[LoopSimplify] Fix updating LCSSA after separating nested loops.

This fixes PR28825. The problem was that we only checked if a value from
a created inner loop is used in the outer loop, and fixed LCSSA for
them. But we missed to fixup LCSSA for values used in exits of the outer
loop.

llvm-svn: 277877

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
index 2846e8f235b..fc5781fdf30 100644
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -376,6 +376,21 @@ static Loop *separateNestedLoop(Loop *L, BasicBlock *Preheader,
         }
       }
     }
+    // We also need to check exit blocks of the outer loop - it might be using
+    // values from what now became an inner loop.
+    SmallVector<BasicBlock*, 8> ExitBlocks;
+    NewOuter->getExitBlocks(ExitBlocks);
+    for (BasicBlock *ExitBB: ExitBlocks) {
+      for (Instruction &I : *ExitBB) {
+        for (Value *Op : I.operands()) {
+          Instruction *OpI = dyn_cast<Instruction>(Op);
+          if (!OpI || !L->contains(OpI))
+            continue;
+          WorklistSet.insert(OpI);
+        }
+      }
+    }
+
     SmallVector<Instruction *, 8> Worklist(WorklistSet.begin(),
                                            WorklistSet.end());
     formLCSSAForInstructions(Worklist, *DT, *LI);