On Thu, Nov 14, 2024 at 4:50 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> On Thu, 2024-11-14 at 16:19 -0800, Andrii Nakryiko wrote:
>
> [...]
>
> > I was also always hoping that we'll eventually optimize the following pattern:
> >
> > r1 = *(global var)
> > if r1 == 1 /* always 1 or 0 */
> > goto +...
> > ...
> >
> >
> > This is extremely common with .rodata global variables, and while the
> > branches are dead code eliminated, memory reads are not. Not sure how
> > involved it would be to do this.
>
> Could you please elaborate a bit.
> For a simple test like below compiler replaces 'flag' with 1,
> so no action is needed from verifier:
>
> const int flag = 1;
now change this to actual .rodata global variable"
const volatile int flag = 1;
>
> SEC("socket")
> __success
> __xlated("foobar")
> int rodata_test(void *ctx)
> {
> if (flag)
> return 1;
> return 0;
> }
>
