[PATCH] D135808: [LoopInterchange] Correcting the profitability checking for vectorization

[Congzhe Cao via Phabricator via llvm-commits]

congzhe added a comment.

In D135808#3861367 <https://reviews.llvm.org/D135808#3861367>, @ram-NK wrote:

> If outer loop dependency direction  "=" and Inner loop dependency direction is "S" and "I" then, loop interchange is considered as profitable. Only two cases of dependency is profitable. But for vectorization, ">" and "<" dependency in outer loop is more profitable when interchanged. After patch [=,<] and [=,>] will be interchanged for vectorization.

I thought what you meant is that after this patch, `[<, =]` and `[>, =]` (not [=,<] and [=,>]) will be interchanged? Because after interchange the dependency vector would become `[=, <]` and `[=, >]` respectively, which could improve potential parallelization and enable finer-grained parallelism, i.e., outer loop parallelism instead of inner loop parallelism. I think this is what `isProfitableForVectorization()` is supposed to be.

I wonder if it makes sense to you @bmahjour ?


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