AST: Update reference temporary mangling

Summary:
Update our mangling to match the discussion on cxx-abi-dev.

This involves using a seq-id instead of an optional number.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D3631

llvm-svn: 208140

1 files changed, 26 insertions, 24 deletions

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index 7105af2a761..4a07fbf5635 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -288,11 +288,13 @@ public:
   void mangleNumber(int64_t Number);
   void mangleFloat(const llvm::APFloat &F);
   void mangleFunctionEncoding(const FunctionDecl *FD);
+  void mangleSeqID(unsigned SeqID);
   void mangleName(const NamedDecl *ND);
   void mangleType(QualType T);
   void mangleNameOrStandardSubstitution(const NamedDecl *ND);
   
 private:
+
   bool mangleSubstitution(const NamedDecl *ND);
   bool mangleSubstitution(QualType T);
   bool mangleSubstitution(TemplateName Template);
@@ -3413,6 +3415,27 @@ void CXXNameMangler::mangleTemplateParameter(unsigned Index) {
     Out << 'T' << (Index - 1) << '_';
 }
 
+void CXXNameMangler::mangleSeqID(unsigned SeqID) {
+  if (SeqID == 1)
+    Out << '0';
+  else if (SeqID > 1) {
+    SeqID--;
+
+    // <seq-id> is encoded in base-36, using digits and upper case letters.
+    char Buffer[7]; // log(2**32) / log(36) ~= 7
+    llvm::MutableArrayRef<char> BufferRef(Buffer);
+    llvm::MutableArrayRef<char>::reverse_iterator I = BufferRef.rbegin();
+
+    for (; SeqID != 0; SeqID /= 36) {
+      unsigned C = SeqID % 36;
+      *I++ = (C < 10 ? '0' + C : 'A' + C - 10);
+    }
+
+    Out.write(I.base(), I - BufferRef.rbegin());
+  }
+  Out << '_';
+}
+
 void CXXNameMangler::mangleExistingSubstitution(QualType type) {
   bool result = mangleSubstitution(type);
   assert(result && "no existing substitution for type");
@@ -3469,28 +3492,8 @@ bool CXXNameMangler::mangleSubstitution(uintptr_t Ptr) {
     return false;
 
   unsigned SeqID = I->second;
-  if (SeqID == 0)
-    Out << "S_";
-  else {
-    SeqID--;
-
-    // <seq-id> is encoded in base-36, using digits and upper case letters.
-    char Buffer[10];
-    char *BufferPtr = std::end(Buffer);
-
-    if (SeqID == 0) *--BufferPtr = '0';
-
-    while (SeqID) {
-      assert(BufferPtr > Buffer && "Buffer overflow!");
-
-      char c = static_cast<char>(SeqID % 36);
-
-      *--BufferPtr =  (c < 10 ? '0' + c : 'A' + c - 10);
-      SeqID /= 36;
-    }
-
-    Out << 'S' << StringRef(BufferPtr, std::end(Buffer) - BufferPtr) << '_';
-  }
+  Out << 'S';
+  mangleSeqID(SeqID);
 
   return true;
 }
@@ -3791,8 +3794,7 @@ void ItaniumMangleContextImpl::mangleReferenceTemporary(const VarDecl *D,
   Mangler.getStream() << "_ZGR";
   Mangler.mangleName(D);
   assert(ManglingNumber > 0 && "Reference temporary mangling number is zero!");
-  if (ManglingNumber > 1)
-    Mangler.mangleNumber(ManglingNumber - 2);
+  Mangler.mangleSeqID(ManglingNumber - 1);
 }
 
 void ItaniumMangleContextImpl::mangleCXXVTable(const CXXRecordDecl *RD,