From 52a80e19ad688091723a52ad53337767bb0ac684 Mon Sep 17 00:00:00 2001
From: Fariborz Jahanian <fjahanian@apple.com>
Date: Wed, 26 Jan 2011 23:08:27 +0000
Subject: [PATCH] Fixes an IRgen bug where __block variable is referenced in
 the block-literal initializer of that variable. // rdar://8893785

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@124332 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGDecl.cpp        | 30 +++++++++++++++++++++++++++---
 lib/CodeGen/CGExpr.cpp        |  9 +++------
 lib/CodeGen/CodeGenFunction.h |  6 +++++-
 test/CodeGenObjC/block-6.m    | 12 ++++++++++++
 4 files changed, 47 insertions(+), 10 deletions(-)
 create mode 100644 test/CodeGenObjC/block-6.m

diff --git a/lib/CodeGen/CGDecl.cpp b/lib/CodeGen/CGDecl.cpp
index 8270e84cb5..f12be98510 100644
--- a/lib/CodeGen/CGDecl.cpp
+++ b/lib/CodeGen/CGDecl.cpp
@@ -305,6 +305,15 @@ unsigned CodeGenFunction::getByRefValueLLVMField(const ValueDecl *VD) const {
   return ByRefValueInfo.find(VD)->second.second;
 }
 
+llvm::Value *CodeGenFunction::BuildBlockByrefAddress(llvm::Value *BaseAddr,
+                                                     const VarDecl *V) {
+  llvm::Value *Loc = Builder.CreateStructGEP(BaseAddr, 1, "forwarding");
+  Loc = Builder.CreateLoad(Loc);
+  Loc = Builder.CreateStructGEP(Loc, getByRefValueLLVMField(V),
+                                V->getNameAsString());
+  return Loc;
+}
+
 /// BuildByRefType - This routine changes a __block variable declared as T x
 ///   into:
 ///
@@ -795,9 +804,6 @@ void CodeGenFunction::EmitAutoVarDecl(const VarDecl &D,
     SpecialInit(*this, D, DeclPtr);
   } else if (Init) {
     llvm::Value *Loc = DeclPtr;
-    if (isByRef)
-      Loc = Builder.CreateStructGEP(DeclPtr, getByRefValueLLVMField(&D), 
-                                    D.getNameAsString());
     
     bool isVolatile = getContext().getCanonicalType(Ty).isVolatileQualified();
     
@@ -844,13 +850,31 @@ void CodeGenFunction::EmitAutoVarDecl(const VarDecl &D,
       }
     } else if (Ty->isReferenceType()) {
       RValue RV = EmitReferenceBindingToExpr(Init, &D);
+      if (isByRef)
+        Loc = Builder.CreateStructGEP(DeclPtr, getByRefValueLLVMField(&D), 
+                                      D.getNameAsString());
       EmitStoreOfScalar(RV.getScalarVal(), Loc, false, Alignment, Ty);
     } else if (!hasAggregateLLVMType(Init->getType())) {
       llvm::Value *V = EmitScalarExpr(Init);
+      if (isByRef) {
+        // When RHS has side-effect, must go through "forwarding' field
+        // to get to the address of the __block variable descriptor.
+        if (Init->HasSideEffects(getContext()))
+          Loc = BuildBlockByrefAddress(DeclPtr, &D);
+        else
+          Loc = Builder.CreateStructGEP(DeclPtr, getByRefValueLLVMField(&D), 
+                                        D.getNameAsString());
+      }
       EmitStoreOfScalar(V, Loc, isVolatile, Alignment, Ty);
     } else if (Init->getType()->isAnyComplexType()) {
+      if (isByRef)
+        Loc = Builder.CreateStructGEP(DeclPtr, getByRefValueLLVMField(&D), 
+                                      D.getNameAsString());
       EmitComplexExprIntoAddr(Init, Loc, isVolatile);
     } else {
+      if (isByRef)
+        Loc = Builder.CreateStructGEP(DeclPtr, getByRefValueLLVMField(&D), 
+                                      D.getNameAsString());
       EmitAggExpr(Init, AggValueSlot::forAddr(Loc, isVolatile, true, false));
     }
   }
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index afc1e0709e..ca80d3dd38 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1164,12 +1164,9 @@ LValue CodeGenFunction::EmitDeclRefLValue(const DeclRefExpr *E) {
       V = CGM.getStaticLocalDeclAddress(VD);
     assert(V && "DeclRefExpr not entered in LocalDeclMap?");
 
-    if (VD->hasAttr<BlocksAttr>()) {
-      V = Builder.CreateStructGEP(V, 1, "forwarding");
-      V = Builder.CreateLoad(V);
-      V = Builder.CreateStructGEP(V, getByRefValueLLVMField(VD),
-                                  VD->getNameAsString());
-    }
+    if (VD->hasAttr<BlocksAttr>())
+      V = BuildBlockByrefAddress(V, VD);
+    
     if (VD->getType()->isReferenceType())
       V = Builder.CreateLoad(V, "tmp");
 
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index dcd6173763..834a1cfa2f 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -811,7 +811,11 @@ public:
   /// getByrefValueFieldNumber - Given a declaration, returns the LLVM field
   /// number that holds the value.
   unsigned getByRefValueLLVMField(const ValueDecl *VD) const;
-  
+
+  /// BuildBlockByrefAddress - Computes address location of the
+  /// variable which is declared as __block.
+  llvm::Value *BuildBlockByrefAddress(llvm::Value *BaseAddr,
+                                      const VarDecl *V);
 private:
   CGDebugInfo *DebugInfo;
 
diff --git a/test/CodeGenObjC/block-6.m b/test/CodeGenObjC/block-6.m
new file mode 100644
index 0000000000..3720a87b9e
--- /dev/null
+++ b/test/CodeGenObjC/block-6.m
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 %s -emit-llvm -o - -fblocks -triple x86_64-apple-darwin10 | FileCheck %s
+// rdar://8893785
+
+void MYFUNC() {
+// CHECK: [[T1:%.*]] = bitcast i8* ()*
+// CHECK-NEXT: [[FORWARDING:%.*]] = getelementptr inbounds [[N_T:%.*]]* [[N:%.*]], i32 0, i32 1
+// CHECK-NEXT: [[T0:%.*]] = load [[N_T]]** [[FORWARDING]]
+// CHECK-NEXT: [[OBSERVER:%.*]] = getelementptr inbounds [[N_T]]* [[T0]], i32 0, i32 6
+// CHECK-NEXT: store i8* [[T1]], i8** [[OBSERVER]]
+  __block id observer = ^{ return observer; };
+}
+
-- 
2.40.0