Auto merge of rust-lang#142070 - matthiaskrgr:rollup-e7lxtuo, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - rust-lang#140638 (UnsafePinned: also include the effects of UnsafeCell)
 - rust-lang#141777 (Do not run PGO/BOLT in x64 Linux alt builds)
 - rust-lang#141938 (update rust offload bootstrap)
 - rust-lang#141962 (rustc-dev-guide subtree update)
 - rust-lang#141965 (`tests/ui`: A New Order [3/N])
 - rust-lang#141970 (implement new `x` flag: `--skip-std-check-if-no-download-rustc`)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

library/core/src/pin/unsafe_pinned.rs

@@ -1,10 +1,13 @@
+use crate::cell::UnsafeCell;
 use crate::marker::{PointerLike, Unpin};
 use crate::ops::{CoerceUnsized, DispatchFromDyn};
 use crate::pin::Pin;
 use crate::{fmt, ptr};
 
-/// This type provides a way to opt-out of typical aliasing rules;
+/// This type provides a way to entirely opt-out of typical aliasing rules;
 /// specifically, `&mut UnsafePinned<T>` is not guaranteed to be a unique pointer.
+/// This also subsumes the effects of `UnsafeCell`, i.e., `&UnsafePinned<T>` may point to data
+/// that is being mutated.
 ///
 /// However, even if you define your type like `pub struct Wrapper(UnsafePinned<...>)`, it is still
 /// very risky to have an `&mut Wrapper` that aliases anything else. Many functions that work
@@ -17,38 +20,24 @@ use crate::{fmt, ptr};
 /// the public API of a library. It is an internal implementation detail of libraries that need to
 /// support aliasing mutable references.
 ///
-/// Further note that this does *not* lift the requirement that shared references must be read-only!
-/// Use `UnsafeCell` for that.
-///
 /// This type blocks niches the same way `UnsafeCell` does.
 #[lang = "unsafe_pinned"]
 #[repr(transparent)]
 #[unstable(feature = "unsafe_pinned", issue = "125735")]
 pub struct UnsafePinned<T: ?Sized> {
-    value: T,
+    value: UnsafeCell<T>,
 }
 
+// Override the manual `!Sync` in `UnsafeCell`.
+#[unstable(feature = "unsafe_pinned", issue = "125735")]
+unsafe impl<T: ?Sized + Sync> Sync for UnsafePinned<T> {}
+
 /// When this type is used, that almost certainly means safe APIs need to use pinning to avoid the
 /// aliases from becoming invalidated. Therefore let's mark this as `!Unpin`. You can always opt
 /// back in to `Unpin` with an `impl` block, provided your API is still sound while unpinned.
 #[unstable(feature = "unsafe_pinned", issue = "125735")]
 impl<T: ?Sized> !Unpin for UnsafePinned<T> {}
 
-/// The type is `Copy` when `T` is to avoid people assuming that `Copy` implies there is no
-/// `UnsafePinned` anywhere. (This is an issue with `UnsafeCell`: people use `Copy` bounds to mean
-/// `Freeze`.) Given that there is no `unsafe impl Copy for ...`, this is also the option that
-/// leaves the user more choices (as they can always wrap this in a `!Copy` type).
-// FIXME(unsafe_pinned): this may be unsound or a footgun?
-#[unstable(feature = "unsafe_pinned", issue = "125735")]
-impl<T: Copy> Copy for UnsafePinned<T> {}
-
-#[unstable(feature = "unsafe_pinned", issue = "125735")]
-impl<T: Copy> Clone for UnsafePinned<T> {
-    fn clone(&self) -> Self {
-        *self
-    }
-}
-
 // `Send` and `Sync` are inherited from `T`. This is similar to `SyncUnsafeCell`, since
 // we eventually concluded that `UnsafeCell` implicitly making things `!Sync` is sometimes
 // unergonomic. A type that needs to be `!Send`/`!Sync` should really have an explicit
@@ -63,7 +52,7 @@ impl<T> UnsafePinned<T> {
     #[must_use]
     #[unstable(feature = "unsafe_pinned", issue = "125735")]
     pub const fn new(value: T) -> Self {
-        UnsafePinned { value }
+        UnsafePinned { value: UnsafeCell::new(value) }
     }
 
     /// Unwraps the value, consuming this `UnsafePinned`.
@@ -72,7 +61,7 @@ impl<T> UnsafePinned<T> {
     #[unstable(feature = "unsafe_pinned", issue = "125735")]
     #[rustc_allow_const_fn_unstable(const_precise_live_drops)]
     pub const fn into_inner(self) -> T {
-        self.value
+        self.value.into_inner()
     }
 }
 

src/bootstrap/src/core/build_steps/check.rs

@@ -77,6 +77,13 @@ impl Step for Std {
     }
 
     fn run(self, builder: &Builder<'_>) {
+        if !builder.download_rustc() && builder.config.skip_std_check_if_no_download_rustc {
+            eprintln!(
+                "WARNING: `--skip-std-check-if-no-download-rustc` flag was passed and `rust.download-rustc` is not available. Skipping."
+            );
+            return;
+        }
+
         builder.require_submodule("library/stdarch", None);
 
         let stage = self.custom_stage.unwrap_or(builder.top_stage);

src/bootstrap/src/core/build_steps/llvm.rs

@@ -443,23 +443,26 @@ impl Step for Llvm {
         // See https://github.com/rust-lang/rust/pull/50104
         cfg.define("LLVM_ENABLE_LIBXML2", "OFF");
 
-        if !enabled_llvm_projects.is_empty() {
-            enabled_llvm_projects.sort();
-            enabled_llvm_projects.dedup();
-            cfg.define("LLVM_ENABLE_PROJECTS", enabled_llvm_projects.join(";"));
-        }
-
         let mut enabled_llvm_runtimes = Vec::new();
 
         if helpers::forcing_clang_based_tests() {
             enabled_llvm_runtimes.push("compiler-rt");
         }
 
+        // This is an experimental flag, which likely builds more than necessary.
+        // We will optimize it when we get closer to releasing it on nightly.
         if builder.config.llvm_offload {
             enabled_llvm_runtimes.push("offload");
             //FIXME(ZuseZ4): LLVM intends to drop the offload dependency on openmp.
             //Remove this line once they achieved it.
             enabled_llvm_runtimes.push("openmp");
+            enabled_llvm_projects.push("compiler-rt");
+        }
+
+        if !enabled_llvm_projects.is_empty() {
+            enabled_llvm_projects.sort();
+            enabled_llvm_projects.dedup();
+            cfg.define("LLVM_ENABLE_PROJECTS", enabled_llvm_projects.join(";"));
         }
 
         if !enabled_llvm_runtimes.is_empty() {

src/bootstrap/src/core/config/config.rs

@@ -423,6 +423,11 @@ pub struct Config {
 
     /// Cache for determining path modifications
     pub path_modification_cache: Arc<Mutex<HashMap<Vec<&'static str>, PathFreshness>>>,
+
+    /// Skip checking the standard library if `rust.download-rustc` isn't available.
+    /// This is mostly for RA as building the stage1 compiler to check the library tree
+    /// on each code change might be too much for some computers.
+    pub skip_std_check_if_no_download_rustc: bool,
 }
 
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
@@ -1507,6 +1512,7 @@ impl Config {
         config.enable_bolt_settings = flags.enable_bolt_settings;
         config.bypass_bootstrap_lock = flags.bypass_bootstrap_lock;
         config.is_running_on_ci = flags.ci.unwrap_or(CiEnv::is_ci());
+        config.skip_std_check_if_no_download_rustc = flags.skip_std_check_if_no_download_rustc;
 
         // Infer the rest of the configuration.
 

src/bootstrap/src/core/config/flags.rs

@@ -182,6 +182,11 @@ pub struct Flags {
     /// Make bootstrap to behave as it's running on the CI environment or not.
     #[arg(global = true, long, value_name = "bool")]
     pub ci: Option<bool>,
+    /// Skip checking the standard library if `rust.download-rustc` isn't available.
+    /// This is mostly for RA as building the stage1 compiler to check the library tree
+    /// on each code change might be too much for some computers.
+    #[arg(global = true, long)]
+    pub skip_std_check_if_no_download_rustc: bool,
 }
 
 impl Flags {

src/bootstrap/src/utils/change_tracker.rs

@@ -416,4 +416,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Warning,
         summary: "Stage0 library no longer matches the in-tree library, which means stage1 compiler now uses the beta library.",
     },
+    ChangeInfo {
+        change_id: 141970,
+        severity: ChangeSeverity::Info,
+        summary: "Added new bootstrap flag `--skip-std-check-if-no-download-rustc` that skips std checks when download-rustc is unavailable. Mainly intended for developers to reduce RA overhead.",
+    },
 ];

src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile

@@ -96,14 +96,13 @@ ENV RUST_CONFIGURE_ARGS \
       --set rust.lto=thin \
       --set rust.codegen-units=1
 
-# Note that `rust.debug` is set to true *only* for `opt-dist`
-ENV SCRIPT python3 ../x.py build --set rust.debug=true opt-dist && \
-    ./build/$HOSTS/stage0-tools-bin/opt-dist linux-ci -- python3 ../x.py dist \
-    --host $HOSTS --target $HOSTS \
-    --include-default-paths \
-    build-manifest bootstrap && \
-    # Use GCC for building GCC, as it seems to behave badly when built with Clang
-    CC=/rustroot/bin/cc CXX=/rustroot/bin/c++ python3 ../x.py dist gcc
+ARG SCRIPT_ARG
+
+COPY host-x86_64/dist-x86_64-linux/dist.sh /scripts/
+COPY host-x86_64/dist-x86_64-linux/dist-alt.sh /scripts/
+
+ENV SCRIPT /scripts/${SCRIPT_ARG}
+
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
 
 # This is the only builder which will create source tarballs

src/ci/docker/host-x86_64/dist-x86_64-linux/dist-alt.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+set -eux
+
+python3 ../x.py dist \
+    --host $HOSTS --target $HOSTS \
+    --include-default-paths \
+    build-manifest bootstrap

src/ci/docker/host-x86_64/dist-x86_64-linux/dist.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -eux
+
+python3 ../x.py build --set rust.debug=true opt-dist
+
+./build/$HOSTS/stage0-tools-bin/opt-dist linux-ci -- python3 ../x.py dist \
+    --host $HOSTS --target $HOSTS \
+    --include-default-paths \
+    build-manifest bootstrap
+
+# Use GCC for building GCC, as it seems to behave badly when built with Clang
+CC=/rustroot/bin/cc CXX=/rustroot/bin/c++ python3 ../x.py dist gcc

src/ci/github-actions/jobs.yml

@@ -10,6 +10,10 @@ runners:
     free_disk: true
     <<: *base-job
 
+  - &job-linux-4c-largedisk
+    os: ubuntu-24.04-4core-16gb
+    <<: *base-job
+
   - &job-linux-8c
     os: ubuntu-24.04-8core-32gb
     <<: *base-job
@@ -105,6 +109,15 @@ envs:
   pr:
     PR_CI_JOB: 1
 
+jobs:
+  dist-x86_64-linux: &job-dist-x86_64-linux
+    name: dist-x86_64-linux
+    env:
+      CODEGEN_BACKENDS: llvm,cranelift
+      DOCKER_SCRIPT: dist.sh
+    <<: *job-linux-36c-codebuild
+
+
 # Jobs that run on each push to a pull request (PR)
 # These jobs automatically inherit envs.pr, to avoid repeating
 # it in each job definition.
@@ -138,10 +151,7 @@ pr:
 # These jobs automatically inherit envs.try, to avoid repeating
 # it in each job definition.
 try:
-  - name: dist-x86_64-linux
-    env:
-      CODEGEN_BACKENDS: llvm,cranelift
-    <<: *job-linux-36c-codebuild
+  - <<: *job-dist-x86_64-linux
 
 # Main CI jobs that have to be green to merge a commit into master
 # These jobs automatically inherit envs.auto, to avoid repeating
@@ -234,16 +244,14 @@ auto:
   - name: dist-x86_64-illumos
     <<: *job-linux-4c
 
-  - name: dist-x86_64-linux
-    env:
-      CODEGEN_BACKENDS: llvm,cranelift
-    <<: *job-linux-36c-codebuild
+  - <<: *job-dist-x86_64-linux
 
   - name: dist-x86_64-linux-alt
     env:
       IMAGE: dist-x86_64-linux
       CODEGEN_BACKENDS: llvm,cranelift
-    <<: *job-linux-16c
+      DOCKER_SCRIPT: dist-alt.sh
+    <<: *job-linux-4c-largedisk
 
   - name: dist-x86_64-musl
     env: