When performing an @throw in ARC, retain + autorelease

the pointer, being sure to do so before running cleanups
associated with that full-expression.  rdar://10042689

llvm-svn: 140945

4 files changed, 29 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index d406e3a0645..96ab3dcd686 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -2386,6 +2386,30 @@ CodeGenFunction::EmitARCRetainAutoreleaseScalarExpr(const Expr *e) {
   return value;
 }
 
+llvm::Value *CodeGenFunction::EmitObjCThrowOperand(const Expr *expr) {
+  // In ARC, retain and autorelease the expression.
+  if (getLangOptions().ObjCAutoRefCount) {
+    // Do so before running any cleanups for the full-expression.
+    // tryEmitARCRetainScalarExpr does make an effort to do things
+    // inside cleanups, but there are crazy cases like
+    //   @throw A().foo;
+    // where a full retain+autorelease is required and would
+    // otherwise happen after the destructor for the temporary.
+    CodeGenFunction::RunCleanupsScope cleanups(*this);
+    if (const ExprWithCleanups *ewc = dyn_cast<ExprWithCleanups>(expr))
+      expr = ewc->getSubExpr();
+
+    return EmitARCRetainAutoreleaseScalarExpr(expr);
+  }
+
+  // Otherwise, use the normal scalar-expression emission.  The
+  // exception machinery doesn't do anything special with the
+  // exception like retaining it, so there's no safety associated with
+  // only running cleanups after the throw has started, and when it
+  // matters it tends to be substantially inferior code.
+  return EmitScalarExpr(expr);
+}
+
 std::pair<LValue,llvm::Value*>
 CodeGenFunction::EmitARCStoreStrong(const BinaryOperator *e,
                                     bool ignored) {
diff --git a/clang/lib/CodeGen/CGObjCGNU.cpp b/clang/lib/CodeGen/CGObjCGNU.cpp
index c948c3270ee..6bdc519a260 100644
--- a/clang/lib/CodeGen/CGObjCGNU.cpp
+++ b/clang/lib/CodeGen/CGObjCGNU.cpp
@@ -2277,7 +2277,7 @@ void CGObjCGNU::EmitThrowStmt(CodeGenFunction &CGF,
   llvm::Value *ExceptionAsObject;
 
   if (const Expr *ThrowExpr = S.getThrowExpr()) {
-    llvm::Value *Exception = CGF.EmitScalarExpr(ThrowExpr);
+    llvm::Value *Exception = CGF.EmitObjCThrowOperand(ThrowExpr);
     ExceptionAsObject = Exception;
   } else {
     assert((!CGF.ObjCEHValueStack.empty() && CGF.ObjCEHValueStack.back()) &&
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index d6eeba292a7..1b317c45f23 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -3204,7 +3204,7 @@ void CGObjCMac::EmitThrowStmt(CodeGen::CodeGenFunction &CGF,
   llvm::Value *ExceptionAsObject;
 
   if (const Expr *ThrowExpr = S.getThrowExpr()) {
-    llvm::Value *Exception = CGF.EmitScalarExpr(ThrowExpr);
+    llvm::Value *Exception = CGF.EmitObjCThrowOperand(ThrowExpr);
     ExceptionAsObject =
       CGF.Builder.CreateBitCast(Exception, ObjCTypes.ObjectPtrTy);
   } else {
@@ -6002,7 +6002,7 @@ void CGObjCNonFragileABIMac::EmitTryStmt(CodeGen::CodeGenFunction &CGF,
 void CGObjCNonFragileABIMac::EmitThrowStmt(CodeGen::CodeGenFunction &CGF,
                                            const ObjCAtThrowStmt &S) {
   if (const Expr *ThrowExpr = S.getThrowExpr()) {
-    llvm::Value *Exception = CGF.EmitScalarExpr(ThrowExpr);
+    llvm::Value *Exception = CGF.EmitObjCThrowOperand(ThrowExpr);
     Exception = CGF.Builder.CreateBitCast(Exception, ObjCTypes.ObjectPtrTy);
     CGF.EmitCallOrInvoke(ObjCTypes.getExceptionThrowFn(), Exception)
       .setDoesNotReturn();
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 19541a97673..0f120923d61 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2141,6 +2141,8 @@ public:
   std::pair<LValue,llvm::Value*>
   EmitARCStoreStrong(const BinaryOperator *e, bool ignored);
 
+  llvm::Value *EmitObjCThrowOperand(const Expr *expr);
+
   llvm::Value *EmitObjCProduceObject(QualType T, llvm::Value *Ptr);
   llvm::Value *EmitObjCConsumeObject(QualType T, llvm::Value *Ptr);
   llvm::Value *EmitObjCExtendObjectLifetime(QualType T, llvm::Value *Ptr);