Richard Kenner wrote:
t1 = y | 2;
y = t1;
are very hard to tell apart at the RTL level. Though it's clear that
a single instruction might best match the expect semantics of the former,
it's a lot less clear that it would for the latter.
I think it would still be OK for the latter, why not?
There was certainly a time when it would not, because a R/M/W cycle on
a device register meant a different thing that a read followed by a write
and the latter is more clearly what the above is supposed to represent.
Whether there is still such hardware around is another question, but
the point is that whether you or I THINK it would be OK really isn't
the issue when talking about legacy code.
What is interesting is whether this translation is appropriate for
modern Intel architecture chips, and as far as I know the answer
is yes.
