[PATCH] D72423: [DemandedBits] Improve accuracy of Add propagator

Mon Jan 13 05:29:48 PST 2020

nikic added a comment.

In D72423#1816715 <https://reviews.llvm.org/D72423#1816715>, @rrika wrote:

> In D72423#1815871 <https://reviews.llvm.org/D72423#1815871>, @nikic wrote:
>
> > @rrika Performing these kinds of tests on IR is both quite inefficient and unnecessary complex. It would be better to extract the code logic (which just operates on APInts) into a separate file, which will allow you to easily test it, and also share the logic with other places doing demanded bits analysis, such as InstCombine and SelectionDAG.
>
>
> Are you suggesting factoring out the logic for addition/subtraction only or all opcodes? Where should this new function live?

At least to start with, only addition/subtraction is fine. I'm not totally sure where it would live, but as we have KnownBits in Support, possibly there?

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D72423/new/

https://reviews.llvm.org/D72423