1 //===--- BackendUtil.cpp - LLVM Backend Utilities -------------------------===//
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 #include "clang/CodeGen/BackendUtil.h"
11 #include "clang/Basic/Diagnostic.h"
12 #include "clang/Basic/TargetOptions.h"
13 #include "clang/Frontend/CodeGenOptions.h"
14 #include "clang/Frontend/FrontendDiagnostic.h"
15 #include "llvm/Module.h"
16 #include "llvm/PassManager.h"
17 #include "llvm/Assembly/PrintModulePass.h"
18 #include "llvm/Bitcode/ReaderWriter.h"
19 #include "llvm/CodeGen/RegAllocRegistry.h"
20 #include "llvm/CodeGen/SchedulerRegistry.h"
21 #include "llvm/Support/CommandLine.h"
22 #include "llvm/Support/FormattedStream.h"
23 #include "llvm/Support/PrettyStackTrace.h"
24 #include "llvm/Support/PassManagerBuilder.h"
25 #include "llvm/Support/Timer.h"
26 #include "llvm/Support/raw_ostream.h"
27 #include "llvm/Target/SubtargetFeature.h"
28 #include "llvm/Target/TargetData.h"
29 #include "llvm/Target/TargetMachine.h"
30 #include "llvm/Target/TargetOptions.h"
31 #include "llvm/Target/TargetRegistry.h"
32 #include "llvm/Transforms/Instrumentation.h"
33 using namespace clang;
34 using namespace llvm;
35 
36 namespace {
37 
38 class EmitAssemblyHelper {
39   Diagnostic &Diags;
40   const CodeGenOptions &CodeGenOpts;
41   const TargetOptions &TargetOpts;
42   Module *TheModule;
43 
44   Timer CodeGenerationTime;
45 
46   mutable PassManager *CodeGenPasses;
47   mutable PassManager *PerModulePasses;
48   mutable FunctionPassManager *PerFunctionPasses;
49 
50 private:
51   PassManager *getCodeGenPasses() const {
52     if (!CodeGenPasses) {
53       CodeGenPasses = new PassManager();
54       CodeGenPasses->add(new TargetData(TheModule));
55     }
56     return CodeGenPasses;
57   }
58 
59   PassManager *getPerModulePasses() const {
60     if (!PerModulePasses) {
61       PerModulePasses = new PassManager();
62       PerModulePasses->add(new TargetData(TheModule));
63     }
64     return PerModulePasses;
65   }
66 
67   FunctionPassManager *getPerFunctionPasses() const {
68     if (!PerFunctionPasses) {
69       PerFunctionPasses = new FunctionPassManager(TheModule);
70       PerFunctionPasses->add(new TargetData(TheModule));
71     }
72     return PerFunctionPasses;
73   }
74 
75   void CreatePasses();
76 
77   /// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
78   ///
79   /// \return True on success.
80   bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS);
81 
82 public:
83   EmitAssemblyHelper(Diagnostic &_Diags,
84                      const CodeGenOptions &CGOpts, const TargetOptions &TOpts,
85                      Module *M)
86     : Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts),
87       TheModule(M), CodeGenerationTime("Code Generation Time"),
88       CodeGenPasses(0), PerModulePasses(0), PerFunctionPasses(0) {}
89 
90   ~EmitAssemblyHelper() {
91     delete CodeGenPasses;
92     delete PerModulePasses;
93     delete PerFunctionPasses;
94   }
95 
96   void EmitAssembly(BackendAction Action, raw_ostream *OS);
97 };
98 
99 }
100 
101 void EmitAssemblyHelper::CreatePasses() {
102   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
103   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.Inlining;
104 
105   // Handle disabling of LLVM optimization, where we want to preserve the
106   // internal module before any optimization.
107   if (CodeGenOpts.DisableLLVMOpts) {
108     OptLevel = 0;
109     Inlining = CodeGenOpts.NoInlining;
110   }
111 
112   PassManagerBuilder PMBuilder;
113   PMBuilder.OptLevel = OptLevel;
114   PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;
115 
116   PMBuilder.DisableSimplifyLibCalls = !CodeGenOpts.SimplifyLibCalls;
117   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
118   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
119 
120   // Figure out TargetLibraryInfo.
121   Triple TargetTriple(TheModule->getTargetTriple());
122   PMBuilder.LibraryInfo = new TargetLibraryInfo(TargetTriple);
123   if (!CodeGenOpts.SimplifyLibCalls)
124     PMBuilder.LibraryInfo->disableAllFunctions();
125 
126   switch (Inlining) {
127   case CodeGenOptions::NoInlining: break;
128   case CodeGenOptions::NormalInlining: {
129     // FIXME: Derive these constants in a principled fashion.
130     unsigned Threshold = 225;
131     if (CodeGenOpts.OptimizeSize == 1)      // -Os
132       Threshold = 75;
133     else if (CodeGenOpts.OptimizeSize == 2) // -Oz
134       Threshold = 25;
135     else if (OptLevel > 2)
136       Threshold = 275;
137     PMBuilder.Inliner = createFunctionInliningPass(Threshold);
138     break;
139   }
140   case CodeGenOptions::OnlyAlwaysInlining:
141     // Respect always_inline.
142     PMBuilder.Inliner = createAlwaysInlinerPass();
143     break;
144   }
145 
146 
147   // Set up the per-function pass manager.
148   FunctionPassManager *FPM = getPerFunctionPasses();
149   if (CodeGenOpts.VerifyModule)
150     FPM->add(createVerifierPass());
151   PMBuilder.populateFunctionPassManager(*FPM);
152 
153   // Set up the per-module pass manager.
154   PassManager *MPM = getPerModulePasses();
155 
156   if (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes) {
157     MPM->add(createGCOVProfilerPass(CodeGenOpts.EmitGcovNotes,
158                                     CodeGenOpts.EmitGcovArcs,
159                                     TargetTriple.isMacOSX()));
160 
161     if (!CodeGenOpts.DebugInfo)
162       MPM->add(createStripSymbolsPass(true));
163   }
164 
165 
166   PMBuilder.populateModulePassManager(*MPM);
167 }
168 
169 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
170                                        formatted_raw_ostream &OS) {
171   // Create the TargetMachine for generating code.
172   std::string Error;
173   std::string Triple = TheModule->getTargetTriple();
174   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
175   if (!TheTarget) {
176     Diags.Report(diag::err_fe_unable_to_create_target) << Error;
177     return false;
178   }
179 
180   // FIXME: Expose these capabilities via actual APIs!!!! Aside from just
181   // being gross, this is also totally broken if we ever care about
182   // concurrency.
183 
184   // Set frame pointer elimination mode.
185   if (!CodeGenOpts.DisableFPElim) {
186     llvm::NoFramePointerElim = false;
187     llvm::NoFramePointerElimNonLeaf = false;
188   } else if (CodeGenOpts.OmitLeafFramePointer) {
189     llvm::NoFramePointerElim = false;
190     llvm::NoFramePointerElimNonLeaf = true;
191   } else {
192     llvm::NoFramePointerElim = true;
193     llvm::NoFramePointerElimNonLeaf = true;
194   }
195 
196   // Set float ABI type.
197   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
198     llvm::FloatABIType = llvm::FloatABI::Soft;
199   else if (CodeGenOpts.FloatABI == "hard")
200     llvm::FloatABIType = llvm::FloatABI::Hard;
201   else {
202     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
203     llvm::FloatABIType = llvm::FloatABI::Default;
204   }
205 
206   llvm::LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
207   llvm::NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
208   llvm::NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
209   NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
210   llvm::UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
211   llvm::UseSoftFloat = CodeGenOpts.SoftFloat;
212 
213   TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);
214 
215   TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
216   TargetMachine::setDataSections    (CodeGenOpts.DataSections);
217 
218   // FIXME: Parse this earlier.
219   if (CodeGenOpts.RelocationModel == "static") {
220     TargetMachine::setRelocationModel(llvm::Reloc::Static);
221   } else if (CodeGenOpts.RelocationModel == "pic") {
222     TargetMachine::setRelocationModel(llvm::Reloc::PIC_);
223   } else {
224     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
225            "Invalid PIC model!");
226     TargetMachine::setRelocationModel(llvm::Reloc::DynamicNoPIC);
227   }
228   // FIXME: Parse this earlier.
229   if (CodeGenOpts.CodeModel == "small") {
230     TargetMachine::setCodeModel(llvm::CodeModel::Small);
231   } else if (CodeGenOpts.CodeModel == "kernel") {
232     TargetMachine::setCodeModel(llvm::CodeModel::Kernel);
233   } else if (CodeGenOpts.CodeModel == "medium") {
234     TargetMachine::setCodeModel(llvm::CodeModel::Medium);
235   } else if (CodeGenOpts.CodeModel == "large") {
236     TargetMachine::setCodeModel(llvm::CodeModel::Large);
237   } else {
238     assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
239     TargetMachine::setCodeModel(llvm::CodeModel::Default);
240   }
241 
242   std::vector<const char *> BackendArgs;
243   BackendArgs.push_back("clang"); // Fake program name.
244   if (!CodeGenOpts.DebugPass.empty()) {
245     BackendArgs.push_back("-debug-pass");
246     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
247   }
248   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
249     BackendArgs.push_back("-limit-float-precision");
250     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
251   }
252   if (llvm::TimePassesIsEnabled)
253     BackendArgs.push_back("-time-passes");
254   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
255     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
256   BackendArgs.push_back(0);
257   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
258                                     const_cast<char **>(&BackendArgs[0]));
259 
260   std::string FeaturesStr;
261   if (TargetOpts.CPU.size() || TargetOpts.Features.size()) {
262     SubtargetFeatures Features;
263     Features.setCPU(TargetOpts.CPU);
264     for (std::vector<std::string>::const_iterator
265            it = TargetOpts.Features.begin(),
266            ie = TargetOpts.Features.end(); it != ie; ++it)
267       Features.AddFeature(*it);
268     FeaturesStr = Features.getString();
269   }
270   TargetMachine *TM = TheTarget->createTargetMachine(Triple, FeaturesStr);
271 
272   if (CodeGenOpts.RelaxAll)
273     TM->setMCRelaxAll(true);
274   if (CodeGenOpts.SaveTempLabels)
275     TM->setMCSaveTempLabels(true);
276   if (CodeGenOpts.NoDwarf2CFIAsm)
277     TM->setMCUseCFI(false);
278 
279   // Create the code generator passes.
280   PassManager *PM = getCodeGenPasses();
281   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
282 
283   switch (CodeGenOpts.OptimizationLevel) {
284   default: break;
285   case 0: OptLevel = CodeGenOpt::None; break;
286   case 3: OptLevel = CodeGenOpt::Aggressive; break;
287   }
288 
289   // Normal mode, emit a .s or .o file by running the code generator. Note,
290   // this also adds codegenerator level optimization passes.
291   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
292   if (Action == Backend_EmitObj)
293     CGFT = TargetMachine::CGFT_ObjectFile;
294   else if (Action == Backend_EmitMCNull)
295     CGFT = TargetMachine::CGFT_Null;
296   else
297     assert(Action == Backend_EmitAssembly && "Invalid action!");
298   if (TM->addPassesToEmitFile(*PM, OS, CGFT, OptLevel,
299                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
300     Diags.Report(diag::err_fe_unable_to_interface_with_target);
301     return false;
302   }
303 
304   return true;
305 }
306 
307 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
308   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
309   llvm::formatted_raw_ostream FormattedOS;
310 
311   CreatePasses();
312   switch (Action) {
313   case Backend_EmitNothing:
314     break;
315 
316   case Backend_EmitBC:
317     getPerModulePasses()->add(createBitcodeWriterPass(*OS));
318     break;
319 
320   case Backend_EmitLL:
321     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
322     getPerModulePasses()->add(createPrintModulePass(&FormattedOS));
323     break;
324 
325   default:
326     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
327     if (!AddEmitPasses(Action, FormattedOS))
328       return;
329   }
330 
331   // Before executing passes, print the final values of the LLVM options.
332   cl::PrintOptionValues();
333 
334   // Run passes. For now we do all passes at once, but eventually we
335   // would like to have the option of streaming code generation.
336 
337   if (PerFunctionPasses) {
338     PrettyStackTraceString CrashInfo("Per-function optimization");
339 
340     PerFunctionPasses->doInitialization();
341     for (Module::iterator I = TheModule->begin(),
342            E = TheModule->end(); I != E; ++I)
343       if (!I->isDeclaration())
344         PerFunctionPasses->run(*I);
345     PerFunctionPasses->doFinalization();
346   }
347 
348   if (PerModulePasses) {
349     PrettyStackTraceString CrashInfo("Per-module optimization passes");
350     PerModulePasses->run(*TheModule);
351   }
352 
353   if (CodeGenPasses) {
354     PrettyStackTraceString CrashInfo("Code generation");
355     CodeGenPasses->run(*TheModule);
356   }
357 }
358 
359 void clang::EmitBackendOutput(Diagnostic &Diags, const CodeGenOptions &CGOpts,
360                               const TargetOptions &TOpts, Module *M,
361                               BackendAction Action, raw_ostream *OS) {
362   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, M);
363 
364   AsmHelper.EmitAssembly(Action, OS);
365 }
366