[MC] Make MCDwarfLineStr class public

[maksfb]

Summary

Add MCDwarfLineStr class to the public API.

Note that MCDwarfLineTableHeader::Emit(), takes MCDwarfLineStr as
an Optional<> parameter making it impossible to use the API if the class
is not publicly defined.

[maksfb]

Friendly ping.

[ayermolo]

Personally patch makes sense. It's inline with all other classes that are exposed, and it's needed for tools that use MC and are working with DWARF 5.

[dblaikie]

Perhaps a unit test demonstrating the sort of thing you want to use this API for?

 Note that MCDwarfLineTableHeader::Emit(), takes MCDwarfLineStr as an Optional<> parameter making it impossible to use the API if the class is not publicly defined.

Presumably you could still pass None to such an API? But yeah, couldn't use whatever functionality is exposed by passing a non-None value.

[maksfb]

 Note that MCDwarfLineTableHeader::Emit(), takes MCDwarfLineStr as an Optional<> parameter making it impossible to use the API if the class is not publicly defined.

Presumably you could still pass None to such an API? But yeah, couldn't use whatever functionality is exposed by passing a non-None value.

I couldn't make None work. Still, would like to have the support for DWARF v5 and will need this interface.

[rafauler]

Unit test

[rafauler]

Fix comments and unnecessary changes to CMakeLists.txt

[maksfb]

Thank you for adding the unit test, @rafaelauler! How does it look, @dblaikie?

[rafauler]

Linter

[maksfb]

Friendly ping.

[alexander-shaposhnikov]

LG

llvm/include/llvm/MC/MCDwarf.h

 #define LLVM_MC_MCDWARF_H
 
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/MC/MCSection.h"
+#include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MD5.h"
 #include <cassert>
 #include <cstdint>
 #include <string>
 #include <tuple>
 #include <utility>
 #include <vector>
 
 namespace llvm {
 
 template <typename T> class ArrayRef;
 class MCAsmBackend;
 class MCContext;
-class MCDwarfLineStr;
 class MCObjectStreamer;
 class MCStreamer;
 class MCSymbol;
 class raw_ostream;
 class SMLoc;
 class SourceMgr;
 
 namespace mcdwarf {
 // Emit the common part of the DWARF 5 range/locations list tables header.
 MCSymbol *emitListsTableHeaderStart(MCStreamer &S);
 } // namespace mcdwarf
 
+/// Manage the .debug_line_str section contents, if we use it.
+class MCDwarfLineStr {
+  MCSymbol *LineStrLabel = nullptr;
+  StringTableBuilder LineStrings{StringTableBuilder::DWARF};
+  bool UseRelocs = false;
+
+public:
+  /// Construct an instance that can emit .debug_line_str (for use in a normal
+  /// v5 line table).
+  explicit MCDwarfLineStr(MCContext &Ctx);
+
+  /// Emit a reference to the string.
+  void emitRef(MCStreamer *MCOS, StringRef Path);
+
+  /// Emit the .debug_line_str section if appropriate.
+  void emitSection(MCStreamer *MCOS);
+};
+
 /// Instances of this class represent the name of the dwarf .file directive and
 /// its associated dwarf file number in the MC file. MCDwarfFile's are created
 /// and uniqued by the MCContext class. In Dwarf 4 file numbers start from 1;
 /// i.e. the entry with file number 1 is the first element in the vector of
 /// DwarfFiles and there is no MCDwarfFile with file number 0. In Dwarf 5 file
 /// numbers start from 0, with the MCDwarfFile with file number 0 being the
 /// primary source file, and file numbers correspond to their index in the
 /// vector.

 public:
   // This emits the Dwarf file and the line tables for all Compile Units.
   static void emit(MCStreamer *MCOS, MCDwarfLineTableParams Params);
 
   // This emits the Dwarf file and the line tables for a given Compile Unit.
   void emitCU(MCStreamer *MCOS, MCDwarfLineTableParams Params,
               Optional<MCDwarfLineStr> &LineStr) const;
 
+  // This emits a single line table associated with a given Section.
+  static void
+  emitOne(MCStreamer *MCOS, MCSection *Section,
+          const MCLineSection::MCDwarfLineEntryCollection &LineEntries);
+
   Expected<unsigned> tryGetFile(StringRef &Directory, StringRef &FileName,
                                 Optional<MD5::MD5Result> Checksum,
                                 Optional<StringRef> Source,
                                 uint16_t DwarfVersion,
                                 unsigned FileNumber = 0);
   unsigned getFile(StringRef &Directory, StringRef &FileName,
                    Optional<MD5::MD5Result> Checksum, Optional<StringRef> Source,
                    uint16_t DwarfVersion, unsigned FileNumber = 0) {

llvm/lib/MC/MCDwarf.cpp

 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCObjectStreamer.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
-#include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/EndianStream.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SourceMgr.h"
MCSymbol *mcdwarf::emitListsTableHeaderStart(MCStreamer &S) {
   S.emitInt16(S.getContext().getDwarfVersion());
   S.AddComment("Address size");
   S.emitInt8(S.getContext().getAsmInfo()->getCodePointerSize());
   S.AddComment("Segment selector size");
   S.emitInt8(0);
   return End;
 }
 
-/// Manage the .debug_line_str section contents, if we use it.
-class llvm::MCDwarfLineStr {
-  MCSymbol *LineStrLabel = nullptr;
-  StringTableBuilder LineStrings{StringTableBuilder::DWARF};
-  bool UseRelocs = false;
-
-public:
-  /// Construct an instance that can emit .debug_line_str (for use in a normal
-  /// v5 line table).
-  explicit MCDwarfLineStr(MCContext &Ctx) {
-    UseRelocs = Ctx.getAsmInfo()->doesDwarfUseRelocationsAcrossSections();
-    if (UseRelocs)
-      LineStrLabel =
-          Ctx.getObjectFileInfo()->getDwarfLineStrSection()->getBeginSymbol();
-  }
-
-  /// Emit a reference to the string.
-  void emitRef(MCStreamer *MCOS, StringRef Path);
-
-  /// Emit the .debug_line_str section if appropriate.
-  void emitSection(MCStreamer *MCOS);
-};
-
 static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
   unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
   if (MinInsnLength == 1)
     return AddrDelta;
   if (AddrDelta % MinInsnLength != 0) {
     // TODO: report this error, but really only once.
     ;
   }
   return AddrDelta / MinInsnLength;
 }
 
+MCDwarfLineStr::MCDwarfLineStr(MCContext &Ctx) {
+  UseRelocs = Ctx.getAsmInfo()->doesDwarfUseRelocationsAcrossSections();
+  if (UseRelocs)
+    LineStrLabel =
+        Ctx.getObjectFileInfo()->getDwarfLineStrSection()->getBeginSymbol();
+}
+
 //
 // This is called when an instruction is assembled into the specified section
 // and if there is information from the last .loc directive that has yet to have
 // a line entry made for it is made.
 //
 void MCDwarfLineEntry::make(MCStreamer *MCOS, MCSection *Section) {
   if (!MCOS->getContext().getDwarfLocSeen())
     return;
makeStartPlusIntExpr(MCContext &Ctx, const MCSymbol &Start, int IntVal) {
   const MCExpr *Res = MCBinaryExpr::create(MCBinaryExpr::Add, LHS, RHS, Ctx);
   return Res;
 }
 
 //
 // This emits the Dwarf line table for the specified section from the entries
 // in the LineSection.
 //
-static inline void emitDwarfLineTable(
+void MCDwarfLineTable::emitOne(
     MCStreamer *MCOS, MCSection *Section,
     const MCLineSection::MCDwarfLineEntryCollection &LineEntries) {
   unsigned FileNum = 1;
   unsigned LastLine = 1;
   unsigned Column = 0;
   unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
   unsigned Isa = 0;
   unsigned Discriminator = 0;

 }
 
 void MCDwarfLineTable::emitCU(MCStreamer *MCOS, MCDwarfLineTableParams Params,
                               Optional<MCDwarfLineStr> &LineStr) const {
   MCSymbol *LineEndSym = Header.Emit(MCOS, Params, LineStr).second;
 
   // Put out the line tables.
   for (const auto &LineSec : MCLineSections.getMCLineEntries())
-    emitDwarfLineTable(MCOS, LineSec.first, LineSec.second);
+    emitOne(MCOS, LineSec.first, LineSec.second);
 
   // This is the end of the section, so set the value of the symbol at the end
   // of this section (that was used in a previous expression).
   MCOS->emitLabel(LineEndSym);
 }
 
 Expected<unsigned> MCDwarfLineTable::tryGetFile(StringRef &Directory,
                                                 StringRef &FileName,

llvm/unittests/MC/CMakeLists.txt

 foreach(t ${LLVM_TARGETS_TO_BUILD})
   if(IS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/${t})
     add_subdirectory(${t})
   endif()
 endforeach()
 
 set(LLVM_LINK_COMPONENTS
   ${LLVM_TARGETS_TO_BUILD}
   MC
   MCDisassembler
   Support
   )
 
 add_llvm_unittest(MCTests
   Disassembler.cpp
   DwarfLineTables.cpp
+  DwarfLineTableHeaders.cpp
   MCInstPrinter.cpp
   StringTableBuilderTest.cpp
   TargetRegistry.cpp
   MCDisassemblerTest.cpp
   )
 

llvm/unittests/MC/DwarfLineTableHeaders.cpp

+//===- llvm/unittest/MC/DwarfLineTableHeaders.cpp -------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/BinaryFormat/Dwarf.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/MC/MCInstrInfo.h"
+#include "llvm/MC/MCObjectStreamer.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/MCTargetOptions.h"
+#include "llvm/Object/Binary.h"
+#include "llvm/Object/ELFObjectFile.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+class DwarfLineTableHeaders : public ::testing::Test {
+public:
+  const char *TripleName = "x86_64-pc-linux";
+  std::unique_ptr<MCRegisterInfo> MRI;
+  std::unique_ptr<MCAsmInfo> MAI;
+  std::unique_ptr<const MCSubtargetInfo> STI;
+  const Target *TheTarget;
+
+  struct StreamerContext {
+    std::unique_ptr<MCObjectFileInfo> MOFI;
+    std::unique_ptr<MCContext> Ctx;
+    std::unique_ptr<const MCInstrInfo> MII;
+    std::unique_ptr<MCStreamer> Streamer;
+  };
+
+  DwarfLineTableHeaders() {
+    llvm::InitializeAllTargetInfos();
+    llvm::InitializeAllTargetMCs();
+    llvm::InitializeAllDisassemblers();
+
+    // If we didn't build x86, do not run the test.
+    std::string Error;
+    TheTarget = TargetRegistry::lookupTarget(TripleName, Error);
+    if (!TheTarget)
+      return;
+
+    MRI.reset(TheTarget->createMCRegInfo(TripleName));
+    MCTargetOptions MCOptions;
+    MAI.reset(TheTarget->createMCAsmInfo(*MRI, TripleName, MCOptions));
+    STI.reset(TheTarget->createMCSubtargetInfo(TripleName, "", ""));
+  }
+
+  /// Create all data structures necessary to operate an assembler
+  StreamerContext createStreamer(raw_pwrite_stream &OS) {
+    StreamerContext Res;
+    Res.Ctx =
+        std::make_unique<MCContext>(Triple(TripleName), MAI.get(), MRI.get(),
+                                    /*MSTI=*/nullptr);
+    Res.MOFI.reset(TheTarget->createMCObjectFileInfo(*Res.Ctx.get(),
+                                                     /*PIC=*/false));
+    Res.Ctx->setObjectFileInfo(Res.MOFI.get());
+
+    Res.MII.reset(TheTarget->createMCInstrInfo());
+    MCCodeEmitter *MCE =
+        TheTarget->createMCCodeEmitter(*Res.MII, *MRI, *Res.Ctx);
+    MCAsmBackend *MAB =
+        TheTarget->createMCAsmBackend(*STI, *MRI, MCTargetOptions());
+    std::unique_ptr<MCObjectWriter> OW = MAB->createObjectWriter(OS);
+    Res.Streamer.reset(TheTarget->createMCObjectStreamer(
+        Triple(TripleName), *Res.Ctx, std::unique_ptr<MCAsmBackend>(MAB),
+        std::move(OW), std::unique_ptr<MCCodeEmitter>(MCE), *STI,
+        /* RelaxAll */ false,
+        /* IncrementalLinkerCompatible */ false,
+        /* DWARFMustBeAtTheEnd */ false));
+    return Res;
+  }
+
+  /// Emit a .debug_line section with the given context parameters
+  void emitDebugLineSection(StreamerContext &C) {
+    MCContext &Ctx = *C.Ctx;
+    MCStreamer *TheStreamer = C.Streamer.get();
+    MCAssembler &Assembler =
+        static_cast<MCObjectStreamer *>(TheStreamer)->getAssembler();
+    TheStreamer->initSections(false, *STI);
+
+    // Create a mock function
+    MCSection *Section = C.MOFI->getTextSection();
+    Section->setHasInstructions(true);
+    TheStreamer->SwitchSection(Section);
+    TheStreamer->emitCFIStartProc(true);
+
+    // Create a mock dwarfloc
+    Ctx.setCurrentDwarfLoc(/*FileNo=*/0, /*Line=*/1, /*Column=*/1, /*Flags=*/0,
+                           /*Isa=*/0, /*Discriminator=*/0);
+    MCDwarfLoc Loc = Ctx.getCurrentDwarfLoc();
+    MCSymbol *LineSym = Ctx.createTempSymbol();
+    // Set the value of the symbol to use for the MCDwarfLineEntry.
+    TheStreamer->emitLabel(LineSym);
+    TheStreamer->emitNops(4, 1, SMLoc(), *STI);
+    TheStreamer->emitCFIEndProc();
+
+    // Start emission of .debug_line
+    TheStreamer->SwitchSection(C.MOFI->getDwarfLineSection());
+    MCDwarfLineTableHeader Header;
+    MCDwarfLineTableParams Params = Assembler.getDWARFLinetableParams();
+    Optional<MCDwarfLineStr> LineStr(None);
+    if (Ctx.getDwarfVersion() >= 5) {
+      LineStr = MCDwarfLineStr(Ctx);
+      Header.setRootFile("dir", "file", None, None);
+    }
+    MCSymbol *LineEndSym = Header.Emit(TheStreamer, Params, LineStr).second;
+
+    // Put out the line tables.
+    MCLineSection::MCDwarfLineEntryCollection LineEntries;
+    MCDwarfLineEntry LineEntry(LineSym, Loc);
+    LineEntries.push_back(LineEntry);
+    MCDwarfLineTable::emitOne(TheStreamer, Section, LineEntries);
+    TheStreamer->emitLabel(LineEndSym);
+    if (LineStr)
+      LineStr->emitSection(TheStreamer);
+  }
+
+  /// Check contents of .debug_line section
+  void verifyDebugLineContents(const llvm::object::ObjectFile &E,
+                               ArrayRef<uint8_t> ExpectedEncoding) {
+    for (const llvm::object::SectionRef &Section : E.sections()) {
+      Expected<StringRef> SectionNameOrErr = Section.getName();
+      ASSERT_TRUE(static_cast<bool>(SectionNameOrErr));
+      StringRef SectionName = *SectionNameOrErr;
+      if (SectionName.empty() || SectionName != ".debug_line")
+        continue;
+      Expected<StringRef> ContentsOrErr = Section.getContents();
+      ASSERT_TRUE(static_cast<bool>(ContentsOrErr));
+      StringRef Contents = *ContentsOrErr;
+      ASSERT_TRUE(Contents.size() > ExpectedEncoding.size());
+      EXPECT_EQ(
+          arrayRefFromStringRef(Contents.slice(0, ExpectedEncoding.size())),
+          ExpectedEncoding);
+      return;
+    }
+    llvm_unreachable(".debug_line not found");
+  }
+
+  ///  Open ObjFileData as an object file and read its .debug_line section
+  void readAndCheckDebugLineContents(StringRef ObjFileData,
+                                     ArrayRef<uint8_t> Expected) {
+    std::unique_ptr<MemoryBuffer> MB =
+        MemoryBuffer::getMemBuffer(ObjFileData, "", false);
+    std::unique_ptr<object::Binary> Bin =
+        cantFail(llvm::object::createBinary(MB->getMemBufferRef()));
+    if (auto *E = dyn_cast<llvm::object::ELFObjectFileBase>(&*Bin)) {
+      return verifyDebugLineContents(*E, Expected);
+    }
+    llvm_unreachable("ELF object file not found");
+  }
+};
+} // namespace
+
+TEST_F(DwarfLineTableHeaders, TestDWARF4HeaderEmission) {
+  if (!MRI)
+    return;
+
+  SmallString<0> EmittedBinContents;
+  raw_svector_ostream VecOS(EmittedBinContents);
+  StreamerContext C = createStreamer(VecOS);
+  C.Ctx->setDwarfVersion(4);
+  emitDebugLineSection(C);
+  C.Streamer->Finish();
+  readAndCheckDebugLineContents(
+      EmittedBinContents.str(),
+      {/*    Total length=*/0x30, 0, 0, 0,
+       /*   DWARF version=*/4, 0,
+       /* Prologue length=*/0x14, 0, 0, 0,
+       /* min_inst_length=*/1,
+       /*max_ops_per_inst=*/1,
+       /* default_is_stmt=*/DWARF2_LINE_DEFAULT_IS_STMT,
+       /*       line_base=*/static_cast<uint8_t>(-5),
+       /*      line_range=*/14,
+       /*     opcode_base=*/13});
+}
+
+TEST_F(DwarfLineTableHeaders, TestDWARF5HeaderEmission) {
+  if (!MRI)
+    return;
+
+  SmallString<0> EmittedBinContents;
+  raw_svector_ostream VecOS(EmittedBinContents);
+  StreamerContext C = createStreamer(VecOS);
+  C.Ctx->setDwarfVersion(5);
+  emitDebugLineSection(C);
+  C.Streamer->Finish();
+  readAndCheckDebugLineContents(
+      EmittedBinContents.str(),
+      {/*    Total length=*/0x43, 0, 0, 0,
+       /*   DWARF version=*/5, 0,
+       /*        ptr size=*/8,
+       /*         segment=*/0,
+       /* Prologue length=*/0x25, 0, 0, 0,
+       /* min_inst_length=*/1,
+       /*max_ops_per_inst=*/1,
+       /* default_is_stmt=*/DWARF2_LINE_DEFAULT_IS_STMT,
+       /*       line_base=*/static_cast<uint8_t>(-5),
+       /*      line_range=*/14,
+       /*     opcode_base=*/13});
+}