revng-revng/lib/EarlyFunctionAnalysis/AttachDebugInfo.cpp

/// \file AttachDebugInfo.cpp
/// \brief A simple pass to attach debug metadata.

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

#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/EarlyFunctionAnalysis/AttachDebugInfo.h"
#include "revng/Pipeline/Location.h"
#include "revng/Pipes/Ranks.h"
#include "revng/Support/FunctionTags.h"

using namespace llvm;

char AttachDebugInfo::ID = 0;

using Register = RegisterPass<AttachDebugInfo>;
static Register X("attach-debug-info", "Attach debug info metadata.");
static Logger<> Log("attach-debug-info");

static void handleBasicBlock(DIBuilder &DIB,
                             llvm::BasicBlock &BB,
                             DISubprogram *RootSubprogram,
                             efa::FunctionMetadata &FM,
                             GeneratedCodeBasicInfo &GCBI) {
  namespace ranks = revng::ranks;

  if (!isJumpTarget(&BB)) {
    revng_log(Log, " Not a jump target " << BB.getName());
    return;
  }

  const efa::BasicBlock *Block = FM.findBlock(GCBI, &BB);
  if (!Block) {
    revng_log(Log, " No metadata for " << BB.getName());
    return;
  }

  revng_log(Log, " " << BB.getName() << ": " << Block->ID().toString());

  llvm::Module &M = *BB.getParent()->getParent();
  DILocation *CurrentDebugLocation = nullptr;
  for (auto &I : BB) {
    if (auto *Call = getCallTo(&I, "newpc")) {
      MetaAddress NewPC = blockIDFromNewPC(Call).start();
      // We cloned `line:` only, but we need full MetaAddress that we keep
      // as `DISubprogram`.
      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 = serializedLocation(ranks::Instruction,
                                                        FM.Entry(),
                                                        Block->ID(),
                                                        NewPC);
      auto Subprogram = DIB.createFunction(RootSubprogram->getFile(), // Scope
                                           NewDebugLocation, // Name
                                           StringRef(), // LinkageName
                                           RootSubprogram->getFile(), // File
                                           1, // LineNo
                                           Type, // Ty (subroutine type)
                                           1, // ScopeLine
                                           DINode::FlagPrototyped, // Flags
                                           SPFlags);
      DIB.finalizeSubprogram(Subprogram);
      auto InlineLocationForMetaAddress = DILocation::get(M.getContext(),
                                                          NewPC.address(),
                                                          0,
                                                          RootSubprogram,
                                                          nullptr);
      // Represent debug info for all the isolated functions as if they were
      // inlined in the root.
      auto InlineLoc = DILocation::get(M.getContext(),
                                       NewPC.address(),
                                       0,
                                       Subprogram,
                                       InlineLocationForMetaAddress);
      CurrentDebugLocation = InlineLoc;
      I.setDebugLoc(CurrentDebugLocation);
    } else {
      I.setDebugLoc(CurrentDebugLocation);
    }
  }
}

bool AttachDebugInfo::runOnModule(llvm::Module &M) {
  DIBuilder DIB(M);
  FunctionMetadataCache *Cache = &getAnalysis<FunctionMetadataCachePass>()
                                    .get();
  auto &GCBI = getAnalysis<GeneratedCodeBasicInfoWrapperPass>().getGCBI();

  // 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.
  DICompileUnit *CU = DIB.createCompileUnit(dwarf::DW_LANG_C,
                                            File,
                                            "revng", // Producer
                                            true, // isOptimized
                                            "", // Flags
                                            0 // RV
  );
  // Create debug info for the 'root' function.
  auto SPFlags = DISubprogram::toSPFlags(false, // isLocalToUnit
                                         true, // isDefinition
                                         false // isOptimized
  );
  auto SPType = DIB.createSubroutineType(DIB.getOrCreateTypeArray({}));
  DISubprogram
    *RootSubprogram = DIB.createFunction(CU->getFile(), // Scope
                                         "root", // Name
                                         StringRef(), // LinkageName
                                         CU->getFile(), // File
                                         1, // LineNo
                                         SPType, // Ty (subroutine type)
                                         1, // ScopeLine
                                         DINode::FlagPrototyped, // Flags
                                         SPFlags);
  DIB.finalizeSubprogram(RootSubprogram);

  for (auto &F : M) {
    // Skip non-isolated functions (e.g. helpers from QEMU).
    if (not FunctionTags::Isolated.isTagOf(&F))
      continue;

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

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

    for (auto &BB : F)
      handleBasicBlock(DIB, BB, RootSubprogram, FM, GCBI);
  }

  return true;
}