Overhaul the AST representation of Objective-C message send

expressions, to improve source-location information, clarify the
actual receiver of the message, and pave the way for proper C++
support. The ObjCMessageExpr node represents four different kinds of
message sends in a single AST node:

  1) Send to a object instance described by an expression (e.g., [x method:5])
  2) Send to a class described by the class name (e.g., [NSString method:5])
  3) Send to a superclass class (e.g, [super method:5] in class method)
  4) Send to a superclass instance (e.g., [super method:5] in instance method)

Previously these four cases where tangled together. Now, they have
more distinct representations. Specific changes:

  1) Unchanged; the object instance is represented by an Expr*.

  2) Previously stored the ObjCInterfaceDecl* referring to the class
  receiving the message. Now stores a TypeSourceInfo* so that we know
  how the class was spelled. This both maintains typedef information
  and opens the door for more complicated C++ types (e.g., dependent
  types). There was an alternative, unused representation of these
  sends by naming the class via an IdentifierInfo *. In practice, we
  either had an ObjCInterfaceDecl *, from which we would get the
  IdentifierInfo *, or we fell into the case below...

  3) Previously represented by a class message whose IdentifierInfo *
  referred to "super". Sema and CodeGen would use isStr("super") to
  determine if they had a send to super. Now represented as a
  "class super" send, where we have both the location of the "super"
  keyword and the ObjCInterfaceDecl* of the superclass we're
  targetting (statically).

  4) Previously represented by an instance message whose receiver is a
  an ObjCSuperExpr, which Sema and CodeGen would check for via
  isa<ObjCSuperExpr>(). Now represented as an "instance super" send,
  where we have both the location of the "super" keyword and the
  ObjCInterfaceDecl* of the superclass we're targetting
  (statically). Note that ObjCSuperExpr only has one remaining use in
  the AST, which is for "super.prop" references.

The new representation of ObjCMessageExpr is 2 pointers smaller than
the old one, since it combines more storage. It also eliminates a leak
when we loaded message-send expressions from a precompiled header. The
representation also feels much cleaner to me; comments welcome!

This patch attempts to maintain the same semantics we previously had
with Objective-C message sends. In several places, there are massive
changes that boil down to simply replacing a nested-if structure such
as:

  if (message has a receiver expression) {
    // instance message
    if (isa<ObjCSuperExpr>(...)) {
     // send to super
    } else {
     // send to an object
   }
  } else {
    // class message
    if (name->isStr("super")) {
      // class send to super
    } else {
      // send to class
    }
  }

with a switch

  switch (E->getReceiverKind()) {
  case ObjCMessageExpr::SuperInstance: ...
  case ObjCMessageExpr::Instance: ...
  case ObjCMessageExpr::SuperClass: ...
  case ObjCMessageExpr::Class:...
  }

There are quite a few places (particularly in the checkers) where
send-to-super is effectively ignored. I've placed FIXMEs in most of
them, and attempted to address send-to-super in a reasonable way. This
could use some review.

llvm-svn: 101972

1 files changed, 25 insertions, 10 deletions

diff --git a/clang/lib/Frontend/PCHWriterStmt.cpp b/clang/lib/Frontend/PCHWriterStmt.cpp
index 9c9f8911157..9a9539bb547 100644
--- a/clang/lib/Frontend/PCHWriterStmt.cpp
+++ b/clang/lib/Frontend/PCHWriterStmt.cpp
@@ -712,18 +712,33 @@ void PCHStmtWriter::VisitObjCImplicitSetterGetterRefExpr(
 void PCHStmtWriter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
   VisitExpr(E);
   Record.push_back(E->getNumArgs());
+  Record.push_back((unsigned)E->getReceiverKind()); // FIXME: stable encoding
+  switch (E->getReceiverKind()) {
+  case ObjCMessageExpr::Instance:
+    Writer.WriteSubStmt(E->getInstanceReceiver());
+    break;
+
+  case ObjCMessageExpr::Class:
+    Writer.AddTypeSourceInfo(E->getClassReceiverTypeInfo(), Record);
+    break;
+
+  case ObjCMessageExpr::SuperClass:
+  case ObjCMessageExpr::SuperInstance:
+    Writer.AddTypeRef(E->getSuperType(), Record);
+    Writer.AddSourceLocation(E->getSuperLoc(), Record);
+    break;
+  }
+
+  if (E->getMethodDecl()) {
+    Record.push_back(1);
+    Writer.AddDeclRef(E->getMethodDecl(), Record);
+  } else {
+    Record.push_back(0);
+    Writer.AddSelectorRef(E->getSelector(), Record);    
+  }
+    
   Writer.AddSourceLocation(E->getLeftLoc(), Record);
   Writer.AddSourceLocation(E->getRightLoc(), Record);
-  Writer.AddSelectorRef(E->getSelector(), Record);
-  Writer.AddDeclRef(E->getMethodDecl(), Record); // optional
-  Writer.WriteSubStmt(E->getReceiver());
-
-  if (!E->getReceiver()) {
-    ObjCMessageExpr::ClassInfo CI = E->getClassInfo();
-    Writer.AddDeclRef(CI.Decl, Record);
-    Writer.AddIdentifierRef(CI.Name, Record);
-    Writer.AddSourceLocation(CI.Loc, Record);
-  }
 
   for (CallExpr::arg_iterator Arg = E->arg_begin(), ArgEnd = E->arg_end();
        Arg != ArgEnd; ++Arg)