Re: Unreferenced lock variables

[stt@houdini.camb.inmet.com (Tucker Taft)]

Tom Moran (tmoran@bix.com) wrote:

: >permission
: >to remove an Initialize/Finalize pair only if there is an assignment

: Ah, so the complete removal of the (seemingly) unused control type
: declaration is a consequence of being able to optimize the case where
: it is in fact used (later)? 
: > Initialize(X);
: >     ...
: >    Finalize(X)
: >    <copy Y to X>
: What happens if the Initialize or Finalize of X, (which will be
: optimized away) modifies Y?  Or is that illegal?

It is certainly not "illegal," but if this rule is adopted, it would
probably be unwise ;-).  

The point of rules like this is to allow controlled objects to be treated 
largely like "normal" variables w.r.t. dead load/store removal, value 
propagation, etc.  

The rule would be analogous to the rule about functions in declared-pure 
packages.  They need not be called under certain circumstances, independent 
of whether they do or do not have "interesting" side-effects.
It is the programmer's responsibility to create operations that
are consistent with the possibility that they might be "optimized away."

--
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA