1 files changed, 43 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index f57997e146e..1c2fb3d1ed0 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9707,3 +9707,46 @@ void SCEVUnionPredicate::add(const SCEVPredicate *N) {
   SCEVToPreds[Key].push_back(N);
   Preds.push_back(N);
 }
+
+PredicatedScalarEvolution::PredicatedScalarEvolution(ScalarEvolution &SE)
+    : SE(SE), Generation(0) {}
+
+const SCEV *PredicatedScalarEvolution::getSCEV(Value *V) {
+  const SCEV *Expr = SE.getSCEV(V);
+  RewriteEntry &Entry = RewriteMap[Expr];
+
+  // If we already have an entry and the version matches, return it.
+  if (Entry.second && Generation == Entry.first)
+    return Entry.second;
+
+  // We found an entry but it's stale. Rewrite the stale entry
+  // acording to the current predicate.
+  if (Entry.second)
+    Expr = Entry.second;
+
+  const SCEV *NewSCEV = SE.rewriteUsingPredicate(Expr, Preds);
+  Entry = {Generation, NewSCEV};
+
+  return NewSCEV;
+}
+
+void PredicatedScalarEvolution::addPredicate(const SCEVPredicate &Pred) {
+  if (Preds.implies(&Pred))
+    return;
+  Preds.add(&Pred);
+  updateGeneration();
+}
+
+const SCEVUnionPredicate &PredicatedScalarEvolution::getUnionPredicate() const {
+  return Preds;
+}
+
+void PredicatedScalarEvolution::updateGeneration() {
+  // If the generation number wrapped recompute everything.
+  if (++Generation == 0) {
+    for (auto &II : RewriteMap) {
+      const SCEV *Rewritten = II.second.second;
+      II.second = {Generation, SE.rewriteUsingPredicate(Rewritten, Preds)};
+    }
+  }
+}