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Oct 4, 2020
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Document new way to not build LLVM #878

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17 changes: 13 additions & 4 deletions src/building/suggested.md
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Expand Up @@ -161,12 +161,21 @@ git worktree add -b my-feature ../rust2 master
You can then use that rust2 folder as a separate workspace for modifying
and building `rustc`!

## Building with system LLVM
## Skipping LLVM Build

By default, LLVM is built from source, and that can take significant amount of
time. An alternative is to use LLVM already installed on your computer.
By default, LLVM is built from source, and that takes significant amount of
time. One way to avoid that is to add this to `config.toml`:

This is specified in the `target` section of `config.toml`:
```toml
[llvm]
download-ci-llvm = true
```

Downloading LLVM from CI is still experimental though, and might not be
available on all platforms. Otherwise, we'd make it a default!
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This does not feel like the right place to indicate planned policy/default, here referring to "we'd make it a default".

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This also was done in the interest of future compatibility. The thing is in flux, so I find it useful:

  • to document it early, even if incomplete
  • to be clear that there might be changes, and that the docs might be out of date
  • to not be super strict with keeping the docs up to date.

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@tshepang tshepang Sep 13, 2020 •
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I was only referring to "Otherwise, we'd make it a default". First sentence is all good.


Another alternative is to use LLVM already installed on your computer. This is
specified in the `target` section of `config.toml`:

```toml
[target.x86_64-unknown-linux-gnu]
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