[lld] r276261 - Instantiate Interp output section only when needed.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Thu Jul 21 06:01:23 2016
New Revision: 276261

URL: http://llvm.org/viewvc/llvm-project?rev=276261&view=rev
Log:
Instantiate Interp output section only when needed.

This change simplifies interaction between Writer and the linker script
because we can make needsInterpSection() a file-scope function.

Modified:
    lld/trunk/ELF/LinkerScript.cpp
    lld/trunk/ELF/Writer.cpp
    lld/trunk/ELF/Writer.h

Modified: lld/trunk/ELF/LinkerScript.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/LinkerScript.cpp?rev=276261&r1=276260&r2=276261&view=diff
==============================================================================
--- lld/trunk/ELF/LinkerScript.cpp (original)
+++ lld/trunk/ELF/LinkerScript.cpp Thu Jul 21 06:01:23 2016
@@ -344,7 +344,7 @@ LinkerScript<ELFT>::createPhdrs(ArrayRef
 
     switch (Cmd.Type) {
     case PT_INTERP:
-      if (needsInterpSection<ELFT>())
+      if (Out<ELFT>::Interp)
         Added.add(Out<ELFT>::Interp);
       break;
     case PT_DYNAMIC:

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=276261&r1=276260&r2=276261&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Thu Jul 21 06:01:23 2016
@@ -112,6 +112,11 @@ void elf::reportDiscarded(InputSectionBa
          << "' in file '" << File->getName() << "'\n";
 }
 
+template <class ELFT> static bool needsInterpSection() {
+  return !Symtab<ELFT>::X->getSharedFiles().empty() &&
+         !Config->DynamicLinker.empty();
+}
+
 template <class ELFT> void elf::writeResult(SymbolTable<ELFT> *Symtab) {
   typedef typename ELFT::uint uintX_t;
   typedef typename ELFT::Ehdr Elf_Ehdr;
@@ -121,7 +126,6 @@ template <class ELFT> void elf::writeRes
   DynamicSection<ELFT> Dynamic;
   EhOutputSection<ELFT> EhFrame;
   GotSection<ELFT> Got;
-  InterpSection<ELFT> Interp;
   PltSection<ELFT> Plt;
   RelocationSection<ELFT> RelaDyn(Config->Rela ? ".rela.dyn" : ".rel.dyn",
                                   Config->ZCombreloc);
@@ -137,6 +141,7 @@ template <class ELFT> void elf::writeRes
   ProgramHeaders.updateAlignment(sizeof(uintX_t));
 
   // Instantiate optional output sections if they are needed.
+  std::unique_ptr<InterpSection<ELFT>> Interp;
   std::unique_ptr<BuildIdSection<ELFT>> BuildId;
   std::unique_ptr<EhFrameHeader<ELFT>> EhFrameHdr;
   std::unique_ptr<GnuHashTableSection<ELFT>> GnuHashTab;
@@ -148,6 +153,9 @@ template <class ELFT> void elf::writeRes
   std::unique_ptr<OutputSection<ELFT>> MipsRldMap;
   std::unique_ptr<VersionDefinitionSection<ELFT>> VerDef;
 
+  if (needsInterpSection<ELFT>())
+    Interp.reset(new InterpSection<ELFT>);
+
   if (Config->BuildId == BuildIdKind::Fnv1)
     BuildId.reset(new BuildIdFnv1<ELFT>);
   else if (Config->BuildId == BuildIdKind::Md5)
@@ -195,7 +203,7 @@ template <class ELFT> void elf::writeRes
   Out<ELFT>::Got = &Got;
   Out<ELFT>::GotPlt = GotPlt.get();
   Out<ELFT>::HashTab = HashTab.get();
-  Out<ELFT>::Interp = &Interp;
+  Out<ELFT>::Interp = Interp.get();
   Out<ELFT>::Plt = &Plt;
   Out<ELFT>::RelaDyn = &RelaDyn;
   Out<ELFT>::RelaPlt = RelaPlt.get();
@@ -474,12 +482,6 @@ uint32_t elf::toPhdrFlags(uint64_t Flags
   return Ret;
 }
 
-// Various helper functions
-template <class ELFT> bool elf::needsInterpSection() {
-  return !Symtab<ELFT>::X->getSharedFiles().empty() &&
-         !Config->DynamicLinker.empty();
-}
-
 template <class ELFT> bool elf::isOutputDynamic() {
   return !Symtab<ELFT>::X->getSharedFiles().empty() || Config->Pic;
 }
@@ -843,7 +845,7 @@ template <class ELFT> void Writer<ELFT>:
 
   // Add .interp at first because some loaders want to see that section
   // on the first page of the executable file when loaded into memory.
-  if (needsInterpSection<ELFT>())
+  if (Out<ELFT>::Interp)
     OutputSections.insert(OutputSections.begin(), Out<ELFT>::Interp);
 
   // This order is not the same as the final output order
@@ -962,7 +964,7 @@ std::vector<PhdrEntry<ELFT>> Writer<ELFT
   Hdr.add(Out<ELFT>::ProgramHeaders);
 
   // PT_INTERP must be the second entry if exists.
-  if (needsInterpSection<ELFT>()) {
+  if (Out<ELFT>::Interp) {
     Phdr &Hdr = *AddHdr(PT_INTERP, toPhdrFlags(Out<ELFT>::Interp->getFlags()));
     Hdr.add(Out<ELFT>::Interp);
   }
@@ -1332,11 +1334,6 @@ template struct elf::PhdrEntry<ELF32BE>;
 template struct elf::PhdrEntry<ELF64LE>;
 template struct elf::PhdrEntry<ELF64BE>;
 
-template bool elf::needsInterpSection<ELF32LE>();
-template bool elf::needsInterpSection<ELF32BE>();
-template bool elf::needsInterpSection<ELF64LE>();
-template bool elf::needsInterpSection<ELF64BE>();
-
 template bool elf::isOutputDynamic<ELF32LE>();
 template bool elf::isOutputDynamic<ELF32BE>();
 template bool elf::isOutputDynamic<ELF64LE>();

Modified: lld/trunk/ELF/Writer.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.h?rev=276261&r1=276260&r2=276261&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.h (original)
+++ lld/trunk/ELF/Writer.h Thu Jul 21 06:01:23 2016
@@ -25,7 +25,6 @@ template <class ELFT> class ObjectFile;
 template <class ELFT> class SymbolTable;
 template <class ELFT> void writeResult(SymbolTable<ELFT> *Symtab);
 template <class ELFT> void markLive();
-template <class ELFT> bool needsInterpSection();
 template <class ELFT> bool isOutputDynamic();
 template <class ELFT> bool isRelroSection(OutputSectionBase<ELFT> *Sec);
 template <class ELFT> bool needsPtLoad(OutputSectionBase<ELFT> *Sec);