Reapply "DebugInfo: Don't put fission type units in comdat sections."

This recommits r208930, r208933, and r208975 (by reverting r209338) and
reverts r209529 (the FIXME to readd this functionality once the tools
were fixed) now that DWP has been fixed to cope with a single section
for all fission type units.

Original commit message:

"Since type units in the dwo file are handled by a debug aware tool,
they don't need to leverage the ELF comdat grouping to implement
deduplication. Avoid creating all the .group sections for these as a
space optimization."

llvm-svn: 213956

include/llvm/MC/MCObjectFileInfo.h

@@ -116,6 +116,7 @@ protected:
 
   /// These are used for the Fission separate debug information files.
   const MCSection *DwarfInfoDWOSection;
+  const MCSection *DwarfTypesDWOSection;
   const MCSection *DwarfAbbrevDWOSection;
   const MCSection *DwarfStrDWOSection;
   const MCSection *DwarfLineDWOSection;
@@ -261,7 +262,9 @@ public:
     return DwarfInfoDWOSection;
   }
   const MCSection *getDwarfTypesSection(uint64_t Hash) const;
-  const MCSection *getDwarfTypesDWOSection(uint64_t Hash) const;
+  const MCSection *getDwarfTypesDWOSection() const {
+    return DwarfTypesDWOSection;
+  }
   const MCSection *getDwarfAbbrevDWOSection() const {
     return DwarfAbbrevDWOSection;
   }

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1640,9 +1640,12 @@ void DwarfDebug::emitSectionLabels() {
   // Dwarf sections base addresses.
   DwarfInfoSectionSym =
       emitSectionSym(Asm, TLOF.getDwarfInfoSection(), "section_info");
-  if (useSplitDwarf())
+  if (useSplitDwarf()) {
     DwarfInfoDWOSectionSym =
         emitSectionSym(Asm, TLOF.getDwarfInfoDWOSection(), "section_info_dwo");
+    DwarfTypesDWOSectionSym =
+        emitSectionSym(Asm, TLOF.getDwarfTypesDWOSection(), "section_types_dwo");
+  }
   DwarfAbbrevSectionSym =
       emitSectionSym(Asm, TLOF.getDwarfAbbrevSection(), "section_abbrev");
   if (useSplitDwarf())
@@ -2406,9 +2409,9 @@ void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
   bool TopLevelType = TypeUnitsUnderConstruction.empty();
   AddrPool.resetUsedFlag();
 
-  auto OwnedUnit =
-      make_unique<DwarfTypeUnit>(InfoHolder.getUnits().size(), CU, Asm, this,
-                                 &InfoHolder, getDwoLineTable(CU));
+  auto OwnedUnit = make_unique<DwarfTypeUnit>(
+      InfoHolder.getUnits().size() + TypeUnitsUnderConstruction.size(), CU, Asm,
+      this, &InfoHolder, getDwoLineTable(CU));
   DwarfTypeUnit &NewTU = *OwnedUnit;
   DIE &UnitDie = NewTU.getUnitDie();
   TU = &NewTU;
@@ -2421,15 +2424,14 @@ void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
   uint64_t Signature = makeTypeSignature(Identifier);
   NewTU.setTypeSignature(Signature);
 
-  if (!useSplitDwarf())
+  if (useSplitDwarf())
+    NewTU.initSection(Asm->getObjFileLowering().getDwarfTypesDWOSection(),
+                      DwarfTypesDWOSectionSym);
+  else {
     CU.applyStmtList(UnitDie);
-
-  // FIXME: Skip using COMDAT groups for type units in the .dwo file once tools
-  // such as DWP ( http://gcc.gnu.org/wiki/DebugFissionDWP ) can cope with it.
-  NewTU.initSection(
-      useSplitDwarf()
-          ? Asm->getObjFileLowering().getDwarfTypesDWOSection(Signature)
-          : Asm->getObjFileLowering().getDwarfTypesSection(Signature));
+    NewTU.initSection(
+        Asm->getObjFileLowering().getDwarfTypesSection(Signature));
+  }
 
   NewTU.setType(NewTU.createTypeDIE(CTy));
 

lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -258,6 +258,7 @@ class DwarfDebug : public AsmPrinterHandler {
   MCSymbol *DwarfDebugLocSectionSym, *DwarfLineSectionSym, *DwarfAddrSectionSym;
   MCSymbol *FunctionBeginSym, *FunctionEndSym;
   MCSymbol *DwarfInfoDWOSectionSym, *DwarfAbbrevDWOSectionSym;
+  MCSymbol *DwarfTypesDWOSectionSym;
   MCSymbol *DwarfStrDWOSectionSym;
   MCSymbol *DwarfGnuPubNamesSectionSym, *DwarfGnuPubTypesSectionSym;
 

lib/CodeGen/AsmPrinter/DwarfUnit.h

@@ -579,6 +579,10 @@ public:
            sizeof(uint32_t);                               // Type DIE Offset
   }
   void initSection(const MCSection *Section);
+  // Bring in the base function (taking two args, including the section symbol)
+  // for use when building DWO type units (they don't go in unique comdat
+  // sections)
+  using DwarfUnit::initSection;
   DwarfCompileUnit &getCU() override { return CU; }
 
 protected:

lib/MC/MCObjectFileInfo.cpp

@@ -561,6 +561,9 @@ void MCObjectFileInfo::InitELFMCObjectFileInfo(Triple T) {
   DwarfInfoDWOSection =
     Ctx->getELFSection(".debug_info.dwo", ELF::SHT_PROGBITS, 0,
                        SectionKind::getMetadata());
+  DwarfTypesDWOSection =
+    Ctx->getELFSection(".debug_types.dwo", ELF::SHT_PROGBITS, 0,
+                       SectionKind::getMetadata());
   DwarfAbbrevDWOSection =
     Ctx->getELFSection(".debug_abbrev.dwo", ELF::SHT_PROGBITS, 0,
                        SectionKind::getMetadata());
@@ -736,6 +739,10 @@ void MCObjectFileInfo::InitCOFFMCObjectFileInfo(Triple T) {
                           COFF::IMAGE_SCN_MEM_DISCARDABLE |
                           COFF::IMAGE_SCN_MEM_READ,
                           SectionKind::getMetadata());
+  DwarfTypesDWOSection =
+      Ctx->getCOFFSection(".debug_types.dwo", COFF::IMAGE_SCN_MEM_DISCARDABLE |
+                                                  COFF::IMAGE_SCN_MEM_READ,
+                          SectionKind::getMetadata());
   DwarfAbbrevDWOSection =
       Ctx->getCOFFSection(".debug_abbrev.dwo",
                           COFF::IMAGE_SCN_MEM_DISCARDABLE |
@@ -847,13 +854,6 @@ const MCSection *MCObjectFileInfo::getDwarfTypesSection(uint64_t Hash) const {
                             SectionKind::getMetadata(), 0, utostr(Hash));
 }
 
-const MCSection *
-MCObjectFileInfo::getDwarfTypesDWOSection(uint64_t Hash) const {
-  return Ctx->getELFSection(".debug_types.dwo", ELF::SHT_PROGBITS,
-                            ELF::SHF_GROUP, SectionKind::getMetadata(), 0,
-                            utostr(Hash));
-}
-
 void MCObjectFileInfo::InitEHFrameSection() {
   if (Env == IsMachO)
     EHFrameSection =

test/DebugInfo/X86/generate-odr-hash.ll

@@ -1,10 +1,12 @@
 ; REQUIRES: object-emission
 
-; RUN: llc %s -o %t -filetype=obj -O0 -generate-type-units -mtriple=x86_64-unknown-linux-gnu
+; RUN: llc < %s -o %t -filetype=obj -O0 -generate-type-units -mtriple=x86_64-unknown-linux-gnu
 ; RUN: llvm-dwarfdump %t | FileCheck --check-prefix=CHECK --check-prefix=SINGLE %s
+; RUN: llvm-readobj -s -t %t | FileCheck --check-prefix=OBJ_COMMON %s
 
-; RUN: llc %s -split-dwarf=Enable -o %t -filetype=obj -O0 -generate-type-units -mtriple=x86_64-unknown-linux-gnu
+; RUN: llc < %s -split-dwarf=Enable -o %t -filetype=obj -O0 -generate-type-units -mtriple=x86_64-unknown-linux-gnu
 ; RUN: llvm-dwarfdump %t | FileCheck --check-prefix=CHECK --check-prefix=FISSION %s
+; RUN: llvm-readobj -s -t %t | FileCheck --check-prefix=OBJ_COMMON --check-prefix=OBJ_FISSION %s
 
 ; Generated from bar.cpp:
 
@@ -161,6 +163,20 @@
 ; CHECK-DAG: [[WOMBAT]] "wombat"
 ; CHECK-DAG: [[FLUFFY]] "echidna::capybara::mongoose::fluffy"
 
+; Make sure debug_types are in comdat groups. This could be more rigid to check
+; that they're the right comdat groups (each type in a separate comdat group,
+; etc)
+; OBJ_COMMON: Name: .debug_types (
+; OBJ_COMMON-NOT: }
+; OBJ_COMMON: SHF_GROUP
+
+; Fission type units don't go in comdat groups, since their linker is debug
+; aware it's handled using the debug info semantics rather than raw ELF object
+; semantics.
+; OBJ_FISSION: Name: .debug_types.dwo (
+; OBJ_FISSION-NOT: SHF_GROUP
+; OBJ_FISSION: }
+
 %struct.bar = type { i8 }
 %"class.echidna::capybara::mongoose::fluffy" = type { i32, i32 }
 %"struct.<anonymous namespace>::walrus" = type { i8 }