DebugInfo: Produce debug_{gnu_}pub{names,types} entries when explicitly requested, even in -gmlt or when empty

Turns out gold doesn't use the DW_AT_GNU_pubnames to decide whether to
parse the rest of the DIEs when building gdb-index. This causes gold to
trip over LLVM's output when there are DW_FORM_ref_addr present.

Gold does use the presence of a debug_gnu_pub{names,types} entry for the
CU to skip parsing the debug_info portion, so make sure that's included
even when empty (technically, when empty there couldn't be any ref_addr
anyway - it only came up when gmlt didn't produce any (even non-empty)
pubnames - but given what that reveals about gold's implementation, this
seems like a good thing to do for consistency).

llvm-svn: 303894

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -760,7 +760,7 @@ void DwarfCompileUnit::emitHeader(bool UseOffsets) {
 /// addGlobalName - Add a new global name to the compile unit.
 void DwarfCompileUnit::addGlobalName(StringRef Name, const DIE &Die,
                                      const DIScope *Context) {
-  if (includeMinimalInlineScopes())
+  if (!DD->hasDwarfPubSections(includeMinimalInlineScopes()))
     return;
   std::string FullName = getParentContextString(Context) + Name.str();
   GlobalNames[FullName] = &Die;
@@ -768,7 +768,7 @@ void DwarfCompileUnit::addGlobalName(StringRef Name, const DIE &Die,
 
 void DwarfCompileUnit::addGlobalNameForTypeUnit(StringRef Name,
                                                 const DIScope *Context) {
-  if (includeMinimalInlineScopes())
+  if (!DD->hasDwarfPubSections(includeMinimalInlineScopes()))
     return;
   std::string FullName = getParentContextString(Context) + Name.str();
   // Insert, allowing the entry to remain as-is if it's already present
@@ -781,7 +781,7 @@ void DwarfCompileUnit::addGlobalNameForTypeUnit(StringRef Name,
 /// Add a new global type to the unit.
 void DwarfCompileUnit::addGlobalType(const DIType *Ty, const DIE &Die,
                                      const DIScope *Context) {
-  if (includeMinimalInlineScopes())
+  if (!DD->hasDwarfPubSections(includeMinimalInlineScopes()))
     return;
   std::string FullName = getParentContextString(Context) + Ty->getName().str();
   GlobalTypes[FullName] = &Die;
@@ -789,7 +789,7 @@ void DwarfCompileUnit::addGlobalType(const DIType *Ty, const DIE &Die,
 
 void DwarfCompileUnit::addGlobalTypeUnitType(const DIType *Ty,
                                              const DIScope *Context) {
-  if (includeMinimalInlineScopes())
+  if (!DD->hasDwarfPubSections(includeMinimalInlineScopes()))
     return;
   std::string FullName = getParentContextString(Context) + Ty->getName().str();
   // Insert, allowing the entry to remain as-is if it's already present

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

@@ -77,8 +77,6 @@ class DwarfCompileUnit final : public DwarfUnit {
 
   bool isDwoUnit() const override;
 
-  bool includeMinimalInlineScopes() const;
-
   DenseMap<const MDNode *, DIE *> &getAbstractSPDies() {
     if (isDwoUnit() && !DD->shareAcrossDWOCUs())
       return AbstractSPDies;
@@ -101,6 +99,8 @@ public:
     return Skeleton;
   }
 
+  bool includeMinimalInlineScopes() const;
+
   void initStmtList();
 
   /// Apply the DW_AT_stmt_list from this compile unit to the specified DIE.

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -252,12 +252,6 @@ DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
   // Handle split DWARF.
   HasSplitDwarf = !Asm->TM.Options.MCOptions.SplitDwarfFile.empty();
 
-  // Pubnames/pubtypes on by default for GDB.
-  if (DwarfPubSections == Default)
-    HasDwarfPubSections = tuneForGDB();
-  else
-    HasDwarfPubSections = DwarfPubSections == Enable;
-
   // SCE defaults to linkage names only for abstract subprograms.
   if (DwarfLinkageNames == DefaultLinkageNames)
     UseAllLinkageNames = !tuneForSCE();
@@ -391,8 +385,20 @@ void DwarfDebug::constructAbstractSubprogramScopeDIE(DwarfCompileUnit &SrcCU,
   }
 }
 
-void DwarfDebug::addGnuPubAttributes(DwarfUnit &U, DIE &D) const {
-  if (!GenerateGnuPubSections)
+bool DwarfDebug::hasDwarfPubSections(bool includeMinimalInlineScopes) const {
+  // Opting in to GNU Pubnames/types overrides the default to ensure these are
+  // generated for things like Gold's gdb_index generation.
+  if (GenerateGnuPubSections)
+    return true;
+
+  if (DwarfPubSections == Default)
+    return tuneForGDB() && !includeMinimalInlineScopes;
+
+  return DwarfPubSections == Enable;
+}
+
+void DwarfDebug::addGnuPubAttributes(DwarfCompileUnit &U, DIE &D) const {
+  if (!hasDwarfPubSections(U.includeMinimalInlineScopes()))
     return;
 
   U.addFlag(D, dwarf::DW_AT_GNU_pubnames);
@@ -718,7 +724,9 @@ void DwarfDebug::endModule() {
   }
 
   // Emit the pubnames and pubtypes sections if requested.
-  if (HasDwarfPubSections) {
+  // The condition is optimistically correct - any CU not using GMLT (&
+  // implicit/default pubnames state) might still have pubnames.
+  if (hasDwarfPubSections(/* gmlt */ false)) {
     emitDebugPubNames(GenerateGnuPubSections);
     emitDebugPubTypes(GenerateGnuPubSections);
   }
@@ -1395,7 +1403,7 @@ void DwarfDebug::emitDebugPubSection(
 
     const auto &Globals = (TheU->*Accessor)();
 
-    if (Globals.empty())
+    if (!hasDwarfPubSections(TheU->includeMinimalInlineScopes()))
       continue;
 
     if (auto *Skeleton = TheU->getSkeleton())

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -246,9 +246,6 @@ class DwarfDebug : public DebugHandlerBase {
       std::pair<std::unique_ptr<DwarfTypeUnit>, const DICompositeType *>, 1>
       TypeUnitsUnderConstruction;
 
-  /// Whether to emit the pubnames/pubtypes sections.
-  bool HasDwarfPubSections;
-
   /// Whether to use the GNU TLS opcode (instead of the standard opcode).
   bool UseGNUTLSOpcode;
 
@@ -415,7 +412,7 @@ class DwarfDebug : public DebugHandlerBase {
 
   /// Flags to let the linker know we have emitted new style pubnames. Only
   /// emit it here if we don't have a skeleton CU for split dwarf.
-  void addGnuPubAttributes(DwarfUnit &U, DIE &D) const;
+  void addGnuPubAttributes(DwarfCompileUnit &U, DIE &D) const;
 
   /// Create new DwarfCompileUnit for the given metadata node with tag
   /// DW_TAG_compile_unit.
@@ -556,6 +553,8 @@ public:
   /// A helper function to check whether the DIE for a given Scope is
   /// going to be null.
   bool isLexicalScopeDIENull(LexicalScope *Scope);
+
+  bool hasDwarfPubSections(bool includeMinimalInlineScopes) const;
 };
 } // End of namespace llvm
 

llvm/test/DebugInfo/Generic/empty.ll

@@ -13,10 +13,14 @@
 ; CHECK-NOT: file_names[
 
 ; CHECK: .debug_pubnames contents:
-; CHECK-NOT: Offset
+; CHECK-NEXT: length = 0x0000000e
+; CHECK-NEXT: Offset
+; CHECK-NEXT: {{^$}}
 
 ; CHECK: .debug_pubtypes contents:
-; CHECK-NOT: Offset
+; CHECK-NEXT: length = 0x0000000e
+; CHECK-NEXT: Offset
+; CHECK-NEXT: {{^$}}
 
 ; Don't emit DW_AT_addr_base when there are no addresses.
 ; FISSION-NOT: DW_AT_GNU_addr_base [DW_FORM_sec_offset]

llvm/test/DebugInfo/X86/empty.ll

@@ -8,10 +8,15 @@
 ; CHECK-NOT: file_names[
 
 ; CHECK: .debug_pubnames contents:
-; CHECK-NOT: Offset
+; CHECK-NEXT: length = 0x0000000e
+; CHECK-NEXT: Offset
+; CHECK-NEXT: {{^$}}
 
 ; CHECK: .debug_pubtypes contents:
-; CHECK-NOT: Offset
+; CHECK-NEXT: length = 0x0000000e
+; CHECK-NEXT: Offset
+; CHECK-NEXT: {{^$}}
+
 
 ; Don't emit DW_AT_addr_base when there are no addresses.
 ; FISSION-NOT: DW_AT_GNU_addr_base [DW_FORM_sec_offset]

llvm/test/DebugInfo/X86/gnu-public-names-empty.ll

@@ -9,6 +9,11 @@
 ; CHECK: DW_AT_GNU_pubnames [DW_FORM_flag_present]   (true)
 ; CHECK-NOT: DW_AT_GNU_pubtypes [
 
+; CHECK: .debug_gnu_pubnames contents:
+; CHECK-NEXT: length = 0x0000000e
+; CHECK-NEXT: Offset
+; CHECK-NEXT: {{^$}}
+
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4}
 

llvm/test/DebugInfo/X86/gnu-public-names-gmlt.ll

@@ -0,0 +1,68 @@
+; RUN: llc -mtriple=x86_64-pc-linux-gnu -filetype=obj < %s -generate-gnu-dwarf-pub-sections | llvm-dwarfdump - | FileCheck --check-prefix=GPUB --check-prefix=CHECK %s
+; RUN: llc -mtriple=x86_64-pc-linux-gnu -filetype=obj < %s -generate-dwarf-pub-sections=Enable | llvm-dwarfdump - | FileCheck --check-prefix=PUB --check-prefix=CHECK %s
+; RUN: llc -mtriple=x86_64-pc-linux-gnu -filetype=obj < %s | llvm-dwarfdump - | FileCheck --check-prefix=NONE %s
+
+; Generated from:
+;   void f1();
+;   inline __attribute__((always_inline)) void f2() {
+;     f1();
+;   }
+;   void f3() {
+;     f2();
+;   }
+;   $ clang++ -gmlt %s -emit-llvm -S
+
+; GPUB: Compile Unit
+; GPUB: DW_AT_GNU_pubnames
+
+; GPUB: .debug_gnu_pubnames contents:
+; PUB: .debug_pubnames contents:
+; CHECK-NEXT: unit_offset = 0x00000000
+; CHECK-NEXT: Name
+; CHECK-NEXT: "f2"
+; CHECK-NEXT: "f3"
+
+; GPUB: .debug_gnu_pubtypes contents:
+; PUB: .debug_pubtypes contents:
+; CHECK-NEXT: length = 0x0000000e version = 0x0002 unit_offset = 0x00000000
+; CHECK-NEXT: Name
+
+; NONE: .debug_pubnames contents:
+; NONE: {{^$}}
+; NONE: .debug_pubtypes contents:
+; NONE: {{^$}}
+; NONE: .debug_gnu_pubnames contents:
+; NONE: {{^$}}
+; NONE: .debug_gnu_pubtypes contents:
+; NONE: {{^$}}
+
+
+; Function Attrs: noinline uwtable
+define void @_Z2f3v() #0 !dbg !7 {
+entry:
+  call void @_Z2f1v(), !dbg !9
+  ret void, !dbg !12
+}
+
+declare void @_Z2f1v() #1
+
+attributes #0 = { noinline uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 5.0.0 (trunk 303768) (llvm/trunk 303774)", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
+!1 = !DIFile(filename: "gnu-public-names-gmlt.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 5.0.0 (trunk 303768) (llvm/trunk 303774)"}
+!7 = distinct !DISubprogram(name: "f3", scope: !1, file: !1, line: 5, type: !8, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !2)
+!9 = !DILocation(line: 3, column: 3, scope: !10, inlinedAt: !11)
+!10 = distinct !DISubprogram(name: "f2", scope: !1, file: !1, line: 2, type: !8, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!11 = distinct !DILocation(line: 6, column: 3, scope: !7)
+!12 = !DILocation(line: 7, column: 1, scope: !7)