[PATCH] D139934: [IndVars] Apply more optimistic SkipLastIter for AND/OR conditions

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev added inline comments.


================
Comment at: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp:1490
+      for (size_t j = 0; j < LeafConditions.size(); j++)
+        if (i != j) {
+          auto EL = SE->computeExitLimitFromCond(L, LeafConditions[j], Inverted,
----------------
nikic wrote:
> I don't really get why we need this quadratic-complexity code. It doesn't look like anything inside here depends on the outer `i`?
`OldCond ` depends on outer `i`. The logic here is following: we have `n` conditions joined through `AND`. Currenly we are handing `i`'th condition. If any **other** condition gives exact same exit count as the whole aggregate, it means that the current condition can be handled w/o last iteration. Scanning these other conditions takes linear time (I guess we could cache something if it's a problem, but they can be rewritten, so it's safer not to).



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  https://reviews.llvm.org/D139934/new/

https://reviews.llvm.org/D139934