Make it LinkOnceODRLinkage

Make the little variable LinkOnceODRLinkage so that it doesn't take up
as much space.

Author: etcwilde

lib/IRGen/IRGenModule.cpp

@@ -1786,9 +1786,10 @@ void IRGenModule::emitSwiftAsyncExtendedFrameInfoWeakRef() {
   // avoid optimizations.
   llvm::GlobalVariable *usage = new llvm::GlobalVariable(
       Module, extendedFramePointerFlagsWeakRef->getType(), false,
-      llvm::GlobalValue::PrivateLinkage,
+      llvm::GlobalValue::LinkOnceODRLinkage,
       static_cast<llvm::GlobalVariable *>(extendedFramePointerFlagsWeakRef),
       "_swift_async_extendedFramePointerFlagsUser");
+  usage->setVisibility(llvm::GlobalValue::HiddenVisibility);
   addUsedGlobal(usage);
 }
 

test/Concurrency/Backdeploy/weak_linking.swift

@@ -16,7 +16,7 @@
 // OLD: declare extern_weak swiftcc i8 @"$sScP8rawValues5UInt8Vvg"
 
 // OPTIMIZED: @swift_async_extendedFramePointerFlags = extern_weak global i8*
-// OPTIMIZED: @_swift_async_extendedFramePointerFlagsUser = private global i8** @swift_async_extendedFramePointerFlags
+// OPTIMIZED: @_swift_async_extendedFramePointerFlagsUser = linkonce_odr hidden global i8** @swift_async_extendedFramePointerFlags
 // OPTIMIZED: @llvm.used =
 // OPTIMIZED-SAME: (i8*** @_swift_async_extendedFramePointerFlagsUser to i8*)