Detect self-referential values.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104957 91177308-0d34-0410-b5e6-96231b3b80d8

test/Other/lint.ll

@@ -122,3 +122,14 @@ exit:
   %t7 = inttoptr i64 %t6 to i32*
   ret i32* %t7
 }
+
+; CHECK: Undefined behavior: Undef pointer dereference
+define i32* @self_reference() {
+entry:
+  unreachable
+exit:
+  %t3 = phi i32* [ %t4, %exit ]
+  %t4 = bitcast i32* %t3 to i32*
+  %x = volatile load i32* %t3
+  br label %exit
+}