Remangler: use the bump pointer allocator instead of std::vector for internal substitution data structures

This avoids mallocs in the runtime.

SR-10028
rdar://problem/48575729

Author: eeckstein

include/swift/Basic/Mangler.h

@@ -78,6 +78,14 @@ class Mangler {
     }
   };
 
+  void addSubstWordsInIdent(const WordReplacement &repl) {
+    SubstWordsInIdent.push_back(repl);
+  }
+
+  void addWord(const SubstitutionWord &word) {
+    Words.push_back(word);
+  }
+
   /// Returns the buffer as a StringRef, needed by mangleIdentifier().
   StringRef getBufferStr() const {
     return StringRef(Storage.data(), Storage.size());

include/swift/Demangling/Demangler.h

@@ -279,7 +279,11 @@ template<typename T> class Vector {
     Capacity = 0;
     Elems = 0;
   }
-  
+
+  void clear() {
+    NumElems = 0;
+  }
+
   iterator begin() { return Elems; }
   iterator end() { return Elems + NumElems; }
 

include/swift/Demangling/ManglingUtils.h

@@ -160,13 +160,13 @@ void mangleIdentifier(Mangler &M, StringRef ident) {
       if (WordIdx >= 0) {
         // We found a word substitution!
         assert(WordIdx < 26);
-        M.SubstWordsInIdent.push_back({wordStartPos, WordIdx});
+        M.addSubstWordsInIdent({wordStartPos, WordIdx});
       } else if (wordLen >= 2 && M.Words.size() < M.MaxNumWords) {
         // It's a new word: remember it.
         // Note: at this time the word's start position is relative to the
         // begin of the identifier. We must update it afterwards so that it is
         // relative to the begin of the whole mangled Buffer.
-        M.Words.push_back({wordStartPos, wordLen});
+        M.addWord({wordStartPos, wordLen});
       }
       wordStartPos = NotInsideWord;
     }
@@ -181,7 +181,7 @@ void mangleIdentifier(Mangler &M, StringRef ident) {
 
   size_t Pos = 0;
   // Add a dummy-word at the end of the list.
-  M.SubstWordsInIdent.push_back({ident.size(), -1});
+  M.addSubstWordsInIdent({ident.size(), -1});
 
   // Mangle a sequence of word substitutions and sub-strings.
   for (size_t Idx = 0, End = M.SubstWordsInIdent.size(); Idx < End; ++Idx) {

lib/Demangling/Remangler.cpp

@@ -155,8 +155,8 @@ class Remangler {
 
   DemanglerPrinter &Buffer;
 
-  std::vector<SubstitutionWord> Words;
-  std::vector<WordReplacement> SubstWordsInIdent;
+  Vector<SubstitutionWord> Words;
+  Vector<WordReplacement> SubstWordsInIdent;
 
   static const size_t MaxNumWords = 26;
 
@@ -172,6 +172,14 @@ class Remangler {
   // A callback for resolving symbolic references.
   SymbolicResolver Resolver;
 
+  void addSubstWordsInIdent(const WordReplacement &repl) {
+    SubstWordsInIdent.push_back(repl, Factory);
+  }
+
+  void addWord(const SubstitutionWord &word) {
+    Words.push_back(word, Factory);
+  }
+
   StringRef getBufferStr() const { return Buffer.getStringRef(); }
 
   void resetBuffer(size_t toPos) { Buffer.resetSize(toPos); }