[GlobalOpt] Correctly update metadata when localizing a global.

Just calling dropAllReferences leaves pointers to the ConstantExpr
behind, so we would eventually crash with a null pointer dereference.

Differential Revision: https://reviews.llvm.org/D32551

llvm-svn: 301575

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index ae9d4ce11e0..bb2ebb46a4b 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -1792,7 +1792,9 @@ static void makeAllConstantUsesInstructions(Constant *C) {
       NewU->insertBefore(UI);
       UI->replaceUsesOfWith(U, NewU);
     }
-    U->dropAllReferences();
+    // We've replaced all the uses, so destroy the constant. (destroyConstant
+    // will update value handles and metadata.)
+    U->destroyConstant();
   }
 }