Delay removal of pubtypes and pubnames

[• rafael]

Summary

The reason for this is that I want to use the lld infrastructure for getting data and relocations.

This means that the data for .debug_gnu_pubnames will be just a InputSection->Data, which means we have to at least create a InputSection.

[grimar]

This looks fine for me as is too, but have few ideas to share.

ELF/InputFiles.cpp

511

What about leaving it here (for consistency with others discarded sections), but marking as dead from start ?

  if (Config->GdbIndex &&
      (Name == ".debug_gnu_pubnames" || Name == ".debug_gnu_pubtypes")) {
   InputSectionBase *Sec = make<InputSection>(this, &Sec, Name);
   Script->discard({Sec});
   return Sec;
}

ELF/SyntheticSections.cpp

1763

Then this can remain getDebugInfoSections.

Or even we can have
GdbIndexSection::addDebugInfo() and call it during createInputSection() to
avoid scanning over input sections at all (though not sure how much iterating over
all input sections hits perfomance).

ELF/InputFiles.cpp

   if (Config->Strip != StripPolicy::None && Name.startswith(".debug"))
     return &InputSection::Discarded;
 
-  // If -gdb-index is given, LLD creates .gdb_index section, and that
-  // section serves the same purpose as .debug_gnu_pub{names,types} sections.
-  // If that's the case, we want to eliminate .debug_gnu_pub{names,types}
-  // because they are redundant and can waste large amount of disk space
-  // (for example, they are about 400 MiB in total for a clang debug build.)
-  if (Config->GdbIndex &&
-      (Name == ".debug_gnu_pubnames" || Name == ".debug_gnu_pubtypes"))
-    return &InputSection::Discarded;
-
   // The linkonce feature is a sort of proto-comdat. Some glibc i386 object
   // files contain definitions of symbol "__x86.get_pc_thunk.bx" in linkonce
   // sections. Drop those sections to avoid duplicate symbol errors.

ELF/SyntheticSections.cpp

   return Ret;
 }
 
-static std::vector<InputSection *> getDebugInfoSections() {
+static std::vector<InputSection *> filterForGdbIndex() {
   std::vector<InputSection *> Ret;
-  for (InputSectionBase *S : InputSections)
-    if (InputSection *IS = dyn_cast<InputSection>(S))
-      if (IS->Name == ".debug_info")
-        Ret.push_back(IS);
+  for (InputSectionBase *S : InputSections) {
+    InputSection *IS = dyn_cast<InputSection>(S);
+    if (!IS)
+      continue;
+    StringRef Name = IS->Name;
+    if (Name == ".debug_info")
+      Ret.push_back(IS);
+
+    // If -gdb-index is given, LLD creates .gdb_index section, and that
+    // section serves the same purpose as .debug_gnu_pub{names,types} sections.
+    // If that's the case, we want to eliminate .debug_gnu_pub{names,types}
+    // because they are redundant and can waste large amount of disk space
+    // (for example, they are about 400 MiB in total for a clang debug build.)
+    if (Name == ".debug_gnu_pubnames" || Name == ".debug_gnu_pubtypes")
+      Script->discard({S});
+  }
   return Ret;
 }
 

 
 template <class ELFT> GdbIndexSection *elf::createGdbIndex() {
   std::vector<GdbIndexChunk> Chunks;
-  for (InputSection *Sec : getDebugInfoSections()) {
+  for (InputSection *Sec : filterForGdbIndex()) {
     InputFile *F = Sec->File;
     std::error_code EC;
     ELFObjectFile<ELFT> Obj(F->MB, EC);