Replace DeclContext's vector of ScopedDecl pointers with a linked list

of ScopedDecls (using the new ScopedDecl::NextDeclInScope
pointer). Performance-wise:

  - It's a net win in memory utilization, since DeclContext is now one
    pointer smaller than it used to be (std::vectors are typically 3
    pointers; we now use 2 pointers) and 
  - Parsing Cocoa.h with -fsyntax-only (with a Release-Asserts Clang)
    is about 1.9% faster than before, most likely because we no longer
    have the memory allocations and copying associated with the
    std::vector.

I'll re-enable serialization of DeclContexts once I've sorted out the
NextDeclarator/NextDeclInScope question.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62001 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 2 deletions

diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index d9765ac4b4..cafe5358d6 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -401,7 +401,8 @@ DeclContext::~DeclContext() {
 }
 
 void DeclContext::DestroyDecls(ASTContext &C) {
-  for (decl_iterator D = Decls.begin(); D != Decls.end(); ++D) {
+  for (decl_iterator D = decls_begin(); D != decls_end(); ++D) {
+    // FIXME: assert that this condition holds.
     if ((*D)->getLexicalDeclContext() == this)
       (*D)->Destroy(C);
   }
@@ -515,7 +516,15 @@ DeclContext *DeclContext::getNextContext() {
 
 void DeclContext::addDecl(ASTContext &Context, ScopedDecl *D, bool AllowLookup) {
   assert(D->getLexicalDeclContext() == this && "Decl inserted into wrong lexical context");
-  Decls.push_back(D);
+  assert(!D->NextDeclInScope && D != LastDecl && 
+         "Decl already inserted into a DeclContext");
+
+  if (FirstDecl) {
+    LastDecl->NextDeclInScope = D;
+    LastDecl = D;
+  } else {
+    FirstDecl = LastDecl = D;
+  }
   if (AllowLookup)
     D->getDeclContext()->insert(Context, D);
 }