[PATCH] LICM: Don't crash when an instruction is used by an unreachable BB

Chandler Carruth chandlerc at gmail.com
Tue Sep 2 01:49:40 PDT 2014

Minor code tweak. Otherwise looks good.

Comment at: lib/Transforms/Scalar/LICM.cpp:601
@@ +600,3 @@
+    Instruction *User = I.user_back();
+    if (DT->isReachableFromEntry(User->getParent())) {
+      // The user must be a PHI node.
I think this would be more clear as:

  if (!DT->isReachableFromEntry(User->getParent())) {

That localizes the unreachable -> undef logic and reduces the indent for the rest.


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