[PATCH] D144162: [AMDGPU] Replace LegacyDA with Uniformity Analysis in AnnotateUniformValues

Mon Feb 20 10:10:48 PST 2023

gandhi21299 added a comment.

In D144162#4138003 <https://reviews.llvm.org/D144162#4138003>, @ruiling wrote:

> I think it is reasonable to match divergent analysis behavior regarding to undef. The other problem that isUniform() return true for a divergent branch instruction makes me wonder: is it the best way to replace use of divergence analysis with uniform analysis one by one? Although I am optimistic about the quality of uniform analysis, I think it may be more helpful to replace all the occurrences of divergence analysis and fix all the bugs uncovered. Ideally, we would have very little test changes. The reason is that one specific pass may not have enough test coverage. Fixing the bugs after switching all the uses of divergence analysis to uniform analysis will make us more confident that we will less likely cause regression. Any different idea?

I tried replacing the analysis in AMDGPUUnifyDivergentExitNodes pass, it causes 20 tests to fail including a few fatal errors. I could imagine a lot more failures may occur after replacing in 8 or so other middle-end passes. Replacing all the occurences in a single patch will be massive. I prefer the one pass at a time approach (like the approach with this patch).

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  https://reviews.llvm.org/D144162/new/

https://reviews.llvm.org/D144162