[NFC] Teach getInnermostLoopFor walk up the loop trees

This should be NFC in current use case of this method, but it will
help to use it for solving more compex tasks in follow-up patches.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354227 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
index 4f1213d92a377ca533172c0ce15ad5ab7d78aa5b..eb8de34c3af1272b71143962cbefad78698207e2 100644 (file)
--- a/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ b/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -94,15 +94,19 @@ static void removeBlockFromLoops(BasicBlock *BB, Loop *FirstLoop,
 /// contains the header of loop \p L.
 static Loop *getInnermostLoopFor(SmallPtrSetImpl<BasicBlock *> &BBs,
                                  Loop &L, LoopInfo &LI) {
-  Loop *StillReachable = nullptr;
+  Loop *Innermost = nullptr;
   for (BasicBlock *BB : BBs) {
     Loop *BBL = LI.getLoopFor(BB);
-    if (BBL && BBL->contains(L.getHeader()))
-      if (!StillReachable ||
-          BBL->getLoopDepth() > StillReachable->getLoopDepth())
-        StillReachable = BBL;
+    while (BBL && !BBL->contains(L.getHeader()))
+      BBL = BBL->getParentLoop();
+    if (BBL == &L)
+      BBL = BBL->getParentLoop();
+    if (!BBL)
+      continue;
+    if (!Innermost || BBL->getLoopDepth() > Innermost->getLoopDepth())
+      Innermost = BBL;
   }
-  return StillReachable;
+  return Innermost;
 }
 
 namespace {