[PATCH] D101553: [Loads] Skip non load/store instructions when finding available load

Teresa Johnson via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri Jun 25 08:50:55 PDT 2021


tejohnson added a comment.

In D101553#2726674 <https://reviews.llvm.org/D101553#2726674>, @nikic wrote:

> Not a big fan of this -- this is effectively whitelisting a specific pattern, and doesn't generalize.
>
> For this code, there are two limits of interest: The total number of instructions we look at, and the number of alias-analysis queries we perform. Currently we limit both through a small number of total instructions. However, the only expensive part, and what needs to be aggressively limited, is the number of alias analysis queries.
>
> I think what we can do here is to have a relatively liberal upper limit on the number of scanned instructions (say 32), while having a tight limit on the number of AA queries or AA query candidates (say 4). This should make the code more resilient against additional bitcast/assume instructions in between, while still limiting compile-time impact.
>
> Do you think something along those lines would address your motivation here?

@nikic ping, I believe I implemented your suggested alternative, ptal


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