[PATCH] D153563: Use LVI to eliminate instructions during VP

Simon Hirst via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Sun Jun 25 22:12:09 PDT 2023

sehirst added a comment.

> TBH the entire patch makes very little sense to me.

Thanks for the review. I think the main problem is that I was unaware of some key `ConstantRange` and `LVI` functionality, namely `icmp()` and `getPredicateAt()`, as you pointed out. Additionally, when I ported this patch from LLVM 15 to main I missed that some of the opportunities to remove instructions I was catching in this patch had already been caught. However, I ran my tests in this patch on main and found missed opportunities to remove `sdiv`, `ashr`, and `lshr` instructions.

I am re-working the patch to remove the duplication and follow the existing methods (e.g. the code to eliminate `udiv`'s in `expandUDivOrURem()` using `ConstantRange::icmp()`).

I'll update this revision in a day or 2, including a fix for the build failure.



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