Instantiate virtual args in function-call usage

[Alexandre Oliva]

On Dec 30, 2000, Alexandre Oliva <aoliva@redhat.com> wrote:

> How about emitting memory USEs right before the call insn, and
> CLOBBERs right after it?

While I don't find time to arrange for reload to adjust MEMs in
CALL_INSN usage notes, here's a patch that implements this change.
I've been using it for a while on new port I'm working on, that makes
extensive use of by-reference arguments to libcalls, and apparently
none of its testsuite failures are caused by this patch.  Ok to
install?