[CodeGenObjC] Place property names in __objc_methname

This allows the property name to deduplicate with the accessor method name.
rdar://58927964

Author: epilk

clang/lib/CodeGen/CGObjCMac.cpp

@@ -4225,7 +4225,8 @@ CGObjCCommonMac::CreateCStringLiteral(StringRef Name, ObjCLabelType Type,
                          : "__TEXT,__cstring,cstring_literals";
     break;
   case ObjCLabelType::PropertyName:
-    Section = "__TEXT,__cstring,cstring_literals";
+    Section = NonFragile ? "__TEXT,__objc_methname,cstring_literals"
+                         : "__TEXT,__cstring,cstring_literals";
     break;
   }
 

clang/test/CodeGenObjC/metadata-symbols-64.m

@@ -17,7 +17,7 @@
 // CHECK: @"_OBJC_METACLASS_RO_$_A" = internal global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"_OBJC_$_INSTANCE_METHODS_A" = internal global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"_OBJC_$_INSTANCE_VARIABLES_A" = internal global {{.*}} section "__DATA, __objc_const", align 8
-// CHECK: @OBJC_PROP_NAME_ATTR_{{[0-9]*}} = private unnamed_addr constant {{.*}} section "__TEXT,__cstring,cstring_literals", align 1
+// CHECK: @OBJC_PROP_NAME_ATTR_{{[0-9]*}} = private unnamed_addr constant {{.*}} section "__TEXT,__objc_methname,cstring_literals", align 1
 // CHECK: @"_OBJC_$_PROP_LIST_A" = internal global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"_OBJC_CLASS_RO_$_A" = internal global {{.*}} section "__DATA, __objc_const", align 8
 // CHECK: @"_OBJC_$_CATEGORY_INSTANCE_METHODS_A_$_Cat" = internal global {{.*}} section "__DATA, __objc_const", align 8