[PATCH] D71115: [TableGen] Add a permissive version of !con.

[Simon Tatham via Phabricator via llvm-commits]

simon_tatham added a comment.

In D71115#1774317 <https://reviews.llvm.org/D71115#1774317>, @nhaehnle wrote:

> using an unset operator could be a more natural way of expressing that than coming up with some artificial operator that is simply thrown away later.


Artificial operators are quite common already in the Tablegen idiom, though, to get round the fact that all dags have to //have// an operator. For example, the inputs and outputs of MC instructions have the form of dags so that each one can have a type and a name, and then they have to have the dummy operators `ins` and `outs` because //something// has to go in the operator slot.

But if you're not opposed to making an unset dag operator legal, then I'll at least look into it!


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