[clang] [llvm] [AMDGPU] Introduce GFX9/10.1/10.3/11 Generic Targets (PR #76955)

[Tony Tye via cfe-commits]

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@@ -520,6 +520,102 @@ Every processor supports every OS ABI (see :ref:`amdgpu-os`) with the following
 
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+Generic processors allow execution of a single code objects on any of the processors that
+it supports. Such code objects may not perform as well as those for the non-generic processors.
+
+Generic processors are only available on code object V6 and above (see :ref:`amdgpu-elf-code-object`).
+
+Generic processor code objects are versioned (see :ref:`amdgpu-elf-header-e_flags-table-v6-onwards`).
+The version number is used by runtimes to determine if a code object can be run on a specific agent.
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t-tye wrote:

This does not really explain how version is used. What about something like:

The version of non-generic code objects is always set to 0.

For a generic code object, adding a new generic member may require the code generated for the generic target to be changed so it can continue to execute on the previous members as well as on the new member. When this happens the generic code object version number is incremented. Each member of the generic target has a version when it was introduced. A generic code object can execute on a specific member if the version of the code object being loaded is >= the version at which the member was introduced.

https://github.com/llvm/llvm-project/pull/76955