DWARF parsing and writing support using LLVM (#2520)

This imports LLVM code for DWARF handling. That code has the
Apache 2 license like us. It's also the same code used to
emit DWARF in the common toolchain, so it seems like a safe choice.

This adds two passes: --dwarfdump which runs the same code LLVM
runs for llvm-dwarfdump. This shows we can parse it ok, and will
be useful for debugging. And --dwarfupdate writes out the DWARF
sections (unchanged from what we read, so it just roundtrips - for
updating we need #2515).

This puts LLVM in thirdparty which is added here.

All the LLVM code is behind USE_LLVM_DWARF, which is on
by default, but off in JS for now, as it increases code size by 20%.

This current approach imports the LLVM files directly. This is not
how they are intended to be used, so it required a bunch of
local changes - more than I expected actually, for the platform-specific
stuff. For now this seems to work, so it may be good enough, but
in the long term we may want to switch to linking against libllvm.
A downside to doing that is that binaryen users would need to
have an LLVM build, and even in the waterfall builds we'd have a
problem - while we ship LLVM there anyhow, we constantly update
it, which means that binaryen would need to be on latest llvm all
the time too (which otherwise, given DWARF is quite stable, we
might not need to constantly update).

An even larger issue is that as I did this work I learned about how
DWARF works in LLVM, and while the reading code is easy to
reuse, the writing code is trickier. The main code path is heavily
integrated with the MC layer, which we don't have - we might want
to create a "fake MC layer" for that, but it sounds hard. Instead,
there is the YAML path which is used mostly for testing, and which
can convert DWARF to and from YAML and from binary. Using
the non-YAML parts there, we can convert binary DWARF to
the YAML layer's nice Info data, then convert that to binary. This
works, however, this is not the path LLVM uses normally, and it
supports only some basic DWARF sections - I had to add ranges
support, in fact. So if we need more complex things, we may end
up needing to use the MC layer approach, or consider some other
DWARF library. However, hopefully that should not affect the core
binaryen code which just calls a library for DWARF stuff.

Helps #2400

1 files changed, 419 insertions, 0 deletions

diff --git a/third_party/llvm-project/DWARFEmitter.cpp b/third_party/llvm-project/DWARFEmitter.cpp
new file mode 100644
index 000000000..dbaa06111
--- /dev/null
+++ b/third_party/llvm-project/DWARFEmitter.cpp
@@ -0,0 +1,419 @@
+//===- DWARFEmitter - Convert YAML to DWARF binary data -------------------===//
+//
+// 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
+/// The DWARF component of yaml2obj. Provided as library code for tests.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ObjectYAML/DWARFEmitter.h"
+#include "DWARFVisitor.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ObjectYAML/DWARFYAML.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/SwapByteOrder.h"
+#include "llvm/Support/YAMLTraits.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <vector>
+
+using namespace llvm;
+
+template <typename T>
+static void writeInteger(T Integer, raw_ostream &OS, bool IsLittleEndian) {
+  if (IsLittleEndian != sys::IsLittleEndianHost)
+    sys::swapByteOrder(Integer);
+  OS.write(reinterpret_cast<char *>(&Integer), sizeof(T));
+}
+
+static void writeVariableSizedInteger(uint64_t Integer, size_t Size,
+                                      raw_ostream &OS, bool IsLittleEndian) {
+  if (8 == Size)
+    writeInteger((uint64_t)Integer, OS, IsLittleEndian);
+  else if (4 == Size)
+    writeInteger((uint32_t)Integer, OS, IsLittleEndian);
+  else if (2 == Size)
+    writeInteger((uint16_t)Integer, OS, IsLittleEndian);
+  else if (1 == Size)
+    writeInteger((uint8_t)Integer, OS, IsLittleEndian);
+  else
+    assert(false && "Invalid integer write size.");
+}
+
+static void ZeroFillBytes(raw_ostream &OS, size_t Size) {
+  std::vector<uint8_t> FillData;
+  FillData.insert(FillData.begin(), Size, 0);
+  OS.write(reinterpret_cast<char *>(FillData.data()), Size);
+}
+
+static void writeInitialLength(const DWARFYAML::InitialLength &Length,
+                               raw_ostream &OS, bool IsLittleEndian) {
+  writeInteger((uint32_t)Length.TotalLength, OS, IsLittleEndian);
+  if (Length.isDWARF64())
+    writeInteger((uint64_t)Length.TotalLength64, OS, IsLittleEndian);
+}
+
+void DWARFYAML::EmitDebugStr(raw_ostream &OS, const DWARFYAML::Data &DI) {
+  for (auto Str : DI.DebugStrings) {
+    OS.write(Str.data(), Str.size());
+    OS.write('\0');
+  }
+}
+
+void DWARFYAML::EmitDebugAbbrev(raw_ostream &OS, const DWARFYAML::Data &DI) {
+  for (auto AbbrevDecl : DI.AbbrevDecls) {
+    encodeULEB128(AbbrevDecl.Code, OS);
+    encodeULEB128(AbbrevDecl.Tag, OS);
+    OS.write(AbbrevDecl.Children);
+    for (auto Attr : AbbrevDecl.Attributes) {
+      encodeULEB128(Attr.Attribute, OS);
+      encodeULEB128(Attr.Form, OS);
+      if (Attr.Form == dwarf::DW_FORM_implicit_const)
+        encodeSLEB128(Attr.Value, OS);
+    }
+    encodeULEB128(0, OS);
+    encodeULEB128(0, OS);
+  }
+}
+
+void DWARFYAML::EmitDebugAranges(raw_ostream &OS, const DWARFYAML::Data &DI) {
+  for (auto Range : DI.ARanges) {
+    auto HeaderStart = OS.tell();
+    writeInitialLength(Range.Length, OS, DI.IsLittleEndian);
+    writeInteger((uint16_t)Range.Version, OS, DI.IsLittleEndian);
+    writeInteger((uint32_t)Range.CuOffset, OS, DI.IsLittleEndian);
+    writeInteger((uint8_t)Range.AddrSize, OS, DI.IsLittleEndian);
+    writeInteger((uint8_t)Range.SegSize, OS, DI.IsLittleEndian);
+
+    auto HeaderSize = OS.tell() - HeaderStart;
+    auto FirstDescriptor = alignTo(HeaderSize, Range.AddrSize * 2);
+    ZeroFillBytes(OS, FirstDescriptor - HeaderSize);
+
+    for (auto Descriptor : Range.Descriptors) {
+      writeVariableSizedInteger(Descriptor.Address, Range.AddrSize, OS,
+                                DI.IsLittleEndian);
+      writeVariableSizedInteger(Descriptor.Length, Range.AddrSize, OS,
+                                DI.IsLittleEndian);
+    }
+    ZeroFillBytes(OS, Range.AddrSize * 2);
+  }
+}
+
+// XXX BINARYEN
+void DWARFYAML::EmitDebugRanges(raw_ostream &OS, const DWARFYAML::Data &DI) {
+  // As DwarfStreamer.cpp says, "The debug_range section
+  // format is totally trivial, consisting just of pairs of address
+  // sized addresses describing the ranges." and apparently it ends
+  // with a null termination of a pair of zeros
+  for (auto Range : DI.Ranges) {
+    writeInteger((uint32_t)Range.Start, OS, DI.IsLittleEndian);
+    writeInteger((uint32_t)Range.End, OS, DI.IsLittleEndian);
+  }
+}
+
+void DWARFYAML::EmitPubSection(raw_ostream &OS,
+                               const DWARFYAML::PubSection &Sect,
+                               bool IsLittleEndian) {
+  writeInitialLength(Sect.Length, OS, IsLittleEndian);
+  writeInteger((uint16_t)Sect.Version, OS, IsLittleEndian);
+  writeInteger((uint32_t)Sect.UnitOffset, OS, IsLittleEndian);
+  writeInteger((uint32_t)Sect.UnitSize, OS, IsLittleEndian);
+  for (auto Entry : Sect.Entries) {
+    writeInteger((uint32_t)Entry.DieOffset, OS, IsLittleEndian);
+    if (Sect.IsGNUStyle)
+      writeInteger((uint32_t)Entry.Descriptor, OS, IsLittleEndian);
+    OS.write(Entry.Name.data(), Entry.Name.size());
+    OS.write('\0');
+  }
+}
+
+namespace {
+/// An extension of the DWARFYAML::ConstVisitor which writes compile
+/// units and DIEs to a stream.
+class DumpVisitor : public DWARFYAML::ConstVisitor {
+  raw_ostream &OS;
+
+protected:
+  void onStartCompileUnit(const DWARFYAML::Unit &CU) override {
+    writeInitialLength(CU.Length, OS, DebugInfo.IsLittleEndian);
+    writeInteger((uint16_t)CU.Version, OS, DebugInfo.IsLittleEndian);
+    if(CU.Version >= 5) {
+      writeInteger((uint8_t)CU.Type, OS, DebugInfo.IsLittleEndian);
+      writeInteger((uint8_t)CU.AddrSize, OS, DebugInfo.IsLittleEndian);
+      writeInteger((uint32_t)CU.AbbrOffset, OS, DebugInfo.IsLittleEndian);
+    }else {
+      writeInteger((uint32_t)CU.AbbrOffset, OS, DebugInfo.IsLittleEndian);
+      writeInteger((uint8_t)CU.AddrSize, OS, DebugInfo.IsLittleEndian);
+    }
+  }
+
+  void onStartDIE(const DWARFYAML::Unit &CU,
+                  const DWARFYAML::Entry &DIE) override {
+    encodeULEB128(DIE.AbbrCode, OS);
+  }
+
+  void onValue(const uint8_t U) override {
+    writeInteger(U, OS, DebugInfo.IsLittleEndian);
+  }
+
+  void onValue(const uint16_t U) override {
+    writeInteger(U, OS, DebugInfo.IsLittleEndian);
+  }
+
+  void onValue(const uint32_t U) override {
+    writeInteger(U, OS, DebugInfo.IsLittleEndian);
+  }
+
+  void onValue(const uint64_t U, const bool LEB = false) override {
+    if (LEB)
+      encodeULEB128(U, OS);
+    else
+      writeInteger(U, OS, DebugInfo.IsLittleEndian);
+  }
+
+  void onValue(const int64_t S, const bool LEB = false) override {
+    if (LEB)
+      encodeSLEB128(S, OS);
+    else
+      writeInteger(S, OS, DebugInfo.IsLittleEndian);
+  }
+
+  void onValue(const StringRef String) override {
+    OS.write(String.data(), String.size());
+    OS.write('\0');
+  }
+
+  void onValue(const MemoryBufferRef MBR) override {
+    OS.write(MBR.getBufferStart(), MBR.getBufferSize());
+  }
+
+public:
+  DumpVisitor(const DWARFYAML::Data &DI, raw_ostream &Out)
+      : DWARFYAML::ConstVisitor(DI), OS(Out) {}
+};
+} // namespace
+
+void DWARFYAML::EmitDebugInfo(raw_ostream &OS, const DWARFYAML::Data &DI) {
+  DumpVisitor Visitor(DI, OS);
+  Visitor.traverseDebugInfo();
+}
+
+static void EmitFileEntry(raw_ostream &OS, const DWARFYAML::File &File) {
+  OS.write(File.Name.data(), File.Name.size());
+  OS.write('\0');
+  encodeULEB128(File.DirIdx, OS);
+  encodeULEB128(File.ModTime, OS);
+  encodeULEB128(File.Length, OS);
+}
+
+void DWARFYAML::EmitDebugLine(raw_ostream &OS, const DWARFYAML::Data &DI) {
+  for (const auto &LineTable : DI.DebugLines) {
+    writeInitialLength(LineTable.Length, OS, DI.IsLittleEndian);
+    uint64_t SizeOfPrologueLength = LineTable.Length.isDWARF64() ? 8 : 4;
+    writeInteger((uint16_t)LineTable.Version, OS, DI.IsLittleEndian);
+    writeVariableSizedInteger(LineTable.PrologueLength, SizeOfPrologueLength,
+                              OS, DI.IsLittleEndian);
+    writeInteger((uint8_t)LineTable.MinInstLength, OS, DI.IsLittleEndian);
+    if (LineTable.Version >= 4)
+      writeInteger((uint8_t)LineTable.MaxOpsPerInst, OS, DI.IsLittleEndian);
+    writeInteger((uint8_t)LineTable.DefaultIsStmt, OS, DI.IsLittleEndian);
+    writeInteger((uint8_t)LineTable.LineBase, OS, DI.IsLittleEndian);
+    writeInteger((uint8_t)LineTable.LineRange, OS, DI.IsLittleEndian);
+    writeInteger((uint8_t)LineTable.OpcodeBase, OS, DI.IsLittleEndian);
+
+    for (auto OpcodeLength : LineTable.StandardOpcodeLengths)
+      writeInteger((uint8_t)OpcodeLength, OS, DI.IsLittleEndian);
+
+    for (auto IncludeDir : LineTable.IncludeDirs) {
+      OS.write(IncludeDir.data(), IncludeDir.size());
+      OS.write('\0');
+    }
+    OS.write('\0');
+
+    for (auto File : LineTable.Files)
+      EmitFileEntry(OS, File);
+    OS.write('\0');
+
+    for (auto Op : LineTable.Opcodes) {
+      writeInteger((uint8_t)Op.Opcode, OS, DI.IsLittleEndian);
+      if (Op.Opcode == 0) {
+        encodeULEB128(Op.ExtLen, OS);
+        writeInteger((uint8_t)Op.SubOpcode, OS, DI.IsLittleEndian);
+        switch (Op.SubOpcode) {
+        case dwarf::DW_LNE_set_address:
+        case dwarf::DW_LNE_set_discriminator:
+          writeVariableSizedInteger(Op.Data, DI.CompileUnits[0].AddrSize, OS,
+                                    DI.IsLittleEndian);
+          break;
+        case dwarf::DW_LNE_define_file:
+          EmitFileEntry(OS, Op.FileEntry);
+          break;
+        case dwarf::DW_LNE_end_sequence:
+          break;
+        default:
+          for (auto OpByte : Op.UnknownOpcodeData)
+            writeInteger((uint8_t)OpByte, OS, DI.IsLittleEndian);
+        }
+      } else if (Op.Opcode < LineTable.OpcodeBase) {
+        switch (Op.Opcode) {
+        case dwarf::DW_LNS_copy:
+        case dwarf::DW_LNS_negate_stmt:
+        case dwarf::DW_LNS_set_basic_block:
+        case dwarf::DW_LNS_const_add_pc:
+        case dwarf::DW_LNS_set_prologue_end:
+        case dwarf::DW_LNS_set_epilogue_begin:
+          break;
+
+        case dwarf::DW_LNS_advance_pc:
+        case dwarf::DW_LNS_set_file:
+        case dwarf::DW_LNS_set_column:
+        case dwarf::DW_LNS_set_isa:
+          encodeULEB128(Op.Data, OS);
+          break;
+
+        case dwarf::DW_LNS_advance_line:
+          encodeSLEB128(Op.SData, OS);
+          break;
+
+        case dwarf::DW_LNS_fixed_advance_pc:
+          writeInteger((uint16_t)Op.Data, OS, DI.IsLittleEndian);
+          break;
+
+        default:
+          for (auto OpData : Op.StandardOpcodeData) {
+            encodeULEB128(OpData, OS);
+          }
+        }
+      }
+    }
+  }
+}
+
+using EmitFuncType = void (*)(raw_ostream &, const DWARFYAML::Data &);
+
+static void
+EmitDebugSectionImpl(const DWARFYAML::Data &DI, EmitFuncType EmitFunc,
+                     StringRef Sec,
+                     StringMap<std::unique_ptr<MemoryBuffer>> &OutputBuffers) {
+  std::string Data;
+  raw_string_ostream DebugInfoStream(Data);
+  EmitFunc(DebugInfoStream, DI);
+  DebugInfoStream.flush();
+  if (!Data.empty())
+    OutputBuffers[Sec] = MemoryBuffer::getMemBufferCopy(Data);
+}
+
+namespace {
+class DIEFixupVisitor : public DWARFYAML::Visitor {
+  uint64_t Length;
+
+public:
+  DIEFixupVisitor(DWARFYAML::Data &DI) : DWARFYAML::Visitor(DI){};
+
+private:
+  virtual void onStartCompileUnit(DWARFYAML::Unit &CU) { Length = 7; }
+
+  virtual void onEndCompileUnit(DWARFYAML::Unit &CU) {
+    CU.Length.setLength(Length);
+  }
+
+  virtual void onStartDIE(DWARFYAML::Unit &CU, DWARFYAML::Entry &DIE) {
+    Length += getULEB128Size(DIE.AbbrCode);
+  }
+
+  virtual void onValue(const uint8_t U) { Length += 1; }
+  virtual void onValue(const uint16_t U) { Length += 2; }
+  virtual void onValue(const uint32_t U) { Length += 4; }
+  virtual void onValue(const uint64_t U, const bool LEB = false) {
+    if (LEB)
+      Length += getULEB128Size(U);
+    else
+      Length += 8;
+  }
+  virtual void onValue(const int64_t S, const bool LEB = false) {
+    if (LEB)
+      Length += getSLEB128Size(S);
+    else
+      Length += 8;
+  }
+  virtual void onValue(const StringRef String) { Length += String.size() + 1; }
+
+  virtual void onValue(const MemoryBufferRef MBR) {
+    Length += MBR.getBufferSize();
+  }
+};
+} // namespace
+
+Expected<StringMap<std::unique_ptr<MemoryBuffer>>>
+DWARFYAML::EmitDebugSections(StringRef YAMLString, bool ApplyFixups,
+                             bool IsLittleEndian) {
+  yaml::Input YIn(YAMLString);
+
+  DWARFYAML::Data DI;
+  DI.IsLittleEndian = IsLittleEndian;
+  YIn >> DI;
+  if (YIn.error())
+    return errorCodeToError(YIn.error());
+
+  if (ApplyFixups) {
+    DIEFixupVisitor DIFixer(DI);
+    DIFixer.traverseDebugInfo();
+  }
+
+  StringMap<std::unique_ptr<MemoryBuffer>> DebugSections;
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugInfo, "debug_info",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugLine, "debug_line",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugStr, "debug_str",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugAbbrev, "debug_abbrev",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugAranges, "debug_aranges",
+                       DebugSections);
+  return std::move(DebugSections);
+}
+
+// XXX BINARYEN <--
+namespace llvm {
+namespace DWARFYAML {
+StringMap<std::unique_ptr<MemoryBuffer>>
+EmitDebugSections(llvm::DWARFYAML::Data &DI, bool ApplyFixups) {
+  if (ApplyFixups) {
+    DIEFixupVisitor DIFixer(DI);
+    DIFixer.traverseDebugInfo();
+  }
+
+  StringMap<std::unique_ptr<MemoryBuffer>> DebugSections;
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugInfo, "debug_info",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugLine, "debug_line",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugStr, "debug_str",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugAbbrev, "debug_abbrev",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugAranges, "debug_aranges",
+                       DebugSections);
+  EmitDebugSectionImpl(DI, &DWARFYAML::EmitDebugRanges, "debug_ranges",
+                       DebugSections); // XXX BINARYEN
+  return std::move(DebugSections);
+}
+} // namespace DWARFYAML
+} // namespace llvm
+// XXX BINARYEN -->