Robert Dewar wrote: >> Making a call here before knowing this is not sensible. In fact, >> I'm tempted to argue that it is generally a bad idea to do >> optimizations that lead to the same expression being evaluated to >> different results without making the user explicitly request them. > People always say this, but they don't really realize what they are > saying. This would mean you could not put variables in registers, and > would essentially totally disable optimization.
I don't see why that demand would prevent register allocation. Maybe you can explain that to me. My point essentially is that it's not a good idea to have "x-y" mean something different in different parts of the code. That's just too hard for the user to understand and deal with properly. > The -O2 flag is exactly a request to do optimizations that may cause > wrong programs to generate different results. Then maybe it shouldn't be the default in autoconf. But wasn't -O3 the set of optimizations considered potentially unsafe? > Note by the way that formally safety-critical or security-critical > software is very unlikely to be compiled at -O2 anyway. Oh, the last formally security-critical application I've been working on (FIPS 140-2 certification pending) *was* compiled with -O2, because the resources on the embedded target device were scarce. But I'm talking about the security of your average desktop system anyways. Andreas
