[TextAPI] Add DylibReader

Add support for reading binary Mach-o dynamic libraries. It uses
libObject APIs for extracting information relavant to TAPI and tbd
files. This includes but is not limited to load commands encode data
like install names, current/compat versions and symbols.

Author: cyndyishida

llvm/include/llvm/TextAPI/DylibReader.h

@@ -0,0 +1,50 @@
+//===- TextAPI/DylibReader.h - TAPI MachO Dylib Reader ----------*- 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// Defines the MachO Dynamic Library Reader.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TEXTAPI_DYLIBREADER_H
+#define LLVM_TEXTAPI_DYLIBREADER_H
+
+#include "llvm/BinaryFormat/Magic.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/TextAPI/ArchitectureSet.h"
+#include "llvm/TextAPI/RecordsSlice.h"
+
+namespace llvm {
+namespace MachO {
+
+namespace DylibReader {
+
+struct ParseOption {
+  /// Determines arch slice to parse.
+  ArchitectureSet Archs = ArchitectureSet::All();
+  /// Capture Mach-O header from binary, primarily load commands.
+  bool MachOHeader = true;
+  /// Capture defined symbols out of export trie and n-list.
+  bool SymbolTable = true;
+  /// Capture undefined symbols too.
+  bool Undefineds = true;
+};
+
+/// Parse Mach-O dynamic libraries to extract TAPI attributes.
+///
+/// \param Buffer Data that points to dylib.
+/// \param Options Determines which attributes to extract.
+/// \return List of record slices.
+Expected<Records> readFile(MemoryBufferRef Buffer, const ParseOption &Opt);
+
+} // namespace DylibReader
+
+} // end namespace MachO.
+} // end namespace llvm.
+
+#endif // LLVM_TEXTAPI_DYLIBREADER_H

llvm/include/llvm/TextAPI/Record.h

@@ -103,6 +103,10 @@ class GlobalRecord : public Record {
 
   bool isFunction() const { return GV == Kind::Function; }
   bool isVariable() const { return GV == Kind::Variable; }
+  void setKind(const Kind V) {
+    if (GV == Kind::Unknown)
+      GV = V;
+  }
 
 private:
   Kind GV;

llvm/include/llvm/TextAPI/RecordsSlice.h

@@ -181,6 +181,8 @@ class RecordsSlice {
   std::unique_ptr<BinaryAttrs> BA{nullptr};
 };
 
+using Records = llvm::SmallVector<std::shared_ptr<RecordsSlice>, 4>;
+
 } // namespace MachO
 } // namespace llvm
 #endif // LLVM_TEXTAPI_RECORDSLICE_H

llvm/include/llvm/TextAPI/TextAPIError.h

@@ -21,7 +21,8 @@ enum class TextAPIErrorCode {
   NoSuchArchitecture,
   EmptyResults,
   GenericFrontendError,
-  InvalidInputFormat
+  InvalidInputFormat,
+  UnsupportedTarget
 };
 
 class TextAPIError : public llvm::ErrorInfo<TextAPIError> {

llvm/lib/TextAPI/CMakeLists.txt

@@ -1,6 +1,7 @@
 add_llvm_component_library(LLVMTextAPI
   Architecture.cpp
   ArchitectureSet.cpp
+  DylibReader.cpp
   InterfaceFile.cpp
   TextStubV5.cpp
   PackedVersion.cpp