Do we ever have a compound assignment like a = b = c?

[Kazu Hirata]

Hi,

Assignment-related expanders like expand_assignment, store_expr, and
store_field can return rtx for the value being assgined to.  For
example, expand_assignment (b, c) would return the rtx of b.

Now, do we ever have an assignment embedded in something like
a = (b = c) or foo (a = b)?  I hear that we gimplify even at -O0.
Even after Temporary Expression Replacement, I don't see any 
assignment embedded in something.

If that's the case, I am thinking about removing the support for
returning rtx.  A lot of code would go away.

Kazu Hirata