revng-revng/lib/EarlyFunctionAnalysis/AttachDebugInfo.cpp

/// \file AttachDebugInfo.cpp
///
/// A simple pass to attach debug metadata.
///
/// This pass visits each function into reverse post order and, each time it
/// finds a call to newpc, updates the "current location". While doing the visit
/// we attach the "current location" to each instruction we meet.
///
/// The debug location we attach refers to a program specific to that program
/// counter which has been virtually inlined into another subprogram that
/// represents the current function.
///
/// Note however, that subprogram representing the current function is not
/// attached the function itself, since otherwise that would trigger a rather
/// strict debug info verification logic, which we currently do not handle.
/// Specifically, if a function as debug information, then all the inlinable
/// call sites targeting it need to have debug information too.

//
// This file is distributed under the MIT License. See LICENSE.md for details.
//

#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Metadata.h"

#include "revng/BasicAnalyses/GeneratedCodeBasicInfo.h"
#include "revng/EarlyFunctionAnalysis/ControlFlowGraphCache.h"
#include "revng/Model/LoadModelPass.h"
#include "revng/Pipeline/Location.h"
#include "revng/Pipeline/RegisterPipe.h"
#include "revng/Pipes/Kinds.h"
#include "revng/Pipes/ModelGlobal.h"
#include "revng/Pipes/Ranks.h"
#include "revng/Support/FunctionTags.h"

using namespace llvm;

static Logger<> Log("attach-debug-info");

class AttachDebugInfo : public pipeline::FunctionPassImpl {
private:
  llvm::Module &M;
  DIBuilder DIB;
  DICompileUnit *CU = nullptr;

public:
  AttachDebugInfo(llvm::ModulePass &Pass,
                  const model::Binary &Binary,
                  llvm::Module &M) :
    pipeline::FunctionPassImpl(Pass), M(M), DIB(M) {}

  static void getAnalysisUsage(llvm::AnalysisUsage &AU) {
    AU.setPreservesAll();
    AU.addRequired<ControlFlowGraphCachePass>();
    AU.addRequired<GeneratedCodeBasicInfoWrapperPass>();
  }

  bool prologue() final;

  bool runOnFunction(const model::Function &ModelFunction,
                     llvm::Function &Function) final;

  bool epilogue() final { return false; }
};

template<>
char pipeline::FunctionPass<AttachDebugInfo>::ID = 0;

static bool isTrue(const llvm::Value *V) {
  return getLimitedValue(V) != 0;
}

static void handleFunction(DIBuilder &DIB,
                           llvm::Function &F,
                           DISubprogram *TheSubprogram,
                           efa::ControlFlowGraph &FM,
                           GeneratedCodeBasicInfo &GCBI) {
  namespace ranks = revng::ranks;

  LLVMContext &Context = F.getParent()->getContext();
  DILocation *CurrentDebugLocation = nullptr;
  BasicBlockID LastJumpTarget;
  for (auto *BB : ReversePostOrderTraversal(&F)) {
    if (not GCBI.isTranslated(BB))
      continue;

    for (auto &I : *BB) {
      if (auto *Call = getCallTo(&I, "newpc")) {
        BasicBlockID Address = blockIDFromNewPC(Call);

        if (isTrue(Call->getArgOperand(NewPCArguments::IsJumpTarget))) {
          const auto &CFG = FM.Blocks();
          if (CFG.contains(Address)) {
            LastJumpTarget = Address;
          } else {
            revng_assert(CFG.at(LastJumpTarget).contains(Address));
          }
        }

        revng_assert(LastJumpTarget.isValid());
        revng_assert(Address.inliningIndex() == LastJumpTarget.inliningIndex());

        auto SPFlags = DISubprogram::toSPFlags(false, /* isLocalToUnit */
                                               true, /* isDefinition*/
                                               false /* isOptimized */);
        auto Type = DIB.createSubroutineType(DIB.getOrCreateTypeArray({}));

        // Let's make the debug location that points back to the binary.
        std::string NewDebugLocation = toString(ranks::Instruction,
                                                FM.Entry(),
                                                LastJumpTarget,
                                                Address.start());
        auto Subprogram = DIB.createFunction(TheSubprogram->getFile(), // Scope
                                             NewDebugLocation, // Name
                                             StringRef(), // LinkageName
                                             TheSubprogram->getFile(), // File
                                             1, // LineNo
                                             Type, // Ty (subroutine type)
                                             1, // ScopeLine
                                             DINode::FlagPrototyped, // Flags
                                             SPFlags);
        DIB.finalizeSubprogram(Subprogram);

        auto InlineLocationForMetaAddress = DILocation::get(Context,
                                                            0,
                                                            0,
                                                            TheSubprogram,
                                                            nullptr);

        // Represent debug info for all the isolated functions as if they were
        // inlined in the root.
        auto InlineLoc = DILocation::get(Context,
                                         0,
                                         0,
                                         Subprogram,
                                         InlineLocationForMetaAddress);

        CurrentDebugLocation = InlineLoc;
      }

      I.setDebugLoc(CurrentDebugLocation);
    }
  }
}

bool AttachDebugInfo::prologue() {
  // This will be used for attaching the !dbg to instructions.
  // TODO: Document how are we going to abuse DILocation fields.
  DIFile *File = DIB.createFile(M.getSourceFileName(), "./");
  // Also add dummy CU.
  CU = DIB.createCompileUnit(dwarf::DW_LANG_C,
                             File,
                             "revng", // Producer
                             true, // isOptimized
                             "", // Flags
                             0 // RV
  );

  return true;
}

bool AttachDebugInfo::runOnFunction(const model::Function &ModelFunction,
                                    llvm::Function &F) {
  ControlFlowGraphCache *Cache = &getAnalysis<ControlFlowGraphCachePass>()
                                    .get();
  auto &GCBI = getAnalysis<GeneratedCodeBasicInfoWrapperPass>().getGCBI();

  // Skip functions with debug-info.
  if (F.getSubprogram())
    return true;

  // Skip declarations
  revng_assert(not F.isDeclaration());

  auto FM = Cache->getControlFlowGraph(&F);
  revng_log(Log,
            "Metadata for Function " << F.getName() << ":"
                                     << FM.Entry().toString());

  // Create debug info for the function.
  auto SPFlags = DISubprogram::toSPFlags(false, // isLocalToUnit
                                         true, // isDefinition
                                         false // isOptimized
  );
  auto SPType = DIB.createSubroutineType(DIB.getOrCreateTypeArray({}));

  DISubprogram
    *TheSubprogram = DIB.createFunction(CU->getFile(), // Scope
                                        F.getName(), // Name
                                        StringRef(), // LinkageName
                                        CU->getFile(), // File
                                        1, // LineNo
                                        SPType, // Ty (subroutine type)
                                        1, // ScopeLine
                                        DINode::FlagPrototyped, // Flags
                                        SPFlags);
  DIB.finalizeSubprogram(TheSubprogram);

  handleFunction(DIB, F, TheSubprogram, FM, GCBI);

  return true;
}

// Note: unfortunately, due to the presence of kinds, we need two distinct pipes

struct AttachDebugInfoToIsolatedPipe {
  static constexpr auto Name = "attach-debug-info-to-isolated";

  std::vector<pipeline::ContractGroup> getContract() const {
    using namespace revng;
    using namespace pipeline;
    return { ContractGroup({ Contract(kinds::CFG,
                                      0,
                                      kinds::Isolated,
                                      1,
                                      InputPreservation::Preserve),
                             Contract(kinds::Isolated,
                                      1,
                                      kinds::Isolated,
                                      1,
                                      InputPreservation::Preserve) }) };
  }

  void run(pipeline::ExecutionContext &EC,
           const revng::pipes::CFGMap &CFGMap,
           pipeline::LLVMContainer &ModuleContainer) {
    llvm::legacy::PassManager Manager;
    Manager.add(new pipeline::LoadExecutionContextPass(&EC,
                                                       ModuleContainer.name()));
    Manager.add(new LoadModelWrapperPass(revng::getModelFromContext(EC)));
    Manager.add(new ControlFlowGraphCachePass(CFGMap));
    Manager.add(new pipeline::FunctionPass<AttachDebugInfo>());
    Manager.run(ModuleContainer.getModule());
  }

  llvm::Error checkPrecondition(const pipeline::Context &Context) const {
    return llvm::Error::success();
  }
};

static pipeline::RegisterPipe<AttachDebugInfoToIsolatedPipe> Y1;

struct AttachDebugInfoToABIEnforcedPipe {
  static constexpr auto Name = "attach-debug-info-to-abi-enforced";

  std::vector<pipeline::ContractGroup> getContract() const {
    using namespace revng;
    using namespace pipeline;
    return { ContractGroup({ Contract(kinds::ABIEnforced,
                                      1,
                                      kinds::ABIEnforced,
                                      1,
                                      InputPreservation::Preserve),
                             Contract(kinds::CFG,
                                      0,
                                      kinds::Isolated,
                                      1,
                                      InputPreservation::Preserve) }) };
  }

  void run(pipeline::ExecutionContext &EC,
           const revng::pipes::CFGMap &CFGMap,
           pipeline::LLVMContainer &ModuleContainer) {
    llvm::legacy::PassManager Manager;
    Manager.add(new pipeline::LoadExecutionContextPass(&EC,
                                                       ModuleContainer.name()));
    Manager.add(new LoadModelWrapperPass(revng::getModelFromContext(EC)));
    Manager.add(new ControlFlowGraphCachePass(CFGMap));
    Manager.add(new pipeline::FunctionPass<AttachDebugInfo>());
    Manager.run(ModuleContainer.getModule());
  }

  llvm::Error checkPrecondition(const pipeline::Context &Context) const {
    return llvm::Error::success();
  }
};

static pipeline::RegisterPipe<AttachDebugInfoToABIEnforcedPipe> Y2;