Optimize.cpp

Go to the documentation of this file.

// FIXME: This file is a bastard child of opt.cpp and llvm-ld's
// Optimize.cpp. This stuff should live in common code.
 
 
//===- Optimize.cpp - Optimize a complete program -------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements all optimization of the linked module for llvm-ld.
//
//===----------------------------------------------------------------------===//
 
#include "klee/Config/Version.h"
#include "klee/Support/OptionCategories.h"
 
#ifdef USE_WORKAROUND_LLVM_PR39177
#include "Passes.h"
#endif
 
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DynamicLibrary.h"
#include "llvm/Support/PluginLoader.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/FunctionAttrs.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Scalar/GVN.h"
 
#if LLVM_VERSION_CODE >= LLVM_VERSION(7, 0)
#include "llvm/Transforms/Utils.h"
#include "llvm/Transforms/InstCombine/InstCombine.h"
#endif
 
using namespace llvm;
 
static cl::opt<bool>
    DisableInline("disable-inlining",
                  cl::desc("Do not run the inliner pass (default=false)"),
                  cl::init(false), cl::cat(klee::ModuleCat));
 
static cl::opt<bool> DisableInternalize(
    "disable-internalize",
    cl::desc("Do not mark all symbols as internal (default=false)"),
    cl::init(false), cl::cat(klee::ModuleCat));
 
static cl::opt<bool> VerifyEach(
    "verify-each",
    cl::desc("Verify intermediate results of all optimization passes (default=false)"),
    cl::init(false),
    cl::cat(klee::ModuleCat));
 
static cl::alias ExportDynamic("export-dynamic",
                               cl::aliasopt(DisableInternalize),
                               cl::desc("Alias for -disable-internalize"));
 
static cl::opt<bool>
    Strip("strip-all", cl::desc("Strip all symbol information from executable"),
          cl::init(false), cl::cat(klee::ModuleCat));
 
static cl::alias A0("s", cl::desc("Alias for --strip-all"),
                    cl::aliasopt(Strip));
 
static cl::opt<bool>
    StripDebug("strip-debug",
               cl::desc("Strip debugger symbol info from executable"),
               cl::init(false), cl::cat(klee::ModuleCat));
 
static cl::alias A1("S", cl::desc("Alias for --strip-debug"),
                    cl::aliasopt(StripDebug));
 
// A utility function that adds a pass to the pass manager but will also add
// a verifier pass after if we're supposed to verify.
static inline void addPass(legacy::PassManager &PM, Pass *P) {
  // Add the pass to the pass manager...
  PM.add(P);
 
  // If we are verifying all of the intermediate steps, add the verifier...
  if (VerifyEach)
    PM.add(createVerifierPass());
}
 
namespace llvm {
 
 
static void AddStandardCompilePasses(legacy::PassManager &PM) {
  PM.add(createVerifierPass());                  // Verify that input is correct
 
  // If the -strip-debug command line option was specified, do it.
  if (StripDebug)
    addPass(PM, createStripSymbolsPass(true));
 
  addPass(PM, createCFGSimplificationPass());    // Clean up disgusting code
  addPass(PM, createPromoteMemoryToRegisterPass());// Kill useless allocas
  addPass(PM, createGlobalOptimizerPass());      // Optimize out global vars
  addPass(PM, createGlobalDCEPass());            // Remove unused fns and globs
#if LLVM_VERSION_CODE >= LLVM_VERSION(11, 0)
  addPass(PM, createSCCPPass());                 // Constant prop with SCCP
#else
  addPass(PM, createIPConstantPropagationPass());// IP Constant Propagation
#endif
  addPass(PM, createDeadArgEliminationPass());   // Dead argument elimination
  addPass(PM, createInstructionCombiningPass()); // Clean up after IPCP & DAE
  addPass(PM, createCFGSimplificationPass());    // Clean up after IPCP & DAE
 
  addPass(PM, createPruneEHPass());              // Remove dead EH info
  addPass(PM, createPostOrderFunctionAttrsLegacyPass());
  addPass(PM, createReversePostOrderFunctionAttrsPass()); // Deduce function attrs
 
  if (!DisableInline)
    addPass(PM, createFunctionInliningPass());   // Inline small functions
  addPass(PM, createArgumentPromotionPass());    // Scalarize uninlined fn args
 
  addPass(PM, createInstructionCombiningPass()); // Cleanup for scalarrepl.
  addPass(PM, createJumpThreadingPass());        // Thread jumps.
  addPass(PM, createCFGSimplificationPass());    // Merge & remove BBs
  addPass(PM, createSROAPass());                 // Break up aggregate allocas
  addPass(PM, createInstructionCombiningPass()); // Combine silly seq's
 
  addPass(PM, createTailCallEliminationPass());  // Eliminate tail calls
  addPass(PM, createCFGSimplificationPass());    // Merge & remove BBs
  addPass(PM, createReassociatePass());          // Reassociate expressions
  addPass(PM, createLoopRotatePass());
  addPass(PM, createLICMPass());                 // Hoist loop invariants
  addPass(PM, createLoopUnswitchPass());         // Unswitch loops.
  // FIXME : Removing instcombine causes nestedloop regression.
  addPass(PM, createInstructionCombiningPass());
  addPass(PM, createIndVarSimplifyPass());       // Canonicalize indvars
  addPass(PM, createLoopDeletionPass());         // Delete dead loops
  addPass(PM, createLoopUnrollPass());           // Unroll small loops
  addPass(PM, createInstructionCombiningPass()); // Clean up after the unroller
  addPass(PM, createGVNPass());                  // Remove redundancies
  addPass(PM, createMemCpyOptPass());            // Remove memcpy / form memset
  addPass(PM, createSCCPPass());                 // Constant prop with SCCP
 
  // Run instcombine after redundancy elimination to exploit opportunities
  // opened up by them.
  addPass(PM, createInstructionCombiningPass());
 
  addPass(PM, createDeadStoreEliminationPass()); // Delete dead stores
  addPass(PM, createAggressiveDCEPass());        // Delete dead instructions
  addPass(PM, createCFGSimplificationPass());    // Merge & remove BBs
  addPass(PM, createStripDeadPrototypesPass());  // Get rid of dead prototypes
  addPass(PM, createConstantMergePass());        // Merge dup global constants
}
 
void Optimize(Module *M, llvm::ArrayRef<const char *> preservedFunctions) {
 
  // Instantiate the pass manager to organize the passes.
  legacy::PassManager Passes;
 
  // If we're verifying, start off with a verification pass.
  if (VerifyEach)
    Passes.add(createVerifierPass());
 
#ifdef USE_WORKAROUND_LLVM_PR39177
  addPass(Passes, new klee::WorkaroundLLVMPR39177Pass());
#endif
 
  // DWD - Run the opt standard pass list as well.
  AddStandardCompilePasses(Passes);
 
  // Now that composite has been compiled, scan through the module, looking
  // for a main function.  If main is defined, mark all other functions
  // internal.
  if (!DisableInternalize) {
    auto PreserveFunctions = [=](const GlobalValue &GV) {
      StringRef GVName = GV.getName();
 
      for (const char *fun : preservedFunctions)
        if (GVName.equals(fun))
          return true;
 
      return false;
    };
    ModulePass *pass = createInternalizePass(PreserveFunctions);
    addPass(Passes, pass);
  }
 
  // Propagate constants at call sites into the functions they call.  This
  // opens opportunities for globalopt (and inlining) by substituting function
  // pointers passed as arguments to direct uses of functions.
  addPass(Passes, createIPSCCPPass());
 
  // Now that we internalized some globals, see if we can hack on them!
  addPass(Passes, createGlobalOptimizerPass());
 
  // Linking modules together can lead to duplicated global constants, only
  // keep one copy of each constant...
  addPass(Passes, createConstantMergePass());
 
  // Remove unused arguments from functions...
  addPass(Passes, createDeadArgEliminationPass());
 
  // Reduce the code after globalopt and ipsccp.  Both can open up significant
  // simplification opportunities, and both can propagate functions through
  // function pointers.  When this happens, we often have to resolve varargs
  // calls, etc, so let instcombine do this.
  addPass(Passes, createInstructionCombiningPass());
 
  if (!DisableInline)
    addPass(Passes, createFunctionInliningPass()); // Inline small functions
 
  addPass(Passes, createPruneEHPass());         // Remove dead EH info
  addPass(Passes, createGlobalOptimizerPass()); // Optimize globals again.
  addPass(Passes, createGlobalDCEPass());       // Remove dead functions
 
  // If we didn't decide to inline a function, check to see if we can
  // transform it to pass arguments by value instead of by reference.
  addPass(Passes, createArgumentPromotionPass());
 
  // The IPO passes may leave cruft around.  Clean up after them.
  addPass(Passes, createInstructionCombiningPass());
  addPass(Passes, createJumpThreadingPass()); // Thread jumps.
  addPass(Passes, createSROAPass()); // Break up allocas
 
  // Run a few AA driven optimizations here and now, to cleanup the code.
  addPass(Passes, createPostOrderFunctionAttrsLegacyPass());
  addPass(Passes, createReversePostOrderFunctionAttrsPass()); // Add nocapture
  addPass(Passes, createGlobalsAAWrapperPass()); // IP alias analysis
 
  addPass(Passes, createLICMPass());                 // Hoist loop invariants
  addPass(Passes, createGVNPass());                  // Remove redundancies
  addPass(Passes, createMemCpyOptPass());            // Remove dead memcpy's
  addPass(Passes, createDeadStoreEliminationPass()); // Nuke dead stores
 
  // Cleanup and simplify the code after the scalar optimizations.
  addPass(Passes, createInstructionCombiningPass());
 
  addPass(Passes, createJumpThreadingPass());           // Thread jumps.
  addPass(Passes, createPromoteMemoryToRegisterPass()); // Cleanup jumpthread.
 
  // Delete basic blocks, which optimization passes may have killed...
  addPass(Passes, createCFGSimplificationPass());
 
  // Now that we have optimized the program, discard unreachable functions...
  addPass(Passes, createGlobalDCEPass());
 
  // If the -s or -S command line options were specified, strip the symbols out
  // of the resulting program to make it smaller.  -s and -S are GNU ld options
  // that we are supporting; they alias -strip-all and -strip-debug.
  if (Strip || StripDebug)
    addPass(Passes, createStripSymbolsPass(StripDebug && !Strip));
 
  // The user's passes may leave cruft around; clean up after them.
  addPass(Passes, createInstructionCombiningPass());
  addPass(Passes, createCFGSimplificationPass());
  addPass(Passes, createAggressiveDCEPass());
  addPass(Passes, createGlobalDCEPass());
 
  // Run our queue of passes all at once now, efficiently.
  Passes.run(*M);
}
}