[ELF] - Get rid of SectionOrder array.

SectionOrder vector was a part of LinkerScript class.

It can be removed because Commands vector contains the 
same information and SectiorOrder is just a subset.

Differential revision: http://reviews.llvm.org/D19171

llvm-svn: 266974
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index dd67fdb..ae21039 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -204,8 +204,7 @@
   // https://sourceware.org/binutils/docs/ld/Orphan-Sections.html#Orphan-Sections.
   for (OutputSectionBase<ELFT> *Sec : Sections) {
     StringRef Name = Sec->getName();
-    auto I = std::find(Opt.SectionOrder.begin(), Opt.SectionOrder.end(), Name);
-    if (I == Opt.SectionOrder.end())
+    if (getSectionOrder(Name) == (uint32_t)-1)
       Opt.Commands.push_back({SectionKind, {}, Name});
   }
 
@@ -249,15 +248,23 @@
   return I->second;
 }
 
-// A compartor to sort output sections. Returns -1 or 1 if both
-// A and B are mentioned in linker scripts. Otherwise, returns 0
-// to use the default rule which is implemented in Writer.cpp.
+template <class ELFT>
+uint32_t LinkerScript<ELFT>::getSectionOrder(StringRef Name) {
+  auto Begin = Opt.Commands.begin();
+  auto End = Opt.Commands.end();
+  auto I = std::find_if(Begin, End, [&](SectionsCommand &N) {
+    return N.Kind == SectionKind && N.SectionName == Name;
+  });
+  return I == End ? (uint32_t)-1 : (I - Begin);
+}
+
+// A compartor to sort output sections. Returns -1 or 1 if
+// A or B are mentioned in linker script. Otherwise, returns 0.
 template <class ELFT>
 int LinkerScript<ELFT>::compareSections(StringRef A, StringRef B) {
-  auto E = Opt.SectionOrder.end();
-  auto I = std::find(Opt.SectionOrder.begin(), E, A);
-  auto J = std::find(Opt.SectionOrder.begin(), E, B);
-  if (I == E || J == E)
+  uint32_t I = getSectionOrder(A);
+  uint32_t J = getSectionOrder(B);
+  if (I == (uint32_t)-1 && J == (uint32_t)-1)
     return 0;
   return I < J ? -1 : 1;
 }
@@ -509,7 +516,6 @@
 
 void ScriptParser::readOutputSectionDescription() {
   StringRef OutSec = next();
-  Opt.SectionOrder.push_back(OutSec);
   Opt.Commands.push_back({SectionKind, {}, OutSec});
   expect(":");
   expect("{");