[llvm] [SCEVDivision] Add SCEVDivisionPrinterPass with corresponding tests (PR #155832)

[Ryotaro Kasuga via llvm-commits]

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@@ -25,8 +25,19 @@ struct SCEVCouldNotCompute;
 
 struct SCEVDivision : public SCEVVisitor<SCEVDivision, void> {
 public:
-  // Computes the Quotient and Remainder of the division of Numerator by
-  // Denominator.
+  /// Computes the Quotient and Remainder of the division of Numerator by
+  /// Denominator. We are not actually performing the division here. Instead, we
+  /// are trying to find SCEV expressions Quotient and Remainder that satisfy:
+  ///
+  /// Numerator = Denominator * Quotient + Remainder
+  ///
+  /// There may be multiple valid answers for Quotient and Remainder. This
+  /// function finds one of them. Especially, there is always a trivial
+  /// solution: (Quotient, Remainder) = (0, Numerator).
+  ///
+  /// Note the following:
+  /// * The condition Remainder < Denominator is NOT necessarily required.
+  /// * Division of constants is performed as signed.
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kasuga-fj wrote:

Added, thanks.

https://github.com/llvm/llvm-project/pull/155832