//===- MachineStripDebug.cpp - Strip debug info ---------------------------===//
//
// 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 removes debug info from everything. It can be used to ensure
/// tests can be debugified without affecting the output MIR.
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/MachineStripDebug.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionAnalysis.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/IR/Analysis.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/Utils/Debugify.h"

#define DEBUG_TYPE "mir-strip-debug"

using namespace llvm;

namespace {

cl::opt<bool>
    OnlyDebugifiedDefault("mir-strip-debugify-only",
                          cl::desc("Should mir-strip-debug only strip debug "
                                   "info from debugified modules by default"),
                          cl::init(true));

bool stripDebugMachineModuleImpl(
    Module &M, bool OnlyDebugified,
    llvm::function_ref<MachineFunction *(Function &)> GetMF) {
  if (OnlyDebugified) {
    NamedMDNode *DebugifyMD = M.getNamedMetadata("llvm.debugify");
    if (!DebugifyMD) {
      LLVM_DEBUG(dbgs() << "Not stripping debug info"
                           " (debugify metadata not found)?\n");
      return false;
    }
  }

  bool Changed = false;
  for (Function &F : M.functions()) {
    MachineFunction *MaybeMF = GetMF(F);
    if (!MaybeMF)
      continue;
    MachineFunction &MF = *MaybeMF;
    for (MachineBasicBlock &MBB : MF) {
      for (MachineInstr &MI : llvm::make_early_inc_range(MBB.instrs())) {
        if (MI.isDebugInstr()) {
          // FIXME: We should remove all of them. However, AArch64 emits an
          //        invalid `DBG_VALUE $lr` with only one operand instead of
          //        the usual three and has a test that depends on it's
          //        preservation. Preserve it for now.
          if (MI.getNumOperands() > 1) {
            LLVM_DEBUG(dbgs() << "Removing debug instruction " << MI);
            MBB.erase_instr(&MI);
            Changed |= true;
            continue;
          }
        }
        if (MI.getDebugLoc()) {
          LLVM_DEBUG(dbgs() << "Removing location " << MI);
          MI.setDebugLoc(DebugLoc());
          Changed |= true;
          continue;
        }
        LLVM_DEBUG(dbgs() << "Keeping " << MI);
      }
    }
  }

  Changed |= stripDebugifyMetadata(M);

  return Changed;
}

struct StripDebugMachineModule : public ModulePass {
  bool runOnModule(Module &M) override {
    MachineModuleInfo &MMI =
        getAnalysis<MachineModuleInfoWrapperPass>().getMMI();
    return stripDebugMachineModuleImpl(
        M, OnlyDebugified, [&MMI](Function &F) -> MachineFunction * {
          return MMI.getMachineFunction(F);
        });
  }

  StripDebugMachineModule() : StripDebugMachineModule(OnlyDebugifiedDefault) {}
  StripDebugMachineModule(bool OnlyDebugified)
      : ModulePass(ID), OnlyDebugified(OnlyDebugified) {}

  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.addRequired<MachineModuleInfoWrapperPass>();
    AU.addPreserved<MachineModuleInfoWrapperPass>();
    AU.setPreservesCFG();
  }

  static char ID; // Pass identification.

protected:
  bool OnlyDebugified;
};
char StripDebugMachineModule::ID = 0;

} // end anonymous namespace

INITIALIZE_PASS_BEGIN(StripDebugMachineModule, DEBUG_TYPE,
                      "Machine Strip Debug Module", false, false)
INITIALIZE_PASS_END(StripDebugMachineModule, DEBUG_TYPE,
                    "Machine Strip Debug Module", false, false)

ModulePass *llvm::createStripDebugMachineModuleLegacyPass(bool OnlyDebugified) {
  return new StripDebugMachineModule(OnlyDebugified);
}

PreservedAnalyses StripDebugMachineModulePass::run(Module &M,
                                                   ModuleAnalysisManager &AM) {
  FunctionAnalysisManager &FAM =
      AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
  const bool Changed = stripDebugMachineModuleImpl(
      M, OnlyDebugifiedDefault, [&FAM](Function &F) -> MachineFunction * {
        return &FAM.getResult<MachineFunctionAnalysis>(F).getMF();
      });
  if (!Changed)
    return PreservedAnalyses::all();

  PreservedAnalyses PA;
  PA.preserve<MachineModuleAnalysis>();
  PA.preserve<FunctionAnalysisManagerModuleProxy>();
  PA.preserveSet<CFGAnalyses>();
  return PA;
}