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<div class="moz-cite-prefix">On 07/07/2014 07:46 PM, Chandler
Carruth wrote:<br>
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<div dir="ltr">So, not really a comment on this specific patch,
but how much more effort do we want to push into the region
support in LLVM?
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<div>Last time I tried to use the region infrastructure I found
it was generally incomplete and no one was happy about relying
on dominance frontiers. Are these still significant concerns?
What is the path forward? I was easily able to rewrite my code
in terms of DominatorTrees instead of regions, and it in some
ways became simpler, so I'm not really sold lots of effort
going into enhancing the support of regions in the optimizer.</div>
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<div>Previously, it seemed like the region infrastructure in the
optimizer served an important role of making it easy to
experiment and explore optimizations in this space without
imposing much maintenance burden for such experiments. But
pushing the region support down into the machine layer seems
much more to do with making this a core part of the expected
optimization strategy, so that's why I'm asking now.</div>
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I asked Tobias about this last week, and his recommendation was that
it would be useful to experiment by porting the existing
infrastructure to the machine layer. He said he hasn't seen the
theoretical O(N^2) behavior be a problem in practice, and it would
be helpful for me to get started with the pass I want to write. I
think the theoretical complexity and any other issues with
RegionInfo are a problem for later<br>
<br>
- Matt<br>
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