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, 302 insertions, 0 deletions

diff --git a/third_party/llvm-project/include/llvm/DebugInfo/DIContext.h b/third_party/llvm-project/include/llvm/DebugInfo/DIContext.h
new file mode 100644
index 000000000..fbebfe634
--- /dev/null
+++ b/third_party/llvm-project/include/llvm/DebugInfo/DIContext.h
@@ -0,0 +1,302 @@
+//===- DIContext.h ----------------------------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines DIContext, an abstract data structure that holds
+// debug information data.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_DICONTEXT_H
+#define LLVM_DEBUGINFO_DICONTEXT_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <tuple>
+#include <utility>
+
+namespace llvm {
+
+/// A format-neutral container for source line information.
+struct DILineInfo {
+  // DILineInfo contains "<invalid>" for function/filename it cannot fetch.
+  static constexpr const char *const BadString = "<invalid>";
+  // Use "??" instead of "<invalid>" to make our output closer to addr2line.
+  static constexpr const char *const Addr2LineBadString = "??";
+  std::string FileName;
+  std::string FunctionName;
+  Optional<StringRef> Source;
+  uint32_t Line = 0;
+  uint32_t Column = 0;
+  uint32_t StartLine = 0;
+
+  // DWARF-specific.
+  uint32_t Discriminator = 0;
+
+  DILineInfo() : FileName(BadString), FunctionName(BadString) {}
+
+  bool operator==(const DILineInfo &RHS) const {
+    return Line == RHS.Line && Column == RHS.Column &&
+           FileName == RHS.FileName && FunctionName == RHS.FunctionName &&
+           StartLine == RHS.StartLine && Discriminator == RHS.Discriminator;
+  }
+
+  bool operator!=(const DILineInfo &RHS) const {
+    return !(*this == RHS);
+  }
+
+  bool operator<(const DILineInfo &RHS) const {
+    return std::tie(FileName, FunctionName, Line, Column, StartLine,
+                    Discriminator) <
+           std::tie(RHS.FileName, RHS.FunctionName, RHS.Line, RHS.Column,
+                    RHS.StartLine, RHS.Discriminator);
+  }
+
+  explicit operator bool() const { return *this != DILineInfo(); }
+
+  void dump(raw_ostream &OS) {
+    OS << "Line info: ";
+    if (FileName != BadString)
+      OS << "file '" << FileName << "', ";
+    if (FunctionName != BadString)
+      OS << "function '" << FunctionName << "', ";
+    OS << "line " << Line << ", ";
+    OS << "column " << Column << ", ";
+    OS << "start line " << StartLine << '\n';
+  }
+};
+
+using DILineInfoTable = SmallVector<std::pair<uint64_t, DILineInfo>, 16>;
+
+/// A format-neutral container for inlined code description.
+class DIInliningInfo {
+  SmallVector<DILineInfo, 4> Frames;
+
+public:
+  DIInliningInfo() = default;
+
+  const DILineInfo & getFrame(unsigned Index) const {
+    assert(Index < Frames.size());
+    return Frames[Index];
+  }
+
+  DILineInfo *getMutableFrame(unsigned Index) {
+    assert(Index < Frames.size());
+    return &Frames[Index];
+  }
+
+  uint32_t getNumberOfFrames() const {
+    return Frames.size();
+  }
+
+  void addFrame(const DILineInfo &Frame) {
+    Frames.push_back(Frame);
+  }
+
+  void resize(unsigned i) {
+    Frames.resize(i);
+  }
+};
+
+/// Container for description of a global variable.
+struct DIGlobal {
+  std::string Name;
+  uint64_t Start = 0;
+  uint64_t Size = 0;
+
+  DIGlobal() : Name(DILineInfo::BadString) {}
+};
+
+struct DILocal {
+  std::string FunctionName;
+  std::string Name;
+  std::string DeclFile;
+  uint64_t DeclLine = 0;
+  Optional<int64_t> FrameOffset;
+  Optional<uint64_t> Size;
+  Optional<uint64_t> TagOffset;
+};
+
+/// A DINameKind is passed to name search methods to specify a
+/// preference regarding the type of name resolution the caller wants.
+enum class DINameKind { None, ShortName, LinkageName };
+
+/// Controls which fields of DILineInfo container should be filled
+/// with data.
+struct DILineInfoSpecifier {
+  enum class FileLineInfoKind { None, Default, AbsoluteFilePath };
+  using FunctionNameKind = DINameKind;
+
+  FileLineInfoKind FLIKind;
+  FunctionNameKind FNKind;
+
+  DILineInfoSpecifier(FileLineInfoKind FLIKind = FileLineInfoKind::Default,
+                      FunctionNameKind FNKind = FunctionNameKind::None)
+      : FLIKind(FLIKind), FNKind(FNKind) {}
+};
+
+/// This is just a helper to programmatically construct DIDumpType.
+enum DIDumpTypeCounter {
+#define HANDLE_DWARF_SECTION(ENUM_NAME, ELF_NAME, CMDLINE_NAME) \
+  DIDT_ID_##ENUM_NAME,
+#include "llvm/BinaryFormat/Dwarf.def"
+#undef HANDLE_DWARF_SECTION
+  DIDT_ID_UUID,
+  DIDT_ID_Count
+};
+static_assert(DIDT_ID_Count <= 32, "section types overflow storage");
+
+/// Selects which debug sections get dumped.
+enum DIDumpType : unsigned {
+  DIDT_Null,
+  DIDT_All             = ~0U,
+#define HANDLE_DWARF_SECTION(ENUM_NAME, ELF_NAME, CMDLINE_NAME) \
+  DIDT_##ENUM_NAME = 1U << DIDT_ID_##ENUM_NAME,
+#include "llvm/BinaryFormat/Dwarf.def"
+#undef HANDLE_DWARF_SECTION
+  DIDT_UUID = 1 << DIDT_ID_UUID,
+};
+
+/// Container for dump options that control which debug information will be
+/// dumped.
+struct DIDumpOptions {
+  unsigned DumpType = DIDT_All;
+  unsigned ChildRecurseDepth = -1U;
+  unsigned ParentRecurseDepth = -1U;
+  uint16_t Version = 0; // DWARF version to assume when extracting.
+  uint8_t AddrSize = 4; // Address byte size to assume when extracting.
+  bool ShowAddresses = true;
+  bool ShowChildren = false;
+  bool ShowParents = false;
+  bool ShowForm = false;
+  bool SummarizeTypes = false;
+  bool Verbose = false;
+  bool DisplayRawContents = false;
+
+  /// Return default option set for printing a single DIE without children.
+  static DIDumpOptions getForSingleDIE() {
+    DIDumpOptions Opts;
+    Opts.ChildRecurseDepth = 0;
+    Opts.ParentRecurseDepth = 0;
+    return Opts;
+  }
+
+  /// Return the options with RecurseDepth set to 0 unless explicitly required.
+  DIDumpOptions noImplicitRecursion() const {
+    DIDumpOptions Opts = *this;
+    if (ChildRecurseDepth == -1U && !ShowChildren)
+      Opts.ChildRecurseDepth = 0;
+    if (ParentRecurseDepth == -1U && !ShowParents)
+      Opts.ParentRecurseDepth = 0;
+    return Opts;
+  }
+};
+
+class DIContext {
+public:
+  enum DIContextKind {
+    CK_DWARF,
+    CK_PDB
+  };
+
+  DIContext(DIContextKind K) : Kind(K) {}
+  virtual ~DIContext() = default;
+
+  DIContextKind getKind() const { return Kind; }
+
+  virtual void dump(raw_ostream &OS, DIDumpOptions DumpOpts) = 0;
+
+  virtual bool verify(raw_ostream &OS, DIDumpOptions DumpOpts = {}) {
+    // No verifier? Just say things went well.
+    return true;
+  }
+
+  virtual DILineInfo getLineInfoForAddress(
+      object::SectionedAddress Address,
+      DILineInfoSpecifier Specifier = DILineInfoSpecifier()) = 0;
+  virtual DILineInfoTable getLineInfoForAddressRange(
+      object::SectionedAddress Address, uint64_t Size,
+      DILineInfoSpecifier Specifier = DILineInfoSpecifier()) = 0;
+  virtual DIInliningInfo getInliningInfoForAddress(
+      object::SectionedAddress Address,
+      DILineInfoSpecifier Specifier = DILineInfoSpecifier()) = 0;
+
+  virtual std::vector<DILocal>
+  getLocalsForAddress(object::SectionedAddress Address) = 0;
+
+private:
+  const DIContextKind Kind;
+};
+
+/// An inferface for inquiring the load address of a loaded object file
+/// to be used by the DIContext implementations when applying relocations
+/// on the fly.
+class LoadedObjectInfo {
+protected:
+  LoadedObjectInfo() = default;
+  LoadedObjectInfo(const LoadedObjectInfo &) = default;
+
+public:
+  virtual ~LoadedObjectInfo() = default;
+
+  /// Obtain the Load Address of a section by SectionRef.
+  ///
+  /// Calculate the address of the given section.
+  /// The section need not be present in the local address space. The addresses
+  /// need to be consistent with the addresses used to query the DIContext and
+  /// the output of this function should be deterministic, i.e. repeated calls
+  /// with the same Sec should give the same address.
+  virtual uint64_t getSectionLoadAddress(const object::SectionRef &Sec) const {
+    return 0;
+  }
+
+  /// If conveniently available, return the content of the given Section.
+  ///
+  /// When the section is available in the local address space, in relocated
+  /// (loaded) form, e.g. because it was relocated by a JIT for execution, this
+  /// function should provide the contents of said section in `Data`. If the
+  /// loaded section is not available, or the cost of retrieving it would be
+  /// prohibitive, this function should return false. In that case, relocations
+  /// will be read from the local (unrelocated) object file and applied on the
+  /// fly. Note that this method is used purely for optimzation purposes in the
+  /// common case of JITting in the local address space, so returning false
+  /// should always be correct.
+  virtual bool getLoadedSectionContents(const object::SectionRef &Sec,
+                                        StringRef &Data) const {
+    return false;
+  }
+
+  // FIXME: This is untested and unused anywhere in the LLVM project, it's
+  // used/needed by Julia (an external project). It should have some coverage
+  // (at least tests, but ideally example functionality).
+  /// Obtain a copy of this LoadedObjectInfo.
+  virtual std::unique_ptr<LoadedObjectInfo> clone() const = 0;
+};
+
+template <typename Derived, typename Base = LoadedObjectInfo>
+struct LoadedObjectInfoHelper : Base {
+protected:
+  LoadedObjectInfoHelper(const LoadedObjectInfoHelper &) = default;
+  LoadedObjectInfoHelper() = default;
+
+public:
+  template <typename... Ts>
+  LoadedObjectInfoHelper(Ts &&... Args) : Base(std::forward<Ts>(Args)...) {}
+
+  std::unique_ptr<llvm::LoadedObjectInfo> clone() const override {
+    return std::make_unique<Derived>(static_cast<const Derived &>(*this));
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_DEBUGINFO_DICONTEXT_H