Auto merge of #136942 - Kobzol:stage0-sccache, r=<try>

Use ccache for stage0 tool builds

r? `@ghost`

Author: bors

.github/workflows/ci.yml

@@ -70,6 +70,7 @@ jobs:
       HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
       DOCKER_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       SCCACHE_BUCKET: rust-lang-ci-sccache2
+      SCCACHE_REGION: us-west-1
       CACHE_DOMAIN: ci-caches.rust-lang.org
     continue-on-error: ${{ matrix.continue_on_error || false }}
     strategy:

src/bootstrap/src/core/build_steps/tool.rs

@@ -164,6 +164,20 @@ pub fn prepare_tool_cargo(
         }
     }
 
+    // The stage0 compiler changes infrequently and does not directly depend on code
+    // in the current working directory. Therefore, caching it with sccache should be
+    // useful.
+    // This is only performed for non-incremental builds, as ccache cannot deal with these.
+    if let Some(ref ccache) = builder.config.ccache {
+        eprintln!(
+            "TOOL SCCACHE CONFIGURED at {}, mode: {:?}, incremental: {}",
+            ccache, mode, builder.config.incremental
+        );
+        if matches!(mode, Mode::ToolBootstrap) && !builder.config.incremental {
+            cargo.env("RUSTC_WRAPPER", ccache);
+        }
+    }
+
     // clippy tests need to know about the stage sysroot. Set them consistently while building to
     // avoid rebuilding when running tests.
     cargo.env("SYSROOT", builder.sysroot(compiler));

src/ci/docker/run.sh

@@ -236,9 +236,15 @@ args=
 if [ "$SCCACHE_BUCKET" != "" ]; then
     args="$args --env SCCACHE_BUCKET"
     args="$args --env SCCACHE_REGION"
-    args="$args --env AWS_ACCESS_KEY_ID"
-    args="$args --env AWS_SECRET_ACCESS_KEY"
     args="$args --env AWS_REGION"
+
+    # Disable S3 authentication for PR builds, because the access keys are missing
+    if [ "$PR_CI_JOB" != "" ]; then
+      args="$args --env SCCACHE_S3_NO_CREDENTIALS=1"
+    else
+      args="$args --env AWS_ACCESS_KEY_ID"
+      args="$args --env AWS_SECRET_ACCESS_KEY"
+    fi
 else
     mkdir -p $HOME/.cache/sccache
     args="$args --env SCCACHE_DIR=/sccache --volume $HOME/.cache/sccache:/sccache"

src/ci/docker/scripts/sccache.sh

@@ -6,10 +6,10 @@ set -ex
 
 case "$(uname -m)" in
     x86_64)
-        url="https://ci-mirrors.rust-lang.org/rustc/2021-08-24-sccache-v0.2.15-x86_64-unknown-linux-musl"
+        url="https://ci-mirrors.rust-lang.org/rustc/2025-01-07-sccache-v0.9.1-x86_64-unknown-linux-musl"
         ;;
     aarch64)
-        url="https://ci-mirrors.rust-lang.org/rustc/2021-08-25-sccache-v0.2.15-aarch64-unknown-linux-musl"
+        url="https://ci-mirrors.rust-lang.org/rustc/2025-01-07-sccache-v0.9.1-aarch64-unknown-linux-musl"
         ;;
     *)
         echo "unsupported architecture: $(uname -m)"

src/ci/run.sh

@@ -279,5 +279,5 @@ if [ "$RUN_CHECK_WITH_PARALLEL_QUERIES" != "" ]; then
 fi
 
 echo "::group::sccache stats"
-sccache --show-stats || true
+sccache --show-adv-stats || true
 echo "::endgroup::"