1 //===-LTOCodeGenerator.cpp - LLVM Link Time Optimizer ---------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the Link Time Optimization library. This library is
11 // intended to be used by linker to optimize code at link time.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/LTO/LTOCodeGenerator.h"
16 #include "llvm/ADT/StringExtras.h"
17 #include "llvm/Analysis/Passes.h"
18 #include "llvm/Analysis/TargetLibraryInfo.h"
19 #include "llvm/Analysis/TargetTransformInfo.h"
20 #include "llvm/Bitcode/ReaderWriter.h"
21 #include "llvm/CodeGen/RuntimeLibcalls.h"
22 #include "llvm/Config/config.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/DerivedTypes.h"
26 #include "llvm/IR/DiagnosticInfo.h"
27 #include "llvm/IR/DiagnosticPrinter.h"
28 #include "llvm/IR/LLVMContext.h"
29 #include "llvm/IR/LegacyPassManager.h"
30 #include "llvm/IR/Mangler.h"
31 #include "llvm/IR/Module.h"
32 #include "llvm/IR/Verifier.h"
33 #include "llvm/InitializePasses.h"
34 #include "llvm/LTO/LTOModule.h"
35 #include "llvm/Linker/Linker.h"
36 #include "llvm/MC/MCAsmInfo.h"
37 #include "llvm/MC/MCContext.h"
38 #include "llvm/MC/SubtargetFeature.h"
39 #include "llvm/Support/CommandLine.h"
40 #include "llvm/Support/FileSystem.h"
41 #include "llvm/Support/FormattedStream.h"
42 #include "llvm/Support/Host.h"
43 #include "llvm/Support/MemoryBuffer.h"
44 #include "llvm/Support/Signals.h"
45 #include "llvm/Support/TargetRegistry.h"
46 #include "llvm/Support/TargetSelect.h"
47 #include "llvm/Support/ToolOutputFile.h"
48 #include "llvm/Support/raw_ostream.h"
49 #include "llvm/Target/TargetLowering.h"
50 #include "llvm/Target/TargetOptions.h"
51 #include "llvm/Target/TargetRegisterInfo.h"
52 #include "llvm/Target/TargetSubtargetInfo.h"
53 #include "llvm/Transforms/IPO.h"
54 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
55 #include "llvm/Transforms/ObjCARC.h"
56 #include <system_error>
57 using namespace llvm;
58 
59 const char* LTOCodeGenerator::getVersionString() {
60 #ifdef LLVM_VERSION_INFO
61   return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
62 #else
63   return PACKAGE_NAME " version " PACKAGE_VERSION;
64 #endif
65 }
66 
67 LTOCodeGenerator::LTOCodeGenerator()
68     : Context(getGlobalContext()), IRLinker(new Module("ld-temp.o", Context)) {
69   initialize();
70 }
71 
72 LTOCodeGenerator::LTOCodeGenerator(std::unique_ptr<LLVMContext> Context)
73     : OwnedContext(std::move(Context)), Context(*OwnedContext),
74       IRLinker(new Module("ld-temp.o", *OwnedContext)), OptLevel(2) {
75   initialize();
76 }
77 
78 void LTOCodeGenerator::initialize() {
79   TargetMach = nullptr;
80   EmitDwarfDebugInfo = false;
81   ScopeRestrictionsDone = false;
82   CodeModel = LTO_CODEGEN_PIC_MODEL_DEFAULT;
83   DiagHandler = nullptr;
84   DiagContext = nullptr;
85   OwnedModule = nullptr;
86 
87   initializeLTOPasses();
88 }
89 
90 void LTOCodeGenerator::destroyMergedModule() {
91   if (OwnedModule) {
92     assert(IRLinker.getModule() == &OwnedModule->getModule() &&
93            "The linker's module should be the same as the owned module");
94     delete OwnedModule;
95     OwnedModule = nullptr;
96   } else if (IRLinker.getModule())
97     IRLinker.deleteModule();
98 }
99 
100 LTOCodeGenerator::~LTOCodeGenerator() {
101   destroyMergedModule();
102 
103   delete TargetMach;
104   TargetMach = nullptr;
105 
106   for (std::vector<char *>::iterator I = CodegenOptions.begin(),
107                                      E = CodegenOptions.end();
108        I != E; ++I)
109     free(*I);
110 }
111 
112 // Initialize LTO passes. Please keep this funciton in sync with
113 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
114 // passes are initialized.
115 void LTOCodeGenerator::initializeLTOPasses() {
116   PassRegistry &R = *PassRegistry::getPassRegistry();
117 
118   initializeInternalizePassPass(R);
119   initializeIPSCCPPass(R);
120   initializeGlobalOptPass(R);
121   initializeConstantMergePass(R);
122   initializeDAHPass(R);
123   initializeInstructionCombiningPassPass(R);
124   initializeSimpleInlinerPass(R);
125   initializePruneEHPass(R);
126   initializeGlobalDCEPass(R);
127   initializeArgPromotionPass(R);
128   initializeJumpThreadingPass(R);
129   initializeSROAPass(R);
130   initializeSROA_DTPass(R);
131   initializeSROA_SSAUpPass(R);
132   initializeFunctionAttrsPass(R);
133   initializeGlobalsModRefPass(R);
134   initializeLICMPass(R);
135   initializeMergedLoadStoreMotionPass(R);
136   initializeGVNPass(R);
137   initializeMemCpyOptPass(R);
138   initializeDCEPass(R);
139   initializeCFGSimplifyPassPass(R);
140 }
141 
142 bool LTOCodeGenerator::addModule(LTOModule *mod) {
143   assert(&mod->getModule().getContext() == &Context &&
144          "Expected module in same context");
145 
146   bool ret = IRLinker.linkInModule(&mod->getModule());
147 
148   const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
149   for (int i = 0, e = undefs.size(); i != e; ++i)
150     AsmUndefinedRefs[undefs[i]] = 1;
151 
152   return !ret;
153 }
154 
155 void LTOCodeGenerator::setModule(LTOModule *Mod) {
156   assert(&Mod->getModule().getContext() == &Context &&
157          "Expected module in same context");
158 
159   // Delete the old merged module.
160   destroyMergedModule();
161   AsmUndefinedRefs.clear();
162 
163   OwnedModule = Mod;
164   IRLinker.setModule(&Mod->getModule());
165 
166   const std::vector<const char*> &Undefs = Mod->getAsmUndefinedRefs();
167   for (int I = 0, E = Undefs.size(); I != E; ++I)
168     AsmUndefinedRefs[Undefs[I]] = 1;
169 }
170 
171 void LTOCodeGenerator::setTargetOptions(TargetOptions options) {
172   Options = options;
173 }
174 
175 void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
176   switch (debug) {
177   case LTO_DEBUG_MODEL_NONE:
178     EmitDwarfDebugInfo = false;
179     return;
180 
181   case LTO_DEBUG_MODEL_DWARF:
182     EmitDwarfDebugInfo = true;
183     return;
184   }
185   llvm_unreachable("Unknown debug format!");
186 }
187 
188 void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
189   switch (model) {
190   case LTO_CODEGEN_PIC_MODEL_STATIC:
191   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
192   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
193   case LTO_CODEGEN_PIC_MODEL_DEFAULT:
194     CodeModel = model;
195     return;
196   }
197   llvm_unreachable("Unknown PIC model!");
198 }
199 
200 bool LTOCodeGenerator::writeMergedModules(const char *path,
201                                           std::string &errMsg) {
202   if (!determineTarget(errMsg))
203     return false;
204 
205   // mark which symbols can not be internalized
206   applyScopeRestrictions();
207 
208   // create output file
209   std::error_code EC;
210   tool_output_file Out(path, EC, sys::fs::F_None);
211   if (EC) {
212     errMsg = "could not open bitcode file for writing: ";
213     errMsg += path;
214     return false;
215   }
216 
217   // write bitcode to it
218   WriteBitcodeToFile(IRLinker.getModule(), Out.os());
219   Out.os().close();
220 
221   if (Out.os().has_error()) {
222     errMsg = "could not write bitcode file: ";
223     errMsg += path;
224     Out.os().clear_error();
225     return false;
226   }
227 
228   Out.keep();
229   return true;
230 }
231 
232 bool LTOCodeGenerator::compileOptimizedToFile(const char **name,
233                                               std::string &errMsg) {
234   // make unique temp .o file to put generated object file
235   SmallString<128> Filename;
236   int FD;
237   std::error_code EC =
238       sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
239   if (EC) {
240     errMsg = EC.message();
241     return false;
242   }
243 
244   // generate object file
245   tool_output_file objFile(Filename.c_str(), FD);
246 
247   bool genResult = compileOptimized(objFile.os(), errMsg);
248   objFile.os().close();
249   if (objFile.os().has_error()) {
250     objFile.os().clear_error();
251     sys::fs::remove(Twine(Filename));
252     return false;
253   }
254 
255   objFile.keep();
256   if (!genResult) {
257     sys::fs::remove(Twine(Filename));
258     return false;
259   }
260 
261   NativeObjectPath = Filename.c_str();
262   *name = NativeObjectPath.c_str();
263   return true;
264 }
265 
266 const void *LTOCodeGenerator::compileOptimized(size_t *length,
267                                                std::string &errMsg) {
268   const char *name;
269   if (!compileOptimizedToFile(&name, errMsg))
270     return nullptr;
271 
272   // read .o file into memory buffer
273   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
274       MemoryBuffer::getFile(name, -1, false);
275   if (std::error_code EC = BufferOrErr.getError()) {
276     errMsg = EC.message();
277     sys::fs::remove(NativeObjectPath);
278     return nullptr;
279   }
280   NativeObjectFile = std::move(*BufferOrErr);
281 
282   // remove temp files
283   sys::fs::remove(NativeObjectPath);
284 
285   // return buffer, unless error
286   if (!NativeObjectFile)
287     return nullptr;
288   *length = NativeObjectFile->getBufferSize();
289   return NativeObjectFile->getBufferStart();
290 }
291 
292 
293 bool LTOCodeGenerator::compile_to_file(const char **name,
294                                        bool disableInline,
295                                        bool disableGVNLoadPRE,
296                                        bool disableVectorization,
297                                        std::string &errMsg) {
298   if (!optimize(disableInline, disableGVNLoadPRE,
299                 disableVectorization, errMsg))
300     return false;
301 
302   return compileOptimizedToFile(name, errMsg);
303 }
304 
305 const void* LTOCodeGenerator::compile(size_t *length,
306                                       bool disableInline,
307                                       bool disableGVNLoadPRE,
308                                       bool disableVectorization,
309                                       std::string &errMsg) {
310   if (!optimize(disableInline, disableGVNLoadPRE,
311                 disableVectorization, errMsg))
312     return nullptr;
313 
314   return compileOptimized(length, errMsg);
315 }
316 
317 bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
318   if (TargetMach)
319     return true;
320 
321   std::string TripleStr = IRLinker.getModule()->getTargetTriple();
322   if (TripleStr.empty())
323     TripleStr = sys::getDefaultTargetTriple();
324   llvm::Triple Triple(TripleStr);
325 
326   // create target machine from info for merged modules
327   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
328   if (!march)
329     return false;
330 
331   // The relocation model is actually a static member of TargetMachine and
332   // needs to be set before the TargetMachine is instantiated.
333   Reloc::Model RelocModel = Reloc::Default;
334   switch (CodeModel) {
335   case LTO_CODEGEN_PIC_MODEL_STATIC:
336     RelocModel = Reloc::Static;
337     break;
338   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
339     RelocModel = Reloc::PIC_;
340     break;
341   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
342     RelocModel = Reloc::DynamicNoPIC;
343     break;
344   case LTO_CODEGEN_PIC_MODEL_DEFAULT:
345     // RelocModel is already the default, so leave it that way.
346     break;
347   }
348 
349   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
350   // the default set of features.
351   SubtargetFeatures Features(MAttr);
352   Features.getDefaultSubtargetFeatures(Triple);
353   std::string FeatureStr = Features.getString();
354   // Set a default CPU for Darwin triples.
355   if (MCpu.empty() && Triple.isOSDarwin()) {
356     if (Triple.getArch() == llvm::Triple::x86_64)
357       MCpu = "core2";
358     else if (Triple.getArch() == llvm::Triple::x86)
359       MCpu = "yonah";
360     else if (Triple.getArch() == llvm::Triple::aarch64)
361       MCpu = "cyclone";
362   }
363 
364   CodeGenOpt::Level CGOptLevel;
365   switch (OptLevel) {
366   case 0:
367     CGOptLevel = CodeGenOpt::None;
368     break;
369   case 1:
370     CGOptLevel = CodeGenOpt::Less;
371     break;
372   case 2:
373     CGOptLevel = CodeGenOpt::Default;
374     break;
375   case 3:
376     CGOptLevel = CodeGenOpt::Aggressive;
377     break;
378   }
379 
380   TargetMach = march->createTargetMachine(TripleStr, MCpu, FeatureStr, Options,
381                                           RelocModel, CodeModel::Default,
382                                           CGOptLevel);
383   return true;
384 }
385 
386 void LTOCodeGenerator::
387 applyRestriction(GlobalValue &GV,
388                  ArrayRef<StringRef> Libcalls,
389                  std::vector<const char*> &MustPreserveList,
390                  SmallPtrSetImpl<GlobalValue*> &AsmUsed,
391                  Mangler &Mangler) {
392   // There are no restrictions to apply to declarations.
393   if (GV.isDeclaration())
394     return;
395 
396   // There is nothing more restrictive than private linkage.
397   if (GV.hasPrivateLinkage())
398     return;
399 
400   SmallString<64> Buffer;
401   TargetMach->getNameWithPrefix(Buffer, &GV, Mangler);
402 
403   if (MustPreserveSymbols.count(Buffer))
404     MustPreserveList.push_back(GV.getName().data());
405   if (AsmUndefinedRefs.count(Buffer))
406     AsmUsed.insert(&GV);
407 
408   // Conservatively append user-supplied runtime library functions to
409   // llvm.compiler.used.  These could be internalized and deleted by
410   // optimizations like -globalopt, causing problems when later optimizations
411   // add new library calls (e.g., llvm.memset => memset and printf => puts).
412   // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
413   if (isa<Function>(GV) &&
414       std::binary_search(Libcalls.begin(), Libcalls.end(), GV.getName()))
415     AsmUsed.insert(&GV);
416 }
417 
418 static void findUsedValues(GlobalVariable *LLVMUsed,
419                            SmallPtrSetImpl<GlobalValue*> &UsedValues) {
420   if (!LLVMUsed) return;
421 
422   ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
423   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
424     if (GlobalValue *GV =
425         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
426       UsedValues.insert(GV);
427 }
428 
429 // Collect names of runtime library functions. User-defined functions with the
430 // same names are added to llvm.compiler.used to prevent them from being
431 // deleted by optimizations.
432 static void accumulateAndSortLibcalls(std::vector<StringRef> &Libcalls,
433                                       const TargetLibraryInfo& TLI,
434                                       const Module &Mod,
435                                       const TargetMachine &TM) {
436   // TargetLibraryInfo has info on C runtime library calls on the current
437   // target.
438   for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
439        I != E; ++I) {
440     LibFunc::Func F = static_cast<LibFunc::Func>(I);
441     if (TLI.has(F))
442       Libcalls.push_back(TLI.getName(F));
443   }
444 
445   SmallPtrSet<const TargetLowering *, 1> TLSet;
446 
447   for (const Function &F : Mod) {
448     const TargetLowering *Lowering =
449         TM.getSubtargetImpl(F)->getTargetLowering();
450 
451     if (Lowering && TLSet.insert(Lowering).second)
452       // TargetLowering has info on library calls that CodeGen expects to be
453       // available, both from the C runtime and compiler-rt.
454       for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
455            I != E; ++I)
456         if (const char *Name =
457                 Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
458           Libcalls.push_back(Name);
459   }
460 
461   array_pod_sort(Libcalls.begin(), Libcalls.end());
462   Libcalls.erase(std::unique(Libcalls.begin(), Libcalls.end()),
463                  Libcalls.end());
464 }
465 
466 void LTOCodeGenerator::applyScopeRestrictions() {
467   if (ScopeRestrictionsDone)
468     return;
469   Module *mergedModule = IRLinker.getModule();
470 
471   // Start off with a verification pass.
472   legacy::PassManager passes;
473   passes.add(createVerifierPass());
474 
475   // mark which symbols can not be internalized
476   Mangler Mangler(TargetMach->getDataLayout());
477   std::vector<const char*> MustPreserveList;
478   SmallPtrSet<GlobalValue*, 8> AsmUsed;
479   std::vector<StringRef> Libcalls;
480   TargetLibraryInfoImpl TLII(Triple(TargetMach->getTargetTriple()));
481   TargetLibraryInfo TLI(TLII);
482 
483   accumulateAndSortLibcalls(Libcalls, TLI, *mergedModule, *TargetMach);
484 
485   for (Module::iterator f = mergedModule->begin(),
486          e = mergedModule->end(); f != e; ++f)
487     applyRestriction(*f, Libcalls, MustPreserveList, AsmUsed, Mangler);
488   for (Module::global_iterator v = mergedModule->global_begin(),
489          e = mergedModule->global_end(); v !=  e; ++v)
490     applyRestriction(*v, Libcalls, MustPreserveList, AsmUsed, Mangler);
491   for (Module::alias_iterator a = mergedModule->alias_begin(),
492          e = mergedModule->alias_end(); a != e; ++a)
493     applyRestriction(*a, Libcalls, MustPreserveList, AsmUsed, Mangler);
494 
495   GlobalVariable *LLVMCompilerUsed =
496     mergedModule->getGlobalVariable("llvm.compiler.used");
497   findUsedValues(LLVMCompilerUsed, AsmUsed);
498   if (LLVMCompilerUsed)
499     LLVMCompilerUsed->eraseFromParent();
500 
501   if (!AsmUsed.empty()) {
502     llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
503     std::vector<Constant*> asmUsed2;
504     for (auto *GV : AsmUsed) {
505       Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
506       asmUsed2.push_back(c);
507     }
508 
509     llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
510     LLVMCompilerUsed =
511       new llvm::GlobalVariable(*mergedModule, ATy, false,
512                                llvm::GlobalValue::AppendingLinkage,
513                                llvm::ConstantArray::get(ATy, asmUsed2),
514                                "llvm.compiler.used");
515 
516     LLVMCompilerUsed->setSection("llvm.metadata");
517   }
518 
519   passes.add(createInternalizePass(MustPreserveList));
520 
521   // apply scope restrictions
522   passes.run(*mergedModule);
523 
524   ScopeRestrictionsDone = true;
525 }
526 
527 /// Optimize merged modules using various IPO passes
528 bool LTOCodeGenerator::optimize(bool DisableInline,
529                                 bool DisableGVNLoadPRE,
530                                 bool DisableVectorization,
531                                 std::string &errMsg) {
532   if (!this->determineTarget(errMsg))
533     return false;
534 
535   Module *mergedModule = IRLinker.getModule();
536 
537   // Mark which symbols can not be internalized
538   this->applyScopeRestrictions();
539 
540   // Instantiate the pass manager to organize the passes.
541   legacy::PassManager passes;
542 
543   // Add an appropriate DataLayout instance for this module...
544   mergedModule->setDataLayout(*TargetMach->getDataLayout());
545 
546   passes.add(
547       createTargetTransformInfoWrapperPass(TargetMach->getTargetIRAnalysis()));
548 
549   Triple TargetTriple(TargetMach->getTargetTriple());
550   PassManagerBuilder PMB;
551   PMB.DisableGVNLoadPRE = DisableGVNLoadPRE;
552   PMB.LoopVectorize = !DisableVectorization;
553   PMB.SLPVectorize = !DisableVectorization;
554   if (!DisableInline)
555     PMB.Inliner = createFunctionInliningPass();
556   PMB.LibraryInfo = new TargetLibraryInfoImpl(TargetTriple);
557   PMB.OptLevel = OptLevel;
558   PMB.VerifyInput = true;
559   PMB.VerifyOutput = true;
560 
561   PMB.populateLTOPassManager(passes);
562 
563   // Run our queue of passes all at once now, efficiently.
564   passes.run(*mergedModule);
565 
566   return true;
567 }
568 
569 bool LTOCodeGenerator::compileOptimized(raw_ostream &out, std::string &errMsg) {
570   if (!this->determineTarget(errMsg))
571     return false;
572 
573   Module *mergedModule = IRLinker.getModule();
574 
575   // Mark which symbols can not be internalized
576   this->applyScopeRestrictions();
577 
578   legacy::PassManager codeGenPasses;
579 
580   formatted_raw_ostream Out(out);
581 
582   // If the bitcode files contain ARC code and were compiled with optimization,
583   // the ObjCARCContractPass must be run, so do it unconditionally here.
584   codeGenPasses.add(createObjCARCContractPass());
585 
586   if (TargetMach->addPassesToEmitFile(codeGenPasses, Out,
587                                       TargetMachine::CGFT_ObjectFile)) {
588     errMsg = "target file type not supported";
589     return false;
590   }
591 
592   // Run the code generator, and write assembly file
593   codeGenPasses.run(*mergedModule);
594 
595   return true;
596 }
597 
598 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
599 /// LTO problems.
600 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
601   for (std::pair<StringRef, StringRef> o = getToken(options);
602        !o.first.empty(); o = getToken(o.second)) {
603     // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
604     // that.
605     if (CodegenOptions.empty())
606       CodegenOptions.push_back(strdup("libLLVMLTO"));
607     CodegenOptions.push_back(strdup(o.first.str().c_str()));
608   }
609 }
610 
611 void LTOCodeGenerator::parseCodeGenDebugOptions() {
612   // if options were requested, set them
613   if (!CodegenOptions.empty())
614     cl::ParseCommandLineOptions(CodegenOptions.size(),
615                                 const_cast<char **>(&CodegenOptions[0]));
616 }
617 
618 void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI,
619                                          void *Context) {
620   ((LTOCodeGenerator *)Context)->DiagnosticHandler2(DI);
621 }
622 
623 void LTOCodeGenerator::DiagnosticHandler2(const DiagnosticInfo &DI) {
624   // Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
625   lto_codegen_diagnostic_severity_t Severity;
626   switch (DI.getSeverity()) {
627   case DS_Error:
628     Severity = LTO_DS_ERROR;
629     break;
630   case DS_Warning:
631     Severity = LTO_DS_WARNING;
632     break;
633   case DS_Remark:
634     Severity = LTO_DS_REMARK;
635     break;
636   case DS_Note:
637     Severity = LTO_DS_NOTE;
638     break;
639   }
640   // Create the string that will be reported to the external diagnostic handler.
641   std::string MsgStorage;
642   raw_string_ostream Stream(MsgStorage);
643   DiagnosticPrinterRawOStream DP(Stream);
644   DI.print(DP);
645   Stream.flush();
646 
647   // If this method has been called it means someone has set up an external
648   // diagnostic handler. Assert on that.
649   assert(DiagHandler && "Invalid diagnostic handler");
650   (*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
651 }
652 
653 void
654 LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
655                                        void *Ctxt) {
656   this->DiagHandler = DiagHandler;
657   this->DiagContext = Ctxt;
658   if (!DiagHandler)
659     return Context.setDiagnosticHandler(nullptr, nullptr);
660   // Register the LTOCodeGenerator stub in the LLVMContext to forward the
661   // diagnostic to the external DiagHandler.
662   Context.setDiagnosticHandler(LTOCodeGenerator::DiagnosticHandler, this,
663                                /* RespectFilters */ true);
664 }
665