[PATCH] D23601: [TII] add new target hook isAdd

[Krzysztof Parzyszek via llvm-commits]

kparzysz added a comment.

In https://reviews.llvm.org/D23601#519181, @hfinkel wrote:

> I'd really like an interface that allows converting from an MI entity to something with known semantics; I think that, with the new generic opcodes being introduced for GlobalISel, we have a good opportunity here. How about the following interface (modulo bikeshedding)?
>
>   MachineOperand *Op0, *Op1, *Op2;
>   if (TII->convertToGenericOp(MI, Op0, Op1, Op2) == G_ADD) {
>     // This MI is equivalent to Op0 = G_ADD Op1, Op2
>   }


I've been planning to implement something along the lines of the m_xxx pattern matching for MachineInstr. There would be some set of predefined generic operations, such as add, mul, shift, etc. but an object that can match an "add" operation could also be annotated with flags indicating that the "add" should be saturating, for example.  In the absence of such annotations, the matched object would acquire such annotations from the instruction that it matched.


https://reviews.llvm.org/D23601