[llvm] [GlobalISel] Document minimum legality requirements for G_IMPLICIT_DEF. (PR #117609)

[Amara Emerson via llvm-commits]

aemerson wrote:

> I don't see any benefit of this change. It makes the state worth. It gives you an escape-hatch that you don't have to query the legalizer in some situations.

That's the entire point of this change. It's pointless to have to query for legality and slow down compilation when LLVM codegen fundamentally breaks when some constructs are not legal.

> All non-Apple:-)

Ok, I was asking to give you the benefit of the doubt. Having clarified that you meant check downstream targets that are private to myself, you're now admitting that your statement before was entirely sarcastic without any purpose in the discussion?



https://github.com/llvm/llvm-project/pull/117609