SCEV: Use AssertingVH to catch dangling BasicBlock* when passes forget

to notify SCEV of a change. Add forgetLoop in a couple of those places.

llvm-svn: 136797

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index 9af338ec7f4..9b16c7cbe13 100644
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -325,6 +325,14 @@ ReprocessLoop:
       DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
                    << ExitingBlock->getName() << "\n");
 
+      // If any reachable control flow within this loop has changed, notify
+      // ScalarEvolution. Currently assume the parent loop doesn't change
+      // (spliting edges doesn't count). If blocks, CFG edges, or other values
+      // in the parent loop change, then we need call to forgetLoop() for the
+      // parent instead.
+      if (SE)
+        SE->forgetLoop(L);
+
       assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
       Changed = true;
       LI->removeBlock(ExitingBlock);