From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeffrey A Law To: Joe Buck Cc: mark AT codesourcery.com, gcc AT gcc.gnu.org, rms AT gnu.org Subject: Re: type based aliasing again Date: Wed, 15 Sep 1999 02:07:00 -0000 Message-id: <1367.937182326@upchuck.cygnus.com> References: <199909091748.KAA14096@atrus.synopsys.com> X-SW-Source: 1999-09/msg00604.html In message < 199909091748.KAA14096@atrus.synopsys.com >you write: > I think we're going to need to try out some patches so that we can > do some experimentation. How many false triggers would we get if > we followed my original naive approach (perhaps using Mark's > alterative B modification: issue the warning but proceed using > the ANSI rules)? Yes. And I think it's important that to get good results for us to use the code which ties alias analysis into the gcse pass. Otherwise we won't be exercising the most likely cause of getting the false positives. > I don't think it's appropriate for us to throw up our hands and say > the problem is too hard. There's a lot of code out there that breaks > the rules, and users will need at least some help finding it. > Otherwise people will just start putting -fno-strict-aliasing > in all their Makefiles, and Mark's work will not benefit users. I'm not suggesting we give up, only that the problem is not as simple as some people seem to think. jeff From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeffrey A Law To: Joe Buck Cc: mark@codesourcery.com, gcc@gcc.gnu.org, rms@gnu.org Subject: Re: type based aliasing again Date: Thu, 30 Sep 1999 18:02:00 -0000 Message-ID: <1367.937182326@upchuck.cygnus.com> References: <199909091748.KAA14096@atrus.synopsys.com> X-SW-Source: 1999-09n/msg00604.html Message-ID: <19990930180200.Lmd1vZETzT4NjAF5fbUW9To9hggcr5R-7ZPB8NxqdCY@z> In message < 199909091748.KAA14096@atrus.synopsys.com >you write: > I think we're going to need to try out some patches so that we can > do some experimentation. How many false triggers would we get if > we followed my original naive approach (perhaps using Mark's > alterative B modification: issue the warning but proceed using > the ANSI rules)? Yes. And I think it's important that to get good results for us to use the code which ties alias analysis into the gcse pass. Otherwise we won't be exercising the most likely cause of getting the false positives. > I don't think it's appropriate for us to throw up our hands and say > the problem is too hard. There's a lot of code out there that breaks > the rules, and users will need at least some help finding it. > Otherwise people will just start putting -fno-strict-aliasing > in all their Makefiles, and Mark's work will not benefit users. I'm not suggesting we give up, only that the problem is not as simple as some people seem to think. jeff