[VectorUtils] Use early_inc_range instead of DelSet (NFC).

[fhahn]

Summary

DelSet was used to avoid invalidating the current iterator while
modifying the map we are iterating over.

By using an early_inc_range, (which increments to iterator 'early',
allowing us to remove the current element), we can get rid of DelSet.

[Ayal]

Yes, that's indeed better, thanks!

(Maybe worth adding a comment that releaseGroup(Group) erases Group from InterleaveGroups, to explain the use of make_early_inc_range; if it's not obvious.)

llvm/lib/Analysis/VectorUtils.cpp

 //===----------- VectorUtils.cpp - Vectorizer utility functions -----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //

 }
 
 void InterleavedAccessInfo::invalidateGroupsRequiringScalarEpilogue() {
   // If no group had triggered the requirement to create an epilogue loop,
   // there is nothing to do.
   if (!requiresScalarEpilogue())
     return;
 
-  // Avoid releasing a Group twice.
-  SmallPtrSet<InterleaveGroup<Instruction> *, 4> DelSet;
-  for (auto &I : InterleaveGroupMap) {
-    InterleaveGroup<Instruction> *Group = I.second;
-    if (Group->requiresScalarEpilogue())
-      DelSet.insert(Group);
-  }
-  assert(!DelSet.empty() && "At least one group must be invalidated, as a "
-                            "scalar epilogue was required");
-  for (auto *Ptr : DelSet) {
+  bool ReleasedGroup = false;
+  for (auto *Group : make_early_inc_range(InterleaveGroups)) {
+    if (!Group->requiresScalarEpilogue())
+      continue;
     LLVM_DEBUG(
         dbgs()
         << "LV: Invalidate candidate interleaved group due to gaps that "
            "require a scalar epilogue (not allowed under optsize) and cannot "
            "be masked (not enabled). \n");
-    releaseGroup(Ptr);
+    releaseGroup(Group);
+    ReleasedGroup = true;
   }
-
+  assert(ReleasedGroup && "At least one group must be invalidated, as a "
+                         "scalar epilogue was required");
+  (void)ReleasedGroup;
   RequiresScalarEpilogue = false;
 }
 
 template <typename InstT>
 void InterleaveGroup<InstT>::addMetadata(InstT *NewInst) const {
   llvm_unreachable("addMetadata can only be used for Instruction");
 }