[Mlir-commits] [mlir] da8d1b5 - [MLIR][Presburger] Fix simplify() of IntegerRelation (#181469)

[llvmlistbot at llvm.org]

Author: Yue Huang
Date: 2026-03-08T11:21:18Z
New Revision: da8d1b52d0d344068a8bd3e46a8af3a692d2efc2

URL: https://github.com/llvm/llvm-project/commit/da8d1b52d0d344068a8bd3e46a8af3a692d2efc2
DIFF: https://github.com/llvm/llvm-project/commit/da8d1b52d0d344068a8bd3e46a8af3a692d2efc2.diff

LOG: [MLIR][Presburger] Fix simplify() of IntegerRelation (#181469)

In `simplify()`, we currently skip all columns from 0 to `firstVar` (the
column of the pivot) when we eliminate inequalities. This is invalid,
because unlike equalities, it is not guaranteed that these columns
contain only zeroes, and a scale by `rowMultiplier` cannot be ignored.
We must not skip any columns for inequalities.

Added: 
    

Modified: 
    mlir/lib/Analysis/Presburger/IntegerRelation.cpp
    mlir/unittests/Analysis/Presburger/IntegerRelationTest.cpp

Removed: 
    


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diff  --git a/mlir/lib/Analysis/Presburger/IntegerRelation.cpp b/mlir/lib/Analysis/Presburger/IntegerRelation.cpp
index cf93fbd9a0dc7..93a725571078e 100644
--- a/mlir/lib/Analysis/Presburger/IntegerRelation.cpp
+++ b/mlir/lib/Analysis/Presburger/IntegerRelation.cpp
@@ -1162,7 +1162,7 @@ bool IntegerRelation::gaussianEliminate() {
       equalities.normalizeRow(i);
     }
     for (unsigned i = 0, ineqs = getNumInequalities(); i < ineqs; ++i) {
-      eliminateFromConstraint(this, i, *pivotRow, firstVar, 0, false);
+      eliminateFromConstraint(this, i, *pivotRow, firstVar, firstVar, false);
       inequalities.normalizeRow(i);
     }
     gcdTightenInequalities();

diff  --git a/mlir/unittests/Analysis/Presburger/IntegerRelationTest.cpp b/mlir/unittests/Analysis/Presburger/IntegerRelationTest.cpp
index b94b86057b650..90753d502d12c 100644
--- a/mlir/unittests/Analysis/Presburger/IntegerRelationTest.cpp
+++ b/mlir/unittests/Analysis/Presburger/IntegerRelationTest.cpp
@@ -741,6 +741,16 @@ TEST(IntegerRelationTest, simplify) {
   EXPECT_TRUE(rel.getNumEqualities() == 2);
 }
 
+TEST(IntegerRelationTest, simplifyRegression) {
+  IntegerRelation rel = parseRelationFromSet("(x, y, z): (2*x + z >= 5, "
+                                             "x + 3*z >= 7, 3*x + y >= 9)",
+                                             3);
+
+  auto simplified = rel;
+  simplified.simplify();
+  EXPECT_TRUE(rel.isEqual(simplified));
+}
+
 TEST(IntegerRelationTest, isFullDim) {
   IntegerRelation rel = parseRelationFromSet("(x): (1 >= 0)", 1);
   EXPECT_TRUE(rel.isFullDim());