[turbofan] Distinguish between change- and truncate-tagged-to-float64.

test/mjsunit/compiler/regress-truncate-number-or-undefined-to-float64.js

Index: test/mjsunit/compiler/regress-truncate-number-or-undefined-to-float64.js
diff --git a/test/mjsunit/regress/regress-crbug-513471.js b/test/mjsunit/compiler/regress-truncate-number-or-undefined-to-float64.js
similarity index 62%
copy from test/mjsunit/regress/regress-crbug-513471.js
copy to test/mjsunit/compiler/regress-truncate-number-or-undefined-to-float64.js
index 48c793e512315284ddf218f8847d9c357280fe95..1dc3042ea7fb83eb2e464873815ca1f38ed26ee2 100644
--- a/test/mjsunit/regress/regress-crbug-513471.js
+++ b/test/mjsunit/compiler/regress-truncate-number-or-undefined-to-float64.js
@@ -4,7 +4,16 @@
 
 // Flags: --allow-natives-syntax
 
-var g = (function*(){});
-var f = g();
+function g(a, b) {
+  a = +a;
+  if (b) {
+    a = undefined;
+  }
+  print(a);
+  return +a;
+}
+
+g(0);
+g(0);
 %OptimizeFunctionOnNextCall(g);
-f.next();
+assertTrue(Number.isNaN(g(0, true)));