[PATCH] D146811: [LSR] Preserve LCSSA when rewriting instruction with PHI user

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev added inline comments.


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Comment at: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:5609
       }
 
       // If LSR splits critical edge and phi node has other pending
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I propose to form `InsertedNonLCSSAInsts` here, because here the order is deterministic.


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Comment at: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp:5654
+  SmallVector<Instruction *, 4> InsertedNonLCSSAInsts;
+  for (auto &[BB, V] : Inserted)
+    if (auto *I = dyn_cast<Instruction>(V))
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The order of iteration here is not deterministic. I don't know if it's a source of any real problem, but we may end up doing slightly different things in different order. If we are especially unlucky, it will be different resulting code. See my other comment where I think it's appropriate to form this vector.



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https://reviews.llvm.org/D146811