[llvm] [BOLT][DWARF] Add support for .debug_names (PR #81062)

[Amir Ayupov via llvm-commits]

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@@ -0,0 +1,613 @@
+//===- bolt/Rewrite/DebugNames.cpp -------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "bolt/Core/DebugNames.h"
+#include "bolt/Core/BinaryContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFExpression.h"
+#include "llvm/DebugInfo/DWARF/DWARFTypeUnit.h"
+#include "llvm/Support/EndianStream.h"
+#include "llvm/Support/LEB128.h"
+
+namespace llvm {
+namespace bolt {
+DWARF5AcceleratorTable::DWARF5AcceleratorTable(
+    const bool CreateDebugNames, BinaryContext &BC,
+    DebugStrWriter &MainBinaryStrWriter)
+    : MainBinaryStrWriter(MainBinaryStrWriter) {
+  NeedToCreate = CreateDebugNames || BC.getDebugNamesSection();
+  if (!NeedToCreate)
+    return;
+  FullTableBuffer = std::make_unique<DebugStrBufferVector>();
+  FullTableStream = std::make_unique<raw_svector_ostream>(*FullTableBuffer);
+  StrBuffer = std::make_unique<DebugStrBufferVector>();
+  StrStream = std::make_unique<raw_svector_ostream>(*StrBuffer);
+  EntriesBuffer = std::make_unique<DebugStrBufferVector>();
+  Entriestream = std::make_unique<raw_svector_ostream>(*EntriesBuffer);
+  AugStringBuffer = std::make_unique<DebugStrBufferVector>();
+  AugStringtream = std::make_unique<raw_svector_ostream>(*AugStringBuffer);
+
+  // Binary has split-dwarf CUs.
+  // Even thought for non-skeleton-cu all names are in .debug_str.dwo section,
+  // for the .debug_names contributions they are in .debug_str section.
+  if (BC.getNumDWOCUs()) {
+    DataExtractor StrData(BC.DwCtx->getDWARFObj().getStrSection(),
+                          BC.DwCtx->isLittleEndian(), 0);
+    uint64_t Offset = 0;
+    uint64_t StrOffset = 0;
+    while (StrData.isValidOffset(Offset)) {
+      Error Err = Error::success();
+      const char *CStr = StrData.getCStr(&Offset, &Err);
+      if (Err) {
+        NeedToCreate = false;
+        errs() << "BOLT-WARNING: [internal-dwarf-error]: Could not extract "
+                  "string from .debug_str section at offset: "
+               << Twine::utohexstr(StrOffset) << ".\n";
+        return;
+      }
+      auto R = StrCacheToOffsetMap.try_emplace(
+          llvm::hash_value(llvm::StringRef(CStr)), StrOffset);
+      if (!R.second)
+        errs() << "BOLT-WARNING: [internal-dwarf-error]: collision occured on "
+               << CStr << " at offset : 0x" << Twine::utohexstr(StrOffset)
+               << ". Previous string offset is: 0x"
+               << Twine::utohexstr(R.first->second) << ".\n";
+      StrOffset = Offset;
+    }
+  }
+}
+
+void DWARF5AcceleratorTable::setCurrentUnit(DWARFUnit &Unit,
+                                            const uint64_t UnitStartOffset) {
+  CurrentUnit = nullptr;
+  CurrentUnitOffset = UnitStartOffset;
+  std::optional<uint64_t> DWOID = Unit.getDWOId();
+  // We process skeleton CUs after DWO Units for it.
+  // Patching offset in CU list to correct one.
+  if (!Unit.isDWOUnit() && DWOID) {
+    auto Iter = CUOffsetsToPatch.find(*DWOID);
+    // Check in case no entries were added from non skeleton DWO section.
+    if (Iter != CUOffsetsToPatch.end())
+      CUList[Iter->second] = UnitStartOffset;
+  }
+}
+
+void DWARF5AcceleratorTable::addUnit(DWARFUnit &Unit,
+                                     const std::optional<uint64_t> &DWOID) {
+  StrOffsetsWriter.clear();
+  StrOffsetsWriter.initialize(Unit);
+  StrSection = Unit.getStringSection();
+  if (Unit.isTypeUnit()) {
+    if (DWOID) {
+      // We adding an entry for a DWO TU. The DWO CU might not have any entries,
+      // so need to add it to the list pre-emptively.
+      auto Iter = CUOffsetsToPatch.insert({*DWOID, CUList.size()});
+      if (Iter.second)
+        CUList.push_back(0xBADBAD);
----------------
aaupov wrote:

Would it make sense to define a constant (e.g. INVALID_CU) instead of using a literal here and below?

https://github.com/llvm/llvm-project/pull/81062