Add DT_REL(A)COUNT tag to .dynamic section

This patch groups relative relocations in a single block
in combrelocs mode and adds DT_RELCOUNT or DT_RELACOUNT
tag to .dynamic section

Differential revision: https://reviews.llvm.org/D23661

llvm-svn: 280210

2 files changed, 13 insertions, 0 deletions

diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 05c4fa903a7..37fc0545206 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -354,11 +354,18 @@ RelocationSection<ELFT>::RelocationSection(StringRef Name, bool Sort)
 
 template <class ELFT>
 void RelocationSection<ELFT>::addReloc(const DynamicReloc<ELFT> &Reloc) {
+  if (Reloc.Type == Target->RelativeRel)
+    ++NumRelativeRelocs;
   Relocs.push_back(Reloc);
 }
 
 template <class ELFT, class RelTy>
 static bool compRelocations(const RelTy &A, const RelTy &B) {
+  bool AIsRel = A.getType(Config->Mips64EL) == Target->RelativeRel;
+  bool BIsRel = B.getType(Config->Mips64EL) == Target->RelativeRel;
+  if (AIsRel != BIsRel)
+    return AIsRel;
+
   return A.getSymbol(Config->Mips64EL) < B.getSymbol(Config->Mips64EL);
 }
 
@@ -661,6 +668,10 @@ template <class ELFT> void DynamicSection<ELFT>::finalize() {
     Add({IsRela ? DT_RELASZ : DT_RELSZ, Out<ELFT>::RelaDyn->getSize()});
     Add({IsRela ? DT_RELAENT : DT_RELENT,
          uintX_t(IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel))});
+
+    size_t NumRelativeRels = Out<ELFT>::RelaDyn->getRelativeRelocCount();
+    if (Config->ZCombreloc && NumRelativeRels)
+      Add({IsRela ? DT_RELACOUNT : DT_RELCOUNT, NumRelativeRels});
   }
   if (Out<ELFT>::RelaPlt && Out<ELFT>::RelaPlt->hasRelocs()) {
     Add({DT_JMPREL, Out<ELFT>::RelaPlt});
diff --git a/lld/ELF/OutputSections.h b/lld/ELF/OutputSections.h
index 213a5211717..b350bef1afb 100644
--- a/lld/ELF/OutputSections.h
+++ b/lld/ELF/OutputSections.h
@@ -377,10 +377,12 @@ public:
   void writeTo(uint8_t *Buf) override;
   bool hasRelocs() const { return !Relocs.empty(); }
   typename Base::Kind getKind() const override { return Base::Reloc; }
+  size_t getRelativeRelocCount() const { return NumRelativeRelocs; }
   static bool classof(const Base *B) { return B->getKind() == Base::Reloc; }
 
 private:
   bool Sort;
+  size_t NumRelativeRelocs = 0;
   std::vector<DynamicReloc<ELFT>> Relocs;
 };