[PATCH] D76701: [MLIR] Add flat affine constraints method to round trip integer set

[Uday Bondhugula via Phabricator via llvm-commits]

bondhugula added a comment.

Thanks for the review, Andy.



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Comment at: mlir/lib/Analysis/AffineStructures.cpp:2719
+        changed = true;
+  } while (changed);
+
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andydavis1 wrote:
> What assures that this doesn't loop forever? 
Good question. Each time `changed` stays true at the end of body, 
one or more new positions (identifiers) have been detected as a floordiv, and memo[<those positions>] becomes non-null; so, the number of null entries for local var positions in memo strictly reduces each iteration (starting from getNumLocalIds()); so this will converge.  Added a comment.


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Comment at: mlir/lib/Analysis/AffineStructures.cpp:2729
+/// equalities..
+static bool isColZero(const FlatAffineConstraints &cst, unsigned pos) {
+  assert(pos < cst.getNumCols() && "position out of bounds");
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andydavis1 wrote:
> Thought we had a method that did this already? Or was it just checking for all ones? If so, maybe it could be combined.
Just scanned through - we do have a `findConstraintWithNonZeroAt` (which also sets the row position if we find one) - it has to be called for either equalities or inequalities. I can actually reuse it from isColZero. Thanks. 


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https://reviews.llvm.org/D76701