From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Date: 9 Aug 93 11:02:22 GMT From: lab.ultra.nyu.edu!kenner@nyu.edu (Richard Kenner) Subject: Re: Query about monitor (passive) task optimization Message-ID: <245aru$34e@cmcl2.NYU.EDU> List-Id: 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.