[PATCH] D92086: Generalized PatternMatch & InstSimplify

[Renato Golin via Phabricator via llvm-commits]

rengolin added a comment.

First, I think this is a good idea and can eventually mitigate the general problem of intrinsics vs. instructions in other LLVM passes.

But I worry we'll end up with too many traits to emulate actual instructions' semantics and we'll go back to the discussions of how much an intrinsic is like an instruction.

As an example, for one type of transformation (say constant folding) an intrinsic-add "acts like an add" (precision), but another transformation (ex loop induction) it doesn't (wrapping semantics).

So, while we can come up with a list of traits that make this one particular match work, we may be faced with a combinatorial number of traits to generalise it to other transformations.

I don't have any particular case in mind, just the general feeling that we'll get stuck half-way through and have to keep a set of traits that can't be easily used by other passes.

But this is not a negative view, just perhaps a request for clarification: how much else did you look at to make sure this can extend to more intrinsics and passes?

Second, there are a lot of clang-format changes on unrelated code lines and it makes it hard to see what's just reformatted and what's really changed.


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  https://reviews.llvm.org/D92086/new/

https://reviews.llvm.org/D92086