[PATCH] D104618: [LoopDeletion] Exploit undef Phi inputs when symbolically executing 1st iteration

[Nikita Popov via Phabricator via llvm-commits]

nikic accepted this revision.
nikic added a comment.
This revision is now accepted and ready to land.

LGTM



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Comment at: llvm/lib/Transforms/Scalar/LoopDeletion.cpp:263
         Value *Incoming = PN.getIncomingValueForBlock(Pred);
+        // Skip undefs. If they are present, we can assume they equal to the
+        // non-undef input.
----------------
nit: they are equal


================
Comment at: llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll:744
 ; CHECK:       if.true:
 ; CHECK-NEXT:    br i1 undef, label [[IF_TRUE_1:%.*]], label [[IF_TRUE_2:%.*]]
 ; CHECK:       if.true.1:
----------------
It would be good to replace these `br i1 undef` by `br i1 %c1` where `%c1` is an arg, to avoid making the code UB.


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https://reviews.llvm.org/D104618