[PATCH] D108399: [LoopPassManager] Assert that MemorySSA is preserved if used

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
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Currently it's possible to silently use a loop pass that does not preserve MemorySSA in a `loop-mssa` pass manager, as we don't statically know which loop passes preserve MemorySSA (as was the case with the legacy pass manager).

However, we can at least add a check after the fact that if MemorySSA is used, then it should also have been preserved. Hopefully this will reduce confusion as seen in https://bugs.llvm.org/show_bug.cgi?id=51020.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D108399

Files:
  llvm/lib/Transforms/Scalar/LoopPassManager.cpp


Index: llvm/lib/Transforms/Scalar/LoopPassManager.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopPassManager.cpp
+++ llvm/lib/Transforms/Scalar/LoopPassManager.cpp
@@ -285,6 +285,10 @@
     else
       PI.runAfterPass<Loop>(*Pass, *L, PassPA);
 
+    if (LAR.MSSA && !PassPA.getChecker<MemorySSAAnalysis>().preserved())
+      report_fatal_error("Loop pass manager using MemorySSA contains a pass "
+                         "that does not preserve MemorySSA");
+
 #ifndef NDEBUG
     // LoopAnalysisResults should always be valid.
     // Note that we don't LAR.SE.verify() because that can change observed SE


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