[PATCH] D108087: [SimpleLoopUnswitch] Create SimpleLoopNestUnswitch pass

[Whitney Tsang via Phabricator via llvm-commits]

Whitney added inline comments.


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Comment at: llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp:2973
+  Instruction *BestUnswitchTI =
+      findBestUnswitchTI(L, DT, LI, AC, AA, TTI, SE, MSSAU, PartialIVInfo,
+                         ExitBlocks, BestUnswitchInvariants);
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When given BestUnswitchTIForLoopNest, why do we want to findBestUnswitchTI?

When given BestUnswitchTIForLoopNest, this code only unswitch if BestUnswitchTIForLoopNest == findBestUnswitchTI. Is it possible that BestUnswitchTIForLoopNest != findBestUnswitchTI only have some loop level?


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Comment at: llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp:2976
+
+  if (BestUnswitchTI == nullptr)
+    return false;
----------------



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Comment at: llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp:2982
+  // unswitching.
+  if (BestUnswitchTIForLoopNest != nullptr &&
+      BestUnswitchTI != BestUnswitchTIForLoopNest)
----------------



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  https://reviews.llvm.org/D108087/new/

https://reviews.llvm.org/D108087