[MLIR] Simplex::normalizeRow: early exit when gcd is one

Reviewed By: bondhugula

Differential Revision: https://reviews.llvm.org/D116672

diff --git a/mlir/lib/Analysis/Presburger/Simplex.cpp b/mlir/lib/Analysis/Presburger/Simplex.cpp
index 1e881aa..3d63ebd 100644 (file)
--- a/mlir/lib/Analysis/Presburger/Simplex.cpp
+++ b/mlir/lib/Analysis/Presburger/Simplex.cpp
@@ -124,10 +124,14 @@ unsigned SimplexBase::addRow(ArrayRef<int64_t> coeffs) {
 void SimplexBase::normalizeRow(unsigned row) {
   int64_t gcd = 0;
   for (unsigned col = 0; col < nCol; ++col) {
-    if (gcd == 1)
-      break;
     gcd = llvm::greatestCommonDivisor(gcd, std::abs(tableau(row, col)));
+    // If the gcd becomes 1 then the row is already normalized.
+    if (gcd == 1)
+      return;
   }
+
+  // Note that the gcd can never become zero since the first element of the row,
+  // the denominator, is non-zero.
   for (unsigned col = 0; col < nCol; ++col)
     tableau(row, col) /= gcd;
 }