[Mlir-commits] [mlir] [mlir][presburger] Implement moveColumns using std::rotate (PR #168243)

[lonely eagle]

https://github.com/linuxlonelyeagle updated https://github.com/llvm/llvm-project/pull/168243

>From b13e220c5e849a0f6505bfcf0fc4bdfc65066cc0 Mon Sep 17 00:00:00 2001
From: linuxlonelyeagle <2020382038 at qq.com>
Date: Sat, 15 Nov 2025 21:26:35 +0000
Subject: [PATCH 1/2] Implement moveColumns using std::rotate.

---
 mlir/lib/Analysis/Presburger/Matrix.cpp | 44 +++++++++++--------------
 1 file changed, 20 insertions(+), 24 deletions(-)

diff --git a/mlir/lib/Analysis/Presburger/Matrix.cpp b/mlir/lib/Analysis/Presburger/Matrix.cpp
index bb6056487512a..7933bec8d6da1 100644
--- a/mlir/lib/Analysis/Presburger/Matrix.cpp
+++ b/mlir/lib/Analysis/Presburger/Matrix.cpp
@@ -255,13 +255,7 @@ void Matrix<T>::fillRow(unsigned row, const T &value) {
 }
 
 // moveColumns is implemented by moving the columns adjacent to the source range
-// to their final position. When moving right (i.e. dstPos > srcPos), the range
-// of the adjacent columns is [srcPos + num, dstPos + num). When moving left
-// (i.e. dstPos < srcPos) the range of the adjacent columns is [dstPos, srcPos).
-// First, zeroed out columns are inserted in the final positions of the adjacent
-// columns. Then, the adjacent columns are moved to their final positions by
-// swapping them with the zeroed columns. Finally, the now zeroed adjacent
-// columns are deleted.
+// to their final position.
 template <typename T>
 void Matrix<T>::moveColumns(unsigned srcPos, unsigned num, unsigned dstPos) {
   if (num == 0)
@@ -276,23 +270,25 @@ void Matrix<T>::moveColumns(unsigned srcPos, unsigned num, unsigned dstPos) {
   assert(dstPos + num <= getNumColumns() &&
          "move destination range exceeds matrix columns");
 
-  unsigned insertCount = offset > 0 ? offset : -offset;
-  unsigned finalAdjStart = offset > 0 ? srcPos : srcPos + num;
-  unsigned curAdjStart = offset > 0 ? srcPos + num : dstPos;
-  // TODO: This can be done using std::rotate.
-  // Insert new zero columns in the positions where the adjacent columns are to
-  // be moved.
-  insertColumns(finalAdjStart, insertCount);
-  // Update curAdjStart if insertion of new columns invalidates it.
-  if (finalAdjStart < curAdjStart)
-    curAdjStart += insertCount;
-
-  // Swap the adjacent columns with inserted zero columns.
-  for (unsigned i = 0; i < insertCount; ++i)
-    swapColumns(finalAdjStart + i, curAdjStart + i);
-
-  // Delete the now redundant zero columns.
-  removeColumns(curAdjStart, insertCount);
+  unsigned numRows = getNumRows();
+  unsigned numCols = getNumReservedColumns();
+
+  if (offset > 0) {
+    // shift the matrix left, see
+    // https://en.cppreference.com/w/cpp/algorithm/rotate.html.
+    for (unsigned i = 0; i < numRows; ++i) {
+      auto begin = data.begin() + i * numCols + srcPos;
+      auto end = data.begin() + i * numCols + dstPos + num;
+      std::rotate(begin, begin + num, end);
+    }
+  } else {
+    // shift the matrix right.
+    for (unsigned i = 0; i < numRows; ++i) {
+      auto begin = data.begin() + i * numCols + srcPos + num;
+      auto end = data.begin() + i * numCols + dstPos;
+      std::rotate(end, begin - num, begin);
+    }
+  }
 }
 
 template <typename T>

>From ed84d828a767dd57bdc8e09990597274fc86e5bb Mon Sep 17 00:00:00 2001
From: linuxlonelyeagle <2020382038 at qq.com>
Date: Sat, 22 Nov 2025 11:18:23 +0000
Subject: [PATCH 2/2] update code and rebase main.

---
 mlir/lib/Analysis/Presburger/Matrix.cpp | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/mlir/lib/Analysis/Presburger/Matrix.cpp b/mlir/lib/Analysis/Presburger/Matrix.cpp
index 7933bec8d6da1..01c607c09f2b3 100644
--- a/mlir/lib/Analysis/Presburger/Matrix.cpp
+++ b/mlir/lib/Analysis/Presburger/Matrix.cpp
@@ -271,23 +271,21 @@ void Matrix<T>::moveColumns(unsigned srcPos, unsigned num, unsigned dstPos) {
          "move destination range exceeds matrix columns");
 
   unsigned numRows = getNumRows();
-  unsigned numCols = getNumReservedColumns();
 
   if (offset > 0) {
-    // shift the matrix left, see
-    // https://en.cppreference.com/w/cpp/algorithm/rotate.html.
+    // Shift the matrix left, because start < end, that std::rotate(start,
+    // middle, end) turns the range [start, end] to [middle, end) + [start,
+    // middle).
     for (unsigned i = 0; i < numRows; ++i) {
-      auto begin = data.begin() + i * numCols + srcPos;
-      auto end = data.begin() + i * numCols + dstPos + num;
-      std::rotate(begin, begin + num, end);
-    }
-  } else {
-    // shift the matrix right.
-    for (unsigned i = 0; i < numRows; ++i) {
-      auto begin = data.begin() + i * numCols + srcPos + num;
-      auto end = data.begin() + i * numCols + dstPos;
-      std::rotate(end, begin - num, begin);
+      std::rotate(&at(i, srcPos), &at(i, srcPos) + num, &at(i, dstPos) + num);
     }
+    return;
+  }
+  // Shift the matrix right. because end < start, that std::rotate(start,
+  // middle, end) turns the range [start, end] to [middle, start) + [end,
+  // middle).
+  for (unsigned i = 0; i < numRows; ++i) {
+    std::rotate(&at(i, dstPos), &at(i, srcPos), &at(i, srcPos) + num);
   }
 }