//===---- CodePreparation.cpp - Code preparation for Scop Detection -------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// The Polly code preparation pass is executed before SCoP detection. Its

// currently only splits the entry block of the SCoP to make room for alloc

// instructions as they are generated during code generation.

//

// XXX: In the future, we should remove the need for this pass entirely and

// instead add this spitting to the code generation pass.

//

//===----------------------------------------------------------------------===//

#include "polly/CodePreparation.h"

#include "polly/LinkAllPasses.h"

#include "polly/Support/ScopHelper.h"

#include "llvm/Analysis/DominanceFrontier.h"

#include "llvm/Analysis/LoopInfo.h"

#include "llvm/Analysis/RegionInfo.h"

#include "llvm/Analysis/ScalarEvolution.h"

using namespace llvm;

using namespace polly;

namespace {

/// Prepare the IR for the scop detection.

///

class CodePreparation : public FunctionPass {

  CodePreparation(const CodePreparation &) = delete;

  const CodePreparation &operator=(const CodePreparation &) = delete;

  LoopInfo *LI;

  ScalarEvolution *SE;

  void clear();

public:

  static char ID;

  explicit CodePreparation() : FunctionPass(ID) {}

  ~CodePreparation();

  /// @name FunctionPass interface.

  //@{

  virtual void getAnalysisUsage(AnalysisUsage &AU) const;

  virtual void releaseMemory();

  virtual bool runOnFunction(Function &F);

  virtual void print(raw_ostream &OS, const Module *) const;

  //@}

};

} // namespace

PreservedAnalyses CodePreparationPass::run(Function &F,

                                           FunctionAnalysisManager &FAM) {

  // Find first non-alloca instruction. Every basic block has a non-alloca

  // instruction, as every well formed basic block has a terminator.

  auto &EntryBlock = F.getEntryBlock();

  BasicBlock::iterator I = EntryBlock.begin();

  while (isa<AllocaInst>(I))

    ++I;

  auto &DT = FAM.getResult<DominatorTreeAnalysis>(F);

  auto &LI = FAM.getResult<LoopAnalysis>(F);

  // splitBlock updates DT, LI and RI.

  splitEntryBlockForAlloca(&EntryBlock, &DT, &LI, nullptr);

  PreservedAnalyses PA;

  PA.preserve<DominatorTreeAnalysis>();

  PA.preserve<LoopAnalysis>();

  return PA;

}

void CodePreparation::clear() {}

CodePreparation::~CodePreparation() { clear(); }

void CodePreparation::getAnalysisUsage(AnalysisUsage &AU) const {

  AU.addRequired<LoopInfoWrapperPass>();

  AU.addRequired<ScalarEvolutionWrapperPass>();

  AU.addPreserved<LoopInfoWrapperPass>();

  AU.addPreserved<RegionInfoPass>();

  AU.addPreserved<DominatorTreeWrapperPass>();

  AU.addPreserved<DominanceFrontierWrapperPass>();

}

bool CodePreparation::runOnFunction(Function &F) {

  if (skipFunction(F))

    return false;

  LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();

  SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();

  splitEntryBlockForAlloca(&F.getEntryBlock(), this);

  return true;

}

void CodePreparation::releaseMemory() { clear(); }

void CodePreparation::print(raw_ostream &OS, const Module *) const {}

char CodePreparation::ID = 0;

char &polly::CodePreparationID = CodePreparation::ID;

Pass *polly::createCodePreparationPass() { return new CodePreparation(); }

INITIALIZE_PASS_BEGIN(CodePreparation, "polly-prepare",

                      "Polly - Prepare code for polly", false, false)

INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)

INITIALIZE_PASS_END(CodePreparation, "polly-prepare",

                    "Polly - Prepare code for polly", false, false)