[PATCH] D23824: [ADCE] Add handling of PHI nodes when removing control flow

[David Callahan via llvm-commits]

david2050 added inline comments.

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Comment at: lib/Transforms/Scalar/ADCE.cpp:463
@@ +462,3 @@
+      }
+      if (CommonReachngDefinition != Value) {
+        // When there are two definitions from "dead" predecessor paths we
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This step is necessary otherwise we delete a branch which determines a live value. It is an artifact of the semantics of PHI nodes. This is about preserving existing structure not translating to a new form. 

And Yes, outside of loops, the baseline code catches almost all cases. The primary motivation was dead, may-be-infinute loops.


https://reviews.llvm.org/D23824