CI: use free runners for i686-gnu jobs

src/ci/docker/host-x86_64/i686-gnu-nopt/Dockerfile

@@ -27,5 +27,5 @@ RUN echo "[rust]" > /config/nopt-std-config.toml
 RUN echo "optimize = false" >> /config/nopt-std-config.toml
 
 ENV RUST_CONFIGURE_ARGS --build=i686-unknown-linux-gnu --disable-optimize-tests
-ENV SCRIPT python3 ../x.py test --stage 0 --config /config/nopt-std-config.toml library/std \
-  && python3 ../x.py --stage 2 test
+ARG SCRIPT_ARG
+ENV SCRIPT=${SCRIPT_ARG}

src/ci/docker/host-x86_64/i686-gnu/Dockerfile

@@ -24,10 +24,5 @@ COPY scripts/sccache.sh /scripts/
 RUN sh /scripts/sccache.sh
 
 ENV RUST_CONFIGURE_ARGS --build=i686-unknown-linux-gnu
-# Skip some tests that are unlikely to be platform specific, to speed up
-# this slow job.
-ENV SCRIPT python3 ../x.py --stage 2 test \
-  --skip src/bootstrap \
-  --skip tests/rustdoc-js \
-  --skip src/tools/error_index_generator \
-  --skip src/tools/linkchecker
+ARG SCRIPT_ARG
+ENV SCRIPT=${SCRIPT_ARG}

src/ci/docker/run.sh

@@ -105,6 +105,23 @@ if [ -f "$docker_dir/$image/Dockerfile" ]; then
     # It seems that it cannot be the same as $IMAGE_TAG, otherwise it overwrites the cache
     CACHE_IMAGE_TAG=${REGISTRY}/${REGISTRY_USERNAME}/rust-ci-cache:${cksum}
 
+    # Docker build arguments.
+    build_args=(
+        "build"
+        "--rm"
+        "-t" "rust-ci"
+        "-f" "$dockerfile"
+        "$context"
+    )
+
+    # If the environment variable DOCKER_SCRIPT is defined,
+    # set the build argument SCRIPT_ARG to DOCKER_SCRIPT.
+    # In this way, we run the script defined in CI,
+    # instead of the one defined in the Dockerfile.
+    if [ -n "${DOCKER_SCRIPT+x}" ]; then
+      build_args+=("--build-arg" "SCRIPT_ARG=${DOCKER_SCRIPT}")
+    fi
+
     # On non-CI jobs, we try to download a pre-built image from the rust-lang-ci
     # ghcr.io registry. If it is not possible, we fall back to building the image
     # locally.
@@ -115,7 +132,7 @@ if [ -f "$docker_dir/$image/Dockerfile" ]; then
             docker tag "${IMAGE_TAG}" rust-ci
         else
             echo "Building local Docker image"
-            retry docker build --rm -t rust-ci -f "$dockerfile" "$context"
+            retry docker "${build_args[@]}"
         fi
     # On PR CI jobs, we don't have permissions to write to the registry cache,
     # but we can still read from it.
@@ -127,13 +144,9 @@ if [ -f "$docker_dir/$image/Dockerfile" ]; then
         # Build the image using registry caching backend
         retry docker \
           buildx \
-          build \
-          --rm \
-          -t rust-ci \
-          -f "$dockerfile" \
+          "${build_args[@]}" \
           --cache-from type=registry,ref=${CACHE_IMAGE_TAG} \
-          --output=type=docker \
-          "$context"
+          --output=type=docker
     # On auto/try builds, we can also write to the cache.
     else
         # Log into the Docker registry, so that we can read/write cache and the final image
@@ -147,14 +160,10 @@ if [ -f "$docker_dir/$image/Dockerfile" ]; then
         # Build the image using registry caching backend
         retry docker \
           buildx \
-          build \
-          --rm \
-          -t rust-ci \
-          -f "$dockerfile" \
+          "${build_args[@]}" \
           --cache-from type=registry,ref=${CACHE_IMAGE_TAG} \
           --cache-to type=registry,ref=${CACHE_IMAGE_TAG},compression=zstd \
-          --output=type=docker \
-          "$context"
+          --output=type=docker
 
         # Print images for debugging purposes
         docker images

src/ci/github-actions/jobs.yml

@@ -58,6 +58,22 @@ envs:
     NO_DEBUG_ASSERTIONS: 1
     NO_OVERFLOW_CHECKS: 1
 
+  # Different set of tests to run tests in parallel in multiple jobs.
+  stage_2_test_set1: &stage_2_test_set1
+    DOCKER_SCRIPT: >-
+      python3 ../x.py --stage 2 test
+      --skip compiler
+      --skip src
+
+  stage_2_test_set2: &stage_2_test_set2
+    DOCKER_SCRIPT: >-
+      python3 ../x.py --stage 2 test
+      --skip tests
+      --skip coverage-map
+      --skip coverage-run
+      --skip library
+      --skip tidyselftest
+
   production:
     &production
     DEPLOY_BUCKET: rust-lang-ci2
@@ -212,11 +228,42 @@ auto:
   - image: dist-x86_64-netbsd
     <<: *job-linux-4c
 
-  - image: i686-gnu
-    <<: *job-linux-8c
+  # The i686-gnu job is split into multiple jobs to run tests in parallel.
+  # i686-gnu-1 skips tests that run in i686-gnu-2.
+  - image: i686-gnu-1
+    env:
+      IMAGE: i686-gnu
+      <<: *stage_2_test_set1
+    <<: *job-linux-4c
 
-  - image: i686-gnu-nopt
-    <<: *job-linux-8c
+  # Skip tests that run in i686-gnu-1
+  - image: i686-gnu-2
+    env:
+      IMAGE: i686-gnu
+      <<: *stage_2_test_set2
+    <<: *job-linux-4c
+
+  # The i686-gnu-nopt job is split into multiple jobs to run tests in parallel.
+  # i686-gnu-nopt-1 skips tests that run in i686-gnu-nopt-2
+  - image: i686-gnu-nopt-1
+    env:
+      IMAGE: i686-gnu-nopt
+      <<: *stage_2_test_set1
+    <<: *job-linux-4c
+
+  # Skip tests that run in i686-gnu-nopt-1
+  - image: i686-gnu-nopt-2
+    env:
+      IMAGE: i686-gnu-nopt
+      DOCKER_SCRIPT: >-
+        python3 ../x.py test --stage 0 --config /config/nopt-std-config.toml library/std &&
+        python3 ../x.py --stage 2 test
+        --skip tests
+        --skip coverage-map
+        --skip coverage-run
+        --skip library
+        --skip tidyselftest
+    <<: *job-linux-4c
 
   - image: mingw-check
     <<: *job-linux-4c