Right, but it would seem this is a good canididate for combination. This
is especially true since often Volatile is used with the sense of Atomic
in Ada, and it is not a bad idea to combine these in practice, giving an
atomic update (right, nothing in the language requires it, but it is
definitely useful!)
I don't disagree that "this" is a good candidate for combination, but
one problem is that by the time you're at that level, you don't easily have
the source correspondance you want.
E.g.,
y |= 2;
and
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.