[Remarks] Move BitstreamRemarkParser helpers to private header (NFC) (llvm#156302)

These helpers are only used in the implementation, and we also don't
expose similar details for the YAMLRemarkParser.

Pull Request: llvm#156302

Author: tobias-stadler

llvm/include/llvm/Remarks/BitstreamRemarkParser.h

@@ -11,7 +11,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/Remarks/BitstreamRemarkParser.h"
 #include "BitstreamRemarkParser.h"
 #include "llvm/Remarks/Remark.h"
 #include "llvm/Support/MemoryBuffer.h"

llvm/lib/Remarks/BitstreamRemarkParser.cpp

@@ -13,10 +13,14 @@
 #ifndef LLVM_LIB_REMARKS_BITSTREAM_REMARK_PARSER_H
 #define LLVM_LIB_REMARKS_BITSTREAM_REMARK_PARSER_H
 
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Bitstream/BitstreamReader.h"
 #include "llvm/Remarks/BitstreamRemarkContainer.h"
-#include "llvm/Remarks/BitstreamRemarkParser.h"
 #include "llvm/Remarks/RemarkFormat.h"
 #include "llvm/Remarks/RemarkParser.h"
+#include "llvm/Support/Error.h"
+#include <array>
 #include <cstdint>
 #include <memory>
 #include <optional>
@@ -26,6 +30,91 @@ namespace remarks {
 
 struct Remark;
 
+/// Helper to parse a META_BLOCK for a bitstream remark container.
+struct BitstreamMetaParserHelper {
+  /// The Bitstream reader.
+  BitstreamCursor &Stream;
+  /// Reference to the storage for the block info.
+  BitstreamBlockInfo &BlockInfo;
+  /// The parsed content: depending on the container type, some fields might be
+  /// empty.
+  std::optional<uint64_t> ContainerVersion;
+  std::optional<uint8_t> ContainerType;
+  std::optional<StringRef> StrTabBuf;
+  std::optional<StringRef> ExternalFilePath;
+  std::optional<uint64_t> RemarkVersion;
+
+  /// Continue parsing with \p Stream. \p Stream is expected to contain a
+  /// ENTER_SUBBLOCK to the META_BLOCK at the current position.
+  /// \p Stream is expected to have a BLOCKINFO_BLOCK set.
+  BitstreamMetaParserHelper(BitstreamCursor &Stream,
+                            BitstreamBlockInfo &BlockInfo);
+
+  /// Parse the META_BLOCK and fill the available entries.
+  /// This helper does not check for the validity of the fields.
+  Error parse();
+};
+
+/// Helper to parse a REMARK_BLOCK for a bitstream remark container.
+struct BitstreamRemarkParserHelper {
+  /// The Bitstream reader.
+  BitstreamCursor &Stream;
+  /// The parsed content: depending on the remark, some fields might be empty.
+  std::optional<uint8_t> Type;
+  std::optional<uint64_t> RemarkNameIdx;
+  std::optional<uint64_t> PassNameIdx;
+  std::optional<uint64_t> FunctionNameIdx;
+  std::optional<uint64_t> SourceFileNameIdx;
+  std::optional<uint32_t> SourceLine;
+  std::optional<uint32_t> SourceColumn;
+  std::optional<uint64_t> Hotness;
+  struct Argument {
+    std::optional<uint64_t> KeyIdx;
+    std::optional<uint64_t> ValueIdx;
+    std::optional<uint64_t> SourceFileNameIdx;
+    std::optional<uint32_t> SourceLine;
+    std::optional<uint32_t> SourceColumn;
+  };
+  std::optional<ArrayRef<Argument>> Args;
+  /// Avoid re-allocating a vector every time.
+  SmallVector<Argument, 8> TmpArgs;
+
+  /// Continue parsing with \p Stream. \p Stream is expected to contain a
+  /// ENTER_SUBBLOCK to the REMARK_BLOCK at the current position.
+  /// \p Stream is expected to have a BLOCKINFO_BLOCK set and to have already
+  /// parsed the META_BLOCK.
+  BitstreamRemarkParserHelper(BitstreamCursor &Stream);
+
+  /// Parse the REMARK_BLOCK and fill the available entries.
+  /// This helper does not check for the validity of the fields.
+  Error parse();
+};
+
+/// Helper to parse any bitstream remark container.
+struct BitstreamParserHelper {
+  /// The Bitstream reader.
+  BitstreamCursor Stream;
+  /// The block info block.
+  BitstreamBlockInfo BlockInfo;
+  /// Start parsing at \p Buffer.
+  BitstreamParserHelper(StringRef Buffer);
+  /// Parse the magic number.
+  Expected<std::array<char, 4>> parseMagic();
+  /// Parse the block info block containing all the abbrevs.
+  /// This needs to be called before calling any other parsing function.
+  Error parseBlockInfoBlock();
+  /// Return true if the next block is a META_BLOCK. This function does not move
+  /// the cursor.
+  Expected<bool> isMetaBlock();
+  /// Return true if the next block is a REMARK_BLOCK. This function does not
+  /// move the cursor.
+  Expected<bool> isRemarkBlock();
+  /// Return true if the parser reached the end of the stream.
+  bool atEndOfStream() { return Stream.AtEndOfStream(); }
+  /// Jump to the end of the stream, skipping everything.
+  void skipToEnd() { return Stream.skipToEnd(); }
+};
+
 /// Parses and holds the state of the latest parsed remark.
 struct BitstreamRemarkParser : public RemarkParser {
   /// The buffer to parse.