### Luanti version
 
```true
Luanti 5.10.0-dev-debug (Linux)
Using LuaJIT 2.1.ROLLING
Built by GCC 14.2
Running on Linux/6.10.6 x86_64
BUILD_TYPE=Debug
RUN_IN_PLACE=1
USE_CURL=1
USE_GETTEXT=1
USE_SOUND=1
STATIC_SHAREDIR="."
STATIC_LOCALEDIR="locale"
```
 
### Irrlicht device
 
X11
 
### Operating system and version
 
GNU Guix System
 
### GPU model
 
Intel GMA 4500 MHD
 
### Active renderer
 
OpenGL 2.1
 
### Summary
 
Luanti is significantly slower with shaders enabled compared to no
shaders when displaying exactly the same thing.  This isn't a new
issue: I get similar results with the same GPU on a different computer
with Minetest 5.6.1 and Debian 12.

Without shaders (22 FPS): https://x0.at/bqPG.png
With shaders (14 FPS): https://x0.at/4KUX.png

Effects that depend on shaders (post-processing, waving nodes, dynamic
shadows) are all disabled.
 
### Steps to reproduce
 
1. Join a world with shaders enabled (make sure it's already generated
   since the mapgen can also slow things down)
2. Disable shaders and join exactly the same world