[llvm] [AMDGPU] Add AMDGPU support for llvm-objcopy (PR #92066)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

Please could you use meaningful commit descriptions for fixups describing what has changed, rather than just repeating the PR title.

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Let's go back to this conversation though:
(From Phabricator)
> That all being said, the requirement for the flag is troubling me. Is there prior art to how to specify the ADMGPU target for an llvm-objcopy-like tool? The existing test shows that you can convert from one target (EM_NONE in the original test) to another target using the -O option, but the new test you've written doesn't demonstrate this behaviour (if I'm not mistaken, if you omitted the -O option, you'd get the same output, as the output target is derived from the input if not otherwise specified). Questions that I have are 1) if the input target was EM_AMDGPU and somebody specified e.g. -O elf32-hexagon, what should happen to any AMDGPU EF_* flag? 2) Similarly, how would you get a different AMDGPU flag? In other words, how would you get llvm-objcopy to add the EF_AMDGPU_MACH_* flag if it wasn't already present?

I don't think these questions have been addressed at all. What is your proposal for this?

https://github.com/llvm/llvm-project/pull/92066