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, 237 insertions, 0 deletions

diff --git a/third_party/llvm-project/include/llvm/Object/Binary.h b/third_party/llvm-project/include/llvm/Object/Binary.h
new file mode 100644
index 000000000..aa5e718f5
--- /dev/null
+++ b/third_party/llvm-project/include/llvm/Object/Binary.h
@@ -0,0 +1,237 @@
+//===- Binary.h - A generic binary file -------------------------*- 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 declares the Binary class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OBJECT_BINARY_H
+#define LLVM_OBJECT_BINARY_H
+
+#include "llvm-c/Types.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Object/Error.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include <algorithm>
+#include <memory>
+#include <utility>
+
+namespace llvm {
+
+class LLVMContext;
+class StringRef;
+
+namespace object {
+
+class Binary {
+private:
+  unsigned int TypeID;
+
+protected:
+  MemoryBufferRef Data;
+
+  Binary(unsigned int Type, MemoryBufferRef Source);
+
+  enum {
+    ID_Archive,
+    ID_MachOUniversalBinary,
+    ID_COFFImportFile,
+    ID_IR,            // LLVM IR
+    ID_TapiUniversal, // Text-based Dynamic Library Stub file.
+    ID_TapiFile,      // Text-based Dynamic Library Stub file.
+
+    ID_Minidump,
+
+    ID_WinRes, // Windows resource (.res) file.
+
+    // Object and children.
+    ID_StartObjects,
+    ID_COFF,
+
+    ID_XCOFF32, // AIX XCOFF 32-bit
+    ID_XCOFF64, // AIX XCOFF 64-bit
+
+    ID_ELF32L, // ELF 32-bit, little endian
+    ID_ELF32B, // ELF 32-bit, big endian
+    ID_ELF64L, // ELF 64-bit, little endian
+    ID_ELF64B, // ELF 64-bit, big endian
+
+    ID_MachO32L, // MachO 32-bit, little endian
+    ID_MachO32B, // MachO 32-bit, big endian
+    ID_MachO64L, // MachO 64-bit, little endian
+    ID_MachO64B, // MachO 64-bit, big endian
+
+    ID_Wasm,
+
+    ID_EndObjects
+  };
+
+  static inline unsigned int getELFType(bool isLE, bool is64Bits) {
+    if (isLE)
+      return is64Bits ? ID_ELF64L : ID_ELF32L;
+    else
+      return is64Bits ? ID_ELF64B : ID_ELF32B;
+  }
+
+  static unsigned int getMachOType(bool isLE, bool is64Bits) {
+    if (isLE)
+      return is64Bits ? ID_MachO64L : ID_MachO32L;
+    else
+      return is64Bits ? ID_MachO64B : ID_MachO32B;
+  }
+
+public:
+  Binary() = delete;
+  Binary(const Binary &other) = delete;
+  virtual ~Binary();
+
+  StringRef getData() const;
+  StringRef getFileName() const;
+  MemoryBufferRef getMemoryBufferRef() const;
+
+  // Cast methods.
+  unsigned int getType() const { return TypeID; }
+
+  // Convenience methods
+  bool isObject() const {
+    return TypeID > ID_StartObjects && TypeID < ID_EndObjects;
+  }
+
+  bool isSymbolic() const {
+    return isIR() || isObject() || isCOFFImportFile() || isTapiFile();
+  }
+
+  bool isArchive() const { return TypeID == ID_Archive; }
+
+  bool isMachOUniversalBinary() const {
+    return TypeID == ID_MachOUniversalBinary;
+  }
+
+  bool isTapiUniversal() const { return TypeID == ID_TapiUniversal; }
+
+  bool isELF() const {
+    return TypeID >= ID_ELF32L && TypeID <= ID_ELF64B;
+  }
+
+  bool isMachO() const {
+    return TypeID >= ID_MachO32L && TypeID <= ID_MachO64B;
+  }
+
+  bool isCOFF() const {
+    return TypeID == ID_COFF;
+  }
+
+  bool isXCOFF() const { return TypeID == ID_XCOFF32 || TypeID == ID_XCOFF64; }
+
+  bool isWasm() const { return TypeID == ID_Wasm; }
+
+  bool isCOFFImportFile() const {
+    return TypeID == ID_COFFImportFile;
+  }
+
+  bool isIR() const {
+    return TypeID == ID_IR;
+  }
+
+  bool isMinidump() const { return TypeID == ID_Minidump; }
+
+  bool isTapiFile() const { return TypeID == ID_TapiFile; }
+
+  bool isLittleEndian() const {
+    return !(TypeID == ID_ELF32B || TypeID == ID_ELF64B ||
+             TypeID == ID_MachO32B || TypeID == ID_MachO64B);
+  }
+
+  bool isWinRes() const { return TypeID == ID_WinRes; }
+
+  Triple::ObjectFormatType getTripleObjectFormat() const {
+    if (isCOFF())
+      return Triple::COFF;
+    if (isMachO())
+      return Triple::MachO;
+    if (isELF())
+      return Triple::ELF;
+    return Triple::UnknownObjectFormat;
+  }
+
+  static std::error_code checkOffset(MemoryBufferRef M, uintptr_t Addr,
+                                     const uint64_t Size) {
+    if (Addr + Size < Addr || Addr + Size < Size ||
+        Addr + Size > uintptr_t(M.getBufferEnd()) ||
+        Addr < uintptr_t(M.getBufferStart())) {
+      return object_error::unexpected_eof;
+    }
+    return std::error_code();
+  }
+};
+
+// Create wrappers for C Binding types (see CBindingWrapping.h).
+DEFINE_ISA_CONVERSION_FUNCTIONS(Binary, LLVMBinaryRef)
+
+/// Create a Binary from Source, autodetecting the file type.
+///
+/// @param Source The data to create the Binary from.
+Expected<std::unique_ptr<Binary>> createBinary(MemoryBufferRef Source,
+                                               LLVMContext *Context = nullptr);
+
+template <typename T> class OwningBinary {
+  std::unique_ptr<T> Bin;
+  std::unique_ptr<MemoryBuffer> Buf;
+
+public:
+  OwningBinary();
+  OwningBinary(std::unique_ptr<T> Bin, std::unique_ptr<MemoryBuffer> Buf);
+  OwningBinary(OwningBinary<T>&& Other);
+  OwningBinary<T> &operator=(OwningBinary<T> &&Other);
+
+  std::pair<std::unique_ptr<T>, std::unique_ptr<MemoryBuffer>> takeBinary();
+
+  T* getBinary();
+  const T* getBinary() const;
+};
+
+template <typename T>
+OwningBinary<T>::OwningBinary(std::unique_ptr<T> Bin,
+                              std::unique_ptr<MemoryBuffer> Buf)
+    : Bin(std::move(Bin)), Buf(std::move(Buf)) {}
+
+template <typename T> OwningBinary<T>::OwningBinary() = default;
+
+template <typename T>
+OwningBinary<T>::OwningBinary(OwningBinary &&Other)
+    : Bin(std::move(Other.Bin)), Buf(std::move(Other.Buf)) {}
+
+template <typename T>
+OwningBinary<T> &OwningBinary<T>::operator=(OwningBinary &&Other) {
+  Bin = std::move(Other.Bin);
+  Buf = std::move(Other.Buf);
+  return *this;
+}
+
+template <typename T>
+std::pair<std::unique_ptr<T>, std::unique_ptr<MemoryBuffer>>
+OwningBinary<T>::takeBinary() {
+  return std::make_pair(std::move(Bin), std::move(Buf));
+}
+
+template <typename T> T* OwningBinary<T>::getBinary() {
+  return Bin.get();
+}
+
+template <typename T> const T* OwningBinary<T>::getBinary() const {
+  return Bin.get();
+}
+
+Expected<OwningBinary<Binary>> createBinary(StringRef Path);
+
+} // end namespace object
+
+} // end namespace llvm
+
+#endif // LLVM_OBJECT_BINARY_H