[GSYM] Add Split Dwarf Support to DwarfTransformer

The convert only worked on CUs in main binary.
If it's a skeleton CU it will now use the DWO CU
when invoking handleDie.

Test Plan:
llvm-lit

Reviewed By: clayborg

Differential Revision: https://reviews.llvm.org/D118521

llvm/lib/DebugInfo/GSYM/DwarfTransformer.cpp

@@ -427,11 +427,28 @@ void DwarfTransformer::handleDie(raw_ostream &OS, CUInfo &CUI, DWARFDie Die) {
 
 Error DwarfTransformer::convert(uint32_t NumThreads) {
   size_t NumBefore = Gsym.getNumFunctionInfos();
+  auto getDie = [&](DWARFUnit &DwarfUnit) -> DWARFDie {
+    DWARFDie ReturnDie = DwarfUnit.getUnitDIE(false);
+    if (llvm::Optional<uint64_t> DWOId = DwarfUnit.getDWOId()) {
+      DWARFUnit *DWOCU = DwarfUnit.getNonSkeletonUnitDIE(false).getDwarfUnit();
+      if (!DWOCU->isDWOUnit()) {
+        std::string DWOName = dwarf::toString(
+            DwarfUnit.getUnitDIE().find(
+                {dwarf::DW_AT_dwo_name, dwarf::DW_AT_GNU_dwo_name}),
+            "");
+        Log << "warning: Unable to retrieve DWO .debug_info section for "
+            << DWOName << "\n";
+      } else {
+        ReturnDie = DWOCU->getUnitDIE(false);
+      }
+    }
+    return ReturnDie;
+  };
   if (NumThreads == 1) {
     // Parse all DWARF data from this thread, use the same string/file table
     // for everything
     for (const auto &CU : DICtx.compile_units()) {
-      DWARFDie Die = CU->getUnitDIE(false);
+      DWARFDie Die = getDie(*CU.get());
       CUInfo CUI(DICtx, dyn_cast<DWARFCompileUnit>(CU.get()));
       handleDie(Log, CUI, Die);
     }
@@ -456,7 +473,7 @@ Error DwarfTransformer::convert(uint32_t NumThreads) {
     // Now convert all DWARF to GSYM in a thread pool.
     std::mutex LogMutex;
     for (const auto &CU : DICtx.compile_units()) {
-      DWARFDie Die = CU->getUnitDIE(false /*CUDieOnly*/);
+      DWARFDie Die = getDie(*CU.get());
       if (Die) {
         CUInfo CUI(DICtx, dyn_cast<DWARFCompileUnit>(CU.get()));
         pool.async([this, CUI, &LogMutex, Die]() mutable {

llvm/test/DebugInfo/X86/fission-no-inline-gsym.ll

@@ -0,0 +1,85 @@
+; RUN: llc -split-dwarf-file=%t.dwo -split-dwarf-output=%t.dwo -O0 < %s -mtriple=x86_64-unknown-linux-gnu -filetype=obj > %t
+; RUN: llvm-gsymutil --convert=%t --out-file=%t.gsym
+; RUN: llvm-gsymutil --address=0x13 %t.gsym | FileCheck %s
+
+; Minor complication: after generating the LLVM IR, it was manually edited so
+; that the 'f1()' call from f3 was reordered to appear between the two inlined
+; f1 calls from f2. This causes f2's inlined_subroutine to use DW_AT_ranges,
+; thus exercising range list generation/referencing which was buggy.
+
+; struct foo {
+;   template<typename T>
+;   static void f2();
+;   static void f3(...);
+; };
+;
+; void f1();
+;
+; template<typename T>
+; inline __attribute__((always_inline)) void foo::f2() {
+;   f1();
+;   f1();
+; }
+;
+; void foo::f3(...) {
+;   if (true) {
+;     f1();
+;     f2<int>();
+;     using ::foo;
+;   }
+; }
+
+; Check that we parse .dwo file when creating gsym file.
+
+; CHECK:      _ZN3foo2f2IiEEvv @ fission-inline.cpp:15 [inlined]
+; CHECK-NEXT:   _ZN3foo2f3Ez + 19 @ fission-inline.cpp:21
+
+; Function Attrs: uwtable
+define void @_ZN3foo2f3Ez(...) #0 align 2 !dbg !10 {
+entry:
+  call void @_Z2f1v(), !dbg !26
+  call void @_Z2f1v(), !dbg !25
+  call void @_Z2f1v(), !dbg !28
+  call void @_Z2f1v(), !dbg !29
+  ret void, !dbg !29
+}
+
+declare void @_Z2f1v() #1
+
+attributes #0 = { uwtable "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!22, !23}
+!llvm.ident = !{!24}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.6.0 ", isOptimized: false, splitDebugFilename: "fission-inline.dwo",  emissionKind: FullDebug, splitDebugInlining: false, file: !1, enums: !2, retainedTypes: !3, globals: !2, imports: !18)
+!1 = !DIFile(filename: "fission-inline.cpp", directory: "")
+!2 = !{}
+!3 = !{!4}
+!4 = !DICompositeType(tag: DW_TAG_structure_type, name: "foo", line: 1, size: 8, align: 8, file: !1, elements: !5, identifier: "_ZTS3foo")
+!5 = !{!6}
+!6 = !DISubprogram(name: "f3", linkageName: "_ZN3foo2f3Ez", line: 4, isLocal: false, isDefinition: false, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 4, file: !1, scope: !4, type: !7)
+!7 = !DISubroutineType(types: !8)
+!8 = !{null, null}
+!10 = distinct !DISubprogram(name: "f3", linkageName: "_ZN3foo2f3Ez", line: 15, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 15, file: !1, scope: !4, type: !7, declaration: !6, retainedNodes: !2)
+!11 = distinct !DISubprogram(name: "f2<int>", linkageName: "_ZN3foo2f2IiEEvv", line: 10, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 10, file: !1, scope: !4, type: !12, templateParams: !14, declaration: !17, retainedNodes: !2)
+!12 = !DISubroutineType(types: !13)
+!13 = !{null}
+!14 = !{!15}
+!15 = !DITemplateTypeParameter(name: "T", type: !16)
+!16 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!17 = !DISubprogram(name: "f2<int>", linkageName: "_ZN3foo2f2IiEEvv", line: 10, isLocal: false, isDefinition: false, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 10, file: !1, scope: !4, type: !12, templateParams: !14)
+!18 = !{!19}
+!19 = !DIImportedEntity(tag: DW_TAG_imported_declaration, file: !1, line: 19, scope: !20, entity: !4)
+!20 = distinct !DILexicalBlock(line: 16, column: 13, file: !1, scope: !21)
+!21 = distinct !DILexicalBlock(line: 16, column: 7, file: !1, scope: !10)
+!22 = !{i32 2, !"Dwarf Version", i32 4}
+!23 = !{i32 2, !"Debug Info Version", i32 3}
+!24 = !{!"clang version 3.6.0 "}
+!25 = !DILocation(line: 17, column: 5, scope: !20)
+!26 = !DILocation(line: 11, column: 3, scope: !11, inlinedAt: !27)
+!27 = !DILocation(line: 18, column: 5, scope: !20)
+!28 = !DILocation(line: 12, column: 3, scope: !11, inlinedAt: !27)
+!29 = !DILocation(line: 12, column: 3, scope: !11, inlinedAt: !30)
+!30 = !DILocation(line: 21, column: 0, scope: !10)