On Mon, Mar 17, 2008 at 7:34 PM, Andrew Haley <[EMAIL PROTECTED]> wrote: > Peter Dolding wrote: > > Ian Lance Taylor wrote: > >> "Peter Dolding" <[EMAIL PROTECTED]> writes: > >> > >> > >>> Since test is in a different object file it gets completely skiped > >>> from optimising even that it should be optimised out. > >>> > >> > >> http://gcc.gnu.org/wiki/LTO_Driver > >> > >> Ian > >> > > Ok that is half my idea. Let it sort out at link stage. But that does > > not cover like libc and dynamic dependencies. > > And it can't, either, at least not on GNU/Linux. When a bug fix is > imported into glibc, every user of glibc immediately benefits. That's one > of the reasons we don't link statically on that system. This is far > more important than the performance issue. > > Andrew. > That would be in the same class as saying cannot optimize out sqrt out of libm because a update might change it.
Not all uses of GNU/Linux are like Distributions Andrew. Sections of glibc passed constants should give 100 percent constant results. I am just proposing a automatic system to find and built data to allow them to be optimize out. Of course even just in a advisement roll to a programmer could be handy. Ok you have just asked for a constant here to be converted to a MD5 password hash. Might be a good idea to make that a internal constant instead of wasting processor time every time at this point. Adviser option or full blown both can be useful to coders. At least some of the same data would have to remain for Adviser. Ie what functions optimize out when passed constants. Full blown could even tell the coder what the possible replacement is even if it don't do it automatically. Its in the same class as lot of other optimizations. Almost no Distribution go and build with every optimization option on. So this one will be no different. Usefulness to programmers looking for blocks of code that should not be there is high as well as useful for speed hunters. I guess you want it done like math functions. Functions selected 1 at a time to be added to the optimizer fix. This is not really useful to a person doing there own internal projects. Peter Dolding
