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/StandardPasses.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/TargetLibraryInfo.h"
30 #include "llvm/Target/TargetMachine.h"
31 #include "llvm/Target/TargetOptions.h"
32 #include "llvm/Target/TargetRegistry.h"
33 #include "llvm/Transforms/Instrumentation.h"
34 using namespace clang;
35 using namespace llvm;
36 
37 namespace {
38 
39 class EmitAssemblyHelper {
40   Diagnostic &Diags;
41   const CodeGenOptions &CodeGenOpts;
42   const TargetOptions &TargetOpts;
43   Module *TheModule;
44 
45   Timer CodeGenerationTime;
46 
47   mutable PassManager *CodeGenPasses;
48   mutable PassManager *PerModulePasses;
49   mutable FunctionPassManager *PerFunctionPasses;
50 
51 private:
52   PassManager *getCodeGenPasses() const {
53     if (!CodeGenPasses) {
54       CodeGenPasses = new PassManager();
55       CodeGenPasses->add(new TargetData(TheModule));
56     }
57     return CodeGenPasses;
58   }
59 
60   PassManager *getPerModulePasses() const {
61     if (!PerModulePasses) {
62       PerModulePasses = new PassManager();
63       PerModulePasses->add(new TargetData(TheModule));
64     }
65     return PerModulePasses;
66   }
67 
68   FunctionPassManager *getPerFunctionPasses() const {
69     if (!PerFunctionPasses) {
70       PerFunctionPasses = new FunctionPassManager(TheModule);
71       PerFunctionPasses->add(new TargetData(TheModule));
72     }
73     return PerFunctionPasses;
74   }
75 
76   void CreatePasses();
77 
78   /// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
79   ///
80   /// \return True on success.
81   bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS);
82 
83 public:
84   EmitAssemblyHelper(Diagnostic &_Diags,
85                      const CodeGenOptions &CGOpts, const TargetOptions &TOpts,
86                      Module *M)
87     : Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts),
88       TheModule(M), CodeGenerationTime("Code Generation Time"),
89       CodeGenPasses(0), PerModulePasses(0), PerFunctionPasses(0) {}
90 
91   ~EmitAssemblyHelper() {
92     delete CodeGenPasses;
93     delete PerModulePasses;
94     delete PerFunctionPasses;
95   }
96 
97   void EmitAssembly(BackendAction Action, raw_ostream *OS);
98 };
99 
100 }
101 
102 void EmitAssemblyHelper::CreatePasses() {
103   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
104   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.Inlining;
105 
106   // Handle disabling of LLVM optimization, where we want to preserve the
107   // internal module before any optimization.
108   if (CodeGenOpts.DisableLLVMOpts) {
109     OptLevel = 0;
110     Inlining = CodeGenOpts.NoInlining;
111   }
112 
113   FunctionPassManager *FPM = getPerFunctionPasses();
114 
115   TargetLibraryInfo *TLI =
116     new TargetLibraryInfo(Triple(TheModule->getTargetTriple()));
117   if (!CodeGenOpts.SimplifyLibCalls)
118     TLI->disableAllFunctions();
119   FPM->add(TLI);
120 
121   // In -O0 if checking is disabled, we don't even have per-function passes.
122   if (CodeGenOpts.VerifyModule)
123     FPM->add(createVerifierPass());
124 
125   // Assume that standard function passes aren't run for -O0.
126   if (OptLevel > 0)
127     llvm::createStandardFunctionPasses(FPM, OptLevel);
128 
129   llvm::Pass *InliningPass = 0;
130   switch (Inlining) {
131   case CodeGenOptions::NoInlining: break;
132   case CodeGenOptions::NormalInlining: {
133     // Set the inline threshold following llvm-gcc.
134     //
135     // FIXME: Derive these constants in a principled fashion.
136     unsigned Threshold = 225;
137     if (CodeGenOpts.OptimizeSize)
138       Threshold = 75;
139     else if (OptLevel > 2)
140       Threshold = 275;
141     InliningPass = createFunctionInliningPass(Threshold);
142     break;
143   }
144   case CodeGenOptions::OnlyAlwaysInlining:
145     InliningPass = createAlwaysInlinerPass();         // Respect always_inline
146     break;
147   }
148 
149   PassManager *MPM = getPerModulePasses();
150 
151   TLI = new TargetLibraryInfo(Triple(TheModule->getTargetTriple()));
152   if (!CodeGenOpts.SimplifyLibCalls)
153     TLI->disableAllFunctions();
154   MPM->add(TLI);
155 
156   if (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes) {
157     MPM->add(createGCOVProfilerPass(CodeGenOpts.EmitGcovNotes,
158                                     CodeGenOpts.EmitGcovArcs));
159     if (!CodeGenOpts.DebugInfo)
160       MPM->add(createStripSymbolsPass(true));
161   }
162 
163   // For now we always create per module passes.
164   llvm::createStandardModulePasses(MPM, OptLevel,
165                                    CodeGenOpts.OptimizeSize,
166                                    CodeGenOpts.UnitAtATime,
167                                    CodeGenOpts.UnrollLoops,
168                                    CodeGenOpts.SimplifyLibCalls,
169                                    /*HaveExceptions=*/true,
170                                    InliningPass);
171 }
172 
173 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
174                                        formatted_raw_ostream &OS) {
175   // Create the TargetMachine for generating code.
176   std::string Error;
177   std::string Triple = TheModule->getTargetTriple();
178   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
179   if (!TheTarget) {
180     Diags.Report(diag::err_fe_unable_to_create_target) << Error;
181     return false;
182   }
183 
184   // FIXME: Expose these capabilities via actual APIs!!!! Aside from just
185   // being gross, this is also totally broken if we ever care about
186   // concurrency.
187 
188   // Set frame pointer elimination mode.
189   if (!CodeGenOpts.DisableFPElim) {
190     llvm::NoFramePointerElim = false;
191     llvm::NoFramePointerElimNonLeaf = false;
192   } else if (CodeGenOpts.OmitLeafFramePointer) {
193     llvm::NoFramePointerElim = false;
194     llvm::NoFramePointerElimNonLeaf = true;
195   } else {
196     llvm::NoFramePointerElim = true;
197     llvm::NoFramePointerElimNonLeaf = true;
198   }
199 
200   // Set float ABI type.
201   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
202     llvm::FloatABIType = llvm::FloatABI::Soft;
203   else if (CodeGenOpts.FloatABI == "hard")
204     llvm::FloatABIType = llvm::FloatABI::Hard;
205   else {
206     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
207     llvm::FloatABIType = llvm::FloatABI::Default;
208   }
209 
210   llvm::LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
211   llvm::NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
212   llvm::NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
213   NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
214   llvm::UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
215   llvm::UseSoftFloat = CodeGenOpts.SoftFloat;
216   UnwindTablesMandatory = CodeGenOpts.UnwindTables;
217 
218   TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);
219 
220   TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
221   TargetMachine::setDataSections    (CodeGenOpts.DataSections);
222 
223   // FIXME: Parse this earlier.
224   if (CodeGenOpts.RelocationModel == "static") {
225     TargetMachine::setRelocationModel(llvm::Reloc::Static);
226   } else if (CodeGenOpts.RelocationModel == "pic") {
227     TargetMachine::setRelocationModel(llvm::Reloc::PIC_);
228   } else {
229     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
230            "Invalid PIC model!");
231     TargetMachine::setRelocationModel(llvm::Reloc::DynamicNoPIC);
232   }
233   // FIXME: Parse this earlier.
234   if (CodeGenOpts.CodeModel == "small") {
235     TargetMachine::setCodeModel(llvm::CodeModel::Small);
236   } else if (CodeGenOpts.CodeModel == "kernel") {
237     TargetMachine::setCodeModel(llvm::CodeModel::Kernel);
238   } else if (CodeGenOpts.CodeModel == "medium") {
239     TargetMachine::setCodeModel(llvm::CodeModel::Medium);
240   } else if (CodeGenOpts.CodeModel == "large") {
241     TargetMachine::setCodeModel(llvm::CodeModel::Large);
242   } else {
243     assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
244     TargetMachine::setCodeModel(llvm::CodeModel::Default);
245   }
246 
247   std::vector<const char *> BackendArgs;
248   BackendArgs.push_back("clang"); // Fake program name.
249   if (!CodeGenOpts.DebugPass.empty()) {
250     BackendArgs.push_back("-debug-pass");
251     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
252   }
253   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
254     BackendArgs.push_back("-limit-float-precision");
255     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
256   }
257   if (llvm::TimePassesIsEnabled)
258     BackendArgs.push_back("-time-passes");
259   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
260     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
261   BackendArgs.push_back(0);
262   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
263                                     const_cast<char **>(&BackendArgs[0]));
264 
265   std::string FeaturesStr;
266   if (TargetOpts.CPU.size() || TargetOpts.Features.size()) {
267     SubtargetFeatures Features;
268     Features.setCPU(TargetOpts.CPU);
269     for (std::vector<std::string>::const_iterator
270            it = TargetOpts.Features.begin(),
271            ie = TargetOpts.Features.end(); it != ie; ++it)
272       Features.AddFeature(*it);
273     FeaturesStr = Features.getString();
274   }
275   TargetMachine *TM = TheTarget->createTargetMachine(Triple, FeaturesStr);
276 
277   if (CodeGenOpts.RelaxAll)
278     TM->setMCRelaxAll(true);
279   if (CodeGenOpts.SaveTempLabels)
280     TM->setMCSaveTempLabels(true);
281 
282   // Create the code generator passes.
283   PassManager *PM = getCodeGenPasses();
284   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
285 
286   switch (CodeGenOpts.OptimizationLevel) {
287   default: break;
288   case 0: OptLevel = CodeGenOpt::None; break;
289   case 3: OptLevel = CodeGenOpt::Aggressive; break;
290   }
291 
292   // Normal mode, emit a .s or .o file by running the code generator. Note,
293   // this also adds codegenerator level optimization passes.
294   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
295   if (Action == Backend_EmitObj)
296     CGFT = TargetMachine::CGFT_ObjectFile;
297   else if (Action == Backend_EmitMCNull)
298     CGFT = TargetMachine::CGFT_Null;
299   else
300     assert(Action == Backend_EmitAssembly && "Invalid action!");
301   if (TM->addPassesToEmitFile(*PM, OS, CGFT, OptLevel,
302                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
303     Diags.Report(diag::err_fe_unable_to_interface_with_target);
304     return false;
305   }
306 
307   return true;
308 }
309 
310 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
311   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
312   llvm::formatted_raw_ostream FormattedOS;
313 
314   CreatePasses();
315   switch (Action) {
316   case Backend_EmitNothing:
317     break;
318 
319   case Backend_EmitBC:
320     getPerModulePasses()->add(createBitcodeWriterPass(*OS));
321     break;
322 
323   case Backend_EmitLL:
324     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
325     getPerModulePasses()->add(createPrintModulePass(&FormattedOS));
326     break;
327 
328   default:
329     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
330     if (!AddEmitPasses(Action, FormattedOS))
331       return;
332   }
333 
334   // Before executing passes, print the final values of the LLVM options.
335   cl::PrintOptionValues();
336 
337   // Run passes. For now we do all passes at once, but eventually we
338   // would like to have the option of streaming code generation.
339 
340   if (PerFunctionPasses) {
341     PrettyStackTraceString CrashInfo("Per-function optimization");
342 
343     PerFunctionPasses->doInitialization();
344     for (Module::iterator I = TheModule->begin(),
345            E = TheModule->end(); I != E; ++I)
346       if (!I->isDeclaration())
347         PerFunctionPasses->run(*I);
348     PerFunctionPasses->doFinalization();
349   }
350 
351   if (PerModulePasses) {
352     PrettyStackTraceString CrashInfo("Per-module optimization passes");
353     PerModulePasses->run(*TheModule);
354   }
355 
356   if (CodeGenPasses) {
357     PrettyStackTraceString CrashInfo("Code generation");
358     CodeGenPasses->run(*TheModule);
359   }
360 }
361 
362 void clang::EmitBackendOutput(Diagnostic &Diags, const CodeGenOptions &CGOpts,
363                               const TargetOptions &TOpts, Module *M,
364                               BackendAction Action, raw_ostream *OS) {
365   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, M);
366 
367   AsmHelper.EmitAssembly(Action, OS);
368 }
369