[clang] [llvm] [clang][docs] Migrate AttributeReference to markdown (PR #215631)

[Reid Kleckner via llvm-commits]

================
@@ -5253,15 +5237,13 @@ memory from those that access global host memory. These new address spaces are
 a subset of the `__global/opencl_global` address space, the full address space
 set model for OpenCL 2.0 with the extension looks as follows:
 
-> generic->global->host
->
-> ->device
->
-> ->private
->
-> ->local
->
-> constant
+```text
+generic->global->host
+               ->device
+       ->private
+       ->local
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rnk wrote:

Yes, I fixed this up by hand. I don't think this is rendering correctly today: https://clang.llvm.org/docs//AttributeReference.html#clang-opencl-global-device-clang-opencl-global-host

https://github.com/llvm/llvm-project/pull/215631