[Option] Store arg strings in a set backed by a BumpPtrAllocator

No functionality change.

This is preparing to move response file parsing into lib/Option so it
can be shared between clang and lld.  This change isn't just a
micro-optimization.  Clang's driver uses a std::set<std::string> to
unique arguments while parsing response files, so this matches that.

llvm-svn: 186319

1 files changed, 11 insertions, 2 deletions

diff --git a/llvm/lib/Option/ArgList.cpp b/llvm/lib/Option/ArgList.cpp
index 15f7e8bf4b8..18a7b5982be 100644
--- a/llvm/lib/Option/ArgList.cpp
+++ b/llvm/lib/Option/ArgList.cpp
@@ -323,9 +323,18 @@ InputArgList::~InputArgList() {
 unsigned InputArgList::MakeIndex(StringRef String0) const {
   unsigned Index = ArgStrings.size();
 
+  // If necessary, make a copy so we can null terminate it.
+  std::string NullTerminated;
+  if (String0.back() != '\0') {
+    NullTerminated.append(String0.data(), String0.size());
+    NullTerminated.push_back('\0');
+    String0 = StringRef(&NullTerminated[0], NullTerminated.size());
+  }
+
   // Tuck away so we have a reliable const char *.
-  SynthesizedStrings.push_back(String0);
-  ArgStrings.push_back(SynthesizedStrings.back().c_str());
+  String0 = SynthesizedStrings.GetOrCreateValue(String0).getKey();
+  assert(String0.back() == '\0');
+  ArgStrings.push_back(String0.data());
 
   return Index;
 }