Svyatoslav Scherbina
63 lines
2.8 KiB
Markdown
63 lines
2.8 KiB
Markdown
# Building Apple LLVM for Kotlin/Native
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This document describes how to compile LLVM distribution and use it to build Kotlin/Native on macOS.
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Usually, you don't need to compile LLVM by yourself: it is downloaded
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automatically when you run or build Kotlin/Native compiler.
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But if you don't want to download prebuilt LLVM or want to experiment with your own distribution,
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you came to the right place.
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## Part 1. Building the right LLVM version for macOS.
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For macOS host we use LLVM from [Apple downstream](https://github.com/apple/llvm-project).
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Branch is [**apple/stable/20190104**](https://github.com/apple/llvm-project/tree/apple/stable/20190104)
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because it is similar (or even the same) to what Apple ships with Xcode 11.*.
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After cloning the repo and changing the branch we perform the following steps to build LLVM toolchain:
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```bash
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mkdir build
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cd build
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cmake -DLLVM_ENABLE_PROJECTS="clang;lld;libcxx;libcxxabi" \
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-DCMAKE_BUILD_TYPE=Release \
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-DLLVM_ENABLE_ASSERTIONS=Off \
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-G Ninja \
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-DCMAKE_INSTALL_PREFIX=clang-llvm-apple-8.0.0-darwin-macos \
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../llvm
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ninja install
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```
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After these steps `clang-llvm-apple-8.0.0-darwin-macos` directory will contain LLVM distribution that is suitable for building Kotlin/Native.
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## Part 2. Building Kotlin/Native against given LLVM distribution.
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By default, Kotlin/Native will try to download LLVM distribution from CDN if it is not present in `$HOME/.konan/dependencies` folder.
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There are two ways to bypass this behaviour.
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#### Option A. Substitute prebuilt distribution.
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This option doesn't require you to edit compiler sources, but a bit harder.
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The compiler checks dependency presence by reading contents of `$HOME/.konan/dependencies/.extracted` file.
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So to avoid LLVM downloading, we should manually add a record to the `.extracted` file:
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1. Create `$HOME/.konan/dependencies/.extracted` file if it is not created.
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2. Add `clang-llvm-apple-8.0.0-darwin-macos` line.
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and put `clang-llvm-apple-8.0.0-darwin-macos` directory from the Part 1 to `$HOME/.konan/dependencies/`.
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#### Option B. Provide an absolute path to the distribution.
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This option requires user to edit [konan.properties file](konan/konan.properties).
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Set `llvmHome.<HOST_NAME>` to an absolute path to your LLVM distribution and
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set `llvmVersion.<HOST_NAME>` to its version.
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For example, provide a path to `clang-llvm-apple-8.0.0-darwin-macos` from the Part 1 and set version to 8.0.0.
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Now we are ready to build Kotlin/Native itself. The process is described in [README.md](README.md).
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## Q&A
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— Can I override `.konan` location?
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— Yes, by setting `$KONAN_DATA_DIR` environment variable. See [HACKING.md](HACKING.md#compiler-environment-variables).
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- Can I use another LLVM distribution without rebuilding Kotlin/Native?
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- Yes, see [HACKING.md](HACKING.md#using-different-llvm-distributions-as-part-of-kotlinnative-compilation-pipeline). |