[lld] r319976 - Add a call to std::vector::reserve.

[Rafael Espindola via llvm-commits]

Author: rafael
Date: Wed Dec  6 14:32:19 2017
New Revision: 319976

URL: http://llvm.org/viewvc/llvm-project?rev=319976&view=rev
Log:
Add a call to std::vector::reserve.

This reduces total allocations when linking clang fsds from 263.21MB
to 174.62MB.

This also has some very nice speed improvements on some
benchmarks. Chromium and clang fsds link 6% faster.

Modified:
    lld/trunk/ELF/Relocations.cpp

Modified: lld/trunk/ELF/Relocations.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Relocations.cpp?rev=319976&r1=319975&r2=319976&view=diff
==============================================================================
--- lld/trunk/ELF/Relocations.cpp (original)
+++ lld/trunk/ELF/Relocations.cpp Wed Dec  6 14:32:19 2017
@@ -867,6 +867,9 @@ template <class ELFT, class RelTy>
 static void scanRelocs(InputSectionBase &Sec, ArrayRef<RelTy> Rels) {
   OffsetGetter GetOffset(Sec);
 
+  // Not all relocations end up in Sec.Relocations, but a lot do.
+  Sec.Relocations.reserve(Rels.size());
+
   for (auto I = Rels.begin(), End = Rels.end(); I != End; ++I) {
     const RelTy &Rel = *I;
     Symbol &Sym = Sec.getFile<ELFT>()->getRelocTargetSym(Rel);