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/ParallelCG.h"
22 #include "llvm/CodeGen/RuntimeLibcalls.h"
23 #include "llvm/Config/config.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/DerivedTypes.h"
27 #include "llvm/IR/DiagnosticInfo.h"
28 #include "llvm/IR/DiagnosticPrinter.h"
29 #include "llvm/IR/LLVMContext.h"
30 #include "llvm/IR/LegacyPassManager.h"
31 #include "llvm/IR/Mangler.h"
32 #include "llvm/IR/Module.h"
33 #include "llvm/IR/Verifier.h"
34 #include "llvm/InitializePasses.h"
35 #include "llvm/LTO/LTOModule.h"
36 #include "llvm/Linker/Linker.h"
37 #include "llvm/MC/MCAsmInfo.h"
38 #include "llvm/MC/MCContext.h"
39 #include "llvm/MC/SubtargetFeature.h"
40 #include "llvm/Support/CommandLine.h"
41 #include "llvm/Support/FileSystem.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 static void handleLTODiagnostic(const DiagnosticInfo &DI) {
68   DiagnosticPrinterRawOStream DP(errs());
69   DI.print(DP);
70   errs() << "\n";
71 }
72 
73 LTOCodeGenerator::LTOCodeGenerator()
74     : Context(getGlobalContext()),
75       MergedModule(new Module("ld-temp.o", Context)),
76       IRLinker(MergedModule.get(), handleLTODiagnostic) {
77   initializeLTOPasses();
78 }
79 
80 LTOCodeGenerator::LTOCodeGenerator(std::unique_ptr<LLVMContext> Context)
81     : OwnedContext(std::move(Context)), Context(*OwnedContext),
82       MergedModule(new Module("ld-temp.o", *OwnedContext)),
83       IRLinker(MergedModule.get(), handleLTODiagnostic) {
84   initializeLTOPasses();
85 }
86 
87 LTOCodeGenerator::~LTOCodeGenerator() {}
88 
89 // Initialize LTO passes. Please keep this function in sync with
90 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
91 // passes are initialized.
92 void LTOCodeGenerator::initializeLTOPasses() {
93   PassRegistry &R = *PassRegistry::getPassRegistry();
94 
95   initializeInternalizePassPass(R);
96   initializeIPSCCPPass(R);
97   initializeGlobalOptPass(R);
98   initializeConstantMergePass(R);
99   initializeDAHPass(R);
100   initializeInstructionCombiningPassPass(R);
101   initializeSimpleInlinerPass(R);
102   initializePruneEHPass(R);
103   initializeGlobalDCEPass(R);
104   initializeArgPromotionPass(R);
105   initializeJumpThreadingPass(R);
106   initializeSROALegacyPassPass(R);
107   initializeSROA_DTPass(R);
108   initializeSROA_SSAUpPass(R);
109   initializeFunctionAttrsPass(R);
110   initializeGlobalsAAWrapperPassPass(R);
111   initializeLICMPass(R);
112   initializeMergedLoadStoreMotionPass(R);
113   initializeGVNPass(R);
114   initializeMemCpyOptPass(R);
115   initializeDCEPass(R);
116   initializeCFGSimplifyPassPass(R);
117 }
118 
119 bool LTOCodeGenerator::addModule(LTOModule *Mod) {
120   assert(&Mod->getModule().getContext() == &Context &&
121          "Expected module in same context");
122 
123   bool ret = IRLinker.linkInModule(&Mod->getModule());
124 
125   const std::vector<const char *> &undefs = Mod->getAsmUndefinedRefs();
126   for (int i = 0, e = undefs.size(); i != e; ++i)
127     AsmUndefinedRefs[undefs[i]] = 1;
128 
129   return !ret;
130 }
131 
132 void LTOCodeGenerator::setModule(std::unique_ptr<LTOModule> Mod) {
133   assert(&Mod->getModule().getContext() == &Context &&
134          "Expected module in same context");
135 
136   AsmUndefinedRefs.clear();
137 
138   MergedModule = Mod->takeModule();
139   IRLinker.setModule(MergedModule.get());
140 
141   const std::vector<const char*> &Undefs = Mod->getAsmUndefinedRefs();
142   for (int I = 0, E = Undefs.size(); I != E; ++I)
143     AsmUndefinedRefs[Undefs[I]] = 1;
144 }
145 
146 void LTOCodeGenerator::setTargetOptions(TargetOptions Options) {
147   this->Options = Options;
148 }
149 
150 void LTOCodeGenerator::setDebugInfo(lto_debug_model Debug) {
151   switch (Debug) {
152   case LTO_DEBUG_MODEL_NONE:
153     EmitDwarfDebugInfo = false;
154     return;
155 
156   case LTO_DEBUG_MODEL_DWARF:
157     EmitDwarfDebugInfo = true;
158     return;
159   }
160   llvm_unreachable("Unknown debug format!");
161 }
162 
163 void LTOCodeGenerator::setOptLevel(unsigned Level) {
164   OptLevel = Level;
165   switch (OptLevel) {
166   case 0:
167     CGOptLevel = CodeGenOpt::None;
168     break;
169   case 1:
170     CGOptLevel = CodeGenOpt::Less;
171     break;
172   case 2:
173     CGOptLevel = CodeGenOpt::Default;
174     break;
175   case 3:
176     CGOptLevel = CodeGenOpt::Aggressive;
177     break;
178   }
179 }
180 
181 bool LTOCodeGenerator::writeMergedModules(const char *Path,
182                                           std::string &ErrMsg) {
183   if (!determineTarget(ErrMsg))
184     return false;
185 
186   // mark which symbols can not be internalized
187   applyScopeRestrictions();
188 
189   // create output file
190   std::error_code EC;
191   tool_output_file Out(Path, EC, sys::fs::F_None);
192   if (EC) {
193     ErrMsg = "could not open bitcode file for writing: ";
194     ErrMsg += Path;
195     return false;
196   }
197 
198   // write bitcode to it
199   WriteBitcodeToFile(MergedModule.get(), Out.os(), ShouldEmbedUselists);
200   Out.os().close();
201 
202   if (Out.os().has_error()) {
203     ErrMsg = "could not write bitcode file: ";
204     ErrMsg += Path;
205     Out.os().clear_error();
206     return false;
207   }
208 
209   Out.keep();
210   return true;
211 }
212 
213 bool LTOCodeGenerator::compileOptimizedToFile(const char **Name,
214                                               std::string &ErrMsg) {
215   // make unique temp .o file to put generated object file
216   SmallString<128> Filename;
217   int FD;
218   std::error_code EC =
219       sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
220   if (EC) {
221     ErrMsg = EC.message();
222     return false;
223   }
224 
225   // generate object file
226   tool_output_file objFile(Filename.c_str(), FD);
227 
228   bool genResult = compileOptimized(&objFile.os(), ErrMsg);
229   objFile.os().close();
230   if (objFile.os().has_error()) {
231     objFile.os().clear_error();
232     sys::fs::remove(Twine(Filename));
233     return false;
234   }
235 
236   objFile.keep();
237   if (!genResult) {
238     sys::fs::remove(Twine(Filename));
239     return false;
240   }
241 
242   NativeObjectPath = Filename.c_str();
243   *Name = NativeObjectPath.c_str();
244   return true;
245 }
246 
247 std::unique_ptr<MemoryBuffer>
248 LTOCodeGenerator::compileOptimized(std::string &ErrMsg) {
249   const char *name;
250   if (!compileOptimizedToFile(&name, ErrMsg))
251     return nullptr;
252 
253   // read .o file into memory buffer
254   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
255       MemoryBuffer::getFile(name, -1, false);
256   if (std::error_code EC = BufferOrErr.getError()) {
257     ErrMsg = EC.message();
258     sys::fs::remove(NativeObjectPath);
259     return nullptr;
260   }
261 
262   // remove temp files
263   sys::fs::remove(NativeObjectPath);
264 
265   return std::move(*BufferOrErr);
266 }
267 
268 bool LTOCodeGenerator::compile_to_file(const char **Name, bool DisableInline,
269                                        bool DisableGVNLoadPRE,
270                                        bool DisableVectorization,
271                                        std::string &ErrMsg) {
272   if (!optimize(DisableInline, DisableGVNLoadPRE, DisableVectorization, ErrMsg))
273     return false;
274 
275   return compileOptimizedToFile(Name, ErrMsg);
276 }
277 
278 std::unique_ptr<MemoryBuffer>
279 LTOCodeGenerator::compile(bool DisableInline, bool DisableGVNLoadPRE,
280                           bool DisableVectorization, std::string &ErrMsg) {
281   if (!optimize(DisableInline, DisableGVNLoadPRE, DisableVectorization, ErrMsg))
282     return nullptr;
283 
284   return compileOptimized(ErrMsg);
285 }
286 
287 bool LTOCodeGenerator::determineTarget(std::string &ErrMsg) {
288   if (TargetMach)
289     return true;
290 
291   std::string TripleStr = MergedModule->getTargetTriple();
292   if (TripleStr.empty()) {
293     TripleStr = sys::getDefaultTargetTriple();
294     MergedModule->setTargetTriple(TripleStr);
295   }
296   llvm::Triple Triple(TripleStr);
297 
298   // create target machine from info for merged modules
299   const Target *march = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
300   if (!march)
301     return false;
302 
303   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
304   // the default set of features.
305   SubtargetFeatures Features(MAttr);
306   Features.getDefaultSubtargetFeatures(Triple);
307   FeatureStr = Features.getString();
308   // Set a default CPU for Darwin triples.
309   if (MCpu.empty() && Triple.isOSDarwin()) {
310     if (Triple.getArch() == llvm::Triple::x86_64)
311       MCpu = "core2";
312     else if (Triple.getArch() == llvm::Triple::x86)
313       MCpu = "yonah";
314     else if (Triple.getArch() == llvm::Triple::aarch64)
315       MCpu = "cyclone";
316   }
317 
318   TargetMach.reset(march->createTargetMachine(TripleStr, MCpu, FeatureStr,
319                                               Options, RelocModel,
320                                               CodeModel::Default, CGOptLevel));
321   return true;
322 }
323 
324 void LTOCodeGenerator::
325 applyRestriction(GlobalValue &GV,
326                  ArrayRef<StringRef> Libcalls,
327                  std::vector<const char*> &MustPreserveList,
328                  SmallPtrSetImpl<GlobalValue*> &AsmUsed,
329                  Mangler &Mangler) {
330   // There are no restrictions to apply to declarations.
331   if (GV.isDeclaration())
332     return;
333 
334   // There is nothing more restrictive than private linkage.
335   if (GV.hasPrivateLinkage())
336     return;
337 
338   SmallString<64> Buffer;
339   TargetMach->getNameWithPrefix(Buffer, &GV, Mangler);
340 
341   if (MustPreserveSymbols.count(Buffer))
342     MustPreserveList.push_back(GV.getName().data());
343   if (AsmUndefinedRefs.count(Buffer))
344     AsmUsed.insert(&GV);
345 
346   // Conservatively append user-supplied runtime library functions to
347   // llvm.compiler.used.  These could be internalized and deleted by
348   // optimizations like -globalopt, causing problems when later optimizations
349   // add new library calls (e.g., llvm.memset => memset and printf => puts).
350   // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
351   if (isa<Function>(GV) &&
352       std::binary_search(Libcalls.begin(), Libcalls.end(), GV.getName()))
353     AsmUsed.insert(&GV);
354 }
355 
356 static void findUsedValues(GlobalVariable *LLVMUsed,
357                            SmallPtrSetImpl<GlobalValue*> &UsedValues) {
358   if (!LLVMUsed) return;
359 
360   ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
361   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
362     if (GlobalValue *GV =
363         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
364       UsedValues.insert(GV);
365 }
366 
367 // Collect names of runtime library functions. User-defined functions with the
368 // same names are added to llvm.compiler.used to prevent them from being
369 // deleted by optimizations.
370 static void accumulateAndSortLibcalls(std::vector<StringRef> &Libcalls,
371                                       const TargetLibraryInfo& TLI,
372                                       const Module &Mod,
373                                       const TargetMachine &TM) {
374   // TargetLibraryInfo has info on C runtime library calls on the current
375   // target.
376   for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
377        I != E; ++I) {
378     LibFunc::Func F = static_cast<LibFunc::Func>(I);
379     if (TLI.has(F))
380       Libcalls.push_back(TLI.getName(F));
381   }
382 
383   SmallPtrSet<const TargetLowering *, 1> TLSet;
384 
385   for (const Function &F : Mod) {
386     const TargetLowering *Lowering =
387         TM.getSubtargetImpl(F)->getTargetLowering();
388 
389     if (Lowering && TLSet.insert(Lowering).second)
390       // TargetLowering has info on library calls that CodeGen expects to be
391       // available, both from the C runtime and compiler-rt.
392       for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
393            I != E; ++I)
394         if (const char *Name =
395                 Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
396           Libcalls.push_back(Name);
397   }
398 
399   array_pod_sort(Libcalls.begin(), Libcalls.end());
400   Libcalls.erase(std::unique(Libcalls.begin(), Libcalls.end()),
401                  Libcalls.end());
402 }
403 
404 void LTOCodeGenerator::applyScopeRestrictions() {
405   if (ScopeRestrictionsDone || !ShouldInternalize)
406     return;
407 
408   // Start off with a verification pass.
409   legacy::PassManager passes;
410   passes.add(createVerifierPass());
411 
412   // mark which symbols can not be internalized
413   Mangler Mangler;
414   std::vector<const char*> MustPreserveList;
415   SmallPtrSet<GlobalValue*, 8> AsmUsed;
416   std::vector<StringRef> Libcalls;
417   TargetLibraryInfoImpl TLII(Triple(TargetMach->getTargetTriple()));
418   TargetLibraryInfo TLI(TLII);
419 
420   accumulateAndSortLibcalls(Libcalls, TLI, *MergedModule, *TargetMach);
421 
422   for (Function &f : *MergedModule)
423     applyRestriction(f, Libcalls, MustPreserveList, AsmUsed, Mangler);
424   for (GlobalVariable &v : MergedModule->globals())
425     applyRestriction(v, Libcalls, MustPreserveList, AsmUsed, Mangler);
426   for (GlobalAlias &a : MergedModule->aliases())
427     applyRestriction(a, Libcalls, MustPreserveList, AsmUsed, Mangler);
428 
429   GlobalVariable *LLVMCompilerUsed =
430     MergedModule->getGlobalVariable("llvm.compiler.used");
431   findUsedValues(LLVMCompilerUsed, AsmUsed);
432   if (LLVMCompilerUsed)
433     LLVMCompilerUsed->eraseFromParent();
434 
435   if (!AsmUsed.empty()) {
436     llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
437     std::vector<Constant*> asmUsed2;
438     for (auto *GV : AsmUsed) {
439       Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
440       asmUsed2.push_back(c);
441     }
442 
443     llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
444     LLVMCompilerUsed =
445       new llvm::GlobalVariable(*MergedModule, ATy, false,
446                                llvm::GlobalValue::AppendingLinkage,
447                                llvm::ConstantArray::get(ATy, asmUsed2),
448                                "llvm.compiler.used");
449 
450     LLVMCompilerUsed->setSection("llvm.metadata");
451   }
452 
453   passes.add(createInternalizePass(MustPreserveList));
454 
455   // apply scope restrictions
456   passes.run(*MergedModule);
457 
458   ScopeRestrictionsDone = true;
459 }
460 
461 /// Optimize merged modules using various IPO passes
462 bool LTOCodeGenerator::optimize(bool DisableInline, bool DisableGVNLoadPRE,
463                                 bool DisableVectorization,
464                                 std::string &ErrMsg) {
465   if (!this->determineTarget(ErrMsg))
466     return false;
467 
468   // Mark which symbols can not be internalized
469   this->applyScopeRestrictions();
470 
471   // Instantiate the pass manager to organize the passes.
472   legacy::PassManager passes;
473 
474   // Add an appropriate DataLayout instance for this module...
475   MergedModule->setDataLayout(TargetMach->createDataLayout());
476 
477   passes.add(
478       createTargetTransformInfoWrapperPass(TargetMach->getTargetIRAnalysis()));
479 
480   Triple TargetTriple(TargetMach->getTargetTriple());
481   PassManagerBuilder PMB;
482   PMB.DisableGVNLoadPRE = DisableGVNLoadPRE;
483   PMB.LoopVectorize = !DisableVectorization;
484   PMB.SLPVectorize = !DisableVectorization;
485   if (!DisableInline)
486     PMB.Inliner = createFunctionInliningPass();
487   PMB.LibraryInfo = new TargetLibraryInfoImpl(TargetTriple);
488   PMB.OptLevel = OptLevel;
489   PMB.VerifyInput = true;
490   PMB.VerifyOutput = true;
491 
492   PMB.populateLTOPassManager(passes);
493 
494   // Run our queue of passes all at once now, efficiently.
495   passes.run(*MergedModule);
496 
497   return true;
498 }
499 
500 bool LTOCodeGenerator::compileOptimized(ArrayRef<raw_pwrite_stream *> Out,
501                                         std::string &ErrMsg) {
502   if (!this->determineTarget(ErrMsg))
503     return false;
504 
505   legacy::PassManager preCodeGenPasses;
506 
507   // If the bitcode files contain ARC code and were compiled with optimization,
508   // the ObjCARCContractPass must be run, so do it unconditionally here.
509   preCodeGenPasses.add(createObjCARCContractPass());
510   preCodeGenPasses.run(*MergedModule);
511 
512   // Do code generation. We need to preserve the module in case the client calls
513   // writeMergedModules() after compilation, but we only need to allow this at
514   // parallelism level 1. This is achieved by having splitCodeGen return the
515   // original module at parallelism level 1 which we then assign back to
516   // MergedModule.
517   MergedModule =
518       splitCodeGen(std::move(MergedModule), Out, MCpu, FeatureStr, Options,
519                    RelocModel, CodeModel::Default, CGOptLevel);
520 
521   return true;
522 }
523 
524 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
525 /// LTO problems.
526 void LTOCodeGenerator::setCodeGenDebugOptions(const char *Options) {
527   for (std::pair<StringRef, StringRef> o = getToken(Options); !o.first.empty();
528        o = getToken(o.second))
529     CodegenOptions.push_back(o.first);
530 }
531 
532 void LTOCodeGenerator::parseCodeGenDebugOptions() {
533   // if options were requested, set them
534   if (!CodegenOptions.empty()) {
535     // ParseCommandLineOptions() expects argv[0] to be program name.
536     std::vector<const char *> CodegenArgv(1, "libLLVMLTO");
537     for (std::string &Arg : CodegenOptions)
538       CodegenArgv.push_back(Arg.c_str());
539     cl::ParseCommandLineOptions(CodegenArgv.size(), CodegenArgv.data());
540   }
541 }
542 
543 void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI,
544                                          void *Context) {
545   ((LTOCodeGenerator *)Context)->DiagnosticHandler2(DI);
546 }
547 
548 void LTOCodeGenerator::DiagnosticHandler2(const DiagnosticInfo &DI) {
549   // Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
550   lto_codegen_diagnostic_severity_t Severity;
551   switch (DI.getSeverity()) {
552   case DS_Error:
553     Severity = LTO_DS_ERROR;
554     break;
555   case DS_Warning:
556     Severity = LTO_DS_WARNING;
557     break;
558   case DS_Remark:
559     Severity = LTO_DS_REMARK;
560     break;
561   case DS_Note:
562     Severity = LTO_DS_NOTE;
563     break;
564   }
565   // Create the string that will be reported to the external diagnostic handler.
566   std::string MsgStorage;
567   raw_string_ostream Stream(MsgStorage);
568   DiagnosticPrinterRawOStream DP(Stream);
569   DI.print(DP);
570   Stream.flush();
571 
572   // If this method has been called it means someone has set up an external
573   // diagnostic handler. Assert on that.
574   assert(DiagHandler && "Invalid diagnostic handler");
575   (*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
576 }
577 
578 void
579 LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
580                                        void *Ctxt) {
581   this->DiagHandler = DiagHandler;
582   this->DiagContext = Ctxt;
583   if (!DiagHandler)
584     return Context.setDiagnosticHandler(nullptr, nullptr);
585   // Register the LTOCodeGenerator stub in the LLVMContext to forward the
586   // diagnostic to the external DiagHandler.
587   Context.setDiagnosticHandler(LTOCodeGenerator::DiagnosticHandler, this,
588                                /* RespectFilters */ true);
589 }
590