[LoopUtils] Make duplicate method a utility. [NFCI]

Summary:
Method appendLoopsToWorklist is duplicate in LoopUnroll and in the
LoopPassManager as an internal method. Make it an utility.

Reviewers: dmgreen, chandlerc, fedor.sergeev, yamauchi

Subscribers: mehdi_amini, hiraditya, zzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73569

1 files changed, 42 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUtils.cpp b/llvm/lib/Transforms/Utils/LoopUtils.cpp
index 472be10..431d0c6 100644
--- a/llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -1450,3 +1450,45 @@ void llvm::setProfileInfoAfterUnrolling(Loop *OrigLoop, Loop *UnrolledLoop,
   setLoopEstimatedTripCount(RemainderLoop, RemainderAverageTripCount,
                             OrigLoopInvocationWeight);
 }
+
+/// Utility that implements appending of loops onto a worklist.
+/// Loops are added in preorder (analogous for reverse postorder for trees),
+/// and the worklist is processed LIFO.
+template <typename RangeT>
+void llvm::appendReversedLoopsToWorklist(
+    RangeT &&Loops, SmallPriorityWorklist<Loop *, 4> &Worklist) {
+  // We use an internal worklist to build up the preorder traversal without
+  // recursion.
+  SmallVector<Loop *, 4> PreOrderLoops, PreOrderWorklist;
+
+  // We walk the initial sequence of loops in reverse because we generally want
+  // to visit defs before uses and the worklist is LIFO.
+  for (Loop *RootL : Loops) {
+    assert(PreOrderLoops.empty() && "Must start with an empty preorder walk.");
+    assert(PreOrderWorklist.empty() &&
+           "Must start with an empty preorder walk worklist.");
+    PreOrderWorklist.push_back(RootL);
+    do {
+      Loop *L = PreOrderWorklist.pop_back_val();
+      PreOrderWorklist.append(L->begin(), L->end());
+      PreOrderLoops.push_back(L);
+    } while (!PreOrderWorklist.empty());
+
+    Worklist.insert(std::move(PreOrderLoops));
+    PreOrderLoops.clear();
+  }
+}
+
+template <typename RangeT>
+void llvm::appendLoopsToWorklist(RangeT &&Loops,
+                                 SmallPriorityWorklist<Loop *, 4> &Worklist) {
+  appendReversedLoopsToWorklist(reverse(Loops), Worklist);
+}
+
+template void llvm::appendLoopsToWorklist<ArrayRef<Loop *> &>(
+    ArrayRef<Loop *> &Loops, SmallPriorityWorklist<Loop *, 4> &Worklist);
+
+void llvm::appendLoopsToWorklist(LoopInfo &LI,
+                                 SmallPriorityWorklist<Loop *, 4> &Worklist) {
+  appendReversedLoopsToWorklist(LI, Worklist);
+}