[PATCH] D36879: [ADCE] Don't mark block with UnreachableInst as live

[Jakub Kuderski via Phabricator via llvm-commits]

kuhar created this revision.
Herald added a subscriber: david2050.
Herald added a reviewer: grosser.

Both ReturnInst and UnreachableInst exit functions, so we can treat them the same in ADCE and not mark them as live. 
The only the CFG nodes corresponding to non-trivial PostDominatorTree roots (i.e. infinite loop blocks) need to be marked as live here for ADCE to work correctly.


https://reviews.llvm.org/D36879

Files:
  lib/Transforms/Scalar/ADCE.cpp


Index: lib/Transforms/Scalar/ADCE.cpp
===================================================================
--- lib/Transforms/Scalar/ADCE.cpp
+++ lib/Transforms/Scalar/ADCE.cpp
@@ -267,9 +267,10 @@
     auto *BB = PDTChild->getBlock();
     auto &Info = BlockInfo[BB];
     // Real function return
-    if (isa<ReturnInst>(Info.Terminator)) {
-      DEBUG(dbgs() << "post-dom root child is a return: " << BB->getName()
-                   << '\n';);
+    if (isa<ReturnInst>(Info.Terminator) ||
+        isa<UnreachableInst>(Info.Terminator)) {
+      DEBUG(dbgs() << "post-dom root child is a return or unreachable: "
+                   << BB->getName() << '\n';);
       continue;
     }
 


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