> To get the data flow yes, but of course the FRE issue is that
> the SSO attribution is lost and we generate wrong code, so actual
> SSO attribution is needed for that.
Sure, but we do not support type punning when it toggles the storage order and
this testcase does that (admittedly in a more subtle way than most cases, as
you need to realize that the bit order is implicitly changed for bitfields).
What needs to be prevented is the optimization of:
g.f3 = { 1, 4 };
into
*(char *) &g.f3 = ...
because the SSO attribution is indeed lost.
> I was mostly questioning SSO on bitfields given bitfield layout might
> be special. I suppose avoiding padding in S0 might make this more
> portable (so signed/unsigned char for f7/f6). The testcase fails
> with that as well before the fix.
SSO on bitfields was the motivating case in Ada though.
--
Eric Botcazou
