[PATCH] D141823: [SCEV] More precise trip multiples

Tue Jan 24 20:22:19 PST 2023

caojoshua added a comment.

> I wonder if it might make sense to address this first? I'm a bit worried that the only test coverage for this functionality we have right now is very indirect, by the effect the multiple has on ranges. It would be great if we could test this functionality directly based on the trip multiple.

This does make sense. Let me try to get this working.

> When I tested the original patch, there was a significant impact on compile-time: http://llvm-compile-time-tracker.com/compare.php?from=68a534e9bf69e7e5f081a515e05f1d3cb4c21761&to=8f3c56e720e64e569f930190b246e4af61be2323&stat=instructions:u But I'm not sure if it's avoidable :(

I was not expecting those numbers. Computing multiples is very similar to GetMinTrailingZeros. The main difference I can think of is that multiples uses GreatestCommonDivisor, but I don't think it should be too expensive, and in most cases it probably just returns 1. I'll look into this as well.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D141823/new/

https://reviews.llvm.org/D141823