Re: Query about monitor (passive) task optimization

[slinky.cs.nyu.edu!slinky.cs.nyu.edu!nobody@nyu.edu (Robert Dewar)]

Regarding Richard's notes on GCC: one point here is that GCC realy does not
do any complex global optimizations of the type attempted in the optimizing
PL1 compiler, at least as far as I understand its structure. Perhaps the
experience that Richard reports is actually a confirmation that such
optimizations are the ones that tend to cause trouble. GCC generates extremely
good local code, and its success in competing against what on paper would
seem to be much more ambitious attempts at optimization just go to show that
concentrating on good local code gets you most of the way without needing
very complex optimizations.

The kind of optimizations we are talking about here: recognizing entire
tasks as obeying a set of restrictions (typically involving intermodule
link time analysis if the bodies are separately compiled), and then performing
(again at link time in the general case) extensive transformations on the
program tree are definitely not the kind of thing that GCC goes in for (GCC
does not even attempt intermodule register allocation, a la MIPS, let alone
more complex intermodule transformations).

Incidentally, if you think that compiling the spec and body of a task in the
same unit is an acceptable restriction for activating this kind of optimizat
ion, then I would react that I would *much* prefer a pragma in the spec to
this kind of severely destructuring kind of restriction.