1 files changed, 12 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/contrib/llvm-project/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
index b7e0e32780b4..083f87436acd 100644
--- a/contrib/llvm-project/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ b/contrib/llvm-project/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -576,6 +576,18 @@ public:
       return false;
     }
 
+    // TODO: Tokens may breach LCSSA form by default. However, the transform for
+    // dead exit blocks requires LCSSA form to be maintained for all values,
+    // tokens included, otherwise it may break use-def dominance (see PR56243).
+    if (!DeadExitBlocks.empty() && !L.isLCSSAForm(DT, /*IgnoreTokens*/ false)) {
+      assert(L.isLCSSAForm(DT, /*IgnoreTokens*/ true) &&
+             "LCSSA broken not by tokens?");
+      LLVM_DEBUG(dbgs() << "Give up constant terminator folding in loop "
+                        << Header->getName()
+                        << ": tokens uses potentially break LCSSA form.\n");
+      return false;
+    }
+
     SE.forgetTopmostLoop(&L);
     // Dump analysis results.
     LLVM_DEBUG(dump());