[Mlir-commits] [mlir] [MLIR][Presburger] Make getSubMatrix exclusive on the right end (PR #190911)

[Yue Huang]

https://github.com/AdUhTkJm created https://github.com/llvm/llvm-project/pull/190911

Currently `getSubMatrix(fromRow, toRow, fromCol, toCol)` forms a submatrix with both ends inclusive. In this way, it's impossible to form an empty submatrix, as the assertions in the function prevents cases where `toRow < fromRow`. However, the functionality is necessary for Barvinok procedures (e.g. we might want to inspect the submatrix for parameters, which will be empty if there's none).

This PR changes it to be inclusive on the left end and exclusive on the right end, making it the same as canonical C++ ranges.

>From e1c69b171fa75c6a9137a23c2caa00cffdadc0a8 Mon Sep 17 00:00:00 2001
From: Yue Huang <yh548 at cam.ac.uk>
Date: Wed, 8 Apr 2026 13:00:01 +0800
Subject: [PATCH] [MLIR][Presburger] Make getSubMatrix exclusive on the right
 end

---
 mlir/include/mlir/Analysis/Presburger/Matrix.h |  3 ++-
 mlir/lib/Analysis/Presburger/Barvinok.cpp      | 15 +++++++--------
 mlir/lib/Analysis/Presburger/Matrix.cpp        | 10 +++++-----
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/mlir/include/mlir/Analysis/Presburger/Matrix.h b/mlir/include/mlir/Analysis/Presburger/Matrix.h
index 4592efda29f70..2ab71b4cb135e 100644
--- a/mlir/include/mlir/Analysis/Presburger/Matrix.h
+++ b/mlir/include/mlir/Analysis/Presburger/Matrix.h
@@ -196,7 +196,8 @@ class Matrix {
 
   // Copy the cells in the intersection of
   // the rows between `fromRows` and `toRows` and
-  // the columns between `fromColumns` and `toColumns`, both inclusive.
+  // the columns between `fromColumns` and `toColumns`, inclusive on the left
+  // but exclusive on the right (same as canonical C++ ranges).
   Matrix<T> getSubMatrix(unsigned fromRow, unsigned toRow, unsigned fromColumn,
                          unsigned toColumn) const;
 
diff --git a/mlir/lib/Analysis/Presburger/Barvinok.cpp b/mlir/lib/Analysis/Presburger/Barvinok.cpp
index c31b27794f01e..e27658a37ad12 100644
--- a/mlir/lib/Analysis/Presburger/Barvinok.cpp
+++ b/mlir/lib/Analysis/Presburger/Barvinok.cpp
@@ -167,9 +167,9 @@ mlir::presburger::detail::solveParametricEquations(FracMatrix equations) {
 
   // If the determinant is zero, there is no unique solution.
   // Thus we return null.
-  if (FracMatrix(equations.getSubMatrix(/*fromRow=*/0, /*toRow=*/d - 1,
+  if (FracMatrix(equations.getSubMatrix(/*fromRow=*/0, /*toRow=*/d,
                                         /*fromColumn=*/0,
-                                        /*toColumn=*/d - 1))
+                                        /*toColumn=*/d))
           .determinant() == 0)
     return std::nullopt;
 
@@ -218,8 +218,8 @@ mlir::presburger::detail::solveParametricEquations(FracMatrix equations) {
   //
   // We copy these columns and return them.
   ParamPoint vertex =
-      equations.getSubMatrix(/*fromRow=*/0, /*toRow=*/d - 1,
-                             /*fromColumn=*/d, /*toColumn=*/numCols - 1);
+      equations.getSubMatrix(/*fromRow=*/0, /*toRow=*/d,
+                             /*fromColumn=*/d, /*toColumn=*/numCols);
   vertex.negateMatrix();
   return vertex;
 }
@@ -345,10 +345,9 @@ mlir::presburger::detail::computePolytopeGeneratingFunction(
     // b2c2 stores the coefficients of the parameters and the constant term.
     FracMatrix a2(numIneqs - numVars, numVars);
     FracMatrix b2c2(numIneqs - numVars, numSymbols + 1);
-    a2 = FracMatrix(
-        remainder.getSubMatrix(0, numIneqs - numVars - 1, 0, numVars - 1));
-    b2c2 = FracMatrix(remainder.getSubMatrix(0, numIneqs - numVars - 1, numVars,
-                                             numVars + numSymbols));
+    a2 = FracMatrix(remainder.getSubMatrix(0, numIneqs - numVars, 0, numVars));
+    b2c2 = FracMatrix(remainder.getSubMatrix(0, numIneqs - numVars, numVars,
+                                             numVars + numSymbols + 1));
 
     // Find the vertex, if any, corresponding to the current subset of
     // inequalities.
diff --git a/mlir/lib/Analysis/Presburger/Matrix.cpp b/mlir/lib/Analysis/Presburger/Matrix.cpp
index 94e9eb5792dab..a2442b9e25fe5 100644
--- a/mlir/lib/Analysis/Presburger/Matrix.cpp
+++ b/mlir/lib/Analysis/Presburger/Matrix.cpp
@@ -392,13 +392,13 @@ Matrix<T> Matrix<T>::getSubMatrix(unsigned fromRow, unsigned toRow,
                                   unsigned fromColumn,
                                   unsigned toColumn) const {
   assert(fromRow <= toRow && "end of row range must be after beginning!");
-  assert(toRow < nRows && "end of row range out of bounds!");
+  assert(toRow <= nRows && "end of row range out of bounds!");
   assert(fromColumn <= toColumn &&
          "end of column range must be after beginning!");
-  assert(toColumn < nColumns && "end of column range out of bounds!");
-  Matrix<T> subMatrix(toRow - fromRow + 1, toColumn - fromColumn + 1);
-  for (unsigned i = fromRow; i <= toRow; ++i)
-    for (unsigned j = fromColumn; j <= toColumn; ++j)
+  assert(toColumn <= nColumns && "end of column range out of bounds!");
+  Matrix<T> subMatrix(toRow - fromRow, toColumn - fromColumn);
+  for (unsigned i = fromRow; i < toRow; ++i)
+    for (unsigned j = fromColumn; j < toColumn; ++j)
       subMatrix(i - fromRow, j - fromColumn) = at(i, j);
   return subMatrix;
 }