[clang] [Clang][OpenCL] Add support for the cl_intel_subgroup_buffer_prefetch (PR #170532)

[Mészáros Gergely via cfe-commits]

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@@ -17660,6 +17667,14 @@ void        __ovld __conv intel_sub_group_block_write_us2( __global ushort* p, u
 void        __ovld __conv intel_sub_group_block_write_us4( __global ushort* p, ushort4 data );
 void        __ovld __conv intel_sub_group_block_write_us8( __global ushort* p, ushort8 data );
 void        __ovld __conv intel_sub_group_block_write_us16( __global ushort* p, ushort16 data );
+
+#if defined(cl_intel_subgroup_buffer_prefetch)
+void __ovld __conv intel_sub_group_block_prefetch_us(const __global ushort *p);
+void __ovld __conv intel_sub_group_block_prefetch_us2(const __global ushort *p);
+void __ovld __conv intel_sub_group_block_prefetch_us4(const __global ushort *p);
+void __ovld __conv intel_sub_group_block_prefetch_us8(const __global ushort *p);
+void __ovld __conv intel_sub_group_block_prefetch_us16(const __global ushort *p);
----------------
Maetveis wrote:

```suggestion
void        __ovld __conv intel_sub_group_block_prefetch_us(const __global ushort *p);
void        __ovld __conv intel_sub_group_block_prefetch_us2(const __global ushort *p);
void        __ovld __conv intel_sub_group_block_prefetch_us4(const __global ushort *p);
void        __ovld __conv intel_sub_group_block_prefetch_us8(const __global ushort *p);
void        __ovld __conv intel_sub_group_block_prefetch_us16(const __global ushort *p);
```

https://github.com/llvm/llvm-project/pull/170532