Special case the creation of relocation sections.

These sections are never looked up and we know when have to create them. Use
that to save adding them to the regular map and avoid a symbol->string->symbol
conversion for the group symbol.

This also makes the implementation independent of the details of how unique
sections are implemented.

llvm-svn: 233539

3 files changed, 20 insertions, 6 deletions

diff --git a/llvm/include/llvm/MC/MCContext.h b/llvm/include/llvm/MC/MCContext.h
index ca4eae53a88..a17e05d87c1 100644
--- a/llvm/include/llvm/MC/MCContext.h
+++ b/llvm/include/llvm/MC/MCContext.h
@@ -194,6 +194,7 @@ namespace llvm {
     StringMap<const MCSectionMachO*> MachOUniquingMap;
     std::map<ELFSectionKey, const MCSectionELF *> ELFUniquingMap;
     std::map<COFFSectionKey, const MCSectionCOFF *> COFFUniquingMap;
+    StringMap<bool> ELFRelSecNames;
 
     /// Do automatic reset in destructor
     bool AutoReset;
@@ -304,6 +305,10 @@ namespace llvm {
                                       StringRef Group, bool Unique,
                                       const char *BeginSymName = nullptr);
 
+    const MCSectionELF *createELFRelSection(StringRef Name, unsigned Type,
+                                            unsigned Flags, unsigned EntrySize,
+                                            const MCSymbol *Group);
+
     void renameELFSection(const MCSectionELF *Section, StringRef Name);
 
     const MCSectionELF *CreateELFGroupSection();
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index c99a3ee5e26..6be37bfd641 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -1167,15 +1167,12 @@ ELFObjectWriter::createRelocationSection(MCAssembler &Asm,
     EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
 
   unsigned Flags = 0;
-  StringRef Group = "";
-  if (Section.getFlags() & ELF::SHF_GROUP) {
+  if (Section.getFlags() & ELF::SHF_GROUP)
     Flags = ELF::SHF_GROUP;
-    Group = Section.getGroup()->getName();
-  }
 
-  const MCSectionELF *RelaSection = Ctx.getELFSection(
+  const MCSectionELF *RelaSection = Ctx.createELFRelSection(
       RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
-      Flags, EntrySize, Group, true);
+      Flags, EntrySize, Section.getGroup());
   return &Asm.getOrCreateSectionData(*RelaSection);
 }
 
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 09de4ee05e6..2afa21219fc 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -275,6 +275,18 @@ void MCContext::renameELFSection(const MCSectionELF *Section, StringRef Name) {
   const_cast<MCSectionELF*>(Section)->setSectionName(CachedName);
 }
 
+const MCSectionELF *
+MCContext::createELFRelSection(StringRef Name, unsigned Type, unsigned Flags,
+                               unsigned EntrySize, const MCSymbol *Group) {
+  StringMap<bool>::iterator I;
+  bool Inserted;
+  std::tie(I, Inserted) = ELFRelSecNames.insert(std::make_pair(Name, true));
+
+  return new (*this)
+      MCSectionELF(I->getKey(), Type, Flags, SectionKind::getReadOnly(),
+                   EntrySize, Group, true, nullptr);
+}
+
 const MCSectionELF *MCContext::getELFSection(StringRef Section, unsigned Type,
                                              unsigned Flags, unsigned EntrySize,
                                              StringRef Group, bool Unique,