Hello.

As mentioned in bug 95498, some conversions do not work. After 
investigation, it turns out that it's caused by multiple casts on an 
expression where it should do a truncation/extension.

I added a testcase, but for some reasons, the tests only pass when ran 
via `./testsuite/jit/test-cast.c.exe`, not when ran via `make check-jit 
RUNTESTFLAGS="-v -v -v  jit.exp=test-cast.c"`.
Furthermore, some other tests failed, but they also fail on master.

Also, I was under the impression that adding `STRIP_TYPE_NOPS (t_expr);` 
in `playback::context::build_cast` would be a better fix for this, but 
that doesn't fix the issue.
Am I missing something?

It's my first contribution to gcc, so I'd need help for fixing the tests 
and also a confirmation that this is the best way to fix this issue.

Thanks.