just a curious question - llvm, mesa

[honeymak]

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g64-dwm-dwl ~ # emerge llvm-core/llvm -pavc

Calculating dependencies... done!
  llvm-core/llvm-21.1.8 pulled in by:
    llvm-core/llvm-toolchain-symlinks-21 requires llvm-core/llvm:21
    llvm-core/llvmgold-21 requires llvm-core/llvm:21[binutils-plugin]
    media-libs/mesa-25.3.3 requires llvm-core/llvm:21[llvm_targets_AMDGPU(+),abi_x86_64(-)]

>>> No packages selected for removal by depclean
Packages installed:   723
Packages in world:    25
Packages in system:   50
Required packages:    723
Number to remove:     0
g64-dwm-dwl ~ # emerge media-libs/mesa -pv

These are the packages that would be merged, in order:

Calculating dependencies... done!
Dependency resolution took 5.20 s (backtrack: 0/20).

[ebuild   R    ] media-libs/mesa-25.3.3::gentoo  USE="X llvm (opengl) proprietary-codecs vulkan wayland zstd -debug -lm-sensors -opencl -sysprof -test -unwind -vaapi -valgrind" ABI_X86="(64) -32 (-x32)" CPU_FLAGS_X86="sse2" LLVM_SLOT="21 -18 -19 -20" VIDEO_CARDS="-asahi -d3d12 (-freedreno) -i915 (-imagination) -intel -lavapipe (-lima) -nouveau -nvk (-panfrost) -r300 -r600 -radeon -radeonsi (-v3d) (-vc4) -virgl (-vivante) -vmware -zink" 0 KiB

Total: 1 package (1 reinstall), Size of downloads: 0 KiB

i am having a minimalist gentoo running
just wondering what pkg depend on llvm
and found mesa is the destination

and there is a use flag in mesa 'llvm'
what if i don't set llvm use flag in mesa, will it use gcc instead? or is llvm already compulsory for mesa?

[Asch]

llvm is for software rendering only. You are safe to disable it. It is even recommended IMO

[grknight]

LLVM in media-libs/mesa is currently hard required for i915 (really old intel, not the kernel driver), lavapipe, radeon, and r300 VIDEO_CARDS settings. opencl USE also is worthless (read: ignored) without llvm USE.

I cannot say what internally this does beyond enabling softpipe gallium fallback instead of llvmpipe.

The llvm USE is certainly able to be removed if none of the above conditions are necessary.

[honeymak]

cool answers........

looks like outta my tech capability......
i guess i will keep it default

thx cool guys

[GDH-gentoo]

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[ebuild   R    ] media-libs/mesa-25.3.3::gentoo ... VIDEO_CARDS="-asahi -d3d12 (-freedreno) -i915 (-imagination) -intel -lavapipe (-lima) -nouveau -nvk (-panfrost) -r300 -r600 -radeon -radeonsi (-v3d) (-vc4) -virgl (-vivante) -vmware -zink" 0 KiB

No video cards that are relevant for Mesa are selected, so...

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[ebuild   R    ] media-libs/mesa-25.3.3::gentoo  USE="X llvm (opengl) proprietary-codecs vulkan wayland zstd -debug -lm-sensors -opencl -sysprof -test -unwind -vaapi -valgrind" ...

... the only reason why LLVM is pulled by Mesa is that the llvm USE flag has been left set. It is set by default in the ebuild, but can be unset with /etc/portage/package.use.