[MLIR][Presburger] Fix a bug with determinant of IntMatrix

[Abhinav271828]

IntMatrix determinant() had a bug where it would try to assign to a null pointer.
A check to avoid this case has been added.

[llvmbot]

@llvm/pr-subscribers-mlir-presburger

@llvm/pr-subscribers-mlir

Author: None (Abhinav271828)

Changes

IntMatrix determinant() had a bug where it would try to assign to a null pointer.
A check to avoid this case has been added.

---

Full diff: https://github.com/llvm/llvm-project/pull/76622.diff

2 Files Affected:

• (modified) mlir/lib/Analysis/Presburger/Matrix.cpp (+3)
• (modified) mlir/unittests/Analysis/Presburger/MatrixTest.cpp (+3)

diff --git a/mlir/lib/Analysis/Presburger/Matrix.cpp b/mlir/lib/Analysis/Presburger/Matrix.cpp
index 25300f84cfc047..1f1188c115a8b5 100644
--- a/mlir/lib/Analysis/Presburger/Matrix.cpp
+++ b/mlir/lib/Analysis/Presburger/Matrix.cpp
@@ -452,6 +452,9 @@ MPInt IntMatrix::determinant(IntMatrix *inverse) const {
   if (detM == 0)
     return MPInt(0);
 
+  if (!inverse)
+    return detM;
+
   *inverse = IntMatrix(nRows, nColumns);
   for (unsigned i = 0; i < nRows; i++)
     for (unsigned j = 0; j < nColumns; j++)
diff --git a/mlir/unittests/Analysis/Presburger/MatrixTest.cpp b/mlir/unittests/Analysis/Presburger/MatrixTest.cpp
index e6e452790f82d1..103619518c15a2 100644
--- a/mlir/unittests/Analysis/Presburger/MatrixTest.cpp
+++ b/mlir/unittests/Analysis/Presburger/MatrixTest.cpp
@@ -251,6 +251,9 @@ TEST(MatrixTest, computeHermiteNormalForm) {
 }
 
 TEST(MatrixTest, inverse) {
+  IntMatrix mat1 = makeIntMatrix(2, 2, {{2, 1}, {7, 0}});
+  EXPECT_EQ(mat1.determinant(), -7);
+
   FracMatrix mat = makeFracMatrix(
       2, 2, {{Fraction(2), Fraction(1)}, {Fraction(7), Fraction(0)}});
   FracMatrix inverse = makeFracMatrix(

[Groverkss]

LGTM