sudo pacman -S mesa intel-compute-runtime
If Ivy Bridge or more recent, install vulkan as well:
sudo pacman -S vulkan-intel vulkan-icd-loader ocl-icd lib32-ocl-icd
Might only be available on AUR.
Section "Device"
Identifier "Intel Graphics"
Driver "modesetting"
Option "AccelMethod" "glamor"
EndSection
Section "Extensions"
Option "Composite" "true"
EndSection
Section "Device"
Identifier "modesetting"
Driver "modesetting"
EndSection