[libclc] libclc: Update pow functions (PR #186890)

[Wenju He via cfe-commits]

================
@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "clc/utils.h"
+
+#ifndef __CLC_IMPL_FUNCTION
+#define __CLC_IMPL_FUNCTION __CLC_FUNCTION
+#endif
+
+#ifndef __CLC_MIN_VECSIZE
+#define __CLC_MIN_VECSIZE 2
+#endif
+
+#ifndef __CLC_RET_TYPE
+#define __CLC_RET_TYPE __CLC_GENTYPE
+#define __CLC_RET_SCALAR_TYPE __CLC_SCALAR_GENTYPE
+#endif
+
+#ifndef __CLC_ARG1_TYPE
+#define __CLC_ARG1_TYPE __CLC_GENTYPE
+#define __CLC_ARG1_SCALAR_TYPE __CLC_SCALAR_GENTYPE
+#endif
+
+#ifndef __CLC_ARG2_TYPE
+#define __CLC_ARG2_TYPE __CLC_GENTYPE
+#define __CLC_ARG2_SCALAR_TYPE __CLC_SCALAR_GENTYPE
----------------
wenju-he wrote:

only need to define __CLC_ARG2_SCALAR_TYPE at use site. __CLC_ARG2_TYPE can be constructed in this file using
```
#define __CLC_ARG2_TYPE __CLC_XCONCAT(__CLC_ARG2_SCALAR_TYPE, __CLC_VECSIZE)
```

https://github.com/llvm/llvm-project/pull/186890