BackendUtil.cpp revision 221345 
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"
34using namespace clang;
35using namespace llvm;
36
37namespace {
38
39class 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
51private:
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
83public:
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
102void 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 == 1) //-Os
138      Threshold = 75;
139    else if (CodeGenOpts.OptimizeSize == 2) //-Oz
140      Threshold = 25;
141    else if (OptLevel > 2)
142      Threshold = 275;
143    InliningPass = createFunctionInliningPass(Threshold);
144    break;
145  }
146  case CodeGenOptions::OnlyAlwaysInlining:
147    InliningPass = createAlwaysInlinerPass();         // Respect always_inline
148    break;
149  }
150
151  PassManager *MPM = getPerModulePasses();
152
153  TLI = new TargetLibraryInfo(Triple(TheModule->getTargetTriple()));
154  if (!CodeGenOpts.SimplifyLibCalls)
155    TLI->disableAllFunctions();
156  MPM->add(TLI);
157
158  if (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes) {
159    MPM->add(createGCOVProfilerPass(CodeGenOpts.EmitGcovNotes,
160                                    CodeGenOpts.EmitGcovArcs));
161    if (!CodeGenOpts.DebugInfo)
162      MPM->add(createStripSymbolsPass(true));
163  }
164
165  // For now we always create per module passes.
166  llvm::createStandardModulePasses(MPM, OptLevel,
167                                   CodeGenOpts.OptimizeSize,
168                                   CodeGenOpts.UnitAtATime,
169                                   CodeGenOpts.UnrollLoops,
170                                   CodeGenOpts.SimplifyLibCalls,
171                                   /*HaveExceptions=*/true,
172                                   InliningPass);
173}
174
175bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
176                                       formatted_raw_ostream &OS) {
177  // Create the TargetMachine for generating code.
178  std::string Error;
179  std::string Triple = TheModule->getTargetTriple();
180  const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
181  if (!TheTarget) {
182    Diags.Report(diag::err_fe_unable_to_create_target) << Error;
183    return false;
184  }
185
186  // FIXME: Expose these capabilities via actual APIs!!!! Aside from just
187  // being gross, this is also totally broken if we ever care about
188  // concurrency.
189
190  // Set frame pointer elimination mode.
191  if (!CodeGenOpts.DisableFPElim) {
192    llvm::NoFramePointerElim = false;
193    llvm::NoFramePointerElimNonLeaf = false;
194  } else if (CodeGenOpts.OmitLeafFramePointer) {
195    llvm::NoFramePointerElim = false;
196    llvm::NoFramePointerElimNonLeaf = true;
197  } else {
198    llvm::NoFramePointerElim = true;
199    llvm::NoFramePointerElimNonLeaf = true;
200  }
201
202  // Set float ABI type.
203  if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
204    llvm::FloatABIType = llvm::FloatABI::Soft;
205  else if (CodeGenOpts.FloatABI == "hard")
206    llvm::FloatABIType = llvm::FloatABI::Hard;
207  else {
208    assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
209    llvm::FloatABIType = llvm::FloatABI::Default;
210  }
211
212  llvm::LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
213  llvm::NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
214  llvm::NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
215  NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
216  llvm::UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
217  llvm::UseSoftFloat = CodeGenOpts.SoftFloat;
218  UnwindTablesMandatory = CodeGenOpts.UnwindTables;
219
220  TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);
221
222  TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
223  TargetMachine::setDataSections    (CodeGenOpts.DataSections);
224
225  // FIXME: Parse this earlier.
226  if (CodeGenOpts.RelocationModel == "static") {
227    TargetMachine::setRelocationModel(llvm::Reloc::Static);
228  } else if (CodeGenOpts.RelocationModel == "pic") {
229    TargetMachine::setRelocationModel(llvm::Reloc::PIC_);
230  } else {
231    assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
232           "Invalid PIC model!");
233    TargetMachine::setRelocationModel(llvm::Reloc::DynamicNoPIC);
234  }
235  // FIXME: Parse this earlier.
236  if (CodeGenOpts.CodeModel == "small") {
237    TargetMachine::setCodeModel(llvm::CodeModel::Small);
238  } else if (CodeGenOpts.CodeModel == "kernel") {
239    TargetMachine::setCodeModel(llvm::CodeModel::Kernel);
240  } else if (CodeGenOpts.CodeModel == "medium") {
241    TargetMachine::setCodeModel(llvm::CodeModel::Medium);
242  } else if (CodeGenOpts.CodeModel == "large") {
243    TargetMachine::setCodeModel(llvm::CodeModel::Large);
244  } else {
245    assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
246    TargetMachine::setCodeModel(llvm::CodeModel::Default);
247  }
248
249  std::vector<const char *> BackendArgs;
250  BackendArgs.push_back("clang"); // Fake program name.
251  if (!CodeGenOpts.DebugPass.empty()) {
252    BackendArgs.push_back("-debug-pass");
253    BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
254  }
255  if (!CodeGenOpts.LimitFloatPrecision.empty()) {
256    BackendArgs.push_back("-limit-float-precision");
257    BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
258  }
259  if (llvm::TimePassesIsEnabled)
260    BackendArgs.push_back("-time-passes");
261  for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
262    BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
263  BackendArgs.push_back(0);
264  llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
265                                    const_cast<char **>(&BackendArgs[0]));
266
267  std::string FeaturesStr;
268  if (TargetOpts.CPU.size() || TargetOpts.Features.size()) {
269    SubtargetFeatures Features;
270    Features.setCPU(TargetOpts.CPU);
271    for (std::vector<std::string>::const_iterator
272           it = TargetOpts.Features.begin(),
273           ie = TargetOpts.Features.end(); it != ie; ++it)
274      Features.AddFeature(*it);
275    FeaturesStr = Features.getString();
276  }
277  TargetMachine *TM = TheTarget->createTargetMachine(Triple, FeaturesStr);
278
279  if (CodeGenOpts.RelaxAll)
280    TM->setMCRelaxAll(true);
281  if (CodeGenOpts.SaveTempLabels)
282    TM->setMCSaveTempLabels(true);
283  if (CodeGenOpts.NoDwarf2CFIAsm)
284    TM->setMCUseCFI(false);
285
286  // Create the code generator passes.
287  PassManager *PM = getCodeGenPasses();
288  CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
289
290  switch (CodeGenOpts.OptimizationLevel) {
291  default: break;
292  case 0: OptLevel = CodeGenOpt::None; break;
293  case 3: OptLevel = CodeGenOpt::Aggressive; break;
294  }
295
296  // Normal mode, emit a .s or .o file by running the code generator. Note,
297  // this also adds codegenerator level optimization passes.
298  TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
299  if (Action == Backend_EmitObj)
300    CGFT = TargetMachine::CGFT_ObjectFile;
301  else if (Action == Backend_EmitMCNull)
302    CGFT = TargetMachine::CGFT_Null;
303  else
304    assert(Action == Backend_EmitAssembly && "Invalid action!");
305  if (TM->addPassesToEmitFile(*PM, OS, CGFT, OptLevel,
306                              /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
307    Diags.Report(diag::err_fe_unable_to_interface_with_target);
308    return false;
309  }
310
311  return true;
312}
313
314void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
315  TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
316  llvm::formatted_raw_ostream FormattedOS;
317
318  CreatePasses();
319  switch (Action) {
320  case Backend_EmitNothing:
321    break;
322
323  case Backend_EmitBC:
324    getPerModulePasses()->add(createBitcodeWriterPass(*OS));
325    break;
326
327  case Backend_EmitLL:
328    FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
329    getPerModulePasses()->add(createPrintModulePass(&FormattedOS));
330    break;
331
332  default:
333    FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
334    if (!AddEmitPasses(Action, FormattedOS))
335      return;
336  }
337
338  // Before executing passes, print the final values of the LLVM options.
339  cl::PrintOptionValues();
340
341  // Run passes. For now we do all passes at once, but eventually we
342  // would like to have the option of streaming code generation.
343
344  if (PerFunctionPasses) {
345    PrettyStackTraceString CrashInfo("Per-function optimization");
346
347    PerFunctionPasses->doInitialization();
348    for (Module::iterator I = TheModule->begin(),
349           E = TheModule->end(); I != E; ++I)
350      if (!I->isDeclaration())
351        PerFunctionPasses->run(*I);
352    PerFunctionPasses->doFinalization();
353  }
354
355  if (PerModulePasses) {
356    PrettyStackTraceString CrashInfo("Per-module optimization passes");
357    PerModulePasses->run(*TheModule);
358  }
359
360  if (CodeGenPasses) {
361    PrettyStackTraceString CrashInfo("Code generation");
362    CodeGenPasses->run(*TheModule);
363  }
364}
365
366void clang::EmitBackendOutput(Diagnostic &Diags, const CodeGenOptions &CGOpts,
367                              const TargetOptions &TOpts, Module *M,
368                              BackendAction Action, raw_ostream *OS) {
369  EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, M);
370
371  AsmHelper.EmitAssembly(Action, OS);
372}
373