//===- llvm/IR/OptBisect/Bisect.cpp - LLVM Bisect support -----------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
/// \file
/// This file implements support for a bisecting optimizations based on a
/// command line option.
//
//===----------------------------------------------------------------------===//

#include "llvm/IR/OptBisect.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/CallGraphSCCPass.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/RegionInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <limits>
#include <string>

using namespace llvm;

static cl::opt<int> OptBisectLimit("opt-bisect-limit", cl::Hidden,
                                   cl::init(std::numeric_limits<int>::max()),
                                   cl::Optional,
                                   cl::desc("Maximum optimization to perform"));

OptBisect::OptBisect() : OptPassGate() {
  BisectEnabled = OptBisectLimit != std::numeric_limits<int>::max();
}

static void printPassMessage(const StringRef &Name, int PassNum,
                             StringRef TargetDesc, bool Running) {
  StringRef Status = Running ? "" : "NOT ";
  errs() << "BISECT: " << Status << "running pass "
         << "(" << PassNum << ") " << Name << " on " << TargetDesc << "\n";
}

static std::string getDescription(const Module &M) {
  return "module (" + M.getName().str() + ")";
}

static std::string getDescription(const Function &F) {
  return "function (" + F.getName().str() + ")";
}

static std::string getDescription(const BasicBlock &BB) {
  return "basic block (" + BB.getName().str() + ") in function (" +
         BB.getParent()->getName().str() + ")";
}

static std::string getDescription(const Loop &L) {
  // FIXME: Move into LoopInfo so we can get a better description
  // (and avoid a circular dependency between IR and Analysis).
  return "loop";
}

static std::string getDescription(const Region &R) {
  // FIXME: Move into RegionInfo so we can get a better description
  // (and avoid a circular dependency between IR and Analysis).
  return "region";
}

static std::string getDescription(const CallGraphSCC &SCC) {
  // FIXME: Move into CallGraphSCCPass to avoid circular dependency between
  // IR and Analysis.
  std::string Desc = "SCC (";
  bool First = true;
  for (CallGraphNode *CGN : SCC) {
    if (First)
      First = false;
    else
      Desc += ", ";
    Function *F = CGN->getFunction();
    if (F)
      Desc += F->getName();
    else
      Desc += "<<null function>>";
  }
  Desc += ")";
  return Desc;
}

bool OptBisect::shouldRunPass(const Pass *P, const Module &U) {
  return !BisectEnabled || checkPass(P->getPassName(), getDescription(U));
}

bool OptBisect::shouldRunPass(const Pass *P, const Function &U) {
  return !BisectEnabled || checkPass(P->getPassName(), getDescription(U));
}

bool OptBisect::shouldRunPass(const Pass *P, const BasicBlock &U) {
  return !BisectEnabled || checkPass(P->getPassName(), getDescription(U));
}

bool OptBisect::shouldRunPass(const Pass *P, const Region &U) {
  return !BisectEnabled || checkPass(P->getPassName(), getDescription(U));
}

bool OptBisect::shouldRunPass(const Pass *P, const Loop &U) {
  return !BisectEnabled || checkPass(P->getPassName(), getDescription(U));
}

bool OptBisect::shouldRunPass(const Pass *P, const CallGraphSCC &U) {
  return !BisectEnabled || checkPass(P->getPassName(), getDescription(U));
}

bool OptBisect::checkPass(const StringRef PassName,
                          const StringRef TargetDesc) {
  assert(BisectEnabled);

  int CurBisectNum = ++LastBisectNum;
  bool ShouldRun = (OptBisectLimit == -1 || CurBisectNum <= OptBisectLimit);
  printPassMessage(PassName, CurBisectNum, TargetDesc, ShouldRun);
  return ShouldRun;
}