Introduce a caching mechanism for macro expanded tokens.

Previously macro expanded tokens were added to Preprocessor's bump allocator and never released,
even after the TokenLexer that were lexing them was finished, thus they were wasting memory.
A very "useful" boost library was causing clang to eat 1 GB just for the expanded macro tokens.

Introduce a special cache that works like a stack; a TokenLexer can add the macro expanded tokens
in the cache, and when it finishes, the tokens are removed from the end of the cache.

Now consumed memory by expanded tokens for that library is ~ 1.5 MB.

Part of rdar://9327049.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134105 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 9 deletions

diff --git a/lib/Lex/TokenLexer.cpp b/lib/Lex/TokenLexer.cpp
index e7cff8bdc3..f30c44e0e6 100644
--- a/lib/Lex/TokenLexer.cpp
+++ b/lib/Lex/TokenLexer.cpp
@@ -284,15 +284,11 @@ void TokenLexer::ExpandFunctionArguments() {
     assert(!OwnsTokens && "This would leak if we already own the token list");
     // This is deleted in the dtor.
     NumTokens = ResultToks.size();
-    llvm::BumpPtrAllocator &Alloc = PP.getPreprocessorAllocator();
-    Token *Res =
-      static_cast<Token *>(Alloc.Allocate(sizeof(Token)*ResultToks.size(),
-                                          llvm::alignOf<Token>()));
-    if (NumTokens)
-      memcpy(Res, &ResultToks[0], NumTokens*sizeof(Token));
-    Tokens = Res;
-
-    // The preprocessor bump pointer owns these tokens, not us.
+    // The tokens will be added to Preprocessor's cache and will be removed
+    // when this TokenLexer finishes lexing them.
+    Tokens = PP.cacheMacroExpandedTokens(this, ResultToks);
+
+    // The preprocessor cache of macro expanded tokens owns these tokens,not us.
     OwnsTokens = false;
   }
 }