[llvm] [LoopUnroll] Rotate loop before unrolling inside of UnrollRuntimeLoopRemainder (PR #148243)

[via llvm-commits]

================
@@ -69,6 +72,18 @@ enum class LoopUnrollResult {
   FullyUnrolled
 };
 
+/// Represents the result of a \c UnrollRuntimeLoopRemainder invocation.
+enum class LoopReminderUnrollResult {
+  /// The loop reminder was not modified.
+  Unmodified,
+
+  /// The loop was rotated, but not unrolled.
+  Rotated,
----------------
annamthomas wrote:

I'd keep this more general: ModifiedNotUnrolled.

For example, we can perhaps allow the loop to be simplified as part of this (if the loop wasn't in simplified form at the time of runtime unrolling).

https://github.com/llvm/llvm-project/pull/148243