From e9c58065939ce1b086fdcdc5e91a49cac3f38f95 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Fri, 12 Feb 2016 20:41:43 +0000
Subject: [PATCH] ELF: Remove use of MapVector from LinkerScript.

We don't have to use a MapVector here. Instead, just std::vector suffices.

llvm-svn: 260724
---
 lld/ELF/Driver.cpp       |  1 -
 lld/ELF/LinkerScript.cpp | 28 ++++++++++++----------------
 lld/ELF/LinkerScript.h   | 11 +++++------
 3 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index ea27580..67b583a 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -296,7 +296,6 @@ template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
   SymbolTable<ELFT> Symtab;
   std::unique_ptr<TargetInfo> TI(createTarget());
   Target = TI.get();
-  Script->finalize();
 
   if (!Config->Shared) {
     // Add entry symbol.
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 4f39acb..1e0e855 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -28,27 +28,22 @@ using namespace lld::elf2;
 
 LinkerScript *elf2::Script;
 
-void LinkerScript::finalize() {
-  for (const std::pair<StringRef, std::vector<StringRef>> &P : Sections)
-    for (StringRef S : P.second)
-      RevSections[S] = P.first;
-}
-
 StringRef LinkerScript::getOutputSection(StringRef S) {
-  return RevSections.lookup(S);
+  return Sections.lookup(S);
 }
 
 bool LinkerScript::isDiscarded(StringRef S) {
-  return RevSections.lookup(S) == "/DISCARD/";
+  return Sections.lookup(S) == "/DISCARD/";
 }
 
+// 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.
 int LinkerScript::compareSections(StringRef A, StringRef B) {
-  auto I = Sections.find(A);
-  auto E = Sections.end();
-  if (I == E)
-    return 0;
-  auto J = Sections.find(B);
-  if (J == E)
+  auto E = SectionOrder.end();
+  auto I = std::find(SectionOrder.begin(), E, A);
+  auto J = std::find(SectionOrder.begin(), E, B);
+  if (I == E || J == E)
     return 0;
   return I < J ? -1 : 1;
 }
@@ -349,14 +344,15 @@ void ScriptParser::readSections() {
 }
 
 void ScriptParser::readOutputSectionDescription() {
-  std::vector<StringRef> &V = Script->Sections[next()];
+  StringRef OutSec = next();
+  Script->SectionOrder.push_back(OutSec);
   expect(":");
   expect("{");
   while (!Error && !skip("}")) {
     next(); // Skip input file name.
     expect("(");
     while (!Error && !skip(")"))
-      V.push_back(next());
+      Script->Sections[next()] = OutSec;
   }
 }
 
diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 7eb0773..bdfcb7d 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -32,15 +32,14 @@ public:
   StringRef getOutputSection(StringRef InputSection);
   bool isDiscarded(StringRef InputSection);
   int compareSections(StringRef A, StringRef B);
-  void finalize();
 
 private:
-  // Map for SECTIONS command. The key is output section name
-  // and a value is a list of input section names.
-  llvm::MapVector<StringRef, std::vector<StringRef>> Sections;
+  // A map for SECTIONS command. The key is input section name
+  // and the value is the corresponding output section name.
+  llvm::DenseMap<StringRef, StringRef> Sections;
 
-  // Inverse map of Sections.
-  llvm::DenseMap<StringRef, StringRef> RevSections;
+  // Output sections are sorted by this order.
+  std::vector<StringRef> SectionOrder;
 
   llvm::BumpPtrAllocator Alloc;
 };
-- 
2.7.4