[libclc] libclc: Add sub_group_reduce_* functions (PR #185294)

[Matt Arsenault via cfe-commits]

================
@@ -0,0 +1,13 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#if defined(__CLC_SCALAR) &&                                                   \
----------------
arsenm wrote:

No, it only adds char/short: 
`If the cl_khr_subgroup_extended_types extension is supported, the generic type
name gentype may additionally be char, uchar, short, and ushort.`

https://github.com/llvm/llvm-project/pull/185294