dsimcha Wrote:
> == Quote from Sean Kelly ([email protected])'s article
> > As an alternative, Walter has stated before that it is invalid for the
> > compiler
> to optimize across asm statement boundaries as well, so a similar effect can
> often
> be had by writing inline asm. Similar requirements apply to shared variables
> as
> well, which can be modified either in-language or by importing
> std.concurrency or
> core.atomic to perform more complex atomic ops. Both of these are likely to
> insert memory barriers when shared variables are accessed however.
>
> Does this include even empty asm statements, for example:
>
> int i; // Volatile.
>
> // Do stuff.
>
> asm {} // No code motion across this.
> i++;
> asm {} // No code motion across this.
>
> // Do more stuff.
I wondered the same thing when writing my response. Personally, I wouldn't
consider this safe because the compiler can trivially determine that the block
is empty and make it vanish. To be safe I think you'd at least have to put a
NOP in there, so I guess you could do something like:
@property void optbar() {
asm { naked; NOP; }
}
void volatile(lazy void exp) {
optbar;
exp();
optbar;
}
int x;
/*volatile*/ int y;
volatile(x = y);
