Add nsw patch

addnsw.patch

diff --git a/ir/instr.cpp b/ir/instr.cpp
index 21e015a..4d93443 100644
--- a/ir/instr.cpp
+++ b/ir/instr.cpp
@@ -367,8 +367,17 @@ StateValue BinOp::toSMT(State &s) const {
   case Add:
     fn = [&](auto a, auto ap, auto b, auto bp) -> StateValue {
       expr non_poison = true;
-      if (flags & NSW)
+      if (flags & NSW) {
+        expr av, a_undefmask, a_undefvar, bv, b_undefmask, b_undefvar;
+        // If a and b are both inputs, strip undef mask away
+        if (Input::match(a, av, a_undefmask, a_undefvar) &&
+            Input::match(b, bv, b_undefmask, b_undefvar)) {
+          a = av;
+          b = bv;
+          non_poison &= a_undefmask && b_undefmask;
+        }
         non_poison &= a.add_no_soverflow(b);
+      }
       if (flags & NUW)
         non_poison &= a.add_no_uoverflow(b);
       return { a + b, move(non_poison) };