[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

llvm/include/llvm/Transforms/Scalar/LoopPassManager.h

@@ -52,6 +52,7 @@
 #include "llvm/IR/PassManager.h"
 #include "llvm/Transforms/Utils/LCSSA.h"
 #include "llvm/Transforms/Utils/LoopSimplify.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
 
 namespace llvm {
 
@@ -101,40 +102,6 @@ using RequireAnalysisLoopPass =
     RequireAnalysisPass<AnalysisT, Loop, LoopAnalysisManager,
                         LoopStandardAnalysisResults &, LPMUpdater &>;
 
-namespace internal {
-/// Helper to implement appending of loops onto a worklist.
-///
-/// We want to process loops in postorder, but the worklist is a LIFO data
-/// structure, so we append to it in *reverse* postorder.
-///
-/// For trees, a preorder traversal is a viable reverse postorder, so we
-/// actually append using a preorder walk algorithm.
-template <typename RangeT>
-inline void appendLoopsToWorklist(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 : reverse(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 LoopPassT> class FunctionToLoopPassAdaptor;
 
 /// This class provides an interface for updating the loop pass manager based
@@ -190,7 +157,7 @@ public:
                                                   "the current loop!");
 #endif
 
-    internal::appendLoopsToWorklist(NewChildLoops, Worklist);
+    appendLoopsToWorklist(NewChildLoops, Worklist);
 
     // Also skip further processing of the current loop--it will be revisited
     // after all of its newly added children are accounted for.
@@ -210,7 +177,7 @@ public:
              "All of the new loops must be siblings of the current loop!");
 #endif
 
-    internal::appendLoopsToWorklist(NewSibLoops, Worklist);
+    appendLoopsToWorklist(NewSibLoops, Worklist);
 
     // No need to skip the current loop or revisit it, as sibling loops
     // shouldn't impact anything.
@@ -324,13 +291,9 @@ public:
     // update them when they mutate the loop nest structure.
     LPMUpdater Updater(Worklist, LAM);
 
-    // Add the loop nests in the reverse order of LoopInfo. For some reason,
-    // they are stored in RPO w.r.t. the control flow graph in LoopInfo. For
-    // the purpose of unrolling, loop deletion, and LICM, we largely want to
-    // work forward across the CFG so that we visit defs before uses and can
-    // propagate simplifications from one loop nest into the next.
-    // FIXME: Consider changing the order in LoopInfo.
-    internal::appendLoopsToWorklist(reverse(LI), Worklist);
+    // Add the loop nests in the reverse order of LoopInfo. See method
+    // declaration.
+    appendLoopsToWorklist(LI, Worklist);
 
     do {
       Loop *L = Worklist.pop_back_val();

llvm/include/llvm/Transforms/Utils/LoopUtils.h

@@ -15,6 +15,7 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/PriorityWorklist.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
@@ -400,6 +401,30 @@ int rewriteLoopExitValues(Loop *L, LoopInfo *LI, TargetLibraryInfo *TLI,
 void setProfileInfoAfterUnrolling(Loop *OrigLoop, Loop *UnrolledLoop,
                                   Loop *RemainderLoop, uint64_t UF);
 
+/// Utility that implements appending of loops onto a worklist given a range.
+/// We want to process loops in postorder, but the worklist is a LIFO data
+/// structure, so we append to it in *reverse* postorder.
+/// For trees, a preorder traversal is a viable reverse postorder, so we
+/// actually append using a preorder walk algorithm.
+template <typename RangeT>
+void appendLoopsToWorklist(RangeT &&, SmallPriorityWorklist<Loop *, 4> &);
+/// Utility that implements appending of loops onto a worklist given a range.
+/// It has the same behavior as appendLoopsToWorklist, but assumes the range of
+/// loops has already been reversed, so it processes loops in the given order.
+template <typename RangeT>
+void appendReversedLoopsToWorklist(RangeT &&,
+                                   SmallPriorityWorklist<Loop *, 4> &);
+
+/// Utility that implements appending of loops onto a worklist given LoopInfo.
+/// Calls the templated utility taking a Range of loops, handing it the Loops
+/// in LoopInfo, iterated in reverse. This is because the loops are stored in
+/// RPO w.r.t. the control flow graph in LoopInfo. For the purpose of unrolling,
+/// loop deletion, and LICM, we largely want to work forward across the CFG so
+/// that we visit defs before uses and can propagate simplifications from one
+/// loop nest into the next. Calls appendReversedLoopsToWorklist with the
+/// already reversed loops in LI.
+/// FIXME: Consider changing the order in LoopInfo.
+void appendLoopsToWorklist(LoopInfo &, SmallPriorityWorklist<Loop *, 4> &);
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_UTILS_LOOPUTILS_H

llvm/lib/Transforms/Scalar/LoopUnrollAndJamPass.cpp

@@ -446,8 +446,10 @@ static bool tryToUnrollAndJamLoop(Function &F, DominatorTree &DT, LoopInfo &LI,
     DidSomething |= formLCSSARecursively(*L, DT, &LI, &SE);
   }
 
+  // Add the loop nests in the reverse order of LoopInfo. See method
+  // declaration.
   SmallPriorityWorklist<Loop *, 4> Worklist;
-  internal::appendLoopsToWorklist(reverse(LI), Worklist);
+  appendLoopsToWorklist(LI, Worklist);
   while (!Worklist.empty()) {
     Loop *L = Worklist.pop_back_val();
     LoopUnrollResult Result =

llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp

@@ -1395,30 +1395,6 @@ PreservedAnalyses LoopFullUnrollPass::run(Loop &L, LoopAnalysisManager &AM,
   return getLoopPassPreservedAnalyses();
 }
 
-template <typename RangeT>
-static SmallVector<Loop *, 8> appendLoopsToWorklist(RangeT &&Loops) {
-  SmallVector<Loop *, 8> Worklist;
-  // We use an internal worklist to build up the preorder traversal without
-  // recursion.
-  SmallVector<Loop *, 4> PreOrderLoops, PreOrderWorklist;
-
-  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.append(PreOrderLoops.begin(), PreOrderLoops.end());
-    PreOrderLoops.clear();
-  }
-  return Worklist;
-}
-
 PreservedAnalyses LoopUnrollPass::run(Function &F,
                                       FunctionAnalysisManager &AM) {
   auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
@@ -1452,7 +1428,10 @@ PreservedAnalyses LoopUnrollPass::run(Function &F,
     Changed |= formLCSSARecursively(*L, DT, &LI, &SE);
   }
 
-  SmallVector<Loop *, 8> Worklist = appendLoopsToWorklist(LI);
+  // Add the loop nests in the reverse order of LoopInfo. See method
+  // declaration.
+  SmallPriorityWorklist<Loop *, 4> Worklist;
+  appendLoopsToWorklist(LI, Worklist);
 
   while (!Worklist.empty()) {
     // Because the LoopInfo stores the loops in RPO, we walk the worklist

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);
+}