Don't warn about missing DWO files when converting mach-o files. (llvm#152598)

Apple uses the DW_AT_GNU_dwo_id for non split DWARF cases. Any compile
units with this attribute would cause many warnings to be emitted:

"warning: Unable to retrieve DWO .debug_info section for"

This patch fixes the DWARFTransformer to not look for skeleton compile
unit in mach-o based binaries and adds a unit test.

Author: clayborg

llvm/include/llvm/DebugInfo/GSYM/DwarfTransformer.h

@@ -43,8 +43,14 @@ class DwarfTransformer {
   ///
   /// \param LDCS Flag to indicate whether we should load the call site
   /// information from DWARF `DW_TAG_call_site` entries
-  DwarfTransformer(DWARFContext &D, GsymCreator &G, bool LDCS = false)
-      : DICtx(D), Gsym(G), LoadDwarfCallSites(LDCS) {}
+  ///
+  /// \param MachO Flag to indicate if the object file is mach-o (Apple's
+  /// executable format). Apple has some compile unit attributes that look like
+  /// split DWARF, but they aren't and they can cause warnins to be emitted
+  /// about missing DWO files.
+  DwarfTransformer(DWARFContext &D, GsymCreator &G, bool LDCS = false,
+                   bool MachO = false)
+      : DICtx(D), Gsym(G), LoadDwarfCallSites(LDCS), IsMachO(MachO) {}
 
   /// Extract the DWARF from the supplied object file and convert it into the
   /// Gsym format in the GsymCreator object that is passed in. Returns an
@@ -97,6 +103,7 @@ class DwarfTransformer {
   DWARFContext &DICtx;
   GsymCreator &Gsym;
   bool LoadDwarfCallSites;
+  bool IsMachO;
 
   friend class DwarfTransformerTest;
 };

llvm/lib/DebugInfo/GSYM/DwarfTransformer.cpp

@@ -629,6 +629,10 @@ Error DwarfTransformer::convert(uint32_t NumThreads, OutputAggregator &Out) {
   size_t NumBefore = Gsym.getNumFunctionInfos();
   auto getDie = [&](DWARFUnit &DwarfUnit) -> DWARFDie {
     DWARFDie ReturnDie = DwarfUnit.getUnitDIE(false);
+    // Apple uses DW_AT_GNU_dwo_id for things other than split DWARF.
+    if (IsMachO)
+      return ReturnDie;
+
     if (DwarfUnit.getDWOId()) {
       DWARFUnit *DWOCU = DwarfUnit.getNonSkeletonUnitDIE(false).getDwarfUnit();
       if (!DWOCU->isDWOUnit())

llvm/tools/llvm-gsymutil/llvm-gsymutil.cpp

@@ -386,7 +386,9 @@ static llvm::Error handleObjectFile(ObjectFile &Obj, const std::string &OutFile,
 
   // Make a DWARF transformer object and populate the ranges of the code
   // so we don't end up adding invalid functions to GSYM data.
-  DwarfTransformer DT(*DICtx, Gsym, LoadDwarfCallSites);
+  bool IsMachO = dyn_cast<object::MachOObjectFile>(&Obj) != nullptr;
+
+  DwarfTransformer DT(*DICtx, Gsym, LoadDwarfCallSites, IsMachO);
   if (!TextRanges.empty())
     Gsym.SetValidTextRanges(TextRanges);
 

llvm/unittests/DebugInfo/GSYM/GSYMTest.cpp

@@ -4899,3 +4899,63 @@ TEST(GSYMTest, TestLookupsOfOverlappingAndUnequalRanges) {
   for (const auto &Line : ExpectedDumpLines)
     EXPECT_TRUE(DumpStr.find(Line) != std::string::npos);
 }
+
+TEST(GSYMTest, TestUnableToLocateDWO) {
+  // Test that llvm-gsymutil will not produce "uanble to locate DWO file" for
+  // Apple binaries. Apple uses DW_AT_GNU_dwo_id for non split DWARF purposes
+  // and this makes llvm-gsymutil create warnings and errors.
+  //
+  // 0x0000000b: DW_TAG_compile_unit
+  //               DW_AT_name        ("main.cpp")
+  //               DW_AT_language    (DW_LANG_C)
+  //               DW_AT_GNU_dwo_id  (0xfffffffe)
+  StringRef yamldata = R"(
+  debug_str:
+    - ''
+    - main.cpp
+  debug_abbrev:
+    - ID:              0
+      Table:
+        - Code:            0x1
+          Tag:             DW_TAG_compile_unit
+          Children:        DW_CHILDREN_no
+          Attributes:
+            - Attribute:       DW_AT_name
+              Form:            DW_FORM_strp
+            - Attribute:       DW_AT_language
+              Form:            DW_FORM_udata
+            - Attribute:       DW_AT_GNU_dwo_id
+              Form:            DW_FORM_data4
+  debug_info:
+    - Length:          0x11
+      Version:         4
+      AbbrevTableID:   0
+      AbbrOffset:      0x0
+      AddrSize:        8
+      Entries:
+        - AbbrCode:        0x1
+          Values:
+            - Value:           0x1
+            - Value:           0x2
+            - Value:           0xFFFFFFFE
+  )";
+  auto ErrOrSections = DWARFYAML::emitDebugSections(yamldata);
+  ASSERT_THAT_EXPECTED(ErrOrSections, Succeeded());
+  std::unique_ptr<DWARFContext> DwarfContext =
+      DWARFContext::create(*ErrOrSections, 8);
+  ASSERT_TRUE(DwarfContext.get() != nullptr);
+  std::string errors;
+  raw_string_ostream OS(errors);
+  OutputAggregator OSAgg(&OS);
+  GsymCreator GC;
+  // Make a DWARF transformer that is MachO (Apple) to avoid warnings about
+  // not finding DWO files.
+  DwarfTransformer DT(*DwarfContext, GC, /*LDCS=*/false, /*MachO*/ true);
+  const uint32_t ThreadCount = 1;
+  ASSERT_THAT_ERROR(DT.convert(ThreadCount, OSAgg), Succeeded());
+  ASSERT_THAT_ERROR(GC.finalize(OSAgg), Succeeded());
+
+  // Make sure this warning is not in the binary
+  std::string warn("warning: Unable to retrieve DWO .debug_info section for");
+  EXPECT_TRUE(errors.find(warn) == std::string::npos);
+}