[PATCH] D83034: [GlobalISel] Don't skip adding predicate matcher

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D83034#2133375 <https://reviews.llvm.org/D83034#2133375>, @dsanders wrote:

> Could you add a test case or point us at a example of an existing test that goes wrong? The description in the commit message is unlikely to be the full story as we already cover loads with non-null MemoryVT's. My best guess is you are attempting to use builtin predicates and custom predicates together. I don't see a reason why that shouldn't be allowed but it's not something that was intended as the goal was aiming to fully remove the custom C++ from the tablegen headers so that tablegen could do some transformations on sextload/zextload and similar to fix DAGISel vs GlobalISel modelling mismatches.


I think the problem is broader than just combining custom predicates and builtin. The emitter here implicitly assumes all of these builtin PatFrag predicates are used exactly as the hierarchy used to define the default/generic load/store patterns. However, the PatFrags are much more free form and you can define a patfrag that combines multiple of these predicates in the same "layer" of the load/store hierarchy. The AMDGPU patterns redefine the entire set of load/store patterns, and in some cases it makes sense to combine all the predicates at once. I had to somewhat artificially add new layers of PatFrags to only apply a single predicate at a time. This also isn't consistently applied (for example, it does work to combine the AddressSpaces predicate and alignment)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83034/new/

https://reviews.llvm.org/D83034