Tactics Ogre - do something about the slow GPU readbacks

[hrydgard]

As mentioned in #10171 (comment) , the game appears to do an unnecessary 48x48 readback every frame. These are very, very expensive, especially on mobile, and if it indeed is something like a leftover debugging feature, I think a compat hack might be in order.

That's because to run this game a bit more smoothly, many people are going to resort to "Skip GPU readbacks", which may cause issues in other games, leading to bug reports etc. If the readbacks are simply not needed, we probably should take them out. Would not do this for other kinds of unnecessary draws, but readbacks are special.

The game does a lot of other readbacks though so this would only partially solve the problem, not actually sure if the whole game plays ok if you disable them all?

Was reminded of this by #16534 .

[nassau-tk]

Android Galaxy S20
Snapdragon865 / RAM12GB
If turn On [Skip GPU Readback] then "Tactics Ogre" will work good FPS but the graphics will broke.
https://user-images.githubusercontent.com/48179091/206950067-daf4f184-a591-4166-b37b-aca86be95ff7.mp4

And, If turn Off [Skip GPU Readback] then "Tactics Ogre" will work bad FPS but the graphics will correctly.
*about 40~55/60fps

On Windows PC.... It will not need [Skip GPU Readback].
Good FPS & Good graphics.
Ryzen7 3700X & Geforce RTX3060

Ge dump here...
ULJM05753_0001.zip

[ghost]

#OT
There's also a performance regression in Dante's Inferno speed/fps down by 6.

VK/OGL
v1.13.2-2456

v1.13.2

ULUS10469.ppdmp.zip

[hrydgard]

That's interesting and I'll take a look, but it doesn't have anything to do with the Tactics Ogre problem.