[PATCH] D36079: Binary search to find a relocation.

[Rui Ueyama via Phabricator via llvm-commits]

ruiu created this revision.
Herald added a subscriber: emaste.

This change makes -gdb-index 40% faster. My test case is self-linking lld.


https://reviews.llvm.org/D36079

Files:
  lld/ELF/GdbIndex.cpp


Index: lld/ELF/GdbIndex.cpp
===================================================================
--- lld/ELF/GdbIndex.cpp
+++ lld/ELF/GdbIndex.cpp
@@ -79,11 +79,13 @@
 Optional<RelocAddrEntry>
 LLDDwarfObj<ELFT>::findAux(const InputSectionBase &Sec, uint64_t Pos,
                            ArrayRef<RelTy> Rels) const {
-  auto I = llvm::find_if(Rels,
-                         [=](const RelTy &Rel) { return Rel.r_offset == Pos; });
-  if (I == Rels.end())
+  auto It = std::lower_bound(
+      Rels.begin(), Rels.end(), Pos,
+      [](const RelTy &A, uint64_t B) { return A.r_offset < B; });
+  if (It == Rels.end() || It->r_offset != Pos)
     return None;
-  const RelTy &Rel = *I;
+  const RelTy &Rel = *It;
+
   const ObjFile<ELFT> *File = Sec.getFile<ELFT>();
   uint32_t SymIndex = Rel.getSymbol(Config->IsMips64EL);
   const typename ELFT::Sym &Sym = File->getELFSymbols()[SymIndex];


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