[SCEV] Factor out getUsedLoops

The patch introduces the new function in ScalarEvolution to get
all loops used in specified SCEV.

This is a preparation for re-writing isKnownPredicate utility as
described in https://reviews.llvm.org/D42417.

Reviewers: sanjoy, mkazantsev, reames
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D43504

llvm-svn: 326072

1 files changed, 12 insertions, 4 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index af1b9ad3037..e75a29bd0a3 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -11341,9 +11341,13 @@ ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
   RemoveSCEVFromBackedgeMap(PredicatedBackedgeTakenCounts);
 }
 
-void ScalarEvolution::addToLoopUseLists(const SCEV *S) {
+void
+ScalarEvolution::getUsedLoops(const SCEV *S,
+                              SmallPtrSetImpl<const Loop *> &LoopsUsed) {
   struct FindUsedLoops {
-    SmallPtrSet<const Loop *, 8> LoopsUsed;
+    FindUsedLoops(SmallPtrSetImpl<const Loop *> &LoopsUsed)
+        : LoopsUsed(LoopsUsed) {}
+    SmallPtrSetImpl<const Loop *> &LoopsUsed;
     bool follow(const SCEV *S) {
       if (auto *AR = dyn_cast<SCEVAddRecExpr>(S))
         LoopsUsed.insert(AR->getLoop());
@@ -11353,10 +11357,14 @@ void ScalarEvolution::addToLoopUseLists(const SCEV *S) {
     bool isDone() const { return false; }
   };
 
-  FindUsedLoops F;
+  FindUsedLoops F(LoopsUsed);
   SCEVTraversal<FindUsedLoops>(F).visitAll(S);
+}
 
-  for (auto *L : F.LoopsUsed)
+void ScalarEvolution::addToLoopUseLists(const SCEV *S) {
+  SmallPtrSet<const Loop *, 8> LoopsUsed;
+  getUsedLoops(S, LoopsUsed);
+  for (auto *L : LoopsUsed)
     LoopUsers[L].push_back(S);
 }