[llvm] [Object] Extract format-agnostic BBAddrMap decoder (PR #188435)

[Haohai Wen via llvm-commits]

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+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements shared utilities for basic-block address maps.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Object/BBAddrMap.h"
+#include "llvm/Object/Error.h"
+
+using namespace llvm;
+using namespace object;
+
+namespace {
+
+// Helper to extract and decode the next ULEB128 value as unsigned int.
+// Returns zero and sets ULEBSizeErr if the ULEB128 value exceeds the unsigned
+// int limit.
+// Also returns zero if ULEBSizeErr is already in an error state.
+// ULEBSizeErr is an out variable if an error occurs.
+template <typename IntTy, std::enable_if_t<std::is_unsigned_v<IntTy>, int> = 0>
+static IntTy readULEB128As(const DataExtractor &Data,
+                           DataExtractor::Cursor &Cur, Error &ULEBSizeErr) {
+  // Bail out and do not extract data if ULEBSizeErr is already set.
+  if (ULEBSizeErr)
+    return 0;
+  uint64_t Offset = Cur.tell();
+  uint64_t Value = Data.getULEB128(Cur);
+  if (Value > std::numeric_limits<IntTy>::max()) {
+    ULEBSizeErr = createError("ULEB128 value at offset 0x" +
+                              Twine::utohexstr(Offset) + " exceeds UINT" +
+                              Twine(std::numeric_limits<IntTy>::digits) +
+                              "_MAX (0x" + Twine::utohexstr(Value) + ")");
+    return 0;
+  }
+  return static_cast<IntTy>(Value);
+}
+} // end anonymous namespace
+
+Expected<std::vector<BBAddrMap>>
+llvm::object::decodeBBAddrMapPayload(AddressExtractor &Extractor,
+                                     std::vector<PGOAnalysisMap> *PGOAnalyses) {
+  const DataExtractor &Data = Extractor.getDataExtractor();
+  std::vector<BBAddrMap> FunctionEntries;
+
+  DataExtractor::Cursor Cur(0);
+  Error ULEBSizeErr = Error::success();
+  Error MetadataDecodeErr = Error::success();
+
+  uint8_t Version = 0;
+  uint16_t Feature = 0;
+  BBAddrMap::Features FeatEnable{};
+  while (!ULEBSizeErr && !MetadataDecodeErr && Cur &&
+         Cur.tell() < Data.getData().size()) {
+    Version = Data.getU8(Cur);
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HaohaiWen wrote:

Done.

https://github.com/llvm/llvm-project/pull/188435