DebugInfo: Add metadata support for disabling DWARF pub sections

In cases where the debugger load time is a worthwhile tradeoff (or less
costly - such as loading from a DWP instead of a variety of DWOs
(possibly over a high-latency/distributed filesystem)) against object
file size, it can be reasonable to disable pubnames and corresponding
gdb-index creation in the linker.

A backend-flag version of this was implemented for NVPTX in
D44385/r327994 - which was fine for NVPTX which wouldn't mix-and-match
CUs. Now that it's going to be a user-facing option (likely powered by
"-gno-pubnames", the same as GCC) it should be encoded in the
DICompileUnit so it can vary per-CU.

After this, likely the NVPTX support should be migrated to the metadata
& the previous flag implementation should be removed.

Reviewers: aprantl

Differential Revision: https://reviews.llvm.org/D50213

llvm-svn: 339939

5 files changed, 68 insertions, 38 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp b/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
index 20b0b8d3fea..119f65e33f5 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
@@ -23,6 +23,7 @@
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetLoweringObjectFile.h"
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
@@ -554,12 +555,21 @@ void llvm::emitDWARF5AccelTable(
     const DwarfDebug &DD, ArrayRef<std::unique_ptr<DwarfCompileUnit>> CUs) {
   std::vector<MCSymbol *> CompUnits;
   for (const auto &CU : enumerate(CUs)) {
+    if (CU.value()->getCUNode()->getNameTableKind() ==
+        DICompileUnit::DebugNameTableKind::None)
+      continue;
     assert(CU.index() == CU.value()->getUniqueID());
     const DwarfCompileUnit *MainCU =
         DD.useSplitDwarf() ? CU.value()->getSkeleton() : CU.value().get();
     CompUnits.push_back(MainCU->getLabelBegin());
   }
 
+  if (CompUnits.empty())
+    return;
+
+  Asm->OutStreamer->SwitchSection(
+      Asm->getObjFileLowering().getDwarfDebugNamesSection());
+
   Contents.finalize(Asm, "names");
   Dwarf5AccelTableWriter<DWARF5AccelTableData>(
       Asm, Contents, CompUnits,
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 322555a2e7d..a74a9f9fccd 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -249,13 +249,13 @@ DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(
     addLinkageName(*VariableDIE, GV->getLinkageName());
 
   if (addToAccelTable) {
-    DD->addAccelName(GV->getName(), *VariableDIE);
+    DD->addAccelName(*CUNode, GV->getName(), *VariableDIE);
 
     // If the linkage name is different than the name, go ahead and output
     // that as well into the name table.
     if (GV->getLinkageName() != "" && GV->getName() != GV->getLinkageName() &&
         DD->useAllLinkageNames())
-      DD->addAccelName(GV->getLinkageName(), *VariableDIE);
+      DD->addAccelName(*CUNode, GV->getLinkageName(), *VariableDIE);
   }
 
   return VariableDIE;
@@ -348,7 +348,7 @@ DIE &DwarfCompileUnit::updateSubprogramScopeDIE(const DISubprogram *SP) {
 
   // Add name to the name table, we do this here because we're guaranteed
   // to have concrete versions of our DW_TAG_subprogram nodes.
-  DD->addSubprogramNames(SP, *SPDie);
+  DD->addSubprogramNames(*CUNode, SP, *SPDie);
 
   return *SPDie;
 }
@@ -486,7 +486,7 @@ DIE *DwarfCompileUnit::constructInlinedScopeDIE(LexicalScope *Scope) {
 
   // Add name to the name table, we do this here because we're guaranteed
   // to have concrete versions of our DW_TAG_inlined_subprogram nodes.
-  DD->addSubprogramNames(InlinedSP, *ScopeDIE);
+  DD->addSubprogramNames(*CUNode, InlinedSP, *ScopeDIE);
 
   return ScopeDIE;
 }
@@ -883,13 +883,17 @@ void DwarfCompileUnit::emitHeader(bool UseOffsets) {
 }
 
 bool DwarfCompileUnit::hasDwarfPubSections() const {
-  // Opting in to GNU Pubnames/types overrides the default to ensure these are
-  // generated for things like Gold's gdb_index generation.
-  if (CUNode->getGnuPubnames())
+  switch (CUNode->getNameTableKind()) {
+  case DICompileUnit::DebugNameTableKind::None:
+    return false;
+    // Opting in to GNU Pubnames/types overrides the default to ensure these are
+    // generated for things like Gold's gdb_index generation.
+  case DICompileUnit::DebugNameTableKind::GNU:
     return true;
-
-  return DD->tuneForGDB() && DD->usePubSections() &&
-         !includeMinimalInlineScopes() && !CUNode->isDebugDirectivesOnly();
+  case DICompileUnit::DebugNameTableKind::Default:
+    return DD->tuneForGDB() && DD->usePubSections() &&
+           !includeMinimalInlineScopes() && !CUNode->isDebugDirectivesOnly();
+  }
 }
 
 /// addGlobalName - Add a new global name to the compile unit.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 6ee1de0dba3..435190669a4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -421,30 +421,35 @@ static StringRef getObjCMethodName(StringRef In) {
 }
 
 // Add the various names to the Dwarf accelerator table names.
-void DwarfDebug::addSubprogramNames(const DISubprogram *SP, DIE &Die) {
+void DwarfDebug::addSubprogramNames(const DICompileUnit &CU,
+                                    const DISubprogram *SP, DIE &Die) {
+  if (getAccelTableKind() != AccelTableKind::Apple &&
+      CU.getNameTableKind() == DICompileUnit::DebugNameTableKind::None)
+    return;
+
   if (!SP->isDefinition())
     return;
 
   if (SP->getName() != "")
-    addAccelName(SP->getName(), Die);
+    addAccelName(CU, SP->getName(), Die);
 
   // If the linkage name is different than the name, go ahead and output that as
   // well into the name table. Only do that if we are going to actually emit
   // that name.
   if (SP->getLinkageName() != "" && SP->getName() != SP->getLinkageName() &&
       (useAllLinkageNames() || InfoHolder.getAbstractSPDies().lookup(SP)))
-    addAccelName(SP->getLinkageName(), Die);
+    addAccelName(CU, SP->getLinkageName(), Die);
 
   // If this is an Objective-C selector name add it to the ObjC accelerator
   // too.
   if (isObjCClass(SP->getName())) {
     StringRef Class, Category;
     getObjCClassCategory(SP->getName(), Class, Category);
-    addAccelObjC(Class, Die);
+    addAccelObjC(CU, Class, Die);
     if (Category != "")
-      addAccelObjC(Category, Die);
+      addAccelObjC(CU, Category, Die);
     // Also add the base method name to the name table.
-    addAccelName(getObjCMethodName(SP->getName()), Die);
+    addAccelName(CU, getObjCMethodName(SP->getName()), Die);
   }
 }
 
@@ -1537,8 +1542,6 @@ void DwarfDebug::emitAccelDebugNames() {
   if (getUnits().empty())
     return;
 
-  Asm->OutStreamer->SwitchSection(
-      Asm->getObjFileLowering().getDwarfDebugNamesSection());
   emitDWARF5AccelTable(Asm, AccelDebugNames, *this, getUnits());
 }
 
@@ -1643,7 +1646,8 @@ void DwarfDebug::emitDebugPubSections() {
     if (!TheU->hasDwarfPubSections())
       continue;
 
-    bool GnuStyle = TheU->getCUNode()->getGnuPubnames();
+    bool GnuStyle = TheU->getCUNode()->getNameTableKind() ==
+                    DICompileUnit::DebugNameTableKind::GNU;
 
     Asm->OutStreamer->SwitchSection(
         GnuStyle ? Asm->getObjFileLowering().getDwarfGnuPubNamesSection()
@@ -2431,11 +2435,16 @@ void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
 // AccelTableKind::Apple, we use the table we got as an argument). If
 // accelerator tables are disabled, this function does nothing.
 template <typename DataT>
-void DwarfDebug::addAccelNameImpl(AccelTable<DataT> &AppleAccel, StringRef Name,
+void DwarfDebug::addAccelNameImpl(const DICompileUnit &CU,
+                                  AccelTable<DataT> &AppleAccel, StringRef Name,
                                   const DIE &Die) {
   if (getAccelTableKind() == AccelTableKind::None)
     return;
 
+  if (getAccelTableKind() != AccelTableKind::Apple &&
+      CU.getNameTableKind() == DICompileUnit::DebugNameTableKind::None)
+    return;
+
   DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
   DwarfStringPoolEntryRef Ref = Holder.getStringPool().getEntry(*Asm, Name);
 
@@ -2453,22 +2462,26 @@ void DwarfDebug::addAccelNameImpl(AccelTable<DataT> &AppleAccel, StringRef Name,
   }
 }
 
-void DwarfDebug::addAccelName(StringRef Name, const DIE &Die) {
-  addAccelNameImpl(AccelNames, Name, Die);
+void DwarfDebug::addAccelName(const DICompileUnit &CU, StringRef Name,
+                              const DIE &Die) {
+  addAccelNameImpl(CU, AccelNames, Name, Die);
 }
 
-void DwarfDebug::addAccelObjC(StringRef Name, const DIE &Die) {
+void DwarfDebug::addAccelObjC(const DICompileUnit &CU, StringRef Name,
+                              const DIE &Die) {
   // ObjC names go only into the Apple accelerator tables.
   if (getAccelTableKind() == AccelTableKind::Apple)
-    addAccelNameImpl(AccelObjC, Name, Die);
+    addAccelNameImpl(CU, AccelObjC, Name, Die);
 }
 
-void DwarfDebug::addAccelNamespace(StringRef Name, const DIE &Die) {
-  addAccelNameImpl(AccelNamespace, Name, Die);
+void DwarfDebug::addAccelNamespace(const DICompileUnit &CU, StringRef Name,
+                                   const DIE &Die) {
+  addAccelNameImpl(CU, AccelNamespace, Name, Die);
 }
 
-void DwarfDebug::addAccelType(StringRef Name, const DIE &Die, char Flags) {
-  addAccelNameImpl(AccelTypes, Name, Die);
+void DwarfDebug::addAccelType(const DICompileUnit &CU, StringRef Name,
+                              const DIE &Die, char Flags) {
+  addAccelNameImpl(CU, AccelTypes, Name, Die);
 }
 
 uint16_t DwarfDebug::getDwarfVersion() const {
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index abf2e43b131..750bbc644d1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -346,8 +346,8 @@ class DwarfDebug : public DebugHandlerBase {
   void constructAbstractSubprogramScopeDIE(DwarfCompileUnit &SrcCU, LexicalScope *Scope);
 
   template <typename DataT>
-  void addAccelNameImpl(AccelTable<DataT> &AppleAccel, StringRef Name,
-                        const DIE &Die);
+  void addAccelNameImpl(const DICompileUnit &CU, AccelTable<DataT> &AppleAccel,
+                        StringRef Name, const DIE &Die);
 
   void finishVariableDefinitions();
 
@@ -608,17 +608,20 @@ public:
     return Ref.resolve();
   }
 
-  void addSubprogramNames(const DISubprogram *SP, DIE &Die);
+  void addSubprogramNames(const DICompileUnit &CU, const DISubprogram *SP,
+                          DIE &Die);
 
   AddressPool &getAddressPool() { return AddrPool; }
 
-  void addAccelName(StringRef Name, const DIE &Die);
+  void addAccelName(const DICompileUnit &CU, StringRef Name, const DIE &Die);
 
-  void addAccelObjC(StringRef Name, const DIE &Die);
+  void addAccelObjC(const DICompileUnit &CU, StringRef Name, const DIE &Die);
 
-  void addAccelNamespace(StringRef Name, const DIE &Die);
+  void addAccelNamespace(const DICompileUnit &CU, StringRef Name,
+                         const DIE &Die);
 
-  void addAccelType(StringRef Name, const DIE &Die, char Flags);
+  void addAccelType(const DICompileUnit &CU, StringRef Name, const DIE &Die,
+                    char Flags);
 
   const MachineFunction *getCurrentFunction() const { return CurFn; }
 
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 011f6548a8b..7335a0bb17e 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -795,7 +795,7 @@ void DwarfUnit::updateAcceleratorTables(const DIScope *Context,
       IsImplementation = CT->getRuntimeLang() == 0 || CT->isObjcClassComplete();
     }
     unsigned Flags = IsImplementation ? dwarf::DW_FLAG_type_implementation : 0;
-    DD->addAccelType(Ty->getName(), TyDIE, Flags);
+    DD->addAccelType(*CUNode, Ty->getName(), TyDIE, Flags);
 
     if (!Context || isa<DICompileUnit>(Context) || isa<DIFile>(Context) ||
         isa<DINamespace>(Context))
@@ -1168,7 +1168,7 @@ DIE *DwarfUnit::getOrCreateNameSpace(const DINamespace *NS) {
     addString(NDie, dwarf::DW_AT_name, NS->getName());
   else
     Name = "(anonymous namespace)";
-  DD->addAccelNamespace(Name, NDie);
+  DD->addAccelNamespace(*CUNode, Name, NDie);
   addGlobalName(Name, NDie, NS->getScope());
   if (NS->getExportSymbols())
     addFlag(NDie, dwarf::DW_AT_export_symbols);
@@ -1417,7 +1417,7 @@ DIE *DwarfUnit::getIndexTyDie() {
   addUInt(*IndexTyDie, dwarf::DW_AT_byte_size, None, sizeof(int64_t));
   addUInt(*IndexTyDie, dwarf::DW_AT_encoding, dwarf::DW_FORM_data1,
           dwarf::DW_ATE_unsigned);
-  DD->addAccelType(Name, *IndexTyDie, /*Flags*/ 0);
+  DD->addAccelType(*CUNode, Name, *IndexTyDie, /*Flags*/ 0);
   return IndexTyDie;
 }