[PATCH] D75428: [MC][ARM] add implicit immediate form for ldrsbt/ldrht/ldrsht

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

I spent a couple minutes experimenting; the following "works":

  def : InstAlias<"ldrsbt${q} $Rt, $Rn2, $Rn", (LDRSBTi GPR:$Rt, GPR:$Rn2, addr_offset_none:$Rn, 256, pred:$q)>, Requires<[IsARM]>;

The immediate doesn't pose a problem, as far as I can tell.

The problem, of course, is that this syntax isn't right.  And there isn't any way to make it right.  For instructions, we do some magic with "Constraints" to infer the second output register, but that currently doesn't work for aliases.

So I guess this approach is fine.  (Of course, there's still the `#0` vs `#-0` issue.)


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  https://reviews.llvm.org/D75428/new/

https://reviews.llvm.org/D75428