From f5125d19e7b466a76a5471286ad2e3d038f8cf86 Mon Sep 17 00:00:00 2001
From: Fariborz Jahanian <fjahanian@apple.com>
Date: Tue, 18 Nov 2008 21:45:40 +0000
Subject: [PATCH] Generate objc_read_weak for __weak objc loads.

llvm-svn: 59553
---
 clang/lib/CodeGen/CGExpr.cpp      |  8 ++++++++
 clang/lib/CodeGen/CGObjCGNU.cpp   |  8 ++++++++
 clang/lib/CodeGen/CGObjCMac.cpp   | 14 +++++++++++++-
 clang/lib/CodeGen/CGObjCRuntime.h |  2 ++
 clang/lib/CodeGen/CGValue.h       |  4 ++++
 5 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 993562592b65..d537c9ca8137 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -151,6 +151,14 @@ LValue CodeGenFunction::EmitLValue(const Expr *E) {
 /// this method emits the address of the lvalue, then loads the result as an
 /// rvalue, returning the rvalue.
 RValue CodeGenFunction::EmitLoadOfLValue(LValue LV, QualType ExprType) {
+  if (LV.isObjcWeak()) {
+    // load of a __weak object. 
+    llvm::Value *AddrWeakObj = LV.getAddress();
+    llvm::Value *read_weak = CGM.getObjCRuntime().EmitObjCWeakCall(*this, 
+                                                                   AddrWeakObj);
+    return RValue::get(read_weak);
+  }
+      
   if (LV.isSimple()) {
     llvm::Value *Ptr = LV.getAddress();
     const llvm::Type *EltTy =
diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index 0833b0832d74..d57710c5e519 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -130,6 +130,8 @@ public:
                              const ObjCAtThrowStmt &S);
   virtual void EmitSynchronizedStmt(CodeGen::CodeGenFunction &CGF,
                                     const ObjCAtSynchronizedStmt &S);
+  virtual llvm::Value * EmitObjCWeakCall(CodeGen::CodeGenFunction &CGF,
+                                         llvm::Value *AddrWeakObj);
 };
 } // end anonymous namespace
 
@@ -968,6 +970,12 @@ void CGObjCGNU::EmitSynchronizedStmt(CodeGen::CodeGenFunction &CGF,
   CGF.ErrorUnsupported(&S, "@synchronized statement");
 }
 
+llvm::Value * CGObjCGNU::EmitObjCWeakCall(CodeGen::CodeGenFunction &CGF,
+                                          llvm::Value *AddrWeakObj)
+{
+  return 0;
+}
+
 CodeGen::CGObjCRuntime *CodeGen::CreateGNUObjCRuntime(CodeGen::CodeGenModule &CGM){
   return new CGObjCGNU(CGM);
 }
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 159183145857..f3cf21eb314b 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -454,7 +454,8 @@ public:
                              const ObjCAtThrowStmt &S);
   virtual void EmitSynchronizedStmt(CodeGen::CodeGenFunction &CGF,
                                     const ObjCAtSynchronizedStmt &S);
-  
+  virtual llvm::Value * EmitObjCWeakCall(CodeGen::CodeGenFunction &CGF,
+                                         llvm::Value *AddrWeakObj); 
 };
 } // end anonymous namespace
 
@@ -1775,6 +1776,17 @@ void CodeGenFunction::EmitJumpThroughFinally(ObjCEHEntry *E,
   EmitBranch(ExecuteTryExit ? E->FinallyBlock : E->FinallyNoExit);
 }
 
+/// EmitObjCWeakCall - Code gen for loading value of a __weak
+/// object: objc_read_weak (id *src)
+///
+llvm::Value * CGObjCMac::EmitObjCWeakCall(CodeGen::CodeGenFunction &CGF,
+                                          llvm::Value *AddrWeakObj)
+{
+  llvm::Value *read_weak = CGF.Builder.CreateCall(ObjCTypes.GcReadWeakFn,
+                                                  AddrWeakObj, "weakobj");
+  return read_weak;
+}
+
 /// EmitSynchronizedStmt - Code gen for @synchronized(expr) stmt;
 /// Effectively generating code for:
 /// objc_sync_enter(expr);
diff --git a/clang/lib/CodeGen/CGObjCRuntime.h b/clang/lib/CodeGen/CGObjCRuntime.h
index 435e1483e386..37544e47e1bc 100644
--- a/clang/lib/CodeGen/CGObjCRuntime.h
+++ b/clang/lib/CodeGen/CGObjCRuntime.h
@@ -145,6 +145,8 @@ public:
                              const ObjCAtThrowStmt &S) = 0;
   virtual void EmitSynchronizedStmt(CodeGen::CodeGenFunction &CGF,
                                     const ObjCAtSynchronizedStmt &S) = 0;
+  virtual llvm::Value * EmitObjCWeakCall(CodeGen::CodeGenFunction &CGF,
+					 llvm::Value *AddrWeakObj) = 0;
 };
 
 /// Creates an instance of an Objective-C runtime class.  
diff --git a/clang/lib/CodeGen/CGValue.h b/clang/lib/CodeGen/CGValue.h
index 505381eb41a2..ef2cb033c95a 100644
--- a/clang/lib/CodeGen/CGValue.h
+++ b/clang/lib/CodeGen/CGValue.h
@@ -138,6 +138,10 @@ private:
   static void SetQualifiers(unsigned Qualifiers, LValue& R) {
     R.Volatile = (Qualifiers&QualType::Volatile)!=0;
     R.Restrict = (Qualifiers&QualType::Restrict)!=0;
+    // FIXME: Convenient place to set objc flags to 0. This
+    // should really be done in a user-defined constructor instead.
+    R.ObjcWeak = 0;
+    R.ObjcStrong = 0;
   }
   
 public: