFilename == "-")
229       OutputFilename = "-";
230     else {
231       // If InputFilename ends in .bc or .ll, remove it.
232       StringRef IFN = InputFilename;
233       if (IFN.endswith(".bc") || IFN.endswith(".ll"))
234         OutputFilename = std::string(IFN.drop_back(3));
235       else if (IFN.endswith(".mir"))
236         OutputFilename = std::string(IFN.drop_back(4));
237       else
238         OutputFilename = std::string(IFN);
239 
240       switch (codegen::getFileType()) {
241       case CGFT_AssemblyFile:
242         if (TargetName[0] == 'c') {
243           if (TargetName[1] == 0)
244             OutputFilename += ".cbe.c";
245           else if (TargetName[1] == 'p' && TargetName[2] == 'p')
246             OutputFilename += ".cpp";
247           else
248             OutputFilename += ".s";
249         } else
250           OutputFilename += ".s";
251         break;
252       case CGFT_ObjectFile:
253         if (OS == Triple::Win32)
254           OutputFilename += ".obj";
255         else
256           OutputFilename += ".o";
257         break;
258       case CGFT_Null:
259         OutputFilename = "-";
260         break;
261       }
262     }
263   }
264 
265   // Decide if we need "binary" output.
266   bool Binary = false;
267   switch (codegen::getFileType()) {
268   case CGFT_AssemblyFile:
269     break;
270   case CGFT_ObjectFile:
271   case CGFT_Null:
272     Binary = true;
273     break;
274   }
275 
276   // Open the file.
277   std::error_code EC;
278   sys::fs::OpenFlags OpenFlags = sys::fs::OF_None;
279   if (!Binary)
280     OpenFlags |= sys::fs::OF_TextWithCRLF;
281   auto FDOut = std::make_unique<ToolOutputFile>(OutputFilename, EC, OpenFlags);
282   if (EC) {
283     reportError(EC.message());
284     return nullptr;
285   }
286 
287   return FDOut;
288 }
289 
290 struct LLCDiagnosticHandler : public DiagnosticHandler {
291   bool *HasError;
292   LLCDiagnosticHandler(bool *HasErrorPtr) : HasError(HasErrorPtr) {}
293   bool handleDiagnostics(const DiagnosticInfo &DI) override {
294     if (DI.getKind() == llvm::DK_SrcMgr) {
295       const auto &DISM = cast<DiagnosticInfoSrcMgr>(DI);
296       const SMDiagnostic &SMD = DISM.getSMDiag();
297 
298       if (SMD.getKind() == SourceMgr::DK_Error)
299         *HasError = true;
300 
301       SMD.print(nullptr, errs());
302 
303       // For testing purposes, we print the LocCookie here.
304       if (DISM.isInlineAsmDiag() && DISM.getLocCookie())
305         WithColor::note() << "!srcloc = " << DISM.getLocCookie() << "\n";
306 
307       return true;
308     }
309 
310     if (DI.getSeverity() == DS_Error)
311       *HasError = true;
312 
313     if (auto *Remark = dyn_cast<DiagnosticInfoOptimizationBase>(&DI))
314       if (!Remark->isEnabled())
315         return true;
316 
317     DiagnosticPrinterRawOStream DP(errs());
318     errs() << LLVMContext::getDiagnosticMessagePrefix(DI.getSeverity()) << ": ";
319     DI.print(DP);
320     errs() << "\n";
321     return true;
322   }
323 };
324 
325 // main - Entry point for the llc compiler.
326 //
327 int main(int argc, char **argv) {
328   InitLLVM X(argc, argv);
329 
330   // Enable debug stream buffering.
331   EnableDebugBuffering = true;
332 
333   LLVMContext Context;
334 
335   // Initialize targets first, so that --version shows registered targets.
336   InitializeAllTargets();
337   InitializeAllTargetMCs();
338   InitializeAllAsmPrinters();
339   InitializeAllAsmParsers();
340 
341   // Initialize codegen and IR passes used by llc so that the -print-after,
342   // -print-before, and -stop-after options work.
343   PassRegistry *Registry = PassRegistry::getPassRegistry();
344   initializeCore(*Registry);
345   initializeCodeGen(*Registry);
346   initializeLoopStrengthReducePass(*Registry);
347   initializeLowerIntrinsicsPass(*Registry);
348   initializeEntryExitInstrumenterPass(*Registry);
349   initializePostInlineEntryExitInstrumenterPass(*Registry);
350   initializeUnreachableBlockElimLegacyPassPass(*Registry);
351   initializeConstantHoistingLegacyPassPass(*Registry);
352   initializeScalarOpts(*Registry);
353   initializeVectorization(*Registry);
354   initializeScalarizeMaskedMemIntrinLegacyPassPass(*Registry);
355   initializeExpandReductionsPass(*Registry);
356   initializeExpandVectorPredicationPass(*Registry);
357   initializeHardwareLoopsPass(*Registry);
358   initializeTransformUtils(*Registry);
359   initializeReplaceWithVeclibLegacyPass(*Registry);
360 
361   // Initialize debugging passes.
362   initializeScavengerTestPass(*Registry);
363 
364   // Register the target printer for --version.
365   cl::AddExtraVersionPrinter(TargetRegistry::printRegisteredTargetsForVersion);
366 
367   cl::ParseCommandLineOptions(argc, argv, "llvm system compiler\n");
368 
369   Context.setDiscardValueNames(DiscardValueNames);
370 
371   // Set a diagnostic handler that doesn't exit on the first error
372   bool HasError = false;
373   Context.setDiagnosticHandler(
374       std::make_unique<LLCDiagnosticHandler>(&HasError));
375 
376   Expected<std::unique_ptr<ToolOutputFile>> RemarksFileOrErr =
377       setupLLVMOptimizationRemarks(Context, RemarksFilename, RemarksPasses,
378                                    RemarksFormat, RemarksWithHotness,
379                                    RemarksHotnessThreshold);
380   if (Error E = RemarksFileOrErr.takeError())
381     reportError(std::move(E), RemarksFilename);
382   std::unique_ptr<ToolOutputFile> RemarksFile = std::move(*RemarksFileOrErr);
383 
384   if (InputLanguage != "" && InputLanguage != "ir" && InputLanguage != "mir")
385     reportError("input language must be '', 'IR' or 'MIR'");
386 
387   // Compile the module TimeCompilations times to give better compile time
388   // metrics.
389   for (unsigned I = TimeCompilations; I; --I)
390     if (int RetVal = compileModule(argv, Context))
391       return RetVal;
392 
393   if (RemarksFile)
394     RemarksFile->keep();
395   return 0;
396 }
397 
398 static bool addPass(PassManagerBase &PM, const char *argv0,
399                     StringRef PassName, TargetPassConfig &TPC) {
400   if (PassName == "none")
401     return false;
402 
403   const PassRegistry *PR = PassRegistry::getPassRegistry();
404   const PassInfo *PI = PR->getPassInfo(PassName);
405   if (!PI) {
406     WithColor::error(errs(), argv0)
407         << "run-pass " << PassName << " is not registered.\n";
408     return true;
409   }
410 
411   Pass *P;
412   if (PI->getNormalCtor())
413     P = PI->getNormalCtor()();
414   else {
415     WithColor::error(errs(), argv0)
416         << "cannot create pass: " << PI->getPassName() << "\n";
417     return true;
418   }
419   std::string Banner = std::string("After ") + std::string(P->getPassName());
420   TPC.addMachinePrePasses();
421   PM.add(P);
422   TPC.addMachinePostPasses(Banner);
423 
424   return false;
425 }
426 
427 static int compileModule(char **argv, LLVMContext &Context) {
428   // Load the module to be compiled...
429   SMDiagnostic Err;
430   std::unique_ptr<Module> M;
431   std::unique_ptr<MIRParser> MIR;
432   Triple TheTriple;
433   std::string CPUStr = codegen::getCPUStr(),
434               FeaturesStr = codegen::getFeaturesStr();
435 
436   // Set attributes on functions as loaded from MIR from command line arguments.
437   auto setMIRFunctionAttributes = [&CPUStr, &FeaturesStr](Function &F) {
438     codegen::setFunctionAttributes(CPUStr, FeaturesStr, F);
439   };
440 
441   auto MAttrs = codegen::getMAttrs();
442   bool SkipModule = codegen::getMCPU() == "help" ||
443                     (!MAttrs.empty() && MAttrs.front() == "help");
444 
445   CodeGenOpt::Level OLvl = CodeGenOpt::Default;
446   switch (OptLevel) {
447   default:
448     WithColor::error(errs(), argv[0]) << "invalid optimization level.\n";
449     return 1;
450   case ' ': break;
451   case '0': OLvl = CodeGenOpt::None; break;
452   case '1': OLvl = CodeGenOpt::Less; break;
453   case '2': OLvl = CodeGenOpt::Default; break;
454   case '3': OLvl = CodeGenOpt::Aggressive; break;
455   }
456 
457   // Parse 'none' or '$major.$minor'. Disallow -binutils-version=0 because we
458   // use that to indicate the MC default.
459   if (!BinutilsVersion.empty() && BinutilsVersion != "none") {
460     StringRef V = BinutilsVersion.getValue();
461     unsigned Num;
462     if (V.consumeInteger(10, Num) || Num == 0 ||
463         !(V.empty() ||
464           (V.consume_front(".") && !V.consumeInteger(10, Num) && V.empty()))) {
465       WithColor::error(errs(), argv[0])
466           << "invalid -binutils-version, accepting 'none' or major.minor\n";
467       return 1;
468     }
469   }
470   TargetOptions Options;
471   auto InitializeOptions = [&](const Triple &TheTriple) {
472     Options = codegen::InitTargetOptionsFromCodeGenFlags(TheTriple);
473     Options.BinutilsVersion =
474         TargetMachine::parseBinutilsVersion(BinutilsVersion);
475     Options.DisableIntegratedAS = NoIntegratedAssembler;
476     Options.MCOptions.ShowMCEncoding = ShowMCEncoding;
477     Options.MCOptions.MCUseDwarfDirectory = DwarfDirectory;
478     Options.MCOptions.AsmVerbose = AsmVerbose;
479     Options.MCOptions.PreserveAsmComments = PreserveComments;
480     Options.MCOptions.IASSearchPaths = IncludeDirs;
481     Options.MCOptions.SplitDwarfFile = SplitDwarfFile;
482   };
483 
484   Optional<Reloc::Model> RM = codegen::getExplicitRelocModel();
485 
486   const Target *TheTarget = nullptr;
487   std::unique_ptr<TargetMachine> Target;
488 
489   // If user just wants to list available options, skip module loading
490   if (!SkipModule) {
491     auto SetDataLayout =
492         [&](StringRef DataLayoutTargetTriple) -> Optional<std::string> {
493       // If we are supposed to override the target triple, do so now.
494       std::string IRTargetTriple = DataLayoutTargetTriple.str();
495       if (!TargetTriple.empty())
496         IRTargetTriple = Triple::normalize(TargetTriple);
497       TheTriple = Triple(IRTargetTriple);
498       if (TheTriple.getTriple().empty())
499         TheTriple.setTriple(sys::getDefaultTargetTriple());
500 
501       std::string Error;
502       TheTarget =
503           TargetRegistry::lookupTarget(codegen::getMArch(), TheTriple, Error);
504       if (!TheTarget) {
505         WithColor::error(errs(), argv[0]) << Error;
506         exit(1);
507       }
508 
509       // On AIX, setting the relocation model to anything other than PIC is
510       // considered a user error.
511       if (TheTriple.isOSAIX() && RM.hasValue() && *RM != Reloc::PIC_)
512         reportError("invalid relocation model, AIX only supports PIC",
513                     InputFilename);
514 
515       InitializeOptions(TheTriple);
516       Target = std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine(
517           TheTriple.getTriple(), CPUStr, FeaturesStr, Options, RM,
518           codegen::getExplicitCodeModel(), OLvl));
519       assert(Target && "Could not allocate target machine!");
520 
521       return Target->createDataLayout().getStringRepresentation();
522     };
523     if (InputLanguage == "mir" ||
524         (InputLanguage == "" && StringRef(InputFilename).endswith(".mir"))) {
525       MIR = createMIRParserFromFile(InputFilename, Err, Context,
526                                     setMIRFunctionAttributes);
527       if (MIR)
528         M = MIR->parseIRModule(SetDataLayout);
529     } else {
530       M = parseIRFile(InputFilename, Err, Context, SetDataLayout);
531     }
532     if (!M) {
533       Err.print(argv[0], WithColor::error(errs(), argv[0]));
534       return 1;
535     }
536     if (!TargetTriple.empty())
537       M->setTargetTriple(Triple::normalize(TargetTriple));
538   } else {
539     TheTriple = Triple(Triple::normalize(TargetTriple));
540     if (TheTriple.getTriple().empty())
541       TheTriple.setTriple(sys::getDefaultTargetTriple());
542 
543     // Get the target specific parser.
544     std::string Error;
545     TheTarget =
546         TargetRegistry::lookupTarget(codegen::getMArch(), TheTriple, Error);
547     if (!TheTarget) {
548       WithColor::error(errs(), argv[0]) << Error;
549       return 1;
550     }
551 
552     // On AIX, setting the relocation model to anything other than PIC is
553     // considered a user error.
554     if (TheTriple.isOSAIX() && RM.hasValue() && *RM != Reloc::PIC_) {
555       WithColor::error(errs(), argv[0])
556           << "invalid relocation model, AIX only supports PIC.\n";
557       return 1;
558     }
559 
560     InitializeOptions(TheTriple);
561     Target = std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine(
562         TheTriple.getTriple(), CPUStr, FeaturesStr, Options, RM,
563         codegen::getExplicitCodeModel(), OLvl));
564     assert(Target && "Could not allocate target machine!");
565 
566     // If we don't have a module then just exit now. We do this down
567     // here since the CPU/Feature help is underneath the target machine
568     // creation.
569     return 0;
570   }
571 
572   assert(M && "Should have exited if we didn't have a module!");
573   if (codegen::getFloatABIForCalls() != FloatABI::Default)
574     Options.FloatABIType = codegen::getFloatABIForCalls();
575 
576   // Figure out where we are going to send the output.
577   std::unique_ptr<ToolOutputFile> Out =
578       GetOutputStream(TheTarget->getName(), TheTriple.getOS(), argv[0]);
579   if (!Out) return 1;
580 
581   std::unique_ptr<ToolOutputFile> DwoOut;
582   if (!SplitDwarfOutputFile.empty()) {
583     std::error_code EC;
584     DwoOut = std::make_unique<ToolOutputFile>(SplitDwarfOutputFile, EC,
585                                                sys::fs::OF_None);
586     if (EC)
587       reportError(EC.message(), SplitDwarfOutputFile);
588   }
589 
590   // Build up all of the passes that we want to do to the module.
591   legacy::PassManager PM;
592 
593   // Add an appropriate TargetLibraryInfo pass for the module's triple.
594   TargetLibraryInfoImpl TLII(Triple(M->getTargetTriple()));
595 
596   // The -disable-simplify-libcalls flag actually disables all builtin optzns.
597   if (DisableSimplifyLibCalls)
598     TLII.disableAllFunctions();
599   PM.add(new TargetLibraryInfoWrapperPass(TLII));
600 
601   // Verify module immediately to catch problems before doInitialization() is
602   // called on any passes.
603   if (!NoVerify && verifyModule(*M, &errs()))
604     reportError("input module cannot be verified", InputFilename);
605 
606   // Override function attributes based on CPUStr, FeaturesStr, and command line
607   // flags.
608   codegen::setFunctionAttributes(CPUStr, FeaturesStr, *M);
609 
610   if (mc::getExplicitRelaxAll() && codegen::getFileType() != CGFT_ObjectFile)
611     WithColor::warning(errs(), argv[0])
612         << ": warning: ignoring -mc-relax-all because filetype != obj";
613 
614   {
615     raw_pwrite_stream *OS = &Out->os();
616 
617     // Manually do the buffering rather than using buffer_ostream,
618     // so we can memcmp the contents in CompileTwice mode
619     SmallVector<char, 0> Buffer;
620     std::unique_ptr<raw_svector_ostream> BOS;
621     if ((codegen::getFileType() != CGFT_AssemblyFile &&
622          !Out->os().supportsSeeking()) ||
623         CompileTwice) {
624       BOS = std::make_unique<raw_svector_ostream>(Buffer);
625       OS = BOS.get();
626     }
627 
628     const char *argv0 = argv[0];
629     LLVMTargetMachine &LLVMTM = static_cast<LLVMTargetMachine &>(*Target);
630     MachineModuleInfoWrapperPass *MMIWP =
631         new MachineModuleInfoWrapperPass(&LLVMTM);
632 
633     // Construct a custom pass pipeline that starts after instruction
634     // selection.
635     if (!RunPassNames->empty()) {
636       if (!MIR) {
637         WithColor::warning(errs(), argv[0])
638             << "run-pass is for .mir file only.\n";
639         return 1;
640       }
641       TargetPassConfig &TPC = *LLVMTM.createPassConfig(PM);
642       if (TPC.hasLimitedCodeGenPipeline()) {
643         WithColor::warning(errs(), argv[0])
644             << "run-pass cannot be used with "
645             << TPC.getLimitedCodeGenPipelineReason(" and ") << ".\n";
646         return 1;
647       }
648 
649       TPC.setDisableVerify(NoVerify);
650       PM.add(&TPC);
651       PM.add(MMIWP);
652       TPC.printAndVerify("");
653       for (const std::string &RunPassName : *RunPassNames) {
654         if (addPass(PM, argv0, RunPassName, TPC))
655           return 1;
656       }
657       TPC.setInitialized();
658       PM.add(createPrintMIRPass(*OS));
659       PM.add(createFreeMachineFunctionPass());
660     } else if (Target->addPassesToEmitFile(
661                    PM, *OS, DwoOut ? &DwoOut->os() : nullptr,
662                    codegen::getFileType(), NoVerify, MMIWP)) {
663       reportError("target does not support generation of this file type");
664     }
665 
666     const_cast<TargetLoweringObjectFile *>(LLVMTM.getObjFileLowering())
667         ->Initialize(MMIWP->getMMI().getContext(), *Target);
668     if (MIR) {
669       assert(MMIWP && "Forgot to create MMIWP?");
670       if (MIR->parseMachineFunctions(*M, MMIWP->getMMI()))
671         return 1;
672     }
673 
674     // Before executing passes, print the final values of the LLVM options.
675     cl::PrintOptionValues();
676 
677     // If requested, run the pass manager over the same module again,
678     // to catch any bugs due to persistent state in the passes. Note that
679     // opt has the same functionality, so it may be worth abstracting this out
680     // in the future.
681     SmallVector<char, 0> CompileTwiceBuffer;
682     if (CompileTwice) {
683       std::unique_ptr<Module> M2(llvm::CloneModule(*M));
684       PM.run(*M2);
685       CompileTwiceBuffer = Buffer;
686       Buffer.clear();
687     }
688 
689     PM.run(*M);
690 
691     auto HasError =
692         ((const LLCDiagnosticHandler *)(Context.getDiagHandlerPtr()))->HasError;
693     if (*HasError)
694       return 1;
695 
696     // Compare the two outputs and make sure they're the same
697     if (CompileTwice) {
698       if (Buffer.size() != CompileTwiceBuffer.size() ||
699           (memcmp(Buffer.data(), CompileTwiceBuffer.data(), Buffer.size()) !=
700            0)) {
701         errs()
702             << "Running the pass manager twice changed the output.\n"
703                "Writing the result of the second run to the specified output\n"
704                "To generate the one-run comparison binary, just run without\n"
705                "the compile-twice option\n";
706         Out->os() << Buffer;
707         Out->keep();
708         return 1;
709       }
710     }
711 
712     if (BOS) {
713       Out->os() << Buffer;
714     }
715   }
716 
717   // Declare success.
718   Out->keep();
719   if (DwoOut)
720     DwoOut->keep();
721 
722   return 0;
723 }
724