[LoopUnroll] Forget block and loop dispositions during unrolling.

After unrolling a loop, the block and loop dispositions need to be
cleared. As we don't know which SCEVs in the loop/blocks may be
impacted, completely clear the cache. This should also fix some cases
where deleted loops remained in the LoopDispositions cache.

This fixes a verification failure surfaced by D134531.

I am planning on reviewing/updating the existing uses of
forgetLoopDispositions to check if they should be replaced by
forgetBlockAndLoopDispositions.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D134612

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 75961a1..6d6c3db 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -465,8 +465,10 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
   if (SE) {
     if (ULO.ForgetAllSCEV)
       SE->forgetAllLoops();
-    else
+    else {
       SE->forgetTopmostLoop(L);
+      SE->forgetBlockAndLoopDispositions();
+    }
   }
 
   if (!LatchIsExiting)