[llvm] [DebugInfo] Support to get TU for hash from .debug_types.dwo section in DWARF4. (PR #161067)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-debuginfo

Author: Liu Ke (Sockke)

<details>
<summary>Changes</summary>

Using the DWP's cu_index/tu_index only loads the DWO units from the .debug_info.dwo section for hash, which works fine in DWARF5. However, tu_index points to .debug_types.dwo section in DWARF4, which can cause the type unit to be lost due to the incorrect loading target. (Related discussion in [811b60f](https://github.com/llvm/llvm-project/commit/811b60f0b99dad4b2989d21dde38d49155b0c4f9))

This patch supports to get the type unit for hash from .debug_types.dwo section in DWARF4.

---
Full diff: https://github.com/llvm/llvm-project/pull/161067.diff


3 Files Affected:

- (modified) llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h (+3-1) 
- (modified) llvm/lib/DebugInfo/DWARF/DWARFContext.cpp (+15-4) 
- (modified) llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp (+15-7) 


``````````diff
diff --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
index 964ff8e396660..3e8d7e8b32fc8 100644
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
@@ -143,7 +143,9 @@ class DWARFUnitVector final : public SmallVector<std::unique_ptr<DWARFUnit>, 1>
       decltype(make_filter_range(std::declval<iterator_range>(), isCompileUnit));
 
   LLVM_ABI DWARFUnit *getUnitForOffset(uint64_t Offset) const;
-  LLVM_ABI DWARFUnit *getUnitForIndexEntry(const DWARFUnitIndex::Entry &E);
+  LLVM_ABI DWARFUnit *
+  getUnitForIndexEntry(const DWARFUnitIndex::Entry &E, DWARFSectionKind Sec,
+                       const DWARFSection *Section = nullptr);
 
   /// Read units from a .debug_info or .debug_types section.  Calls made
   /// before finishedInfoUnits() are assumed to be for .debug_info sections,
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
index 73df62abaf023..c40042c2958e4 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFContext.cpp
@@ -1344,9 +1344,20 @@ void DWARFContext::dump(
 DWARFTypeUnit *DWARFContext::getTypeUnitForHash(uint64_t Hash, bool IsDWO) {
   DWARFUnitVector &DWOUnits = State->getDWOUnits();
   if (const auto &TUI = getTUIndex()) {
-    if (const auto *R = TUI.getFromHash(Hash))
-      return dyn_cast_or_null<DWARFTypeUnit>(
-          DWOUnits.getUnitForIndexEntry(*R));
+    if (const auto *R = TUI.getFromHash(Hash)) {
+      if (TUI.getVersion() >= 5)
+        return dyn_cast_or_null<DWARFTypeUnit>(
+            DWOUnits.getUnitForIndexEntry(*R, DW_SECT_INFO));
+      else {
+        DWARFUnit *TypesUnit = nullptr;
+        getDWARFObj().forEachTypesDWOSections([&](const DWARFSection &S) {
+          if (!TypesUnit)
+            TypesUnit =
+                DWOUnits.getUnitForIndexEntry(*R, DW_SECT_EXT_TYPES, &S);
+        });
+        return dyn_cast_or_null<DWARFTypeUnit>(TypesUnit);
+      }
+    }
     return nullptr;
   }
   return State->getTypeUnitMap(IsDWO).lookup(Hash);
@@ -1358,7 +1369,7 @@ DWARFCompileUnit *DWARFContext::getDWOCompileUnitForHash(uint64_t Hash) {
   if (const auto &CUI = getCUIndex()) {
     if (const auto *R = CUI.getFromHash(Hash))
       return dyn_cast_or_null<DWARFCompileUnit>(
-          DWOUnits.getUnitForIndexEntry(*R));
+          DWOUnits.getUnitForIndexEntry(*R, DW_SECT_INFO));
     return nullptr;
   }
 
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index ef59c82fc6a01..da0bf03e1ac57 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -161,17 +161,24 @@ DWARFUnit *DWARFUnitVector::getUnitForOffset(uint64_t Offset) const {
   return nullptr;
 }
 
-DWARFUnit *
-DWARFUnitVector::getUnitForIndexEntry(const DWARFUnitIndex::Entry &E) {
-  const auto *CUOff = E.getContribution(DW_SECT_INFO);
+DWARFUnit *DWARFUnitVector::getUnitForIndexEntry(const DWARFUnitIndex::Entry &E,
+                                                 DWARFSectionKind Sec,
+                                                 const DWARFSection *Section) {
+  const auto *CUOff = E.getContribution(Sec);
   if (!CUOff)
     return nullptr;
 
   uint64_t Offset = CUOff->getOffset();
-  auto end = begin() + getNumInfoUnits();
+  auto begin = this->begin();
+  auto end = begin + getNumInfoUnits();
+
+  if (Sec == DW_SECT_EXT_TYPES) {
+    begin = end;
+    end = this->end();
+  }
 
   auto *CU =
-      std::upper_bound(begin(), end, CUOff->getOffset(),
+      std::upper_bound(begin, end, CUOff->getOffset(),
                        [](uint64_t LHS, const std::unique_ptr<DWARFUnit> &RHS) {
                          return LHS < RHS->getNextUnitOffset();
                        });
@@ -181,13 +188,14 @@ DWARFUnitVector::getUnitForIndexEntry(const DWARFUnitIndex::Entry &E) {
   if (!Parser)
     return nullptr;
 
-  auto U = Parser(Offset, DW_SECT_INFO, nullptr, &E);
+  auto U = Parser(Offset, Sec, Section, &E);
   if (!U)
     return nullptr;
 
   auto *NewCU = U.get();
   this->insert(CU, std::move(U));
-  ++NumInfoUnits;
+  if (Sec == DW_SECT_INFO)
+    ++NumInfoUnits;
   return NewCU;
 }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/161067