[llvm] [LV, VP]VP intrinsics support for the Loop Vectorizer + adding new tail-folding mode using EVL. (PR #76172)

[Alexey Bataev via llvm-commits]

================
@@ -4733,6 +4755,36 @@ LoopVectorizationCostModel::computeMaxVF(ElementCount UserVF, unsigned UserIC) {
   // FIXME: look for a smaller MaxVF that does divide TC rather than masking.
   if (Legal->prepareToFoldTailByMasking()) {
     CanFoldTailByMasking = true;
+    if (getTailFoldingStyle() == TailFoldingStyle::None)
+      return MaxFactors;
+
+    if (UserIC > 1) {
+      LLVM_DEBUG(dbgs() << "LV: Preference for VP intrinsics indicated. Will "
+                           "not generate VP intrinsics since interleave count "
----------------
alexey-bataev wrote:

Reworked it.

https://github.com/llvm/llvm-project/pull/76172