Revert r340904 "[llvm-mc] - Allow to set custom flags for debug sections."

It broke PPC64 BB:
http://lab.llvm.org:8011/builders/clang-ppc64be-linux/builds/23252

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340906 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -424,9 +424,6 @@ static SectionKind getELFKindForNamedSection(StringRef Name, SectionKind K) {
       Name.startswith(".llvm.linkonce.tb."))
     return SectionKind::getThreadBSS();
 
-  if (Name.startswith(".debug_"))
-    return SectionKind::getMetadata();
-
   return K;
 }
 

lib/MC/MCContext.cpp

@@ -394,15 +394,6 @@ MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
   auto IterBool = ELFUniquingMap.insert(
       std::make_pair(ELFSectionKey{Section.str(), Group, UniqueID}, nullptr));
   auto &Entry = *IterBool.first;
-  MCSectionELF *&Sec = Entry.second;
-  if (!IterBool.second) {
-    // We want to let users add additional flags even for sections with
-    // defaults. For example, .debug_str has "MS" flags by default and user
-    // might want to add "E".
-    Sec->setFlags(Sec->getFlags() | Flags);
-    return Sec;
-  }
-
   if (!IterBool.second)
     return Entry.second;
 
@@ -416,9 +407,10 @@ MCSectionELF *MCContext::getELFSection(const Twine &Section, unsigned Type,
   else
     Kind = SectionKind::getReadOnly();
 
-  Sec = createELFSectionImpl(CachedName, Type, Flags, Kind, EntrySize, GroupSym,
-                             UniqueID, Associated);
-  return Sec;
+  MCSectionELF *Result = createELFSectionImpl(
+      CachedName, Type, Flags, Kind, EntrySize, GroupSym, UniqueID, Associated);
+  Entry.second = Result;
+  return Result;
 }
 
 MCSectionELF *MCContext::createELFGroupSection(const MCSymbolELF *Group) {

test/MC/ELF/section-flags.s

@@ -1,12 +0,0 @@
-# RUN: llvm-mc -triple x86_64-pc-linux-gnu %s -filetype=obj -o %t.o
-# RUN: llvm-readobj -s --elf-output-style=GNU %t.o | FileCheck %s
-
-## Check we are able to set the custom flag ('E') for debug sections.
-# CHECK: .debug_info   {{.*}}  E
-# CHECK: .debug_str    {{.*}}  EMS
-
-.section .debug_info,"e"
-nop
-
-.section .debug_str,"eMS",@progbits,1
-nop