On Sun, Jun 06, 2021 at 04:37:29PM -0700, Paul E. McKenney wrote: > > > The barrier() thing can work - all we need to do is to simply make it > > > impossible for gcc to validly create anything but a conditional > > > branch. > > > > And the only foolproof way of doing that is by writing a branch. [ ... ] > > I am saying that if you depend on that some C code you write will result > > in some particular machine code, without actually *forcing* the compiler > > to output that exact machine code, then you will be disappointed. Maybe > > not today, and maybe it will take years, if you are lucky. > > > > (s/forcing/instructing/ of course, compilers have feelings too!) > > OK, I will bite... > > What would you suggest as a way of instructing the compiler to emit the > conditional branch that we are looking for? You write it in the assembler code. Yes, it sucks. But it is the only way to get a branch if you really want one. Now, you do not really need one here anyway, so there may be some other way to satisfy the actual requirements. Segher
