From 3f11c8c97ef3ad587b1b1c6e079c390b533ba9b7 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Thu, 24 Dec 2015 08:41:12 +0000
Subject: [PATCH] Split functions and add comments. NFC.

llvm-svn: 256369
---
 lld/ELF/InputFiles.cpp | 46 ++++++++++++++++++++++++++----------------
 lld/ELF/InputFiles.h   |  1 +
 lld/ELF/Target.cpp     |  9 +++++++--
 3 files changed, 37 insertions(+), 19 deletions(-)

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index c0fbe03d1b12..3c7f5ba4d824 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -110,6 +110,9 @@ void elf2::ObjectFile<ELFT>::parse(DenseSet<StringRef> &Comdats) {
   initializeSymbols();
 }
 
+// Sections with SHT_GROUP and comdat bits define comdat section groups.
+// They are identified and deduplicated by group name. This function
+// returns a group name.
 template <class ELFT>
 StringRef ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
   const ELFFile<ELFT> &Obj = this->ELFObj;
@@ -222,27 +225,36 @@ void elf2::ObjectFile<ELFT>::initializeSections(DenseSet<StringRef> &Comdats) {
       break;
     }
     default:
-      ErrorOr<StringRef> NameOrErr = this->ELFObj.getSectionName(&Sec);
-      error(NameOrErr);
-      StringRef Name = *NameOrErr;
-      if (Name == ".note.GNU-stack")
-        Sections[I] = &InputSection<ELFT>::Discarded;
-      else if (Name == ".eh_frame")
-        Sections[I] =
-            new (this->EHAlloc.Allocate()) EHInputSection<ELFT>(this, &Sec);
-      else if (Config->EMachine == EM_MIPS && Name == ".reginfo")
-        Sections[I] =
-            new (this->Alloc) MipsReginfoInputSection<ELFT>(this, &Sec);
-      else if (shouldMerge<ELFT>(Sec))
-        Sections[I] =
-            new (this->MAlloc.Allocate()) MergeInputSection<ELFT>(this, &Sec);
-      else
-        Sections[I] = new (this->Alloc) InputSection<ELFT>(this, &Sec);
-      break;
+      Sections[I] = createInputSection(Sec);
     }
   }
 }
 
+template <class ELFT> InputSectionBase<ELFT> *
+elf2::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec) {
+  ErrorOr<StringRef> NameOrErr = this->ELFObj.getSectionName(&Sec);
+  error(NameOrErr);
+  StringRef Name = *NameOrErr;
+
+  // .note.GNU-stack is a marker section to control the presence of
+  // PT_GNU_STACK segment in outputs. Since the presence of the segment
+  // is controlled only by the command line option (-z execstack) in LLD,
+  // .note.GNU-stack is ignored.
+  if (Name == ".note.GNU-stack")
+    return &InputSection<ELFT>::Discarded;
+
+  // A MIPS object file has a special section that contains register
+  // usage info, which needs to be handled by the linker specially.
+  if (Config->EMachine == EM_MIPS && Name == ".reginfo")
+    return new (this->Alloc) MipsReginfoInputSection<ELFT>(this, &Sec);
+
+  if (Name == ".eh_frame")
+    return new (this->EHAlloc.Allocate()) EHInputSection<ELFT>(this, &Sec);
+  if (shouldMerge<ELFT>(Sec))
+    return new (this->MAlloc.Allocate()) MergeInputSection<ELFT>(this, &Sec);
+  return new (this->Alloc) InputSection<ELFT>(this, &Sec);
+}
+
 template <class ELFT> void elf2::ObjectFile<ELFT>::initializeSymbols() {
   this->initStringTable();
   Elf_Sym_Range Syms = this->getNonLocalSymbols();
diff --git a/lld/ELF/InputFiles.h b/lld/ELF/InputFiles.h
index d30268bd260b..8363acb9f2b9 100644
--- a/lld/ELF/InputFiles.h
+++ b/lld/ELF/InputFiles.h
@@ -124,6 +124,7 @@ public:
 private:
   void initializeSections(llvm::DenseSet<StringRef> &Comdats);
   void initializeSymbols();
+  InputSectionBase<ELFT> *createInputSection(const Elf_Shdr &Sec);
 
   SymbolBody *createSymbolBody(StringRef StringTable, const Elf_Sym *Sym);
 
diff --git a/lld/ELF/Target.cpp b/lld/ELF/Target.cpp
index ea15ef939665..a80c672b8d28 100644
--- a/lld/ELF/Target.cpp
+++ b/lld/ELF/Target.cpp
@@ -1453,9 +1453,14 @@ bool MipsTargetInfo<ELFT>::isRelRelative(uint32_t Type) const {
   }
 }
 
+// _gp is a MIPS-specific ABI-defined symbol which points to
+// a location that is relative to GOT. This function returns
+// the value for the symbol.
 template <class ELFT> typename ELFFile<ELFT>::uintX_t getMipsGpAddr() {
-  const unsigned GPOffset = 0x7ff0;
-  return Out<ELFT>::Got->getVA() ? (Out<ELFT>::Got->getVA() + GPOffset) : 0;
+  unsigned GPOffset = 0x7ff0;
+  if (uint64_t V = Out<ELFT>::Got->getVA())
+    return V + GPOffset;
+  return 0;
 }
 
 template uint32_t getMipsGpAddr<ELF32LE>();