Test bootstrapping of rustc using cg_clif

.github/workflows/bootstrap_rustc.yml

@@ -0,0 +1,44 @@
+name: Bootstrap rustc using cg_clif
+
+on:
+  - push
+
+jobs:
+  bootstrap_rustc:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Cache cargo installed crates
+      uses: actions/cache@v2
+      with:
+        path: ~/.cargo/bin
+        key: ${{ runner.os }}-cargo-installed-crates
+
+    - name: Cache cargo registry and index
+      uses: actions/cache@v2
+      with:
+        path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+        key: ${{ runner.os }}-cargo-registry-and-index-${{ hashFiles('**/Cargo.lock') }}
+
+    - name: Cache cargo target dir
+      uses: actions/cache@v2
+      with:
+        path: target
+        key: ${{ runner.os }}-cargo-build-target-${{ hashFiles('rust-toolchain', '**/Cargo.lock') }}
+
+    - name: Prepare dependencies
+      run: |
+        git config --global user.email "user@example.com"
+        git config --global user.name "User"
+        ./prepare.sh
+
+    - name: Test
+      run: |
+        # Enable backtraces for easier debugging
+        export RUST_BACKTRACE=1
+
+        ./scripts/test_bootstrap.sh

scripts/test_bootstrap.sh

@@ -0,0 +1,65 @@
+#!/bin/bash
+set -e
+
+cd $(dirname "$0")/../
+
+./build.sh
+source build/config.sh
+
+echo "[TEST] Bootstrap of rustc"
+git clone https://github.com/rust-lang/rust.git || true
+pushd rust
+git fetch
+git checkout -- .
+git checkout $(rustc -V | cut -d' ' -f3 | tr -d '(')
+
+git apply - <<EOF
+diff --git a/.gitmodules b/.gitmodules
+index 984113151de..c1e9d960d56 100644
+--- a/.gitmodules
++++ b/.gitmodules
+@@ -34,10 +34,6 @@
+ [submodule "src/doc/edition-guide"]
+ 	path = src/doc/edition-guide
+ 	url = https://github.com/rust-lang/edition-guide.git
+-[submodule "src/llvm-project"]
+-	path = src/llvm-project
+-	url = https://github.com/rust-lang/llvm-project.git
+-	branch = rustc/11.0-2020-10-12
+ [submodule "src/doc/embedded-book"]
+ 	path = src/doc/embedded-book
+ 	url = https://github.com/rust-embedded/book.git
+diff --git a/compiler/rustc_data_structures/Cargo.toml b/compiler/rustc_data_structures/Cargo.toml
+index 23e689fcae7..5f077b765b6 100644
+--- a/compiler/rustc_data_structures/Cargo.toml
++++ b/compiler/rustc_data_structures/Cargo.toml
+@@ -32,7 +32,6 @@ tempfile = "3.0.5"
+
+ [dependencies.parking_lot]
+ version = "0.11"
+-features = ["nightly"]
+
+ [target.'cfg(windows)'.dependencies]
+ winapi = { version = "0.3", features = ["fileapi", "psapi"] }
+EOF
+
+cat > config.toml <<EOF
+[llvm]
+ninja = false
+
+[build]
+rustc = "$(pwd)/../build/cg_clif"
+cargo = "$(rustup which cargo)"
+full-bootstrap = true
+local-rebuild = true
+
+[rust]
+codegen-backends = ["cranelift"]
+EOF
+
+rm -r compiler/rustc_codegen_cranelift/{Cargo.*,src}
+cp ../Cargo.* compiler/rustc_codegen_cranelift/
+cp -r ../src compiler/rustc_codegen_cranelift/src
+
+./x.py build --stage 1 library/std
+popd

src/bin/cg_clif.rs

@@ -27,11 +27,13 @@ impl rustc_driver::Callbacks for CraneliftPassesCallbacks {
         config.opts.cg.panic = Some(PanicStrategy::Abort);
         config.opts.debugging_opts.panic_abort_tests = true;
         config.opts.maybe_sysroot = Some(
-            std::env::current_exe()
-                .unwrap()
-                .parent()
-                .unwrap()
-                .join("sysroot"),
+            config.opts.maybe_sysroot.clone().unwrap_or(
+                std::env::current_exe()
+                    .unwrap()
+                    .parent()
+                    .unwrap()
+                    .join("sysroot"),
+            ),
         );
     }
 }