tools/llvm-ld/Optimize.cpp

   1 //===- Optimize.cpp - Optimize a complete program -------------------------===//
   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 all optimization of the linked module for llvm-ld.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Module.h"
  15 #include "llvm/PassManager.h"
  16 #include "llvm/Analysis/Passes.h"
  17 #include "llvm/Analysis/LoopPass.h"
  18 #include "llvm/Analysis/Verifier.h"
  19 #include "llvm/Support/CommandLine.h"
  20 #include "llvm/System/DynamicLibrary.h"
  21 #include "llvm/Target/TargetData.h"
  22 #include "llvm/Target/TargetMachine.h"
  23 #include "llvm/Transforms/IPO.h"
  24 #include "llvm/Transforms/Scalar.h"
  25 #include "llvm/Support/PassNameParser.h"
  26 #include "llvm/Support/PluginLoader.h"
  27 #include <iostream>
  28 using namespace llvm;
  29
  30 // Pass Name Options as generated by the PassNameParser
  31 static cl::list<const PassInfo*, bool, PassNameParser>
  32   OptimizationList(cl::desc("Optimizations available:"));
  33
  34 //Don't verify at the end
  35 static cl::opt<bool> DontVerify("disable-verify", cl::ReallyHidden);
  36
  37 static cl::opt<bool> DisableInline("disable-inlining",
  38   cl::desc("Do not run the inliner pass"));
  39
  40 static cl::opt<bool>
  41 DisableOptimizations("disable-opt",
  42   cl::desc("Do not run any optimization passes"));
  43
  44 static cl::opt<bool> DisableInternalize("disable-internalize",
  45   cl::desc("Do not mark all symbols as internal"));
  46
  47 static cl::opt<bool> VerifyEach("verify-each",
  48  cl::desc("Verify intermediate results of all passes"));
  49
  50 static cl::alias ExportDynamic("export-dynamic",
  51   cl::aliasopt(DisableInternalize),
  52   cl::desc("Alias for -disable-internalize"));
  53
  54 static cl::opt<bool> Strip("strip-all",
  55   cl::desc("Strip all symbol info from executable"));
  56
  57 static cl::alias A0("s", cl::desc("Alias for --strip-all"),
  58   cl::aliasopt(Strip));
  59
  60 static cl::opt<bool> StripDebug("strip-debug",
  61   cl::desc("Strip debugger symbol info from executable"));
  62
  63 static cl::alias A1("S", cl::desc("Alias for --strip-debug"),
  64   cl::aliasopt(StripDebug));
  65
  66 // A utility function that adds a pass to the pass manager but will also add
  67 // a verifier pass after if we're supposed to verify.
  68 static inline void addPass(PassManager &PM, Pass *P) {
  69   // Add the pass to the pass manager...
  70   PM.add(P);
  71
  72   // If we are verifying all of the intermediate steps, add the verifier...
  73   if (VerifyEach)
  74     PM.add(createVerifierPass());
  75 }
  76
  77 namespace llvm {
  78
  79 /// Optimize - Perform link time optimizations. This will run the scalar
  80 /// optimizations, any loaded plugin-optimization modules, and then the
  81 /// inter-procedural optimizations if applicable.
  82 void Optimize(Module* M) {
  83
  84   // Instantiate the pass manager to organize the passes.
  85   PassManager Passes;
  86
  87   // If we're verifying, start off with a verification pass.
  88   if (VerifyEach)
  89     Passes.add(createVerifierPass());
  90
  91   // Add an appropriate TargetData instance for this module...
  92   addPass(Passes, new TargetData(M));
  93
  94   if (!DisableOptimizations) {
  95     // Now that composite has been compiled, scan through the module, looking
  96     // for a main function.  If main is defined, mark all other functions
  97     // internal.
  98     if (!DisableInternalize)
  99       addPass(Passes, createInternalizePass(true));
 100
 101     // Propagate constants at call sites into the functions they call.  This
 102     // opens opportunities for globalopt (and inlining) by substituting function
 103     // pointers passed as arguments to direct uses of functions.
 104     addPass(Passes, createIPSCCPPass());
 105
 106     // Now that we internalized some globals, see if we can hack on them!
 107     addPass(Passes, createGlobalOptimizerPass());
 108
 109     // Linking modules together can lead to duplicated global constants, only
 110     // keep one copy of each constant...
 111     addPass(Passes, createConstantMergePass());
 112
 113     // Remove unused arguments from functions...
 114     addPass(Passes, createDeadArgEliminationPass());
 115
 116     // Reduce the code after globalopt and ipsccp.  Both can open up significant
 117     // simplification opportunities, and both can propagate functions through
 118     // function pointers.  When this happens, we often have to resolve varargs
 119     // calls, etc, so let instcombine do this.
 120     addPass(Passes, createInstructionCombiningPass());
 121
 122     if (!DisableInline)
 123       addPass(Passes, createFunctionInliningPass()); // Inline small functions
 124
 125     addPass(Passes, createPruneEHPass());            // Remove dead EH info
 126     addPass(Passes, createGlobalOptimizerPass());    // Optimize globals again.
 127     addPass(Passes, createGlobalDCEPass());          // Remove dead functions
 128
 129     // If we didn't decide to inline a function, check to see if we can
 130     // transform it to pass arguments by value instead of by reference.
 131     addPass(Passes, createArgumentPromotionPass());
 132
 133     // The IPO passes may leave cruft around.  Clean up after them.
 134     addPass(Passes, createInstructionCombiningPass());
 135     addPass(Passes, createJumpThreadingPass());        // Thread jumps.
 136     addPass(Passes, createScalarReplAggregatesPass()); // Break up allocas
 137
 138     // Run a few AA driven optimizations here and now, to cleanup the code.
 139     addPass(Passes, createFunctionAttrsPass());      // Add nocapture
 140     addPass(Passes, createGlobalsModRefPass());      // IP alias analysis
 141
 142     addPass(Passes, createLICMPass());               // Hoist loop invariants
 143     addPass(Passes, createGVNPass());                // Remove redundancies
 144     addPass(Passes, createMemCpyOptPass());          // Remove dead memcpy's
 145     addPass(Passes, createDeadStoreEliminationPass()); // Nuke dead stores
 146
 147     // Cleanup and simplify the code after the scalar optimizations.
 148     addPass(Passes, createInstructionCombiningPass());
 149
 150     addPass(Passes, createJumpThreadingPass());        // Thread jumps.
 151     addPass(Passes, createPromoteMemoryToRegisterPass()); // Cleanup jumpthread.
 152
 153     // Delete basic blocks, which optimization passes may have killed...
 154     addPass(Passes, createCFGSimplificationPass());
 155
 156     // Now that we have optimized the program, discard unreachable functions...
 157     addPass(Passes, createGlobalDCEPass());
 158   }
 159
 160   // If the -s or -S command line options were specified, strip the symbols out
 161   // of the resulting program to make it smaller.  -s and -S are GNU ld options
 162   // that we are supporting; they alias -strip-all and -strip-debug.
 163   if (Strip || StripDebug)
 164     addPass(Passes, createStripSymbolsPass(StripDebug && !Strip));
 165
 166   // Create a new optimization pass for each one specified on the command line
 167   std::auto_ptr<TargetMachine> target;
 168   for (unsigned i = 0; i < OptimizationList.size(); ++i) {
 169     const PassInfo *Opt = OptimizationList[i];
 170     if (Opt->getNormalCtor())
 171       addPass(Passes, Opt->getNormalCtor()());
 172     else
 173       std::cerr << "llvm-ld: cannot create pass: " << Opt->getPassName()
 174                 << "\n";
 175   }
 176
 177   // The user's passes may leave cruft around. Clean up after them them but
 178   // only if we haven't got DisableOptimizations set
 179   if (!DisableOptimizations) {
 180     addPass(Passes, createInstructionCombiningPass());
 181     addPass(Passes, createCFGSimplificationPass());
 182     addPass(Passes, createAggressiveDCEPass());
 183     addPass(Passes, createGlobalDCEPass());
 184   }
 185
 186   // Make sure everything is still good.
 187   if (!DontVerify)
 188     Passes.add(createVerifierPass());
 189
 190   // Run our queue of passes all at once now, efficiently.
 191   Passes.run(*M);
 192 }
 193
 194 }