Re: Query about monitor (passive) task optimization

[lab.ultra.nyu.edu!kenner@nyu.edu (Richard Kenner)]

In article <244lfv$6o@schonberg.cs.nyu.edu> dewar@cs.nyu.edu (Robert Dewar) wri
tes:
>Fran Allen, of IBM, once said in a talk I heard (I don't know if this is
>in print) that nearly half of the optimizations in the IBM optimizating PL1
>compiler were disconnected during the maintenance process.

I've heard the same thing, but I can say that it's not universally
true.  In the few years I've been involved in GCC maintenance, I can
only think of a very few example of optimizations that have had to be
turned off.  The only major one that comes to mind is that we used to
fold the C expression
		(&foo != 0)
as always being false until someone pointed out "pragma weak" in
System V.

Sometimes we disable some special case of an optimization until we can
fix it, but we usually do so within a few weeks.  The last such
incident was that RMS had to disable some shift simplification on July
26 in an obscure case because some general routine wasn't working
properly, but I fixed that function and reenabled the optimization
yesterday.