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Mark Knecht posted on Sat, 15 Apr 2017 17:45:43 -0700 as excerpted: |
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> My wife is not looking for high performance and the machine uses |
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> nvidia-drivers. (If it matters) |
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> |
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> As best I can tell using equery the only package that seems to want it |
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> is mesa and there's a llvm flag implying maybe I can turn it off. I'm |
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> updating her machine and it's been grinding away on this one package for |
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> over 2 hours now. If it's not really required then I'd like to write it |
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> out of my future. |
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Please turn off the HTML posts. |
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General: |
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LLVM is a compiler, like gcc, but newer so in some cases not as |
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optimizing and licensed differently. Developers and some maintainers |
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like it because being a different implementation, it detects different |
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problems. Of course as a result code often has to be ported to work with |
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it if it has previously only been built with gcc, but once that work is |
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done, building on both compilers is a useful way to catch certain new |
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problems /before/ they get into actual shipped and running binaries. |
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Apple and the BSD folks like it because of the license. Unlike gcc, |
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which takes pains to make binary-blob plugins both illegal and broken, |
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they're allowed with llvm. So people can do the open core thing and keep |
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their secret sauce, whether it's super-optimizing or a useful hook for |
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the NSA, secret. |
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The llvm license also allows embedding parts of it into other programs as |
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JIT-compilers (just-in-time), etc, while gcc makes this problematic on |
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two fronts, technically gcc is simply not designed for it, it's more |
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monolithic and harder to suitably modularize, and legally, of course the |
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resulting code will need to be gplv3 or compatible licensed, as is gcc |
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itself, and many authors object to that. But the newer llvm code is |
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already more modular, and the more liberal license allows embedding in |
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non-gpl3-compatible code. |
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Specific: |
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The LLVM license works better with the MIT-licensed X11/Mesa/Wayland, and |
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they've taken advantage of this and its modularity to use it to implement |
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their shadow compilers and etc for newer open-gl, egl, and vulkan. This |
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is effectively an instance of the JIT-compiler/VM embedding mentioned in |
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paragraph 3 above. |
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LLVM is also used, via the same mesa machinery I believe, to enable opencl |
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(using the gpus as compute nodes to accelerate certain calculations, |
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probably most popularly bitcoin generation). |
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AMD's Radeon X11/mesa/wayland drivers to some extent and AMDGPU to a much |
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larger extent, depend on this this code. If you're running amdgpu |
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graphics, disabling this will really cripple your card and drivers if |
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they work at all, while with radeon, it's a bit more optional and indeed |
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unnecessary for the older cards, while the newer cards make use of it for |
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some opengl features (but AFAIK radeon isn't getting vulkan at all). |
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If you're not using radeon/amdgpu, you can probably disable it with |
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little consequence. |
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-- |
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Duncan - List replies preferred. No HTML msgs. |
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"Every nonfree program has a lord, a master -- |
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and if you use the program, he is your master." Richard Stallman |
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