commit 5429c82db2295f191c05fca42659b2998224c1fe
author Johannes Doerfert <johannes@jdoerfert.de> Sat Jan 11 23:30:36 2020 -0600
committer Johannes Doerfert <johannes@jdoerfert.de> Thu Jan 23 18:42:45 2020 -0600
tree 889d1f30ddab32a7d01f0785da67df196d0c4554
parent ff6254dc2679d06174cb13ef5a79da1835461cd5

[Attributor][FIX] Avoid dangling pointers during code deletion

It can happen that we have instructions in the ToBeDeletedInsts set
which are deleted earlier already. To avoid dangling pointers we use
weak tracking handles.

llvm/lib/Transforms/IPO/Attributor.cpp

diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
index c65925b..648dc8f 100644
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -6131,12 +6131,14 @@
     for (Instruction *I : TerminatorsToFold)
       ConstantFoldTerminator(I->getParent());
 
-    for (Instruction *I : ToBeDeletedInsts) {
-      I->replaceAllUsesWith(UndefValue::get(I->getType()));
-      if (!isa<PHINode>(I) && isInstructionTriviallyDead(I))
-        DeadInsts.push_back(I);
-      else
-        I->eraseFromParent();
+    for (auto &V : ToBeDeletedInsts) {
+      if (Instruction *I = dyn_cast_or_null<Instruction>(V)) {
+        I->replaceAllUsesWith(UndefValue::get(I->getType()));
+        if (!isa<PHINode>(I) && isInstructionTriviallyDead(I))
+          DeadInsts.push_back(I);
+        else
+          I->eraseFromParent();
+      }
     }
 
     RecursivelyDeleteTriviallyDeadInstructions(DeadInsts);