Add codegen test.

Author: cjgillot

tests/codegen/inherit_overflow.rs

@@ -0,0 +1,14 @@
+// compile-flags: -Zmir-enable-passes=+Inline,+ConstProp --crate-type lib
+// revisions: ASSERT NOASSERT
+//[ASSERT] compile-flags: -Coverflow-checks=on
+//[NOASSERT] compile-flags: -Coverflow-checks=off
+
+// CHECK-LABEL: define{{.*}} @assertion
+// ASSERT: tail call void @_ZN4core9panicking5panic17h
+// NOASSERT: ret i8 0
+#[no_mangle]
+pub fn assertion() -> u8 {
+    // Optimized MIR will replace this `CheckedBinaryOp` by `const (0, true)`.
+    // Verify that codegen does or does not emit the panic.
+    <u8 as std::ops::Add>::add(255, 1)
+}