[Mlir-commits] [mlir] [mlir][IR] Fix bug in AffineExpr simplifier `lhs % rhs` where `lhs = lhs floordiv rhs` (PR #119245)

[Kunwar Grover]

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@@ -129,3 +129,24 @@ TEST(AffineExprTest, d0PlusD0FloorDivNeg2) {
   auto sum = d0 + d0.floorDiv(-2) * 2;
   ASSERT_EQ(toString(sum), "d0 + (d0 floordiv -2) * 2");
 }
+
+TEST(AffineExprTEst, simpleAffineExprFlattenerRegression) {
+
+  // Regression test for a bug where mod simplification was not handled
+  // properly when `lhs % rhs` was happened to have the property that `lhs
+  // floordiv rhs = lhs`.
+  MLIRContext ctx;
+  OpBuilder b(&ctx);
+
+  auto d0 = b.getAffineDimExpr(0);
+  auto d1 = b.getAffineDimExpr(1);
+
+  // Manually replace variables by constants to avoid constant folding.
+  AffineExpr expr = (d0 - (d1 + 2)).floorDiv(8) % 8;
+  expr = expr.replaceDims(
+      {b.getAffineConstantExpr(1), b.getAffineConstantExpr(1)});
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Groverkss wrote:

I think what you wanted was to use `b.getAffineDimExpr(1)`. I can reproduce the error with that.

https://github.com/llvm/llvm-project/pull/119245