diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index b277b571829d6..78df4a8f6e02e 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -26,7 +26,8 @@
 //!   assumptions about their semantics: For `memcpy`, `memmove`, `memset`, `memcmp`, and `bcmp`, if
 //!   the `n` parameter is 0, the function is assumed to not be UB. Furthermore, for `memcpy`, if
 //!   source and target pointer are equal, the function is assumed to not be UB.
-//!   (Note that these are [standard assumptions](https://reviews.llvm.org/D86993) among compilers.)
+//!   (Note that these are standard assumptions among compilers:
+//!   [clang](https://reviews.llvm.org/D86993) and [GCC](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32667) do the same.)
 //!   These functions are often provided by the system libc, but can also be provided by the
 //!   [compiler-builtins crate](https://crates.io/crates/compiler_builtins).
 //!   Note that the library does not guarantee that it will always make these assumptions, so Rust
diff --git a/library/std/src/os/linux/fs.rs b/library/std/src/os/linux/fs.rs
index 479bbcc17a89e..ab0b2a3eda3f5 100644
--- a/library/std/src/os/linux/fs.rs
+++ b/library/std/src/os/linux/fs.rs
@@ -329,7 +329,14 @@ pub trait MetadataExt {
 impl MetadataExt for Metadata {
     #[allow(deprecated)]
     fn as_raw_stat(&self) -> &raw::stat {
-        unsafe { &*(self.as_inner().as_inner() as *const libc::stat64 as *const raw::stat) }
+        #[cfg(target_env = "musl")]
+        unsafe {
+            &*(self.as_inner().as_inner() as *const libc::stat as *const raw::stat)
+        }
+        #[cfg(not(target_env = "musl"))]
+        unsafe {
+            &*(self.as_inner().as_inner() as *const libc::stat64 as *const raw::stat)
+        }
     }
     fn st_dev(&self) -> u64 {
         self.as_inner().as_inner().st_dev as u64
diff --git a/library/std/src/sys/unix/fd.rs b/library/std/src/sys/unix/fd.rs
index 6c4f408426a94..bf1fb3123c4ce 100644
--- a/library/std/src/sys/unix/fd.rs
+++ b/library/std/src/sys/unix/fd.rs
@@ -126,9 +126,17 @@ impl FileDesc {
     }
 
     pub fn read_at(&self, buf: &mut [u8], offset: u64) -> io::Result<usize> {
-        #[cfg(not(any(target_os = "linux", target_os = "android", target_os = "hurd")))]
+        #[cfg(not(any(
+            all(target_os = "linux", not(target_env = "musl")),
+            target_os = "android",
+            target_os = "hurd"
+        )))]
         use libc::pread as pread64;
-        #[cfg(any(target_os = "linux", target_os = "android", target_os = "hurd"))]
+        #[cfg(any(
+            all(target_os = "linux", not(target_env = "musl")),
+            target_os = "android",
+            target_os = "hurd"
+        ))]
         use libc::pread64;
 
         unsafe {
@@ -285,9 +293,17 @@ impl FileDesc {
     }
 
     pub fn write_at(&self, buf: &[u8], offset: u64) -> io::Result<usize> {
-        #[cfg(not(any(target_os = "linux", target_os = "android", target_os = "hurd")))]
+        #[cfg(not(any(
+            all(target_os = "linux", not(target_env = "musl")),
+            target_os = "android",
+            target_os = "hurd"
+        )))]
         use libc::pwrite as pwrite64;
-        #[cfg(any(target_os = "linux", target_os = "android", target_os = "hurd"))]
+        #[cfg(any(
+            all(target_os = "linux", not(target_env = "musl")),
+            target_os = "android",
+            target_os = "hurd"
+        ))]
         use libc::pwrite64;
 
         unsafe {
diff --git a/library/std/src/sys/unix/fs.rs b/library/std/src/sys/unix/fs.rs
index e1c58f2ba3c37..40eb910fdc388 100644
--- a/library/std/src/sys/unix/fs.rs
+++ b/library/std/src/sys/unix/fs.rs
@@ -40,13 +40,17 @@ use libc::{c_int, mode_t};
 ))]
 use libc::c_char;
 #[cfg(any(
-    target_os = "linux",
+    all(target_os = "linux", not(target_env = "musl")),
     target_os = "emscripten",
     target_os = "android",
-    target_os = "hurd",
+    target_os = "hurd"
 ))]
 use libc::dirfd;
-#[cfg(any(target_os = "linux", target_os = "emscripten", target_os = "hurd"))]
+#[cfg(any(
+    all(target_os = "linux", not(target_env = "musl")),
+    target_os = "emscripten",
+    target_os = "hurd"
+))]
 use libc::fstatat64;
 #[cfg(any(
     target_os = "android",
@@ -57,9 +61,10 @@ use libc::fstatat64;
     target_os = "aix",
     target_os = "nto",
     target_os = "vita",
+    all(target_os = "linux", target_env = "musl"),
 ))]
 use libc::readdir as readdir64;
-#[cfg(any(target_os = "linux", target_os = "hurd"))]
+#[cfg(any(all(target_os = "linux", not(target_env = "musl")), target_os = "hurd"))]
 use libc::readdir64;
 #[cfg(any(target_os = "emscripten", target_os = "l4re"))]
 use libc::readdir64_r;
@@ -84,7 +89,7 @@ use libc::{
     lstat as lstat64, off64_t, open as open64, stat as stat64,
 };
 #[cfg(not(any(
-    target_os = "linux",
+    all(target_os = "linux", not(target_env = "musl")),
     target_os = "emscripten",
     target_os = "l4re",
     target_os = "android",
@@ -95,7 +100,7 @@ use libc::{
     lstat as lstat64, off_t as off64_t, open as open64, stat as stat64,
 };
 #[cfg(any(
-    target_os = "linux",
+    all(target_os = "linux", not(target_env = "musl")),
     target_os = "emscripten",
     target_os = "l4re",
     target_os = "hurd"
@@ -853,10 +858,10 @@ impl DirEntry {
 
     #[cfg(all(
         any(
-            target_os = "linux",
+            all(target_os = "linux", not(target_env = "musl")),
             target_os = "emscripten",
             target_os = "android",
-            target_os = "hurd",
+            target_os = "hurd"
         ),
         not(miri)
     ))]
@@ -882,7 +887,7 @@ impl DirEntry {
 
     #[cfg(any(
         not(any(
-            target_os = "linux",
+            all(target_os = "linux", not(target_env = "musl")),
             target_os = "emscripten",
             target_os = "android",
             target_os = "hurd",
diff --git a/src/bootstrap/src/core/build_steps/dist.rs b/src/bootstrap/src/core/build_steps/dist.rs
index b578c5ec29500..197ce78d8859c 100644
--- a/src/bootstrap/src/core/build_steps/dist.rs
+++ b/src/bootstrap/src/core/build_steps/dist.rs
@@ -1305,6 +1305,10 @@ impl Step for CodegenBackend {
             return None;
         }
 
+        if !builder.config.rust_codegen_backends.contains(&self.backend) {
+            return None;
+        }
+
         if self.backend == "cranelift" {
             if !target_supports_cranelift_backend(self.compiler.host) {
                 builder.info("target not supported by rustc_codegen_cranelift. skipping");
@@ -1343,12 +1347,15 @@ impl Step for CodegenBackend {
         let backends_dst = PathBuf::from("lib").join(&backends_rel);
 
         let backend_name = format!("rustc_codegen_{}", backend);
+        let mut found_backend = false;
         for backend in fs::read_dir(&backends_src).unwrap() {
             let file_name = backend.unwrap().file_name();
             if file_name.to_str().unwrap().contains(&backend_name) {
                 tarball.add_file(backends_src.join(file_name), &backends_dst, 0o644);
+                found_backend = true;
             }
         }
+        assert!(found_backend);
 
         Some(tarball.generate())
     }
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 5b5334b0a5572..f56e46010f371 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -1274,8 +1274,9 @@ impl Config {
         }
 
         config.initial_rustc = if let Some(rustc) = build.rustc {
-            // FIXME(#115065): re-enable this check
-            // config.check_build_rustc_version(&rustc);
+            if !flags.skip_stage0_validation {
+                config.check_build_rustc_version(&rustc);
+            }
             PathBuf::from(rustc)
         } else {
             config.download_beta_toolchain();
diff --git a/src/bootstrap/src/core/config/flags.rs b/src/bootstrap/src/core/config/flags.rs
index dea5530354494..64af114f998ea 100644
--- a/src/bootstrap/src/core/config/flags.rs
+++ b/src/bootstrap/src/core/config/flags.rs
@@ -155,6 +155,9 @@ pub struct Flags {
     /// Enable BOLT link flags
     #[arg(global(true), long)]
     pub enable_bolt_settings: bool,
+    /// Skip stage0 compiler validation
+    #[arg(global(true), long)]
+    pub skip_stage0_validation: bool,
     /// Additional reproducible artifacts that should be added to the reproducible artifacts archive.
     #[arg(global(true), long)]
     pub reproducible_artifact: Vec<String>,
diff --git a/src/ci/docker/run.sh b/src/ci/docker/run.sh
index 99e3ce199f451..0b535532f695b 100755
--- a/src/ci/docker/run.sh
+++ b/src/ci/docker/run.sh
@@ -288,6 +288,7 @@ docker \
   --env DIST_TRY_BUILD \
   --env PR_CI_JOB \
   --env OBJDIR_ON_HOST="$objdir" \
+  --env CODEGEN_BACKENDS \
   --init \
   --rm \
   rust-ci \
diff --git a/src/etc/completions/x.py.fish b/src/etc/completions/x.py.fish
index 85fcc37fd8163..48796988868ed 100644
--- a/src/etc/completions/x.py.fish
+++ b/src/etc/completions/x.py.fish
@@ -28,6 +28,7 @@ complete -c x.py -n "__fish_use_subcommand" -l dry-run -d 'dry run; don\'t build
 complete -c x.py -n "__fish_use_subcommand" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_use_subcommand" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_use_subcommand" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_use_subcommand" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_use_subcommand" -s h -l help -d 'Print help'
 complete -c x.py -n "__fish_use_subcommand" -f -a "build" -d 'Compile either the compiler or libraries'
 complete -c x.py -n "__fish_use_subcommand" -f -a "check" -d 'Compile either the compiler or libraries, using cargo check'
@@ -73,6 +74,7 @@ complete -c x.py -n "__fish_seen_subcommand_from build" -l dry-run -d 'dry run;
 complete -c x.py -n "__fish_seen_subcommand_from build" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from build" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from build" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from build" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from build" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from check" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from check" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -105,6 +107,7 @@ complete -c x.py -n "__fish_seen_subcommand_from check" -l dry-run -d 'dry run;
 complete -c x.py -n "__fish_seen_subcommand_from check" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from check" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from check" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from check" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from check" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from clippy" -s A -d 'clippy lints to allow' -r
 complete -c x.py -n "__fish_seen_subcommand_from clippy" -s D -d 'clippy lints to deny' -r
@@ -141,6 +144,7 @@ complete -c x.py -n "__fish_seen_subcommand_from clippy" -l dry-run -d 'dry run;
 complete -c x.py -n "__fish_seen_subcommand_from clippy" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from clippy" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from clippy" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from clippy" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from clippy" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from fix" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from fix" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -172,6 +176,7 @@ complete -c x.py -n "__fish_seen_subcommand_from fix" -l dry-run -d 'dry run; do
 complete -c x.py -n "__fish_seen_subcommand_from fix" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from fix" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from fix" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from fix" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from fix" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from fmt" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from fmt" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -204,6 +209,7 @@ complete -c x.py -n "__fish_seen_subcommand_from fmt" -l dry-run -d 'dry run; do
 complete -c x.py -n "__fish_seen_subcommand_from fmt" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from fmt" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from fmt" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from fmt" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from fmt" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from doc" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from doc" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -237,6 +243,7 @@ complete -c x.py -n "__fish_seen_subcommand_from doc" -l dry-run -d 'dry run; do
 complete -c x.py -n "__fish_seen_subcommand_from doc" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from doc" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from doc" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from doc" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from doc" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from test" -l skip -d 'skips tests matching SUBSTRING, if supported by test tool. May be passed multiple times' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from test" -l test-args -d 'extra arguments to be passed for the test tool being used (e.g. libtest, compiletest or rustdoc)' -r
@@ -281,6 +288,7 @@ complete -c x.py -n "__fish_seen_subcommand_from test" -l dry-run -d 'dry run; d
 complete -c x.py -n "__fish_seen_subcommand_from test" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from test" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from test" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from test" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from test" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from bench" -l test-args -r
 complete -c x.py -n "__fish_seen_subcommand_from bench" -l config -d 'TOML configuration file for build' -r -F
@@ -313,6 +321,7 @@ complete -c x.py -n "__fish_seen_subcommand_from bench" -l dry-run -d 'dry run;
 complete -c x.py -n "__fish_seen_subcommand_from bench" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from bench" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from bench" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from bench" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from bench" -s h -l help -d 'Print help'
 complete -c x.py -n "__fish_seen_subcommand_from clean" -l stage -d 'Clean a specific stage without touching other artifacts. By default, every stage is cleaned if this option is not used' -r
 complete -c x.py -n "__fish_seen_subcommand_from clean" -l config -d 'TOML configuration file for build' -r -F
@@ -345,6 +354,7 @@ complete -c x.py -n "__fish_seen_subcommand_from clean" -l dry-run -d 'dry run;
 complete -c x.py -n "__fish_seen_subcommand_from clean" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from clean" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from clean" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from clean" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from clean" -s h -l help -d 'Print help'
 complete -c x.py -n "__fish_seen_subcommand_from dist" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from dist" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -376,6 +386,7 @@ complete -c x.py -n "__fish_seen_subcommand_from dist" -l dry-run -d 'dry run; d
 complete -c x.py -n "__fish_seen_subcommand_from dist" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from dist" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from dist" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from dist" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from dist" -s h -l help -d 'Print help'
 complete -c x.py -n "__fish_seen_subcommand_from install" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from install" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -407,6 +418,7 @@ complete -c x.py -n "__fish_seen_subcommand_from install" -l dry-run -d 'dry run
 complete -c x.py -n "__fish_seen_subcommand_from install" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from install" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from install" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from install" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from install" -s h -l help -d 'Print help'
 complete -c x.py -n "__fish_seen_subcommand_from run" -l args -d 'arguments for the tool' -r
 complete -c x.py -n "__fish_seen_subcommand_from run" -l config -d 'TOML configuration file for build' -r -F
@@ -439,6 +451,7 @@ complete -c x.py -n "__fish_seen_subcommand_from run" -l dry-run -d 'dry run; do
 complete -c x.py -n "__fish_seen_subcommand_from run" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from run" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from run" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from run" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from run" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from setup" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from setup" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -470,6 +483,7 @@ complete -c x.py -n "__fish_seen_subcommand_from setup" -l dry-run -d 'dry run;
 complete -c x.py -n "__fish_seen_subcommand_from setup" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from setup" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from setup" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from setup" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from setup" -s h -l help -d 'Print help (see more with \'--help\')'
 complete -c x.py -n "__fish_seen_subcommand_from suggest" -l config -d 'TOML configuration file for build' -r -F
 complete -c x.py -n "__fish_seen_subcommand_from suggest" -l build-dir -d 'Build directory, overrides `build.build-dir` in `config.toml`' -r -f -a "(__fish_complete_directories)"
@@ -502,4 +516,5 @@ complete -c x.py -n "__fish_seen_subcommand_from suggest" -l dry-run -d 'dry run
 complete -c x.py -n "__fish_seen_subcommand_from suggest" -l json-output -d 'use message-format=json'
 complete -c x.py -n "__fish_seen_subcommand_from suggest" -l llvm-profile-generate -d 'generate PGO profile with llvm built for rustc'
 complete -c x.py -n "__fish_seen_subcommand_from suggest" -l enable-bolt-settings -d 'Enable BOLT link flags'
+complete -c x.py -n "__fish_seen_subcommand_from suggest" -l skip-stage0-validation -d 'Skip stage0 compiler validation'
 complete -c x.py -n "__fish_seen_subcommand_from suggest" -s h -l help -d 'Print help (see more with \'--help\')'
diff --git a/src/etc/completions/x.py.ps1 b/src/etc/completions/x.py.ps1
index 07e1b0ace9da2..2fed1be726925 100644
--- a/src/etc/completions/x.py.ps1
+++ b/src/etc/completions/x.py.ps1
@@ -54,6 +54,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
             [CompletionResult]::new('build', 'build', [CompletionResultType]::ParameterValue, 'Compile either the compiler or libraries')
@@ -106,6 +107,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -145,6 +147,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -188,6 +191,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -226,6 +230,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -265,6 +270,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -305,6 +311,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -356,6 +363,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -395,6 +403,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
             break
@@ -434,6 +443,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
             break
@@ -472,6 +482,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
             break
@@ -510,6 +521,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
             break
@@ -549,6 +561,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -587,6 +600,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
@@ -626,6 +640,7 @@ Register-ArgumentCompleter -Native -CommandName 'x.py' -ScriptBlock {
             [CompletionResult]::new('--json-output', 'json-output', [CompletionResultType]::ParameterName, 'use message-format=json')
             [CompletionResult]::new('--llvm-profile-generate', 'llvm-profile-generate', [CompletionResultType]::ParameterName, 'generate PGO profile with llvm built for rustc')
             [CompletionResult]::new('--enable-bolt-settings', 'enable-bolt-settings', [CompletionResultType]::ParameterName, 'Enable BOLT link flags')
+            [CompletionResult]::new('--skip-stage0-validation', 'skip-stage0-validation', [CompletionResultType]::ParameterName, 'Skip stage0 compiler validation')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help (see more with ''--help'')')
             break
diff --git a/src/etc/completions/x.py.sh b/src/etc/completions/x.py.sh
index 241bc058e7be2..f22d7e3e131da 100644
--- a/src/etc/completions/x.py.sh
+++ b/src/etc/completions/x.py.sh
@@ -61,7 +61,7 @@ _x.py() {
 
     case "${cmd}" in
         x.py)
-            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]... build check clippy fix fmt doc test bench clean dist install run setup suggest"
+            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]... build check clippy fix fmt doc test bench clean dist install run setup suggest"
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 1 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -171,7 +171,7 @@ _x.py() {
             return 0
             ;;
         x.py__bench)
-            opts="-v -i -j -h --test-args --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --test-args --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -285,7 +285,7 @@ _x.py() {
             return 0
             ;;
         x.py__build)
-            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -395,7 +395,7 @@ _x.py() {
             return 0
             ;;
         x.py__check)
-            opts="-v -i -j -h --all-targets --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --all-targets --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -505,7 +505,7 @@ _x.py() {
             return 0
             ;;
         x.py__clean)
-            opts="-v -i -j -h --all --stage --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --all --stage --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -615,7 +615,7 @@ _x.py() {
             return 0
             ;;
         x.py__clippy)
-            opts="-A -D -W -F -v -i -j -h --fix --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-A -D -W -F -v -i -j -h --fix --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -741,7 +741,7 @@ _x.py() {
             return 0
             ;;
         x.py__dist)
-            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -851,7 +851,7 @@ _x.py() {
             return 0
             ;;
         x.py__doc)
-            opts="-v -i -j -h --open --json --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --open --json --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -961,7 +961,7 @@ _x.py() {
             return 0
             ;;
         x.py__fix)
-            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -1071,7 +1071,7 @@ _x.py() {
             return 0
             ;;
         x.py__fmt)
-            opts="-v -i -j -h --check --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --check --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -1181,7 +1181,7 @@ _x.py() {
             return 0
             ;;
         x.py__install)
-            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -1291,7 +1291,7 @@ _x.py() {
             return 0
             ;;
         x.py__run)
-            opts="-v -i -j -h --args --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --args --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -1405,7 +1405,7 @@ _x.py() {
             return 0
             ;;
         x.py__setup)
-            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [<PROFILE>|hook|vscode|link] [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [<PROFILE>|hook|vscode|link] [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -1515,7 +1515,7 @@ _x.py() {
             return 0
             ;;
         x.py__suggest)
-            opts="-v -i -j -h --run --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --run --verbose --incremental --config --build-dir --build --host --target --exclude --skip --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
@@ -1625,7 +1625,7 @@ _x.py() {
             return 0
             ;;
         x.py__test)
-            opts="-v -i -j -h --no-fail-fast --skip --test-args --rustc-args --no-doc --doc --bless --extra-checks --force-rerun --only-modified --compare-mode --pass --run --rustfix-coverage --verbose --incremental --config --build-dir --build --host --target --exclude --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --reproducible-artifact --set --help [PATHS]... [ARGS]..."
+            opts="-v -i -j -h --no-fail-fast --skip --test-args --rustc-args --no-doc --doc --bless --extra-checks --force-rerun --only-modified --compare-mode --pass --run --rustfix-coverage --verbose --incremental --config --build-dir --build --host --target --exclude --include-default-paths --rustc-error-format --on-fail --dry-run --stage --keep-stage --keep-stage-std --src --jobs --warnings --error-format --json-output --color --llvm-skip-rebuild --rust-profile-generate --rust-profile-use --llvm-profile-use --llvm-profile-generate --enable-bolt-settings --skip-stage0-validation --reproducible-artifact --set --help [PATHS]... [ARGS]..."
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 2 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
diff --git a/src/etc/completions/x.py.zsh b/src/etc/completions/x.py.zsh
index 89959701a062e..1e5a7b5aa8967 100644
--- a/src/etc/completions/x.py.zsh
+++ b/src/etc/completions/x.py.zsh
@@ -48,6 +48,7 @@ _x.py() {
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help]' \
 '--help[Print help]' \
 '::paths -- paths for the subcommand:_files' \
@@ -96,6 +97,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -137,6 +139,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -182,6 +185,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -222,6 +226,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -263,6 +268,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -305,6 +311,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -358,6 +365,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -399,6 +407,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help]' \
 '--help[Print help]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -440,6 +449,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help]' \
 '--help[Print help]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -480,6 +490,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help]' \
 '--help[Print help]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -520,6 +531,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help]' \
 '--help[Print help]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -561,6 +573,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
@@ -601,6 +614,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '::profile -- Either the profile for `config.toml` or another setup action. May be omitted to set up interactively:_files' \
@@ -643,6 +657,7 @@ _arguments "${_arguments_options[@]}" \
 '--json-output[use message-format=json]' \
 '--llvm-profile-generate[generate PGO profile with llvm built for rustc]' \
 '--enable-bolt-settings[Enable BOLT link flags]' \
+'--skip-stage0-validation[Skip stage0 compiler validation]' \
 '-h[Print help (see more with '\''--help'\'')]' \
 '--help[Print help (see more with '\''--help'\'')]' \
 '*::paths -- paths for the subcommand:_files' \
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index f2447b877ca80..4d4c102e69eaa 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -498,7 +498,7 @@ fn clean_generic_param_def<'tcx>(
 ) -> GenericParamDef {
     let (name, kind) = match def.kind {
         ty::GenericParamDefKind::Lifetime => {
-            (def.name, GenericParamDefKind::Lifetime { outlives: vec![] })
+            (def.name, GenericParamDefKind::Lifetime { outlives: ThinVec::new() })
         }
         ty::GenericParamDefKind::Type { has_default, synthetic, .. } => {
             let default = if has_default {
@@ -515,7 +515,7 @@ fn clean_generic_param_def<'tcx>(
                 def.name,
                 GenericParamDefKind::Type {
                     did: def.def_id,
-                    bounds: vec![], // These are filled in from the where-clauses.
+                    bounds: ThinVec::new(), // These are filled in from the where-clauses.
                     default: default.map(Box::new),
                     synthetic,
                 },
@@ -567,7 +567,7 @@ fn clean_generic_param<'tcx>(
                     })
                     .collect()
             } else {
-                Vec::new()
+                ThinVec::new()
             };
             (param.name.ident().name, GenericParamDefKind::Lifetime { outlives })
         }
@@ -580,7 +580,7 @@ fn clean_generic_param<'tcx>(
                     .filter_map(|x| clean_generic_bound(x, cx))
                     .collect()
             } else {
-                Vec::new()
+                ThinVec::new()
             };
             (
                 param.name.ident().name,
@@ -636,7 +636,7 @@ pub(crate) fn clean_generics<'tcx>(
             match param.kind {
                 GenericParamDefKind::Lifetime { .. } => unreachable!(),
                 GenericParamDefKind::Type { did, ref bounds, .. } => {
-                    cx.impl_trait_bounds.insert(did.into(), bounds.clone());
+                    cx.impl_trait_bounds.insert(did.into(), bounds.to_vec());
                 }
                 GenericParamDefKind::Const { .. } => unreachable!(),
             }
@@ -3146,7 +3146,7 @@ fn clean_bound_vars<'tcx>(
                 name,
                 kind: GenericParamDefKind::Type {
                     did,
-                    bounds: Vec::new(),
+                    bounds: ThinVec::new(),
                     default: None,
                     synthetic: false,
                 },
diff --git a/src/librustdoc/clean/simplify.rs b/src/librustdoc/clean/simplify.rs
index eea8c1906c5b5..627f15e67ac30 100644
--- a/src/librustdoc/clean/simplify.rs
+++ b/src/librustdoc/clean/simplify.rs
@@ -145,7 +145,7 @@ pub(crate) fn move_bounds_to_generic_parameters(generics: &mut clean::Generics)
                 ..
             }) = generics.params.iter_mut().find(|param| &param.name == arg)
         {
-            param_bounds.append(bounds);
+            param_bounds.extend(bounds.drain(..));
         } else if let WherePredicate::RegionPredicate { lifetime: Lifetime(arg), bounds } = &mut pred
             && let Some(GenericParamDef {
                 kind: GenericParamDefKind::Lifetime { outlives: param_bounds },
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index 449aac4cfc8b7..455228d04efa7 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1325,8 +1325,8 @@ impl WherePredicate {
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub(crate) enum GenericParamDefKind {
-    Lifetime { outlives: Vec<Lifetime> },
-    Type { did: DefId, bounds: Vec<GenericBound>, default: Option<Box<Type>>, synthetic: bool },
+    Lifetime { outlives: ThinVec<Lifetime> },
+    Type { did: DefId, bounds: ThinVec<GenericBound>, default: Option<Box<Type>>, synthetic: bool },
     Const { ty: Box<Type>, default: Option<Box<String>>, is_host_effect: bool },
 }
 
@@ -1344,7 +1344,7 @@ pub(crate) struct GenericParamDef {
 
 impl GenericParamDef {
     pub(crate) fn lifetime(name: Symbol) -> Self {
-        Self { name, kind: GenericParamDefKind::Lifetime { outlives: Vec::new() } }
+        Self { name, kind: GenericParamDefKind::Lifetime { outlives: ThinVec::new() } }
     }
 
     pub(crate) fn is_synthetic_param(&self) -> bool {
@@ -2521,7 +2521,7 @@ mod size_asserts {
     static_assert_size!(DocFragment, 32);
     static_assert_size!(GenericArg, 32);
     static_assert_size!(GenericArgs, 32);
-    static_assert_size!(GenericParamDef, 56);
+    static_assert_size!(GenericParamDef, 40);
     static_assert_size!(Generics, 16);
     static_assert_size!(Item, 56);
     static_assert_size!(ItemKind, 56);
diff --git a/tests/assembly/closure-inherit-target-feature.rs b/tests/assembly/closure-inherit-target-feature.rs
index 248026034526a..7acda76e25f0e 100644
--- a/tests/assembly/closure-inherit-target-feature.rs
+++ b/tests/assembly/closure-inherit-target-feature.rs
@@ -1,4 +1,5 @@
 // only-x86_64
+// ignore-sgx Tests incompatible with LVI mitigations
 // assembly-output: emit-asm
 // make sure the feature is not enabled at compile-time
 // compile-flags: -C opt-level=3 -C target-feature=-sse4.1 -C llvm-args=-x86-asm-syntax=intel