lib/Transforms/IPO/PassManagerBuilder.cpp

//===- PassManagerBuilder.cpp - Build Standard Pass -----------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the PassManagerBuilder class, which is used to set up a
// "standard" optimization sequence suitable for languages like C and C++.
//
//===----------------------------------------------------------------------===//


#include "llvm/Transforms/IPO/PassManagerBuilder.h"

#include "llvm/PassManager.h"
#include "llvm/DefaultPasses.h"
#include "llvm/PassManager.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/Verifier.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/IPO.h"

using namespace llvm;

PassManagerBuilder::PassManagerBuilder() {
    OptLevel = 2;
    SizeLevel = 0;
    LibraryInfo = 0;
    Inliner = 0;
    DisableSimplifyLibCalls = false;
    DisableUnitAtATime = false;
    DisableUnrollLoops = false;
}

PassManagerBuilder::~PassManagerBuilder() {
  delete LibraryInfo;
  delete Inliner;
}

void PassManagerBuilder::addExtension(ExtensionPointTy Ty, ExtensionFn Fn) {
  Extensions.push_back(std::make_pair(Ty, Fn));
}

void PassManagerBuilder::addExtensionsToPM(ExtensionPointTy ETy,
                                           PassManagerBase &PM) const {
  for (unsigned i = 0, e = Extensions.size(); i != e; ++i)
    if (Extensions[i].first == ETy)
      Extensions[i].second(*this, PM);
}

void
PassManagerBuilder::addInitialAliasAnalysisPasses(PassManagerBase &PM) const {
  // Add TypeBasedAliasAnalysis before BasicAliasAnalysis so that
  // BasicAliasAnalysis wins if they disagree. This is intended to help
  // support "obvious" type-punning idioms.
  PM.add(createTypeBasedAliasAnalysisPass());
  PM.add(createBasicAliasAnalysisPass());
}

void PassManagerBuilder::populateFunctionPassManager(FunctionPassManager &FPM) {
  addExtensionsToPM(EP_EarlyAsPossible, FPM);

  // Add LibraryInfo if we have some.
  if (LibraryInfo) FPM.add(new TargetLibraryInfo(*LibraryInfo));

  if (OptLevel == 0) return;

  addInitialAliasAnalysisPasses(FPM);

  FPM.add(createCFGSimplificationPass());
  FPM.add(createScalarReplAggregatesPass());
  FPM.add(createEarlyCSEPass());
  FPM.add(createLowerExpectIntrinsicPass());
}

void PassManagerBuilder::populateModulePassManager(PassManagerBase &MPM) {
  // If all optimizations are disabled, just run the always-inline pass.
  if (OptLevel == 0) {
    if (Inliner) {
      MPM.add(Inliner);
      Inliner = 0;
    }
    return;
  }

  // Add LibraryInfo if we have some.
  if (LibraryInfo) MPM.add(new TargetLibraryInfo(*LibraryInfo));

  addInitialAliasAnalysisPasses(MPM);

  if (!DisableUnitAtATime) {
    MPM.add(createGlobalOptimizerPass());     // Optimize out global vars

    MPM.add(createIPSCCPPass());              // IP SCCP
    MPM.add(createDeadArgEliminationPass());  // Dead argument elimination

    MPM.add(createInstructionCombiningPass());// Clean up after IPCP & DAE
    MPM.add(createCFGSimplificationPass());   // Clean up after IPCP & DAE
  }

  // Start of CallGraph SCC passes.
  if (!DisableUnitAtATime)
    MPM.add(createPruneEHPass());             // Remove dead EH info
  if (Inliner) {
    MPM.add(Inliner);
    Inliner = 0;
  }
  if (!DisableUnitAtATime)
    MPM.add(createFunctionAttrsPass());       // Set readonly/readnone attrs
  if (OptLevel > 2)
    MPM.add(createArgumentPromotionPass());   // Scalarize uninlined fn args

  // Start of function pass.
  // Break up aggregate allocas, using SSAUpdater.
  MPM.add(createScalarReplAggregatesPass(-1, false));
  MPM.add(createEarlyCSEPass());              // Catch trivial redundancies
  if (!DisableSimplifyLibCalls)
    MPM.add(createSimplifyLibCallsPass());    // Library Call Optimizations
  MPM.add(createJumpThreadingPass());         // Thread jumps.
  MPM.add(createCorrelatedValuePropagationPass()); // Propagate conditionals
  MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
  MPM.add(createInstructionCombiningPass());  // Combine silly seq's

  MPM.add(createTailCallEliminationPass());   // Eliminate tail calls
  MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
  MPM.add(createReassociatePass());           // Reassociate expressions
  MPM.add(createLoopRotatePass());            // Rotate Loop
  MPM.add(createLICMPass());                  // Hoist loop invariants
  MPM.add(createLoopUnswitchPass(SizeLevel || OptLevel < 3));
  MPM.add(createInstructionCombiningPass());
  MPM.add(createIndVarSimplifyPass());        // Canonicalize indvars
  MPM.add(createLoopIdiomPass());             // Recognize idioms like memset.
  MPM.add(createLoopDeletionPass());          // Delete dead loops
  if (!DisableUnrollLoops)
    MPM.add(createLoopUnrollPass());          // Unroll small loops
  addExtensionsToPM(EP_LoopOptimizerEnd, MPM);

  if (OptLevel > 1)
    MPM.add(createGVNPass());                 // Remove redundancies
  MPM.add(createMemCpyOptPass());             // Remove memcpy / form memset
  MPM.add(createSCCPPass());                  // Constant prop with SCCP

  // Run instcombine after redundancy elimination to exploit opportunities
  // opened up by them.
  MPM.add(createInstructionCombiningPass());
  MPM.add(createJumpThreadingPass());         // Thread jumps
  MPM.add(createCorrelatedValuePropagationPass());
  MPM.add(createDeadStoreEliminationPass());  // Delete dead stores

  addExtensionsToPM(EP_ScalarOptimizerLate, MPM);

  MPM.add(createAggressiveDCEPass());         // Delete dead instructions
  MPM.add(createCFGSimplificationPass());     // Merge & remove BBs
  MPM.add(createInstructionCombiningPass());  // Clean up after everything.

  if (!DisableUnitAtATime) {
    // FIXME: We shouldn't bother with this anymore.
    MPM.add(createStripDeadPrototypesPass()); // Get rid of dead prototypes

    // GlobalOpt already deletes dead functions and globals, at -O3 try a
    // late pass of GlobalDCE.  It is capable of deleting dead cycles.
    if (OptLevel > 2)
      MPM.add(createGlobalDCEPass());         // Remove dead fns and globals.

    if (OptLevel > 1)
      MPM.add(createConstantMergePass());     // Merge dup global constants
  }
}

void PassManagerBuilder::populateLTOPassManager(PassManagerBase &PM,
                                                bool Internalize,
                                                bool RunInliner) {
  // Provide AliasAnalysis services for optimizations.
  addInitialAliasAnalysisPasses(PM);

  // 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 (Internalize)
    PM.add(createInternalizePass(true));

  // 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.
  PM.add(createIPSCCPPass());

  // Now that we internalized some globals, see if we can hack on them!
  PM.add(createGlobalOptimizerPass());

  // Linking modules together can lead to duplicated global constants, only
  // keep one copy of each constant.
  PM.add(createConstantMergePass());

  // Remove unused arguments from functions.
  PM.add(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.
  PM.add(createInstructionCombiningPass());

  // Inline small functions
  if (RunInliner)
    PM.add(createFunctionInliningPass());

  PM.add(createPruneEHPass());   // Remove dead EH info.

  // Optimize globals again if we ran the inliner.
  if (RunInliner)
    PM.add(createGlobalOptimizerPass());
  PM.add(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.
  PM.add(createArgumentPromotionPass());

  // The IPO passes may leave cruft around.  Clean up after them.
  PM.add(createInstructionCombiningPass());
  PM.add(createJumpThreadingPass());
  // Break up allocas
  PM.add(createScalarReplAggregatesPass());

  // Run a few AA driven optimizations here and now, to cleanup the code.
  PM.add(createFunctionAttrsPass()); // Add nocapture.
  PM.add(createGlobalsModRefPass()); // IP alias analysis.

  PM.add(createLICMPass());      // Hoist loop invariants.
  PM.add(createGVNPass());       // Remove redundancies.
  PM.add(createMemCpyOptPass()); // Remove dead memcpys.
  // Nuke dead stores.
  PM.add(createDeadStoreEliminationPass());

  // Cleanup and simplify the code after the scalar optimizations.
  PM.add(createInstructionCombiningPass());

  PM.add(createJumpThreadingPass());

  // Delete basic blocks, which optimization passes may have killed.
  PM.add(createCFGSimplificationPass());

  // Now that we have optimized the program, discard unreachable functions.
  PM.add(createGlobalDCEPass());
}