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diff --git a/compiler/rustc_codegen_cranelift/build_system/usage.txt b/compiler/rustc_codegen_cranelift/build_system/usage.txt
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+The build system of cg_clif.
+
+USAGE:
+    ./y.rs prepare [--out-dir DIR]
+    ./y.rs build [--debug] [--sysroot none|clif|llvm] [--out-dir DIR] [--no-unstable-features]
+    ./y.rs test [--debug] [--sysroot none|clif|llvm] [--out-dir DIR] [--no-unstable-features]
+    ./y.rs abi-cafe [--debug] [--sysroot none|clif|llvm] [--out-dir DIR] [--no-unstable-features]
+    ./y.rs bench [--debug] [--sysroot none|clif|llvm] [--out-dir DIR] [--no-unstable-features]
+
+OPTIONS:
+    --debug
+            Build cg_clif and the standard library in debug mode rather than release mode.
+            Warning: An unoptimized cg_clif is very slow.
+
+    --sysroot none|clif|llvm
+            Which sysroot libraries to use:
+            `none` will not include any standard library in the sysroot.
+            `clif` will build the standard library using Cranelift.
+            `llvm` will use the pre-compiled standard library of rustc which is compiled with LLVM.
+
+    --out-dir DIR
+            Specify the directory in which the download, build and dist directories are stored.
+            By default this is the working directory.
+
+    --no-unstable-features
+            Some features are not yet ready for production usage. This option will disable these
+            features. This includes the JIT mode and inline assembly support.
+
+REQUIREMENTS:
+    * Rustup: The build system has a hard coded dependency on rustup to install the right nightly
+      version and make sure it is used where necessary.
+    * Git: `./y.rs prepare` uses git for applying patches and on Windows for downloading test repos.
+    * Curl and tar (non-Windows only): Used by `./y.rs prepare` to download a single commit for
+      repos. Git will be used to clone the whole repo when using Windows.
+    * [Hyperfine](https://github.com/sharkdp/hyperfine/): Used for benchmarking with `./y.rs bench`.