Under ARC, when we're passing the address of a strong variable

to an out-parameter using the indirect-writeback conversion,
and we copied the current value of the variable to the temporary,
make sure that we register an intrinsic use of that value with
the optimizer so that the value won't get released until we have
a chance to retain it.

rdar://13195034

llvm-svn: 177813

1 files changed, 15 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index f53f2a97c60..9ee3c8b60e0 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -1707,6 +1707,21 @@ llvm::Value *CodeGenFunction::EmitObjCExtendObjectLifetime(QualType type,
   return EmitARCRetainAutorelease(type, value);
 }
 
+/// Given a number of pointers, inform the optimizer that they're
+/// being intrinsically used up until this point in the program.
+void CodeGenFunction::EmitARCIntrinsicUse(ArrayRef<llvm::Value*> values) {
+  llvm::Constant *&fn = CGM.getARCEntrypoints().clang_arc_use;
+  if (!fn) {
+    llvm::FunctionType *fnType =
+      llvm::FunctionType::get(CGM.VoidTy, ArrayRef<llvm::Type*>(), true);
+    fn = CGM.CreateRuntimeFunction(fnType, "clang.arc.use");
+  }
+
+  // This isn't really a "runtime" function, but as an intrinsic it
+  // doesn't really matter as long as we align things up.
+  EmitNounwindRuntimeCall(fn, values);
+}
+
 
 static llvm::Constant *createARCRuntimeFunction(CodeGenModule &CGM,
                                                 llvm::FunctionType *type,