[dsymutil] Move string pool into its own implementatino file. NFC.

The DwarfLinker implementation is already relatively large with over 4k
LOC. This commit moves the implementation of NonRelocatableStringpool
into a separate cpp file.

llvm-svn: 326425
diff --git a/llvm/tools/dsymutil/NonRelocatableStringpool.cpp b/llvm/tools/dsymutil/NonRelocatableStringpool.cpp
new file mode 100644
index 0000000..d943b79
--- /dev/null
+++ b/llvm/tools/dsymutil/NonRelocatableStringpool.cpp
@@ -0,0 +1,51 @@
+//===- NonRelocatableStringpool.cpp - A simple stringpool  ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "NonRelocatableStringpool.h"
+
+namespace llvm {
+namespace dsymutil {
+
+DwarfStringPoolEntryRef NonRelocatableStringpool::getEntry(StringRef S) {
+  if (S.empty() && !Strings.empty())
+    return EmptyString;
+
+  auto I = Strings.insert({S, DwarfStringPoolEntry()});
+  auto &Entry = I.first->second;
+  if (I.second || Entry.Index == -1U) {
+    Entry.Index = NumEntries++;
+    Entry.Offset = CurrentEndOffset;
+    Entry.Symbol = nullptr;
+    CurrentEndOffset += S.size() + 1;
+  }
+  return DwarfStringPoolEntryRef(*I.first);
+}
+
+StringRef NonRelocatableStringpool::internString(StringRef S) {
+  DwarfStringPoolEntry Entry{nullptr, 0, -1U};
+  auto InsertResult = Strings.insert({S, Entry});
+  return InsertResult.first->getKey();
+}
+
+std::vector<DwarfStringPoolEntryRef>
+NonRelocatableStringpool::getEntries() const {
+  std::vector<DwarfStringPoolEntryRef> Result;
+  Result.reserve(Strings.size());
+  for (const auto &E : Strings)
+    Result.emplace_back(E);
+  std::sort(
+      Result.begin(), Result.end(),
+      [](const DwarfStringPoolEntryRef A, const DwarfStringPoolEntryRef B) {
+        return A.getIndex() < B.getIndex();
+      });
+  return Result;
+}
+
+} // namespace dsymutil
+} // namespace llvm