On 2024-09-27 21:23, Jonas Oberhauser wrote:
[...]
That idea seems to be confirmed by this (atrocious, not to be copied!)
example:
int fct_escape_address_of_b(void)
{
int *a, *b;
do {
a = READ_ONCE(p);
asm volatile ("" : : : "memory");
b = READ_ONCE(p);
} while (a != b);
// really really hide b
int **p = &b;
OPTIMIZER_HIDE_VAR(p);
asm volatile ("" : : : "memory");
return *b;
}
This also does not generate any additional instructions, unlike just
using OPTIMIZER_HIDE_VAR(b).
What is the advantage of defining OPTIMIZE_HIDE_VAR the way it currently
works instead of like above?
Did you try it on godbolt.org ? Does it have the intended effect ?
By the looks of it, you're just creating another version of @b called
"p", which is then never used and would be discarded by further
optimization. I'm unsure what you are trying to achieve here.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
