[clang] [AMDGPU] Support the OpenCL generic addrspace feature by default (PR #137636)

[Juan Manuel Martinez Caamaño via cfe-commits]

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@@ -155,3 +155,11 @@
 #endif
 #pragma OPENCL EXTENSION cl_amd_media_ops2: enable
 
+#if (__OPENCL_C_VERSION__ >= 300)
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jmmartinez wrote:

I don't understand, isn't `__opencl_c_generic_address_space` available by default with `OPENCL_C_VERSION >= 200` (from reading `opencl-c-base.h`) ?

https://github.com/llvm/llvm-project/pull/137636