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/Host.h"
42 #include "llvm/Support/MemoryBuffer.h"
43 #include "llvm/Support/Signals.h"
44 #include "llvm/Support/TargetRegistry.h"
45 #include "llvm/Support/TargetSelect.h"
46 #include "llvm/Support/ToolOutputFile.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include "llvm/Target/TargetLowering.h"
49 #include "llvm/Target/TargetOptions.h"
50 #include "llvm/Target/TargetRegisterInfo.h"
51 #include "llvm/Target/TargetSubtargetInfo.h"
52 #include "llvm/Transforms/IPO.h"
53 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
54 #include "llvm/Transforms/ObjCARC.h"
55 #include <system_error>
56 using namespace llvm;
57 
58 const char* LTOCodeGenerator::getVersionString() {
59 #ifdef LLVM_VERSION_INFO
60   return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
61 #else
62   return PACKAGE_NAME " version " PACKAGE_VERSION;
63 #endif
64 }
65 
66 LTOCodeGenerator::LTOCodeGenerator()
67     : Context(getGlobalContext()), IRLinker(new Module("ld-temp.o", Context)) {
68   initialize();
69 }
70 
71 LTOCodeGenerator::LTOCodeGenerator(std::unique_ptr<LLVMContext> Context)
72     : OwnedContext(std::move(Context)), Context(*OwnedContext),
73       IRLinker(new Module("ld-temp.o", *OwnedContext)), OptLevel(2) {
74   initialize();
75 }
76 
77 void LTOCodeGenerator::initialize() {
78   TargetMach = nullptr;
79   EmitDwarfDebugInfo = false;
80   ScopeRestrictionsDone = false;
81   CodeModel = LTO_CODEGEN_PIC_MODEL_DEFAULT;
82   DiagHandler = nullptr;
83   DiagContext = nullptr;
84   OwnedModule = nullptr;
85   ShouldInternalize = true;
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                      /* ShouldPreserveUseListOrder */ true);
220   Out.os().close();
221 
222   if (Out.os().has_error()) {
223     errMsg = "could not write bitcode file: ";
224     errMsg += path;
225     Out.os().clear_error();
226     return false;
227   }
228 
229   Out.keep();
230   return true;
231 }
232 
233 bool LTOCodeGenerator::compileOptimizedToFile(const char **name,
234                                               std::string &errMsg) {
235   // make unique temp .o file to put generated object file
236   SmallString<128> Filename;
237   int FD;
238   std::error_code EC =
239       sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
240   if (EC) {
241     errMsg = EC.message();
242     return false;
243   }
244 
245   // generate object file
246   tool_output_file objFile(Filename.c_str(), FD);
247 
248   bool genResult = compileOptimized(objFile.os(), errMsg);
249   objFile.os().close();
250   if (objFile.os().has_error()) {
251     objFile.os().clear_error();
252     sys::fs::remove(Twine(Filename));
253     return false;
254   }
255 
256   objFile.keep();
257   if (!genResult) {
258     sys::fs::remove(Twine(Filename));
259     return false;
260   }
261 
262   NativeObjectPath = Filename.c_str();
263   *name = NativeObjectPath.c_str();
264   return true;
265 }
266 
267 const void *LTOCodeGenerator::compileOptimized(size_t *length,
268                                                std::string &errMsg) {
269   const char *name;
270   if (!compileOptimizedToFile(&name, errMsg))
271     return nullptr;
272 
273   // read .o file into memory buffer
274   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
275       MemoryBuffer::getFile(name, -1, false);
276   if (std::error_code EC = BufferOrErr.getError()) {
277     errMsg = EC.message();
278     sys::fs::remove(NativeObjectPath);
279     return nullptr;
280   }
281   NativeObjectFile = std::move(*BufferOrErr);
282 
283   // remove temp files
284   sys::fs::remove(NativeObjectPath);
285 
286   // return buffer, unless error
287   if (!NativeObjectFile)
288     return nullptr;
289   *length = NativeObjectFile->getBufferSize();
290   return NativeObjectFile->getBufferStart();
291 }
292 
293 
294 bool LTOCodeGenerator::compile_to_file(const char **name,
295                                        bool disableInline,
296                                        bool disableGVNLoadPRE,
297                                        bool disableVectorization,
298                                        std::string &errMsg) {
299   if (!optimize(disableInline, disableGVNLoadPRE,
300                 disableVectorization, errMsg))
301     return false;
302 
303   return compileOptimizedToFile(name, errMsg);
304 }
305 
306 const void* LTOCodeGenerator::compile(size_t *length,
307                                       bool disableInline,
308                                       bool disableGVNLoadPRE,
309                                       bool disableVectorization,
310                                       std::string &errMsg) {
311   if (!optimize(disableInline, disableGVNLoadPRE,
312                 disableVectorization, errMsg))
313     return nullptr;
314 
315   return compileOptimized(length, errMsg);
316 }
317 
318 bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
319   if (TargetMach)
320     return true;
321 
322   std::string TripleStr = IRLinker.getModule()->getTargetTriple();
323   if (TripleStr.empty())
324     TripleStr = sys::getDefaultTargetTriple();
325   llvm::Triple Triple(TripleStr);
326 
327   // create target machine from info for merged modules
328   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
329   if (!march)
330     return false;
331 
332   // The relocation model is actually a static member of TargetMachine and
333   // needs to be set before the TargetMachine is instantiated.
334   Reloc::Model RelocModel = Reloc::Default;
335   switch (CodeModel) {
336   case LTO_CODEGEN_PIC_MODEL_STATIC:
337     RelocModel = Reloc::Static;
338     break;
339   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
340     RelocModel = Reloc::PIC_;
341     break;
342   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
343     RelocModel = Reloc::DynamicNoPIC;
344     break;
345   case LTO_CODEGEN_PIC_MODEL_DEFAULT:
346     // RelocModel is already the default, so leave it that way.
347     break;
348   }
349 
350   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
351   // the default set of features.
352   SubtargetFeatures Features(MAttr);
353   Features.getDefaultSubtargetFeatures(Triple);
354   std::string FeatureStr = Features.getString();
355   // Set a default CPU for Darwin triples.
356   if (MCpu.empty() && Triple.isOSDarwin()) {
357     if (Triple.getArch() == llvm::Triple::x86_64)
358       MCpu = "core2";
359     else if (Triple.getArch() == llvm::Triple::x86)
360       MCpu = "yonah";
361     else if (Triple.getArch() == llvm::Triple::aarch64)
362       MCpu = "cyclone";
363   }
364 
365   CodeGenOpt::Level CGOptLevel;
366   switch (OptLevel) {
367   case 0:
368     CGOptLevel = CodeGenOpt::None;
369     break;
370   case 1:
371     CGOptLevel = CodeGenOpt::Less;
372     break;
373   case 2:
374     CGOptLevel = CodeGenOpt::Default;
375     break;
376   case 3:
377     CGOptLevel = CodeGenOpt::Aggressive;
378     break;
379   }
380 
381   TargetMach = march->createTargetMachine(TripleStr, MCpu, FeatureStr, Options,
382                                           RelocModel, CodeModel::Default,
383                                           CGOptLevel);
384   return true;
385 }
386 
387 void LTOCodeGenerator::
388 applyRestriction(GlobalValue &GV,
389                  ArrayRef<StringRef> Libcalls,
390                  std::vector<const char*> &MustPreserveList,
391                  SmallPtrSetImpl<GlobalValue*> &AsmUsed,
392                  Mangler &Mangler) {
393   // There are no restrictions to apply to declarations.
394   if (GV.isDeclaration())
395     return;
396 
397   // There is nothing more restrictive than private linkage.
398   if (GV.hasPrivateLinkage())
399     return;
400 
401   SmallString<64> Buffer;
402   TargetMach->getNameWithPrefix(Buffer, &GV, Mangler);
403 
404   if (MustPreserveSymbols.count(Buffer))
405     MustPreserveList.push_back(GV.getName().data());
406   if (AsmUndefinedRefs.count(Buffer))
407     AsmUsed.insert(&GV);
408 
409   // Conservatively append user-supplied runtime library functions to
410   // llvm.compiler.used.  These could be internalized and deleted by
411   // optimizations like -globalopt, causing problems when later optimizations
412   // add new library calls (e.g., llvm.memset => memset and printf => puts).
413   // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
414   if (isa<Function>(GV) &&
415       std::binary_search(Libcalls.begin(), Libcalls.end(), GV.getName()))
416     AsmUsed.insert(&GV);
417 }
418 
419 static void findUsedValues(GlobalVariable *LLVMUsed,
420                            SmallPtrSetImpl<GlobalValue*> &UsedValues) {
421   if (!LLVMUsed) return;
422 
423   ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
424   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
425     if (GlobalValue *GV =
426         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
427       UsedValues.insert(GV);
428 }
429 
430 // Collect names of runtime library functions. User-defined functions with the
431 // same names are added to llvm.compiler.used to prevent them from being
432 // deleted by optimizations.
433 static void accumulateAndSortLibcalls(std::vector<StringRef> &Libcalls,
434                                       const TargetLibraryInfo& TLI,
435                                       const Module &Mod,
436                                       const TargetMachine &TM) {
437   // TargetLibraryInfo has info on C runtime library calls on the current
438   // target.
439   for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
440        I != E; ++I) {
441     LibFunc::Func F = static_cast<LibFunc::Func>(I);
442     if (TLI.has(F))
443       Libcalls.push_back(TLI.getName(F));
444   }
445 
446   SmallPtrSet<const TargetLowering *, 1> TLSet;
447 
448   for (const Function &F : Mod) {
449     const TargetLowering *Lowering =
450         TM.getSubtargetImpl(F)->getTargetLowering();
451 
452     if (Lowering && TLSet.insert(Lowering).second)
453       // TargetLowering has info on library calls that CodeGen expects to be
454       // available, both from the C runtime and compiler-rt.
455       for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
456            I != E; ++I)
457         if (const char *Name =
458                 Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
459           Libcalls.push_back(Name);
460   }
461 
462   array_pod_sort(Libcalls.begin(), Libcalls.end());
463   Libcalls.erase(std::unique(Libcalls.begin(), Libcalls.end()),
464                  Libcalls.end());
465 }
466 
467 void LTOCodeGenerator::applyScopeRestrictions() {
468   if (ScopeRestrictionsDone || !ShouldInternalize)
469     return;
470   Module *mergedModule = IRLinker.getModule();
471 
472   // Start off with a verification pass.
473   legacy::PassManager passes;
474   passes.add(createVerifierPass());
475 
476   // mark which symbols can not be internalized
477   Mangler Mangler(TargetMach->getDataLayout());
478   std::vector<const char*> MustPreserveList;
479   SmallPtrSet<GlobalValue*, 8> AsmUsed;
480   std::vector<StringRef> Libcalls;
481   TargetLibraryInfoImpl TLII(Triple(TargetMach->getTargetTriple()));
482   TargetLibraryInfo TLI(TLII);
483 
484   accumulateAndSortLibcalls(Libcalls, TLI, *mergedModule, *TargetMach);
485 
486   for (Module::iterator f = mergedModule->begin(),
487          e = mergedModule->end(); f != e; ++f)
488     applyRestriction(*f, Libcalls, MustPreserveList, AsmUsed, Mangler);
489   for (Module::global_iterator v = mergedModule->global_begin(),
490          e = mergedModule->global_end(); v !=  e; ++v)
491     applyRestriction(*v, Libcalls, MustPreserveList, AsmUsed, Mangler);
492   for (Module::alias_iterator a = mergedModule->alias_begin(),
493          e = mergedModule->alias_end(); a != e; ++a)
494     applyRestriction(*a, Libcalls, MustPreserveList, AsmUsed, Mangler);
495 
496   GlobalVariable *LLVMCompilerUsed =
497     mergedModule->getGlobalVariable("llvm.compiler.used");
498   findUsedValues(LLVMCompilerUsed, AsmUsed);
499   if (LLVMCompilerUsed)
500     LLVMCompilerUsed->eraseFromParent();
501 
502   if (!AsmUsed.empty()) {
503     llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
504     std::vector<Constant*> asmUsed2;
505     for (auto *GV : AsmUsed) {
506       Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
507       asmUsed2.push_back(c);
508     }
509 
510     llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
511     LLVMCompilerUsed =
512       new llvm::GlobalVariable(*mergedModule, ATy, false,
513                                llvm::GlobalValue::AppendingLinkage,
514                                llvm::ConstantArray::get(ATy, asmUsed2),
515                                "llvm.compiler.used");
516 
517     LLVMCompilerUsed->setSection("llvm.metadata");
518   }
519 
520   passes.add(createInternalizePass(MustPreserveList));
521 
522   // apply scope restrictions
523   passes.run(*mergedModule);
524 
525   ScopeRestrictionsDone = true;
526 }
527 
528 /// Optimize merged modules using various IPO passes
529 bool LTOCodeGenerator::optimize(bool DisableInline,
530                                 bool DisableGVNLoadPRE,
531                                 bool DisableVectorization,
532                                 std::string &errMsg) {
533   if (!this->determineTarget(errMsg))
534     return false;
535 
536   Module *mergedModule = IRLinker.getModule();
537 
538   // Mark which symbols can not be internalized
539   this->applyScopeRestrictions();
540 
541   // Instantiate the pass manager to organize the passes.
542   legacy::PassManager passes;
543 
544   // Add an appropriate DataLayout instance for this module...
545   mergedModule->setDataLayout(*TargetMach->getDataLayout());
546 
547   passes.add(
548       createTargetTransformInfoWrapperPass(TargetMach->getTargetIRAnalysis()));
549 
550   Triple TargetTriple(TargetMach->getTargetTriple());
551   PassManagerBuilder PMB;
552   PMB.DisableGVNLoadPRE = DisableGVNLoadPRE;
553   PMB.LoopVectorize = !DisableVectorization;
554   PMB.SLPVectorize = !DisableVectorization;
555   if (!DisableInline)
556     PMB.Inliner = createFunctionInliningPass();
557   PMB.LibraryInfo = new TargetLibraryInfoImpl(TargetTriple);
558   PMB.OptLevel = OptLevel;
559   PMB.VerifyInput = true;
560   PMB.VerifyOutput = true;
561 
562   PMB.populateLTOPassManager(passes);
563 
564   // Run our queue of passes all at once now, efficiently.
565   passes.run(*mergedModule);
566 
567   return true;
568 }
569 
570 bool LTOCodeGenerator::compileOptimized(raw_pwrite_stream &out,
571                                         std::string &errMsg) {
572   if (!this->determineTarget(errMsg))
573     return false;
574 
575   Module *mergedModule = IRLinker.getModule();
576 
577   legacy::PassManager codeGenPasses;
578 
579   // If the bitcode files contain ARC code and were compiled with optimization,
580   // the ObjCARCContractPass must be run, so do it unconditionally here.
581   codeGenPasses.add(createObjCARCContractPass());
582 
583   if (TargetMach->addPassesToEmitFile(codeGenPasses, out,
584                                       TargetMachine::CGFT_ObjectFile)) {
585     errMsg = "target file type not supported";
586     return false;
587   }
588 
589   // Run the code generator, and write assembly file
590   codeGenPasses.run(*mergedModule);
591 
592   return true;
593 }
594 
595 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
596 /// LTO problems.
597 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
598   for (std::pair<StringRef, StringRef> o = getToken(options);
599        !o.first.empty(); o = getToken(o.second)) {
600     // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
601     // that.
602     if (CodegenOptions.empty())
603       CodegenOptions.push_back(strdup("libLLVMLTO"));
604     CodegenOptions.push_back(strdup(o.first.str().c_str()));
605   }
606 }
607 
608 void LTOCodeGenerator::parseCodeGenDebugOptions() {
609   // if options were requested, set them
610   if (!CodegenOptions.empty())
611     cl::ParseCommandLineOptions(CodegenOptions.size(),
612                                 const_cast<char **>(&CodegenOptions[0]));
613 }
614 
615 void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI,
616                                          void *Context) {
617   ((LTOCodeGenerator *)Context)->DiagnosticHandler2(DI);
618 }
619 
620 void LTOCodeGenerator::DiagnosticHandler2(const DiagnosticInfo &DI) {
621   // Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
622   lto_codegen_diagnostic_severity_t Severity;
623   switch (DI.getSeverity()) {
624   case DS_Error:
625     Severity = LTO_DS_ERROR;
626     break;
627   case DS_Warning:
628     Severity = LTO_DS_WARNING;
629     break;
630   case DS_Remark:
631     Severity = LTO_DS_REMARK;
632     break;
633   case DS_Note:
634     Severity = LTO_DS_NOTE;
635     break;
636   }
637   // Create the string that will be reported to the external diagnostic handler.
638   std::string MsgStorage;
639   raw_string_ostream Stream(MsgStorage);
640   DiagnosticPrinterRawOStream DP(Stream);
641   DI.print(DP);
642   Stream.flush();
643 
644   // If this method has been called it means someone has set up an external
645   // diagnostic handler. Assert on that.
646   assert(DiagHandler && "Invalid diagnostic handler");
647   (*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
648 }
649 
650 void
651 LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
652                                        void *Ctxt) {
653   this->DiagHandler = DiagHandler;
654   this->DiagContext = Ctxt;
655   if (!DiagHandler)
656     return Context.setDiagnosticHandler(nullptr, nullptr);
657   // Register the LTOCodeGenerator stub in the LLVMContext to forward the
658   // diagnostic to the external DiagHandler.
659   Context.setDiagnosticHandler(LTOCodeGenerator::DiagnosticHandler, this,
660                                /* RespectFilters */ true);
661 }
662