http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52441
--- Comment #1 from Kazumoto Kojima <kkojima at gcc dot gnu.org> 2012-03-01 22:00:14 UTC --- (In reply to comment #0) > The sign/zero extensions in the caller (_xx) are not emitted when using the > original Renesas ABI (-mrenesas), which is correct. Correct for efficiency, but not for robustness :-) > Maybe this double sign/zero extension has some historical reason for some ABI > backwards compatibilities in the GNU SH ABI... but shouldn't it actually be > safe to leave out the sign/zero extensions on one side of the function call > (either caller or callee)? I don't know any historical reason but x86 uses that double sign/zero extension too. It wouldn't be a safe ABI change. There can exist hand written functions depending that behavior. It's too late to change the default behavior, I think. Of course, you can add a new -m option or function attribute changing it, though it shouldn't be default for non Renesas ABI.
