Fix SimplifyLibcalls and ValueTracking to check mayBeOverridden
before performing optimizations based on constant string values.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79384 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index 02b26bd..761c309 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -438,7 +438,8 @@
   // variable that is a constant and is initialized. The referenced constant
   // initializer is the array that we'll use for optimization.
   GlobalVariable* GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
-  if (!GV || !GV->isConstant() || !GV->hasInitializer())
+  if (!GV || !GV->isConstant() || !GV->hasInitializer() ||
+      GV->mayBeOverridden())
     return 0;
   Constant *GlobalInit = GV->getInitializer();