[MLIR][Presburger] Make printing aligned to assist in debugging (#107648)

Hello Arjun! Please allow me to contribute this patch as it helps me
debugging significantly! When the 1's and 0's don't line up when
debugging farkas lemma of numerous polyhedrons using simplex lexmin
solver, it is truly straining on the eyes. Hopefully this patch can help
others!

The unfortunate part is the lack of testcase as I'm not sure how to add
testcase for debug dumps. :) However, you can add this testcase to the
SimplexTest.cpp to witness the nice printing!

```c++
TEST(SimplexTest, DumpTest) {
  int COLUMNS = 2;
  int ROWS = 2;
  LexSimplex simplex(COLUMNS * 2);
  IntMatrix m1(ROWS, COLUMNS * 2 + 1);
  // Adding LHS columns.
  for (int i = 0; i < ROWS; i++) {
    // an arbitrary formula to test all kinds of integers
    for (int j = 0; j < COLUMNS; j++) 
      m1(i, j) = i + (2 << (i % 3)) * (-1 * ((i + j) % 2));
  }
  // Adding RHS columns.
  for (int i = 0; i < ROWS; i++) {
    for (int j = 0; j < COLUMNS; j++)
      m1(i, j + COLUMNS) = j - (3 << (j % 4)) * (-1 * ((i + j * 2) % 2));
  }
  for (int i = 0; i < m1.getNumRows(); i++) {
    ArrayRef<DynamicAPInt> curRow = m1.getRow(i);
    simplex.addInequality(curRow);
  }
  IntegerRelation rel =
      parseRelationFromSet("(x, y, z)[] : (z - x - 17 * y == 0, x - 11 * z >= 1)",2);
  simplex.dump();
  m1.dump();
  rel.dump();
}
```

```
rows = 2, columns = 7
var: c3, c4, c5, c6
con: r0 [>=0], r1 [>=0]
r0: -1, r1: -2
c0: denom, c1: const, c2: 2147483647, c3: 0, c4: 1, c5: 2, c6: 3
  1  0  1  0 -2  0  1
  1  0 -8 -3  1  3  7

  0 -2  0  1  0
 -3  1  3  7  0
Domain: 2, Range: 1, Symbols: 0, Locals: 0
2 constraints
 -1  -17  1   0   = 0
  1   0  -11 -1  >= 0

```

Author: kaitingwang

mlir/include/mlir/Analysis/Presburger/Utils.h

@@ -17,7 +17,9 @@
 #include "llvm/ADT/DynamicAPInt.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallBitVector.h"
+#include "llvm/Support/raw_ostream.h"
 #include <optional>
+#include <string>
 
 namespace mlir {
 namespace presburger {
@@ -292,6 +294,54 @@ std::vector<Fraction> multiplyPolynomials(ArrayRef<Fraction> a,
 
 bool isRangeZero(ArrayRef<Fraction> arr);
 
+/// Example usage:
+/// Print .12, 3.4, 56.7
+/// preAlign = ".", minSpacing = 1,
+///    .12   .12
+///   3.4   3.4
+///  56.7  56.7
+struct PrintTableMetrics {
+  // If unknown, set to 0 and pass the struct into updatePrintMetrics.
+  unsigned maxPreIndent;
+  unsigned maxPostIndent;
+  std::string preAlign;
+};
+
+/// Iterate over each val in the table and update 'm' where
+/// .maxPreIndent and .maxPostIndent are initialized to 0.
+/// class T is any type that can be handled by llvm::raw_string_ostream.
+template <class T>
+void updatePrintMetrics(T val, PrintTableMetrics &m) {
+  std::string str;
+  llvm::raw_string_ostream(str) << val;
+  if (str.empty())
+    return;
+  unsigned preIndent = str.find(m.preAlign);
+  preIndent = (preIndent != std::string::npos) ? preIndent + 1 : 0;
+  m.maxPreIndent = std::max(m.maxPreIndent, preIndent);
+  m.maxPostIndent =
+      std::max(m.maxPostIndent, (unsigned int)(str.length() - preIndent));
+}
+
+/// Print val in the table with metrics specified in 'm'.
+template <class T>
+void printWithPrintMetrics(raw_ostream &os, T val, unsigned minSpacing,
+                           const PrintTableMetrics &m) {
+  std::string str;
+  llvm::raw_string_ostream(str) << val;
+  unsigned preIndent;
+  if (!str.empty()) {
+    preIndent = str.find(m.preAlign);
+    preIndent = (preIndent != std::string::npos) ? preIndent + 1 : 0;
+  } else {
+    preIndent = 0;
+  }
+  for (unsigned i = 0; i < (minSpacing + m.maxPreIndent - preIndent); ++i)
+    os << " ";
+  os << str;
+  for (unsigned i = 0; i < m.maxPostIndent - (str.length() - preIndent); ++i)
+    os << " ";
+}
 } // namespace presburger
 } // namespace mlir
 

mlir/lib/Analysis/Presburger/IntegerRelation.cpp

@@ -32,7 +32,10 @@
 #include <cassert>
 #include <functional>
 #include <memory>
+#include <numeric>
 #include <optional>
+#include <sstream>
+#include <string>
 #include <utility>
 #include <vector>
 
@@ -2589,19 +2592,26 @@ void IntegerRelation::mergeAndCompose(const IntegerRelation &other) {
 void IntegerRelation::print(raw_ostream &os) const {
   assert(hasConsistentState());
   printSpace(os);
+  PrintTableMetrics ptm = {0, 0, "-"};
+  for (unsigned i = 0, e = getNumEqualities(); i < e; ++i)
+    for (unsigned j = 0, f = getNumCols(); j < f; ++j)
+      updatePrintMetrics<DynamicAPInt>(atEq(i, j), ptm);
+  for (unsigned i = 0, e = getNumInequalities(); i < e; ++i)
+    for (unsigned j = 0, f = getNumCols(); j < f; ++j)
+      updatePrintMetrics<DynamicAPInt>(atIneq(i, j), ptm);
+  // Print using PrintMetrics.
+  unsigned MIN_SPACING = 1;
   for (unsigned i = 0, e = getNumEqualities(); i < e; ++i) {
-    os << " ";
     for (unsigned j = 0, f = getNumCols(); j < f; ++j) {
-      os << atEq(i, j) << "\t";
+      printWithPrintMetrics<DynamicAPInt>(os, atEq(i, j), MIN_SPACING, ptm);
     }
-    os << "= 0\n";
+    os << "  = 0\n";
   }
   for (unsigned i = 0, e = getNumInequalities(); i < e; ++i) {
-    os << " ";
     for (unsigned j = 0, f = getNumCols(); j < f; ++j) {
-      os << atIneq(i, j) << "\t";
+      printWithPrintMetrics<DynamicAPInt>(os, atIneq(i, j), MIN_SPACING, ptm);
     }
-    os << ">= 0\n";
+    os << " >= 0\n";
   }
   os << '\n';
 }

mlir/lib/Analysis/Presburger/Matrix.cpp

@@ -398,10 +398,16 @@ Matrix<T> Matrix<T>::getSubMatrix(unsigned fromRow, unsigned toRow,
 
 template <typename T>
 void Matrix<T>::print(raw_ostream &os) const {
-  for (unsigned row = 0; row < nRows; ++row) {
+  PrintTableMetrics ptm = {0, 0, "-"};
+  for (unsigned row = 0; row < nRows; ++row)
     for (unsigned column = 0; column < nColumns; ++column)
-      os << at(row, column) << ' ';
-    os << '\n';
+      updatePrintMetrics<T>(at(row, column), ptm);
+  unsigned MIN_SPACING = 1;
+  for (unsigned row = 0; row < nRows; ++row) {
+    for (unsigned column = 0; column < nColumns; ++column) {
+      printWithPrintMetrics<T>(os, at(row, column), MIN_SPACING, ptm);
+    }
+    os << "\n";
   }
 }
 

mlir/lib/Analysis/Presburger/Simplex.cpp

@@ -2153,9 +2153,16 @@ void SimplexBase::print(raw_ostream &os) const {
   for (unsigned col = 2, e = getNumColumns(); col < e; ++col)
     os << ", c" << col << ": " << colUnknown[col];
   os << '\n';
-  for (unsigned row = 0, numRows = getNumRows(); row < numRows; ++row) {
+  PrintTableMetrics ptm = {0, 0, "-"};
+  for (unsigned row = 0, numRows = getNumRows(); row < numRows; ++row)
     for (unsigned col = 0, numCols = getNumColumns(); col < numCols; ++col)
-      os << tableau(row, col) << '\t';
+      updatePrintMetrics<DynamicAPInt>(tableau(row, col), ptm);
+  unsigned MIN_SPACING = 1;
+  for (unsigned row = 0, numRows = getNumRows(); row < numRows; ++row) {
+    for (unsigned col = 0, numCols = getNumColumns(); col < numCols; ++col) {
+      printWithPrintMetrics<DynamicAPInt>(os, tableau(row, col), MIN_SPACING,
+                                          ptm);
+    }
     os << '\n';
   }
   os << '\n';