[DWARF] Don't process .debug_info relocations for DWO Context

When we build with split dwarf in single mode the .o files that contain both "normal" debug sections and dwo sections, along with relocaiton sections for "normal" debug sections.
When we create DWARF context in DWARFObjInMemory we process relocations and store them in the map for .debug_info, etc section.
For DWO Context we also do it for non dwo dwarf sections. Which I believe is not necessary. This leads to a lot of memory being wasted. We observed 70GB extra memory being used.

I went with context sensitive approach, flag is passed in. I am not sure if it's always safe not to process relocations for regular debug sections if Obj contains .dwo sections.
If it is alternatvie might be just to scan, in constructor, sections and if there are .dwo sections not to process regular debug ones.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D106624

llvm/include/llvm/DebugInfo/DWARF/DWARFContext.h

@@ -387,9 +387,12 @@ class DWARFContext : public DIContext {
 
   function_ref<void(Error)> getWarningHandler() { return WarningHandler; }
 
+  enum class ProcessDebugRelocations { Process, Ignore };
+
   static std::unique_ptr<DWARFContext>
-  create(const object::ObjectFile &Obj, const LoadedObjectInfo *L = nullptr,
-         std::string DWPName = "",
+  create(const object::ObjectFile &Obj,
+         ProcessDebugRelocations RelocAction = ProcessDebugRelocations::Process,
+         const LoadedObjectInfo *L = nullptr, std::string DWPName = "",
          std::function<void(Error)> RecoverableErrorHandler =
              WithColor::defaultErrorHandler,
          std::function<void(Error)> WarningHandler =

llvm/lib/DebugInfo/DWARF/DWARFContext.cpp

@@ -1411,7 +1411,8 @@ DWARFContext::getDWOContext(StringRef AbsolutePath) {
 
   auto S = std::make_shared<DWOFile>();
   S->File = std::move(Obj.get());
-  S->Context = DWARFContext::create(*S->File.getBinary());
+  S->Context = DWARFContext::create(*S->File.getBinary(),
+                                    ProcessDebugRelocations::Ignore);
   *Entry = S;
   auto *Ctxt = S->Context.get();
   return std::shared_ptr<DWARFContext>(std::move(S), Ctxt);
@@ -1652,7 +1653,9 @@ class DWARFObjInMemory final : public DWARFObject {
     }
   }
   DWARFObjInMemory(const object::ObjectFile &Obj, const LoadedObjectInfo *L,
-                   function_ref<void(Error)> HandleError, function_ref<void(Error)> HandleWarning )
+                   function_ref<void(Error)> HandleError,
+                   function_ref<void(Error)> HandleWarning,
+                   DWARFContext::ProcessDebugRelocations RelocAction)
       : IsLittleEndian(Obj.isLittleEndian()),
         AddressSize(Obj.getBytesInAddress()), FileName(Obj.getFileName()),
         Obj(&Obj) {
@@ -1735,7 +1738,12 @@ class DWARFObjInMemory final : public DWARFObject {
         S.Data = Data;
       }
 
-      if (RelocatedSection == Obj.section_end())
+      if (RelocatedSection != Obj.section_end() && Name.contains(".dwo"))
+        HandleWarning(
+            createError("Unexpected relocations for dwo section " + Name));
+
+      if (RelocatedSection == Obj.section_end() ||
+          (RelocAction == DWARFContext::ProcessDebugRelocations::Ignore))
         continue;
 
       StringRef RelSecName;
@@ -1772,18 +1780,10 @@ class DWARFObjInMemory final : public DWARFObject {
         if (RelSecName == "debug_info")
           Map = &static_cast<DWARFSectionMap &>(InfoSections[*RelocatedSection])
                      .Relocs;
-        else if (RelSecName == "debug_info.dwo")
-          Map = &static_cast<DWARFSectionMap &>(
-                     InfoDWOSections[*RelocatedSection])
-                     .Relocs;
         else if (RelSecName == "debug_types")
           Map =
               &static_cast<DWARFSectionMap &>(TypesSections[*RelocatedSection])
                    .Relocs;
-        else if (RelSecName == "debug_types.dwo")
-          Map = &static_cast<DWARFSectionMap &>(
-                     TypesDWOSections[*RelocatedSection])
-                     .Relocs;
         else
           continue;
       }
@@ -1966,12 +1966,13 @@ class DWARFObjInMemory final : public DWARFObject {
 } // namespace
 
 std::unique_ptr<DWARFContext>
-DWARFContext::create(const object::ObjectFile &Obj, const LoadedObjectInfo *L,
-                     std::string DWPName,
+DWARFContext::create(const object::ObjectFile &Obj,
+                     ProcessDebugRelocations RelocAction,
+                     const LoadedObjectInfo *L, std::string DWPName,
                      std::function<void(Error)> RecoverableErrorHandler,
                      std::function<void(Error)> WarningHandler) {
-  auto DObj =
-      std::make_unique<DWARFObjInMemory>(Obj, L, RecoverableErrorHandler, WarningHandler);
+  auto DObj = std::make_unique<DWARFObjInMemory>(
+      Obj, L, RecoverableErrorHandler, WarningHandler, RelocAction);
   return std::make_unique<DWARFContext>(std::move(DObj), std::move(DWPName),
                                         RecoverableErrorHandler,
                                         WarningHandler);

llvm/lib/DebugInfo/Symbolize/Symbolize.cpp

@@ -600,7 +600,9 @@ LLVMSymbolizer::getOrCreateModuleInfo(const std::string &ModuleName) {
     }
   }
   if (!Context)
-    Context = DWARFContext::create(*Objects.second, nullptr, Opts.DWPName);
+    Context = DWARFContext::create(
+        *Objects.second, DWARFContext::ProcessDebugRelocations::Process,
+        nullptr, Opts.DWPName);
   return createModuleInfo(Objects.first, std::move(Context), ModuleName);
 }
 

llvm/test/DebugInfo/X86/dwarfdump-rela-dwo.s

@@ -0,0 +1,57 @@
+# Test objective to verify warning is printed if DWO secton has relocations.
+#
+# RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o %t.o
+# RUN: llvm-dwarfdump --debug-info %t.o | FileCheck %s
+# RUN: llvm-dwarfdump --debug-info %t.o 2> %t.txt
+# RUN: cat %t.txt | FileCheck %s --check-prefix=PART2
+
+        .section .debug_str.dwo,"MSe",@progbits,1
+.dwo_producer:
+        .asciz "Handmade DWO producer"
+.dwo_CU_5:
+        .asciz "V5_dwo_compile_unit"
+
+        .section	.debug_str_offsets.dwo,"e",@progbits
+        .long	Lstr_offsets_end-Lstr_offsets_start                              # Length of String Offsets Set
+        Lstr_offsets_start:
+	.short	5
+	.short	0
+	.long	.dwo_producer-.debug_str.dwo
+	.long	.dwo_CU_5-.debug_str.dwo
+        Lstr_offsets_end:
+
+# And a .dwo copy for the .dwo sections.
+        .section .debug_abbrev.dwo,"e",@progbits
+        .byte 0x01  # Abbrev code
+        .byte 0x11  # DW_TAG_compile_unit
+        .byte 0x00  # DW_CHILDREN_no
+        .byte 0x25  # DW_AT_producer
+        .byte 0x0e  # DW_FORM_strp
+        .byte 0x03  # DW_AT_name
+        .byte 0x25  # DW_FORM_strx1
+        .byte 0x00  # EOM(1)
+        .byte 0x00  # EOM(2)
+
+        .section .debug_info.dwo,"e",@progbits
+# CHECK-LABEL: .debug_info.dwo
+
+# DWARF v5 split CU header.
+        .long  CU_split_5_end-CU_split_5_version # Length of Unit
+CU_split_5_version:
+        .short 5                # DWARF version number
+        .byte 5                 # DWARF Unit Type
+        .byte 8                 # Address Size (in bytes)
+        .long 0 # Offset Into Abbrev. Section
+        .quad 0x5a              # DWO ID
+# The split compile-unit DIE, with DW_AT_producer, DW_AT_name, DW_AT_stmt_list.
+        .byte 1
+        .long .dwo_producer
+        .byte 1
+        .byte 0 # NULL
+CU_split_5_end:
+
+# CHECK: 0x00000000: Compile Unit: length = 0x00000017, format = DWARF32, version = 0x0005, unit_type = DW_UT_split_compile, abbr_offset = 0x0000, addr_size = 0x08, DWO_id = 0x000000000000005a (next unit at 0x0000001b)
+# CHECK: 0x00000014: DW_TAG_compile_unit
+# CHECK-NEXT: DW_AT_producer	("Handmade DWO producer")
+# CHECK-NEXT: DW_AT_name	("V5_dwo_compile_unit")
+# PART2: warning: Unexpected relocations for dwo section rela.debug_info.dwo

llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp

@@ -536,8 +536,9 @@ static bool handleBuffer(StringRef Filename, MemoryBufferRef Buffer,
   };
   if (auto *Obj = dyn_cast<ObjectFile>(BinOrErr->get())) {
     if (filterArch(*Obj)) {
-      std::unique_ptr<DWARFContext> DICtx =
-          DWARFContext::create(*Obj, nullptr, "", RecoverableErrorHandler);
+      std::unique_ptr<DWARFContext> DICtx = DWARFContext::create(
+          *Obj, DWARFContext::ProcessDebugRelocations::Process, nullptr, "",
+          RecoverableErrorHandler);
       if (!HandleObj(*Obj, *DICtx, Filename, OS))
         Result = false;
     }
@@ -548,8 +549,9 @@ static bool handleBuffer(StringRef Filename, MemoryBufferRef Buffer,
       if (auto MachOOrErr = ObjForArch.getAsObjectFile()) {
         auto &Obj = **MachOOrErr;
         if (filterArch(Obj)) {
-          std::unique_ptr<DWARFContext> DICtx =
-              DWARFContext::create(Obj, nullptr, "", RecoverableErrorHandler);
+          std::unique_ptr<DWARFContext> DICtx = DWARFContext::create(
+              Obj, DWARFContext::ProcessDebugRelocations::Process, nullptr, "",
+              RecoverableErrorHandler);
           if (!HandleObj(Obj, *DICtx, ObjName, OS))
             Result = false;
         }

llvm/tools/llvm-readobj/DwarfCFIEHPrinter.h

@@ -185,7 +185,8 @@ void PrinterContext<ELFT>::printEHFrame(const Elf_Shdr *EHFrameShdr) const {
     reportError(DataOrErr.takeError(), ObjF.getFileName());
 
   // Construct DWARFDataExtractor to handle relocations ("PC Begin" fields).
-  std::unique_ptr<DWARFContext> DICtx = DWARFContext::create(ObjF, nullptr);
+  std::unique_ptr<DWARFContext> DICtx = DWARFContext::create(
+      ObjF, DWARFContext::ProcessDebugRelocations::Process, nullptr);
   DWARFDataExtractor DE(DICtx->getDWARFObj(),
                         DICtx->getDWARFObj().getEHFrameSection(),
                         ELFT::TargetEndianness == support::endianness::little,

llvm/tools/llvm-rtdyld/llvm-rtdyld.cpp

@@ -413,8 +413,9 @@ static int printLineInfoForInput(bool LoadObjects, bool UseDebugObj) {
       }
     }
 
-    std::unique_ptr<DIContext> Context =
-        DWARFContext::create(*SymbolObj, LoadedObjInfo.get());
+    std::unique_ptr<DIContext> Context = DWARFContext::create(
+        *SymbolObj, DWARFContext::ProcessDebugRelocations::Process,
+        LoadedObjInfo.get());
 
     std::vector<std::pair<SymbolRef, uint64_t>> SymAddr =
         object::computeSymbolSizes(*SymbolObj);

llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

@@ -2519,8 +2519,9 @@ TEST(DWARFDebugInfo, TestErrorReporting) {
 
   // DWARFContext parses whole file and finds the two errors we expect.
   int Errors = 0;
-  std::unique_ptr<DWARFContext> Ctx1 =
-      DWARFContext::create(**Obj, nullptr, "", [&](Error E) {
+  std::unique_ptr<DWARFContext> Ctx1 = DWARFContext::create(
+      **Obj, DWARFContext::ProcessDebugRelocations::Process, nullptr, "",
+      [&](Error E) {
         ++Errors;
         consumeError(std::move(E));
       });