Fix for LoopInfo::updateUnloop. Remove subloop blocks from former

ancestor loops.

I have a unit test that depends on scev-unroll, which unfortunately
isn't checked in. But I will check it in when I can.

llvm-svn: 137341

1 files changed, 29 insertions, 16 deletions

diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index 7bbe506fe1e..af35462544e 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -411,6 +411,8 @@ public:
 
   void updateBlockParents();
 
+  void removeBlocksFromAncestors();
+
   void updateSubloopParents();
 
 protected:
@@ -467,6 +469,31 @@ void UnloopUpdater::updateBlockParents() {
   }
 }
 
+/// removeBlocksFromAncestors - Remove unloop's blocks from all ancestors below
+/// their new parents.
+void UnloopUpdater::removeBlocksFromAncestors() {
+  // Remove unloop's blocks from all ancestors below their new parents.
+  for (Loop::block_iterator BI = Unloop->block_begin(),
+         BE = Unloop->block_end(); BI != BE; ++BI) {
+    Loop *NewParent = LI->getLoopFor(*BI);
+    // If this block is an immediate subloop, remove all blocks (including
+    // nested subloops) from ancestors below the new parent loop.
+    // Otherwise, if this block is in a nested subloop, skip it.
+    if (SubloopParents.count(NewParent))
+      NewParent = SubloopParents[NewParent];
+    else if (Unloop->contains(NewParent))
+      continue;
+
+    // Remove blocks from former Ancestors except Unloop itself which will be
+    // deleted.
+    for (Loop *OldParent = Unloop->getParentLoop(); OldParent != NewParent;
+         OldParent = OldParent->getParentLoop()) {
+      assert(OldParent && "new loop is not an ancestor of the original");
+      OldParent->removeBlockFromLoop(*BI);
+    }
+  }
+}
+
 /// updateSubloopParents - Update the parent loop for all subloops directly
 /// nested within unloop.
 void UnloopUpdater::updateSubloopParents() {
@@ -605,22 +632,8 @@ void LoopInfo::updateUnloop(Loop *Unloop) {
   UnloopUpdater Updater(Unloop, this);
   Updater.updateBlockParents();
 
-  // Remove unloop's blocks from all ancestors below their new parents.
-  for (Loop::block_iterator BI = Unloop->block_begin(),
-         BE = Unloop->block_end(); BI != BE; ++BI) {
-    Loop *NewParent = getLoopFor(*BI);
-    // If this block is in a subloop, skip it.
-    if (Unloop->contains(NewParent))
-      continue;
-
-    // Remove blocks from former Ancestors except Unloop itself which will be
-    // deleted.
-    for (Loop *OldParent = Unloop->getParentLoop(); OldParent != NewParent;
-         OldParent = OldParent->getParentLoop()) {
-      assert(OldParent && "new loop is not an ancestor of the original");
-      OldParent->removeBlockFromLoop(*BI);
-    }
-  }
+  // Remove blocks from former ancestor loops.
+  Updater.removeBlocksFromAncestors();
 
   // Add direct subloops as children in their new parent loop.
   Updater.updateSubloopParents();