On Mon, Jun 07, 2021 at 08:27:12AM -0700, Paul E. McKenney wrote:

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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.

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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.

Hmmm...  What do you see Peter asking for that is different than what
I am asking for?  ;-)

I don't know what you are referring to, sorry?

I know what you asked for: literally some way to tell the compiler to
emit a conditional branch.  If that is what you want, the only way to
make sure that is what you get is by writing exactly that in assembler.


Segher