[lld] r275665 - Make Verdef and Verdaux adjacent in the version definition section.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Fri Jul 15 21:29:45 2016
New Revision: 275665

URL: http://llvm.org/viewvc/llvm-project?rev=275665&view=rev
Log:
Make Verdef and Verdaux adjacent in the version definition section.

Previously, Verdefs and Verdauxs are separated in the section.
The new layout is easier to write as we do not have to maintain
two pointers and can avoid passing a reference to a pointer.

Modified:
    lld/trunk/ELF/OutputSections.cpp
    lld/trunk/ELF/OutputSections.h

Modified: lld/trunk/ELF/OutputSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=275665&r1=275664&r2=275665&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.cpp (original)
+++ lld/trunk/ELF/OutputSections.cpp Fri Jul 15 21:29:45 2016
@@ -1498,39 +1498,35 @@ template <class ELFT> void VersionDefini
   this->Header.sh_info = getVerDefNum();
 }
 
-template <class Elf_Verdef, class Elf_Verdaux>
-static void writeDefinition(Elf_Verdef *&Verdef, Elf_Verdaux *&Verdaux,
-                            uint32_t Flags, uint32_t Index, StringRef Name,
-                            size_t StrTabOffset) {
+template <class ELFT>
+void VersionDefinitionSection<ELFT>::writeOne(uint8_t *Buf, uint32_t Index,
+                                              StringRef Name, size_t NameOff) {
+  auto *Verdef = reinterpret_cast<Elf_Verdef *>(Buf);
   Verdef->vd_version = 1;
   Verdef->vd_cnt = 1;
-  Verdef->vd_aux =
-      reinterpret_cast<char *>(Verdaux) - reinterpret_cast<char *>(Verdef);
-  Verdef->vd_next = sizeof(Elf_Verdef);
-
-  Verdef->vd_flags = Flags;
+  Verdef->vd_aux = sizeof(Elf_Verdef);
+  Verdef->vd_next = sizeof(Elf_Verdef) + sizeof(Elf_Verdaux);
+  Verdef->vd_flags = (Index == 1 ? VER_FLG_BASE : 0);
   Verdef->vd_ndx = Index;
   Verdef->vd_hash = hashSysv(Name);
-  ++Verdef;
 
-  Verdaux->vda_name = StrTabOffset;
+  auto *Verdaux = reinterpret_cast<Elf_Verdaux *>(Buf + sizeof(Elf_Verdef));
+  Verdaux->vda_name = NameOff;
   Verdaux->vda_next = 0;
-  ++Verdaux;
 }
 
 template <class ELFT>
 void VersionDefinitionSection<ELFT>::writeTo(uint8_t *Buf) {
-  Elf_Verdef *Verdef = reinterpret_cast<Elf_Verdef *>(Buf);
-  Elf_Verdaux *Verdaux =
-      reinterpret_cast<Elf_Verdaux *>(Verdef + getVerDefNum());
+  writeOne(Buf, 1, getFileDefName(), FileDefNameOff);
 
-  writeDefinition(Verdef, Verdaux, VER_FLG_BASE, 1, getFileDefName(),
-                  FileDefNameOff);
+  for (Version &V : Config->SymbolVersions) {
+    Buf += sizeof(Elf_Verdef) + sizeof(Elf_Verdaux);
+    writeOne(Buf, V.Id, V.Name, V.NameOff);
+  }
 
-  for (Version &V : Config->SymbolVersions)
-    writeDefinition(Verdef, Verdaux, 0, V.Id, V.Name, V.NameOff);
-
-  Verdef[-1].vd_next = 0;
+  // Need to terminate the last version definition.
+  Elf_Verdef *Verdef = reinterpret_cast<Elf_Verdef *>(Buf);
+  Verdef->vd_next = 0;
 }
 
 template <class ELFT>

Modified: lld/trunk/ELF/OutputSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=275665&r1=275664&r2=275665&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.h (original)
+++ lld/trunk/ELF/OutputSections.h Fri Jul 15 21:29:45 2016
@@ -262,12 +262,15 @@ class VersionDefinitionSection final : p
   typedef typename ELFT::Verdef Elf_Verdef;
   typedef typename ELFT::Verdaux Elf_Verdaux;
 
-  unsigned FileDefNameOff;
-
 public:
   VersionDefinitionSection();
   void finalize() override;
   void writeTo(uint8_t *Buf) override;
+
+private:
+  void writeOne(uint8_t *Buf, uint32_t Index, StringRef Name, size_t NameOff);
+
+  unsigned FileDefNameOff;
 };
 
 // The .gnu.version section specifies the required version of each symbol in the