Fix simplification of x + x//c*-c to x mod c. (#98909)

There was no check that rhs is actually a multiplication.
llvm · Jul 15, 2024 · dd7d81e · dd7d81e
1 parent becceca
commit dd7d81e
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/mlir/lib/IR/AffineExpr.cpp b/mlir/lib/IR/AffineExpr.cpp
@@ -751,8 +751,10 @@ static AffineExpr simplifyAdd(AffineExpr lhs, AffineExpr rhs) {
   }
 
   // Process lrhs, which is 'expr floordiv c'.
+  // expr + (expr // c * -c) = expr % c
   AffineBinaryOpExpr lrBinOpExpr = dyn_cast<AffineBinaryOpExpr>(lrhs);
-  if (!lrBinOpExpr || lrBinOpExpr.getKind() != AffineExprKind::FloorDiv)
+  if (!lrBinOpExpr || rhs.getKind() != AffineExprKind::Mul ||
+      lrBinOpExpr.getKind() != AffineExprKind::FloorDiv)
     return nullptr;
 
   llrhs = lrBinOpExpr.getLHS();

diff --git a/mlir/unittests/IR/AffineExprTest.cpp b/mlir/unittests/IR/AffineExprTest.cpp
@@ -98,3 +98,11 @@ TEST(AffineExprTest, divisionSimplification) {
   ASSERT_EQ((d0 * 6).ceilDiv(4).getKind(), AffineExprKind::CeilDiv);
   ASSERT_EQ((d0 * 6).ceilDiv(-2), d0 * -3);
 }
+
+TEST(AffineExprTest, modSimplificationRegression) {
+  MLIRContext ctx;
+  OpBuilder b(&ctx);
+  auto d0 = b.getAffineDimExpr(0);
+  auto sum = d0 + d0.floorDiv(3).floorDiv(-3);
+  ASSERT_EQ(sum.getKind(), AffineExprKind::Add);
+}