[LV] Apply sink-after & interleave-groups as VPlan transformations (NFCI)

This recommits 11ed1c0239fd51fd2f064311dc7725277ed0a994 (reverted in
9f08ce0d2197d4f163dfa4633eae2347ce8fc881 for failing an assert) with a fix:
tryToWidenMemory() now first checks if the widening decision is to interleave,
thus maintaining previous behavior where tryToInterleaveMemory() was called
first, giving priority to interleave decisions over widening/scalarization. This
commit adds the test case that exposed this bug as a LIT.

1 files changed, 20 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp
index 4b80d1fb20a..bc32e54be72 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlan.cpp
@@ -275,18 +275,35 @@ void VPRegionBlock::execute(VPTransformState *State) {
 }
 
 void VPRecipeBase::insertBefore(VPRecipeBase *InsertPos) {
+  assert(!Parent && "Recipe already in some VPBasicBlock");
+  assert(InsertPos->getParent() &&
+         "Insertion position not in any VPBasicBlock");
   Parent = InsertPos->getParent();
   Parent->getRecipeList().insert(InsertPos->getIterator(), this);
 }
 
+void VPRecipeBase::insertAfter(VPRecipeBase *InsertPos) {
+  assert(!Parent && "Recipe already in some VPBasicBlock");
+  assert(InsertPos->getParent() &&
+         "Insertion position not in any VPBasicBlock");
+  Parent = InsertPos->getParent();
+  Parent->getRecipeList().insertAfter(InsertPos->getIterator(), this);
+}
+
+void VPRecipeBase::removeFromParent() {
+  assert(getParent() && "Recipe not in any VPBasicBlock");
+  getParent()->getRecipeList().remove(getIterator());
+  Parent = nullptr;
+}
+
 iplist<VPRecipeBase>::iterator VPRecipeBase::eraseFromParent() {
+  assert(getParent() && "Recipe not in any VPBasicBlock");
   return getParent()->getRecipeList().erase(getIterator());
 }
 
 void VPRecipeBase::moveAfter(VPRecipeBase *InsertPos) {
-  InsertPos->getParent()->getRecipeList().splice(
-      std::next(InsertPos->getIterator()), getParent()->getRecipeList(),
-      getIterator());
+  removeFromParent();
+  insertAfter(InsertPos);
 }
 
 void VPInstruction::generateInstruction(VPTransformState &State,