radv: Use atomics to read query results.
The volatile pattern gives me flaky results for 32-bit builds on
ChromeOS Android. This is because on 32-bit the volatile 64-bit
loads gets split into 2 32-bit loads each.
So if we read the lower dword first and then the upper dword, it
can happen that the upper dword is already changed but the lower
dword isn't yet. In particular for occlusion queries this gives
false readings, as the upper dword commonly only constains the
ready bit.
With the GCC atomic intrinsics we get a call to __atomic_load_8
in libatomic.so which does the right thing.
An alternative fix would be to explicitly split the 32-bit loads
in the right order and do a bunch of retries if things change, though
that gets messy quickly and for 32-bit builds only doesn't feel worth
it that much.
CC: mesa-stable
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6933>
1 file changed
