Refactor BitcodeReader: move Metadata and ValueId handling in their own class/file

Summary:
I'm planning on changing the way we load metadata to enable laziness.
I'm getting lost in this gigantic files, and gigantic class that is the bitcode
reader. This is a first toward splitting it in a few coarse components that
are more easily understandable.

Reviewers: pcc, tejohnson

Subscribers: mgorny, llvm-commits, dexonsmith

Differential Revision: https://reviews.llvm.org/D27646

llvm-svn: 289461

1 files changed, 79 insertions, 0 deletions

diff --git a/llvm/lib/Bitcode/Reader/MetadataLoader.h b/llvm/lib/Bitcode/Reader/MetadataLoader.h
new file mode 100644
index 00000000000..3f7b64307da
--- /dev/null
+++ b/llvm/lib/Bitcode/Reader/MetadataLoader.h
@@ -0,0 +1,79 @@
+//===-- Bitcode/Reader/MetadataLoader.h - Load Metadatas -------*- C++ -*-====//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This class handles loading Metadatas.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_BITCODE_READER_METADATALOADER_H
+#define LLVM_LIB_BITCODE_READER_METADATALOADER_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Error.h"
+
+#include <functional>
+#include <memory>
+
+namespace llvm {
+class BitcodeReaderValueList;
+class BitstreamCursor;
+class DISubprogram;
+class Error;
+class Function;
+class Instruction;
+class Metadata;
+class MDNode;
+class Module;
+class Type;
+
+/// Helper class that handles loading Metadatas and keeping them available.
+class MetadataLoader {
+  class MetadataLoaderImpl;
+  std::unique_ptr<MetadataLoaderImpl> Pimpl;
+  Error parseMetadata(bool ModuleLevel);
+
+public:
+  ~MetadataLoader();
+  MetadataLoader(BitstreamCursor &Stream, Module &TheModule,
+                 BitcodeReaderValueList &ValueList,
+                 std::function<Type *(unsigned)> getTypeByID);
+  MetadataLoader &operator=(MetadataLoader &&);
+  MetadataLoader(MetadataLoader &&);
+
+  // Parse a module metadata block
+  Error parseModuleMetadata() { return parseMetadata(true); }
+
+  // Parse a function metadata block
+  Error parseFunctionMetadata() { return parseMetadata(false); }
+
+  // Return true there are remaining unresolved forward references.
+  bool hasFwdRefs() const;
+
+  /// Return the given metadata, creating a replaceable forward reference if
+  /// necessary.
+  Metadata *getMetadataFwdRef(unsigned Idx);
+
+  MDNode *getMDNodeFwdRefOrNull(unsigned Idx);
+
+  /// Return the DISubprogra metadata for a Function if any, null otherwise.
+  DISubprogram *lookupSubprogramForFunction(Function *F);
+
+  /// Parse a `METADATA_ATTACHMENT` block for a function.
+  Error parseMetadataAttachment(
+      Function &F, const SmallVectorImpl<Instruction *> &InstructionList);
+
+  /// Parse a `METADATA_KIND` block for the current module.
+  Error parseMetadataKinds();
+
+  unsigned size() const;
+  void shrinkTo(unsigned N);
+};
+}
+
+#endif // LLVM_LIB_BITCODE_READER_METADATALOADER_H