Auto merge of #145906 - samueltardieu:rollup-p8ibzhz, r=samueltardieu

Rollup of 9 pull requests

Successful merges:

 - rust-lang/rust#144499 (ci: Begin running ui tests with `rust.debuginfo-level-tests=1`)
 - rust-lang/rust#145790 (Improve dist for gnullvm hosts)
 - rust-lang/rust#145792 (Use attribute name in message for "outer attr used as inner attr" errors)
 - rust-lang/rust#145840 (rustc_codegen_ssa: More comprehensive RISC-V ELF flags)
 - rust-lang/rust#145876 (Enable building/disting standard library in stage 0)
 - rust-lang/rust#145887 (bootstrap: Don't panic if codegen-backends is set to empty)
 - rust-lang/rust#145888 (platform-support: Fix LoongArch32 host column)
 - rust-lang/rust#145892 (add a flag to codegen fn attrs for foreign items)
 - rust-lang/rust#145901 (Fix typo in comment of library/alloc/src/raw_vec/mod.rs)

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

15 files changed, 103 insertions, 74 deletions

diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index a4976139fe9..d30005c8d51 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -167,8 +167,13 @@ impl Step for Std {
     fn run(self, builder: &Builder<'_>) -> Self::Output {
         let target = self.target;
 
-        // We already have std ready to be used for stage 0.
-        if self.build_compiler.stage == 0 {
+        // In most cases, we already have the std ready to be used for stage 0.
+        // However, if we are doing a local rebuild (so the build compiler can compile the standard
+        // library even on stage 0), and we're cross-compiling (so the stage0 standard library for
+        // *target* is not available), we still allow the stdlib to be built here.
+        if self.build_compiler.stage == 0
+            && !(builder.local_rebuild && target != builder.host_target)
+        {
             let compiler = self.build_compiler;
             builder.ensure(StdLink::from_std(self, compiler));
 
@@ -1332,9 +1337,7 @@ pub fn rustc_cargo_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetS
         cargo.env("CFG_OMIT_GIT_HASH", "1");
     }
 
-    if let Some(backend) = builder.config.default_codegen_backend(target) {
-        cargo.env("CFG_DEFAULT_CODEGEN_BACKEND", backend.name());
-    }
+    cargo.env("CFG_DEFAULT_CODEGEN_BACKEND", builder.config.default_codegen_backend(target).name());
 
     let libdir_relative = builder.config.libdir_relative().unwrap_or_else(|| Path::new("lib"));
     let target_config = builder.config.target_config.get(&target);
diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index a6156cad6fc..abe79405984 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -1850,7 +1850,7 @@ HELP: You can add it into `bootstrap.toml` in `rust.codegen-backends = [{name:?}
             // Tells compiletest which codegen backend to use.
             // It is used to e.g. ignore tests that don't support that codegen backend.
             cmd.arg("--default-codegen-backend")
-                .arg(builder.config.default_codegen_backend(compiler.host).unwrap().name());
+                .arg(builder.config.default_codegen_backend(compiler.host).name());
         }
 
         if builder.build.config.llvm_enzyme {
diff --git a/src/bootstrap/src/core/builder/cargo.rs b/src/bootstrap/src/core/builder/cargo.rs
index 9c417952a5f..cdf6fe573e5 100644
--- a/src/bootstrap/src/core/builder/cargo.rs
+++ b/src/bootstrap/src/core/builder/cargo.rs
@@ -1323,12 +1323,7 @@ impl Builder<'_> {
 
             if let Some(limit) = limit
                 && (build_compiler_stage == 0
-                    || self
-                        .config
-                        .default_codegen_backend(target)
-                        .cloned()
-                        .unwrap_or_default()
-                        .is_llvm())
+                    || self.config.default_codegen_backend(target).is_llvm())
             {
                 rustflags.arg(&format!("-Cllvm-args=-import-instr-limit={limit}"));
             }
diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index 27e416359a9..f794f4e079a 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -1435,22 +1435,30 @@ impl<'a> Builder<'a> {
         // FIXME: make the `Std` step return some type-level "proof" that std was indeed built,
         // and then require passing that to all Cargo invocations that we do.
 
-        // The "stage 0" std is always precompiled and comes with the stage0 compiler, so we have
-        // special logic for it, to avoid creating needless and confusing Std steps that don't
+        // The "stage 0" std is almost always precompiled and comes with the stage0 compiler, so we
+        // have special logic for it, to avoid creating needless and confusing Std steps that don't
         // actually build anything.
+        // We only allow building the stage0 stdlib if we do a local rebuild, so the stage0 compiler
+        // actually comes from in-tree sources, and we're cross-compiling, so the stage0 for the
+        // given `target` is not available.
         if compiler.stage == 0 {
             if target != compiler.host {
-                panic!(
-                    r"It is not possible to build the standard library for `{target}` using the stage0 compiler.
+                if self.local_rebuild {
+                    self.ensure(Std::new(compiler, target))
+                } else {
+                    panic!(
+                        r"It is not possible to build the standard library for `{target}` using the stage0 compiler.
 You have to build a stage1 compiler for `{}` first, and then use it to build a standard library for `{target}`.
+Alternatively, you can set `build.local-rebuild=true` and use a stage0 compiler built from in-tree sources.
 ",
-                    compiler.host
-                )
+                        compiler.host
+                    )
+                }
+            } else {
+                // We still need to link the prebuilt standard library into the ephemeral stage0 sysroot
+                self.ensure(StdLink::from_std(Std::new(compiler, target), compiler));
+                None
             }
-
-            // We still need to link the prebuilt standard library into the ephemeral stage0 sysroot
-            self.ensure(StdLink::from_std(Std::new(compiler, target), compiler));
-            None
         } else {
             // This step both compiles the std and links it into the compiler's sysroot.
             // Yes, it's quite magical and side-effecty.. would be nice to refactor later.
diff --git a/src/bootstrap/src/core/builder/tests.rs b/src/bootstrap/src/core/builder/tests.rs
index f7067d11450..3c2cb782850 100644
--- a/src/bootstrap/src/core/builder/tests.rs
+++ b/src/bootstrap/src/core/builder/tests.rs
@@ -854,6 +854,18 @@ mod snapshot {
     }
 
     #[test]
+    fn build_library_stage_0_local_rebuild() {
+        let ctx = TestCtx::new();
+        insta::assert_snapshot!(
+            ctx.config("build")
+                .path("library")
+                .stage(0)
+                .targets(&[TEST_TRIPLE_1])
+                .args(&["--set", "build.local-rebuild=true"])
+                .render_steps(), @"[build] rustc 0 <host> -> std 0 <target1>");
+    }
+
+    #[test]
     fn build_library_stage_1() {
         let ctx = TestCtx::new();
         insta::assert_snapshot!(
@@ -1697,6 +1709,22 @@ mod snapshot {
     }
 
     #[test]
+    fn dist_library_stage_0_local_rebuild() {
+        let ctx = TestCtx::new();
+        insta::assert_snapshot!(
+            ctx.config("dist")
+                .path("rust-std")
+                .stage(0)
+                .targets(&[TEST_TRIPLE_1])
+                .args(&["--set", "build.local-rebuild=true"])
+                .render_steps(), @r"
+        [build] rustc 0 <host> -> std 0 <target1>
+        [build] rustc 0 <host> -> RustInstaller 1 <host>
+        [dist] rustc 0 <host> -> std 0 <target1>
+        ");
+    }
+
+    #[test]
     fn check_compiler_no_explicit_stage() {
         let ctx = TestCtx::new();
         insta::assert_snapshot!(
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 3e9c8ccb4fa..a8eb563015f 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -969,31 +969,38 @@ impl Config {
             | Subcommand::Vendor { .. } => flags_stage.unwrap_or(0),
         };
 
-        // Now check that the selected stage makes sense, and if not, print a warning and end
+        let local_rebuild = build_local_rebuild.unwrap_or(false);
+
+        let check_stage0 = |kind: &str| {
+            if local_rebuild {
+                eprintln!("WARNING: running {kind} in stage 0. This might not work as expected.");
+            } else {
+                eprintln!(
+                    "ERROR: cannot {kind} anything on stage 0. Use at least stage 1 or set build.local-rebuild=true and use a stage0 compiler built from in-tree sources."
+                );
+                exit!(1);
+            }
+        };
+
+        // Now check that the selected stage makes sense, and if not, print an error and end
         match (stage, &flags_cmd) {
             (0, Subcommand::Build { .. }) => {
-                eprintln!("ERROR: cannot build anything on stage 0. Use at least stage 1.");
-                exit!(1);
+                check_stage0("build");
             }
             (0, Subcommand::Check { .. }) => {
-                eprintln!("ERROR: cannot check anything on stage 0. Use at least stage 1.");
-                exit!(1);
+                check_stage0("check");
             }
             (0, Subcommand::Doc { .. }) => {
-                eprintln!("ERROR: cannot document anything on stage 0. Use at least stage 1.");
-                exit!(1);
+                check_stage0("doc");
             }
             (0, Subcommand::Clippy { .. }) => {
-                eprintln!("ERROR: cannot run clippy on stage 0. Use at least stage 1.");
-                exit!(1);
+                check_stage0("clippy");
             }
             (0, Subcommand::Dist) => {
-                eprintln!("ERROR: cannot dist anything on stage 0. Use at least stage 1.");
-                exit!(1);
+                check_stage0("dist");
             }
             (0, Subcommand::Install) => {
-                eprintln!("ERROR: cannot install anything on stage 0. Use at least stage 1.");
-                exit!(1);
+                check_stage0("install");
             }
             _ => {}
         }
@@ -1234,7 +1241,7 @@ impl Config {
             llvm_use_libcxx: llvm_use_libcxx.unwrap_or(false),
             llvm_use_linker,
             llvm_version_suffix,
-            local_rebuild: build_local_rebuild.unwrap_or(false),
+            local_rebuild,
             locked_deps: build_locked_deps.unwrap_or(false),
             low_priority: build_low_priority.unwrap_or(false),
             mandir: install_mandir.map(PathBuf::from),
@@ -1663,8 +1670,9 @@ impl Config {
 
     /// Returns the codegen backend that should be configured as the *default* codegen backend
     /// for a rustc compiled by bootstrap.
-    pub fn default_codegen_backend(&self, target: TargetSelection) -> Option<&CodegenBackendKind> {
-        self.enabled_codegen_backends(target).first()
+    pub fn default_codegen_backend(&self, target: TargetSelection) -> &CodegenBackendKind {
+        // We're guaranteed to have always at least one codegen backend listed.
+        self.enabled_codegen_backends(target).first().unwrap()
     }
 
     pub fn jemalloc(&self, target: TargetSelection) -> bool {
diff --git a/src/bootstrap/src/core/config/toml/rust.rs b/src/bootstrap/src/core/config/toml/rust.rs
index 7f111094c3f..c54df456d52 100644
--- a/src/bootstrap/src/core/config/toml/rust.rs
+++ b/src/bootstrap/src/core/config/toml/rust.rs
@@ -415,6 +415,10 @@ pub(crate) fn parse_codegen_backends(
         };
         found_backends.push(backend);
     }
+    if found_backends.is_empty() {
+        eprintln!("ERROR: `{section}.codegen-backends` should not be set to `[]`");
+        exit!(1);
+    }
     found_backends
 }
 
diff --git a/src/bootstrap/src/utils/change_tracker.rs b/src/bootstrap/src/utils/change_tracker.rs
index 073954e9337..606d88d3db4 100644
--- a/src/bootstrap/src/utils/change_tracker.rs
+++ b/src/bootstrap/src/utils/change_tracker.rs
@@ -526,4 +526,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "The `optimized-compiler-builtins` option now accepts a path to an existing compiler-rt builtins library.",
     },
+    ChangeInfo {
+        change_id: 145876,
+        severity: ChangeSeverity::Info,
+        summary: "It is now possible to `check/build/dist` the standard stage 0 library if you use a stage0 rustc built from in-tree sources. This is useful for quickly cross-compiling the standard library. You have to enable build.local-rebuild for this to work.",
+    },
 ];
diff --git a/src/ci/docker/host-x86_64/dist-aarch64-windows-gnullvm/Dockerfile b/src/ci/docker/host-x86_64/dist-aarch64-windows-gnullvm/Dockerfile
index cdbc1cda025..0bb51af817a 100644
--- a/src/ci/docker/host-x86_64/dist-aarch64-windows-gnullvm/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-aarch64-windows-gnullvm/Dockerfile
@@ -26,23 +26,10 @@ ENV CC_aarch64_pc_windows_gnullvm=aarch64-w64-mingw32-clang \
 
 ENV HOST=aarch64-pc-windows-gnullvm
 
-# We are bootstrapping this target and cannot use previously built artifacts.
-# Without this option Clang is given `"-I/checkout/obj/build/aarch64-pc-windows-gnullvm/ci-llvm/include"`
-# despite no such directory existing:
-# $ ls obj/dist-windows-gnullvm/build/aarch64-pc-windows-gnullvm/ -1
-# llvm
-# stage2
-ENV NO_DOWNLOAD_CI_LLVM 1
-
 ENV RUST_CONFIGURE_ARGS \
-    --enable-extended \
+    --enable-full-tools \
     --enable-profiler \
     --enable-sanitizers \
-    --disable-docs \
-    --set llvm.download-ci-llvm=false \
-    --set rust.llvm-tools=false
-# LLVM cross tools are not installed into expected location so copying fails.
-# Probably will solve itself once this target can host itself on Windows.
-# --enable-full-tools \
+    --disable-docs
 
 ENV SCRIPT python3 ../x.py dist --host $HOST --target $HOST
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-windows-gnullvm/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-windows-gnullvm/Dockerfile
index 1ee3951beb5..da0c065c854 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-windows-gnullvm/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-windows-gnullvm/Dockerfile
@@ -28,23 +28,10 @@ ENV CC_i686_pc_windows_gnullvm=i686-w64-mingw32-clang \
 ENV HOST=x86_64-pc-windows-gnullvm
 ENV TARGETS=i686-pc-windows-gnullvm,x86_64-pc-windows-gnullvm
 
-# We are bootstrapping this target and cannot use previously built artifacts.
-# Without this option Clang is given `"-I/checkout/obj/build/aarch64-pc-windows-gnullvm/ci-llvm/include"`
-# despite no such directory existing:
-# $ ls obj/dist-windows-gnullvm/build/aarch64-pc-windows-gnullvm/ -1
-# llvm
-# stage2
-ENV NO_DOWNLOAD_CI_LLVM 1
-
 ENV RUST_CONFIGURE_ARGS \
-    --enable-extended \
+    --enable-full-tools \
     --enable-profiler \
     --enable-sanitizers \
-    --disable-docs \
-    --set llvm.download-ci-llvm=false \
-    --set rust.llvm-tools=false
-# LLVM cross tools are not installed into expected location so copying fails.
-# Probably will solve itself once these targets can host themselves on Windows.
-# --enable-full-tools \
+    --disable-docs
 
 ENV SCRIPT python3 ../x.py dist --host $HOST --target $TARGETS
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-debug/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-debug/Dockerfile
index b97568b0819..5052d86f0ac 100644
--- a/src/ci/docker/host-x86_64/x86_64-gnu-debug/Dockerfile
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-debug/Dockerfile
@@ -38,11 +38,15 @@ ENV RUST_CONFIGURE_ARGS \
       --build=x86_64-unknown-linux-gnu \
       --enable-debug \
       --enable-lld \
+      --set rust.debuginfo-level-tests=1 \
       --set llvm.use-linker=lld \
       --set target.x86_64-unknown-linux-gnu.linker=clang \
       --set target.x86_64-unknown-linux-gnu.cc=clang \
       --set target.x86_64-unknown-linux-gnu.cxx=clang++
 
+# This job checks:
+# - That ui tests can be built with `-Cdebuginfo=1`
+
 # This job appears to be checking two separate things:
 # - That we can build the compiler with `--enable-debug`
 #   (without necessarily testing the result).
@@ -51,4 +55,5 @@ ENV RUST_CONFIGURE_ARGS \
 
 ENV SCRIPT \
   python3 ../x.py --stage 2 build && \
+  python3 ../x.py --stage 2 test tests/ui && \
   python3 ../x.py --stage 2 test tests/run-make
diff --git a/src/doc/rustc/src/platform-support.md b/src/doc/rustc/src/platform-support.md
index 22d32a29b36..2f815bcd141 100644
--- a/src/doc/rustc/src/platform-support.md
+++ b/src/doc/rustc/src/platform-support.md
@@ -328,8 +328,8 @@ target | std | host | notes
 [`i686-win7-windows-msvc`](platform-support/win7-windows-msvc.md) | ✓ |   | 32-bit Windows 7 support [^x86_32-floats-return-ABI] [^win32-msvc-alignment]
 [`i686-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  | [^x86_32-floats-return-ABI]
 [`loongarch64-unknown-linux-ohos`](platform-support/openharmony.md) | ✓ |   | LoongArch64 OpenHarmony
-[`loongarch32-unknown-none`](platform-support/loongarch-none.md) | * | LoongArch32 Bare-metal (ILP32D ABI)
-[`loongarch32-unknown-none-softfloat`](platform-support/loongarch-none.md) | * | LoongArch32 Bare-metal (ILP32S ABI)
+[`loongarch32-unknown-none`](platform-support/loongarch-none.md) | * |   | LoongArch32 Bare-metal (ILP32D ABI)
+[`loongarch32-unknown-none-softfloat`](platform-support/loongarch-none.md) | * |   | LoongArch32 Bare-metal (ILP32S ABI)
 [`m68k-unknown-linux-gnu`](platform-support/m68k-unknown-linux-gnu.md) | ? |  | Motorola 680x0 Linux
 [`m68k-unknown-none-elf`](platform-support/m68k-unknown-none-elf.md) |  |  | Motorola 680x0
 `mips-unknown-linux-gnu` | ✓ | ✓ | MIPS Linux (kernel 4.4, glibc 2.23)
diff --git a/src/tools/clippy/clippy_lints/src/missing_inline.rs b/src/tools/clippy/clippy_lints/src/missing_inline.rs
index b16924babd1..d02952eb487 100644
--- a/src/tools/clippy/clippy_lints/src/missing_inline.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_inline.rs
@@ -190,5 +190,5 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
 /// and a rustc warning would be triggered, see #15301
 fn fn_is_externally_exported(cx: &LateContext<'_>, def_id: DefId) -> bool {
     let attrs = cx.tcx.codegen_fn_attrs(def_id);
-    attrs.contains_extern_indicator(cx.tcx, def_id)
+    attrs.contains_extern_indicator()
 }
diff --git a/src/tools/miri/src/bin/miri.rs b/src/tools/miri/src/bin/miri.rs
index d9e374c414c..ae1b25f8857 100644
--- a/src/tools/miri/src/bin/miri.rs
+++ b/src/tools/miri/src/bin/miri.rs
@@ -279,7 +279,7 @@ impl rustc_driver::Callbacks for MiriBeRustCompilerCalls {
                                 return None;
                             }
                             let codegen_fn_attrs = tcx.codegen_fn_attrs(local_def_id);
-                            if codegen_fn_attrs.contains_extern_indicator(tcx, local_def_id.into())
+                            if codegen_fn_attrs.contains_extern_indicator()
                                 || codegen_fn_attrs
                                     .flags
                                     .contains(CodegenFnAttrFlags::USED_COMPILER)
diff --git a/src/tools/miri/src/helpers.rs b/src/tools/miri/src/helpers.rs
index 1b5d9d50996..e0c077e9931 100644
--- a/src/tools/miri/src/helpers.rs
+++ b/src/tools/miri/src/helpers.rs
@@ -134,8 +134,7 @@ pub fn iter_exported_symbols<'tcx>(
     for def_id in crate_items.definitions() {
         let exported = tcx.def_kind(def_id).has_codegen_attrs() && {
             let codegen_attrs = tcx.codegen_fn_attrs(def_id);
-            codegen_attrs.contains_extern_indicator(tcx, def_id.into())
-                || codegen_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
+            codegen_attrs.contains_extern_indicator()
                 || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER)
                 || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
         };