[PATCH] D77870: [MLIR] Introduce utility to hoist affine if/else conditions

[Uday Bondhugula via Phabricator via llvm-commits]

bondhugula added a comment.

In D77870#1974419 <https://reviews.llvm.org/D77870#1974419>, @nicolasvasilache wrote:

> This seems like it would be easy to generalize.
>  What facilities are concretely missing to make this transformation work on more general loops and conditionals?


Take a look at the checks on invariance / validity - you'll have to do all kinds of value provenance to do something equivalent on other loop ops - depending on whether you already know what hoisting you'd like to do. Conditionals/loops returning values also add additional complexity. With affine, all of this becomes clean and trivial. That said, the mechanical movement of blocks would be similar - but that's about a couple of dozen lines of code here.

> Could it be implemented it in a more general fashion with LoopLikeInterface and other interfaces, if appropriate?
> 
> The same questions apply to full/partial tile separation, unrolling, L/S forwarding and maybe others.

Reg. unrolling - at the time op interfaces were introduced, I thought about whether something could be moved to the loop like op interface - it just was not at all worth it; the amount of sharing was tiny enough a fraction to make it pointless. More so with full/partial tile separation (the code moving the blocks is a small part embedded in). L/S fwd'ing relies on affine dependence analysis - the actual mechanics of it which is the last step are trivial. In all these cases, you'll find the mechanics at the end could be reused, but you'll have to weigh how heavy those are. One should still have op interfaces like LoadLikeOp, StoreLikeOp, IfLikeOp for future purposes to share mechanics.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77870/new/

https://reviews.llvm.org/D77870