Auto merge of #3892 - rust-lang:rustup-2024-09-16, r=RalfJung

Automatic Rustup

42 files changed, 795 insertions, 320 deletions

diff --git a/src/bootstrap/defaults/config.library.toml b/src/bootstrap/defaults/config.library.toml
index 087544397f5..5447565a4b0 100644
--- a/src/bootstrap/defaults/config.library.toml
+++ b/src/bootstrap/defaults/config.library.toml
@@ -13,4 +13,5 @@ lto = "off"
 
 [llvm]
 # Will download LLVM from CI if available on your platform.
-download-ci-llvm = "if-unchanged"
+# If you intend to modify `src/llvm-project`, use `"if-unchanged"` or `false` instead.
+download-ci-llvm = true
diff --git a/src/bootstrap/defaults/config.tools.toml b/src/bootstrap/defaults/config.tools.toml
index 75ad37ce335..efb56996bcd 100644
--- a/src/bootstrap/defaults/config.tools.toml
+++ b/src/bootstrap/defaults/config.tools.toml
@@ -17,4 +17,5 @@ compiler-docs = true
 
 [llvm]
 # Will download LLVM from CI if available on your platform.
-download-ci-llvm = "if-unchanged"
+# If you intend to modify `src/llvm-project`, use `"if-unchanged"` or `false` instead.
+download-ci-llvm = true
diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index bb07d478f71..e1ab1e7599e 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -1760,6 +1760,49 @@ impl Step for Assemble {
             return target_compiler;
         }
 
+        // We prepend this bin directory to the user PATH when linking Rust binaries. To
+        // avoid shadowing the system LLD we rename the LLD we provide to `rust-lld`.
+        let libdir = builder.sysroot_libdir(target_compiler, target_compiler.host);
+        let libdir_bin = libdir.parent().unwrap().join("bin");
+        t!(fs::create_dir_all(&libdir_bin));
+
+        if builder.config.llvm_enabled(target_compiler.host) {
+            let llvm::LlvmResult { llvm_config, .. } =
+                builder.ensure(llvm::Llvm { target: target_compiler.host });
+            if !builder.config.dry_run() && builder.config.llvm_tools_enabled {
+                let llvm_bin_dir =
+                    command(llvm_config).arg("--bindir").run_capture_stdout(builder).stdout();
+                let llvm_bin_dir = Path::new(llvm_bin_dir.trim());
+
+                // Since we've already built the LLVM tools, install them to the sysroot.
+                // This is the equivalent of installing the `llvm-tools-preview` component via
+                // rustup, and lets developers use a locally built toolchain to
+                // build projects that expect llvm tools to be present in the sysroot
+                // (e.g. the `bootimage` crate).
+                for tool in LLVM_TOOLS {
+                    let tool_exe = exe(tool, target_compiler.host);
+                    let src_path = llvm_bin_dir.join(&tool_exe);
+                    // When using `download-ci-llvm`, some of the tools
+                    // may not exist, so skip trying to copy them.
+                    if src_path.exists() {
+                        builder.copy_link(&src_path, &libdir_bin.join(&tool_exe));
+                    }
+                }
+            }
+        }
+
+        let maybe_install_llvm_bitcode_linker = |compiler| {
+            if builder.config.llvm_bitcode_linker_enabled {
+                let src_path = builder.ensure(crate::core::build_steps::tool::LlvmBitcodeLinker {
+                    compiler,
+                    target: target_compiler.host,
+                    extra_features: vec![],
+                });
+                let tool_exe = exe("llvm-bitcode-linker", target_compiler.host);
+                builder.copy_link(&src_path, &libdir_bin.join(tool_exe));
+            }
+        };
+
         // If we're downloading a compiler from CI, we can use the same compiler for all stages other than 0.
         if builder.download_rustc() {
             builder.ensure(Std::new(target_compiler, target_compiler.host));
@@ -1772,6 +1815,9 @@ impl Step for Assemble {
             if target_compiler.stage == builder.top_stage {
                 builder.info(&format!("Creating a sysroot for stage{stage} compiler (use `rustup toolchain link 'name' build/host/stage{stage}`)", stage=target_compiler.stage));
             }
+
+            maybe_install_llvm_bitcode_linker(target_compiler);
+
             return target_compiler;
         }
 
@@ -1880,11 +1926,6 @@ impl Step for Assemble {
 
         copy_codegen_backends_to_sysroot(builder, build_compiler, target_compiler);
 
-        // We prepend this bin directory to the user PATH when linking Rust binaries. To
-        // avoid shadowing the system LLD we rename the LLD we provide to `rust-lld`.
-        let libdir = builder.sysroot_libdir(target_compiler, target_compiler.host);
-        let libdir_bin = libdir.parent().unwrap().join("bin");
-        t!(fs::create_dir_all(&libdir_bin));
         if let Some(lld_install) = lld_install {
             let src_exe = exe("lld", target_compiler.host);
             let dst_exe = exe("rust-lld", target_compiler.host);
@@ -1920,40 +1961,7 @@ impl Step for Assemble {
             );
         }
 
-        if builder.config.llvm_enabled(target_compiler.host) {
-            let llvm::LlvmResult { llvm_config, .. } =
-                builder.ensure(llvm::Llvm { target: target_compiler.host });
-            if !builder.config.dry_run() && builder.config.llvm_tools_enabled {
-                let llvm_bin_dir =
-                    command(llvm_config).arg("--bindir").run_capture_stdout(builder).stdout();
-                let llvm_bin_dir = Path::new(llvm_bin_dir.trim());
-
-                // Since we've already built the LLVM tools, install them to the sysroot.
-                // This is the equivalent of installing the `llvm-tools-preview` component via
-                // rustup, and lets developers use a locally built toolchain to
-                // build projects that expect llvm tools to be present in the sysroot
-                // (e.g. the `bootimage` crate).
-                for tool in LLVM_TOOLS {
-                    let tool_exe = exe(tool, target_compiler.host);
-                    let src_path = llvm_bin_dir.join(&tool_exe);
-                    // When using `download-ci-llvm`, some of the tools
-                    // may not exist, so skip trying to copy them.
-                    if src_path.exists() {
-                        builder.copy_link(&src_path, &libdir_bin.join(&tool_exe));
-                    }
-                }
-            }
-        }
-
-        if builder.config.llvm_bitcode_linker_enabled {
-            let src_path = builder.ensure(crate::core::build_steps::tool::LlvmBitcodeLinker {
-                compiler: build_compiler,
-                target: target_compiler.host,
-                extra_features: vec![],
-            });
-            let tool_exe = exe("llvm-bitcode-linker", target_compiler.host);
-            builder.copy_link(&src_path, &libdir_bin.join(tool_exe));
-        }
+        maybe_install_llvm_bitcode_linker(build_compiler);
 
         // Ensure that `libLLVM.so` ends up in the newly build compiler directory,
         // so that it can be found when the newly built `rustc` is run.
diff --git a/src/bootstrap/src/core/build_steps/dist.rs b/src/bootstrap/src/core/build_steps/dist.rs
index b0bd18792be..294a56b3e97 100644
--- a/src/bootstrap/src/core/build_steps/dist.rs
+++ b/src/bootstrap/src/core/build_steps/dist.rs
@@ -1011,11 +1011,7 @@ impl Step for PlainSourceTarball {
         write_git_info(builder.rust_info().info(), plain_dst_src);
         write_git_info(builder.cargo_info.info(), &plain_dst_src.join("./src/tools/cargo"));
 
-        // If we're building from git or tarball sources, we need to vendor
-        // a complete distribution.
-        if builder.rust_info().is_managed_git_subrepository()
-            || builder.rust_info().is_from_tarball()
-        {
+        if builder.config.dist_vendor {
             builder.require_and_update_all_submodules();
 
             // Vendor all Cargo dependencies
diff --git a/src/bootstrap/src/core/config/config.rs b/src/bootstrap/src/core/config/config.rs
index 9271e809853..555a6a7f8bd 100644
--- a/src/bootstrap/src/core/config/config.rs
+++ b/src/bootstrap/src/core/config/config.rs
@@ -308,6 +308,7 @@ pub struct Config {
     pub dist_compression_formats: Option<Vec<String>>,
     pub dist_compression_profile: String,
     pub dist_include_mingw_linker: bool,
+    pub dist_vendor: bool,
 
     // libstd features
     pub backtrace: bool, // support for RUST_BACKTRACE
@@ -933,6 +934,7 @@ define_config! {
         compression_formats: Option<Vec<String>> = "compression-formats",
         compression_profile: Option<String> = "compression-profile",
         include_mingw_linker: Option<bool> = "include-mingw-linker",
+        vendor: Option<bool> = "vendor",
     }
 }
 
@@ -2028,13 +2030,19 @@ impl Config {
                 compression_formats,
                 compression_profile,
                 include_mingw_linker,
+                vendor,
             } = dist;
             config.dist_sign_folder = sign_folder.map(PathBuf::from);
             config.dist_upload_addr = upload_addr;
             config.dist_compression_formats = compression_formats;
             set(&mut config.dist_compression_profile, compression_profile);
             set(&mut config.rust_dist_src, src_tarball);
-            set(&mut config.dist_include_mingw_linker, include_mingw_linker)
+            set(&mut config.dist_include_mingw_linker, include_mingw_linker);
+            config.dist_vendor = vendor.unwrap_or_else(|| {
+                // If we're building from git or tarball sources, enable it by default.
+                config.rust_info.is_managed_git_subrepository()
+                    || config.rust_info.is_from_tarball()
+            });
         }
 
         if let Some(r) = rustfmt {
@@ -2739,6 +2747,8 @@ impl Config {
                 return false;
             }
 
+            // Fetching the LLVM submodule is unnecessary for self-tests.
+            #[cfg(not(feature = "bootstrap-self-test"))]
             self.update_submodule("src/llvm-project");
 
             // Check for untracked changes in `src/llvm-project`.
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index b339905cce1..df2acd8b76b 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -349,10 +349,14 @@ impl Build {
         };
         let Some(initial_libdir) = find_initial_libdir() else {
             panic!(
-                "couldn't determine `initial_libdir` \
-                from target dir {initial_target_dir:?} \
-                and sysroot {initial_sysroot:?}"
-            )
+                "couldn't determine `initial_libdir`:
+- config.initial_rustc:      {rustc:?}
+- initial_target_libdir_str: {initial_target_libdir_str:?}
+- initial_target_dir:        {initial_target_dir:?}
+- initial_sysroot:           {initial_sysroot:?}
+",
+                rustc = config.initial_rustc,
+            );
         };
 
         let version = std::fs::read_to_string(src.join("src").join("version"))
diff --git a/src/bootstrap/src/utils/change_tracker.rs b/src/bootstrap/src/utils/change_tracker.rs
index 99bcc6e0787..379cd568647 100644
--- a/src/bootstrap/src/utils/change_tracker.rs
+++ b/src/bootstrap/src/utils/change_tracker.rs
@@ -255,4 +255,14 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Warning,
         summary: "`download-ci-llvm = true` now checks if CI llvm is available and has become the default for the compiler profile",
     },
+    ChangeInfo {
+        change_id: 130202,
+        severity: ChangeSeverity::Info,
+        summary: "'tools' and 'library' profiles switched `download-ci-llvm` option from `if-unchanged` to `true`.",
+    },
+    ChangeInfo {
+        change_id: 130110,
+        severity: ChangeSeverity::Info,
+        summary: "New option `dist.vendor` added to control whether bootstrap should vendor dependencies for dist tarball.",
+    },
 ];
diff --git a/src/ci/docker/host-x86_64/x86_64-gnu-llvm-19/Dockerfile b/src/ci/docker/host-x86_64/x86_64-gnu-llvm-19/Dockerfile
new file mode 100644
index 00000000000..44328b078ad
--- /dev/null
+++ b/src/ci/docker/host-x86_64/x86_64-gnu-llvm-19/Dockerfile
@@ -0,0 +1,62 @@
+FROM ubuntu:24.10
+
+ARG DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+  g++ \
+  gcc-multilib \
+  make \
+  ninja-build \
+  file \
+  curl \
+  ca-certificates \
+  python3 \
+  git \
+  cmake \
+  sudo \
+  gdb \
+  llvm-19-tools \
+  llvm-19-dev \
+  libedit-dev \
+  libssl-dev \
+  pkg-config \
+  zlib1g-dev \
+  xz-utils \
+  nodejs \
+  mingw-w64 \
+  # libgccjit dependencies
+  flex \
+  libmpfr-dev \
+  libgmp-dev \
+  libmpc3 \
+  libmpc-dev \
+  && rm -rf /var/lib/apt/lists/*
+
+# Install powershell (universal package) so we can test x.ps1 on Linux
+# FIXME: need a "universal" version that supports libicu74, but for now it still works to ignore that dep.
+RUN curl -sL "https://github.com/PowerShell/PowerShell/releases/download/v7.3.1/powershell_7.3.1-1.deb_amd64.deb" > powershell.deb && \
+    dpkg --ignore-depends=libicu72 -i powershell.deb && \
+    rm -f powershell.deb
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+# We are disabling CI LLVM since this builder is intentionally using a host
+# LLVM, rather than the typical src/llvm-project LLVM.
+ENV NO_DOWNLOAD_CI_LLVM 1
+ENV EXTERNAL_LLVM 1
+
+# Using llvm-link-shared due to libffi issues -- see #34486
+ENV RUST_CONFIGURE_ARGS \
+      --build=x86_64-unknown-linux-gnu \
+      --llvm-root=/usr/lib/llvm-19 \
+      --enable-llvm-link-shared \
+      --set rust.thin-lto-import-instr-limit=10
+
+COPY host-x86_64/dist-x86_64-linux/shared.sh /scripts/
+COPY host-x86_64/dist-x86_64-linux/build-gccjit.sh /scripts/
+
+RUN /scripts/build-gccjit.sh /scripts
+
+COPY scripts/x86_64-gnu-llvm.sh /tmp/script.sh
+ENV SCRIPT /tmp/script.sh
diff --git a/src/ci/github-actions/jobs.yml b/src/ci/github-actions/jobs.yml
index 41d3b311749..f65083eec47 100644
--- a/src/ci/github-actions/jobs.yml
+++ b/src/ci/github-actions/jobs.yml
@@ -24,6 +24,10 @@ runners:
     os: macos-14
     <<: *base-job
 
+  - &job-windows
+    os: windows-2022
+    <<: *base-job
+
   - &job-windows-8c
     os: windows-2022-8core-32gb
     <<: *base-job
@@ -247,6 +251,11 @@ auto:
   - image: x86_64-gnu-distcheck
     <<: *job-linux-8c
 
+  - image: x86_64-gnu-llvm-19
+    env:
+      RUST_BACKTRACE: 1
+    <<: *job-linux-8c
+
   - image: x86_64-gnu-llvm-18
     env:
       RUST_BACKTRACE: 1
@@ -383,7 +392,7 @@ auto:
         python x.py miri --stage 2 library/alloc --test-args notest &&
         python x.py miri --stage 2 library/std --test-args notest
       RUST_CONFIGURE_ARGS: --build=x86_64-pc-windows-msvc --enable-lld
-    <<: *job-windows-8c
+    <<: *job-windows
 
   # 32/64-bit MinGW builds.
   #
diff --git a/src/doc/unstable-book/src/language-features/trait-upcasting.md b/src/doc/unstable-book/src/language-features/trait-upcasting.md
index 3697ae38f9d..a5f99cc86f2 100644
--- a/src/doc/unstable-book/src/language-features/trait-upcasting.md
+++ b/src/doc/unstable-book/src/language-features/trait-upcasting.md
@@ -12,7 +12,6 @@ so long as `Bar: Foo`.
 
 ```rust,edition2018
 #![feature(trait_upcasting)]
-#![allow(incomplete_features)]
 
 trait Foo {}
 
diff --git a/src/librustdoc/html/render/search_index.rs b/src/librustdoc/html/render/search_index.rs
index b84c22ac746..86b719c46e8 100644
--- a/src/librustdoc/html/render/search_index.rs
+++ b/src/librustdoc/html/render/search_index.rs
@@ -847,7 +847,7 @@ enum SimplifiedParam {
 ///
 /// This function also works recursively.
 #[instrument(level = "trace", skip(tcx, res, rgen, cache))]
-fn simplify_fn_type<'tcx, 'a>(
+fn simplify_fn_type<'a, 'tcx>(
     self_: Option<&'a Type>,
     generics: &Generics,
     arg: &'a Type,
@@ -1192,7 +1192,7 @@ fn simplify_fn_type<'tcx, 'a>(
     }
 }
 
-fn simplify_fn_constraint<'tcx, 'a>(
+fn simplify_fn_constraint<'a, 'tcx>(
     self_: Option<&'a Type>,
     generics: &Generics,
     constraint: &'a clean::AssocItemConstraint,
diff --git a/src/tools/cargo b/src/tools/cargo
-Subproject c1fa840a85eca53818895901a53fae34247448b
+Subproject a9a418d1a22f29e7dfd034e3b93f15657e608a2
diff --git a/src/tools/clippy/clippy_config/src/msrvs.rs b/src/tools/clippy/clippy_config/src/msrvs.rs
index e17458b3310..a2b4b6e256f 100644
--- a/src/tools/clippy/clippy_config/src/msrvs.rs
+++ b/src/tools/clippy/clippy_config/src/msrvs.rs
@@ -17,6 +17,7 @@ macro_rules! msrv_aliases {
 
 // names may refer to stabilized feature flags or library items
 msrv_aliases! {
+    1,83,0 { CONST_EXTERN_FN }
     1,83,0 { CONST_FLOAT_BITS_CONV }
     1,81,0 { LINT_REASONS_STABILIZATION }
     1,80,0 { BOX_INTO_ITER}
@@ -27,7 +28,7 @@ msrv_aliases! {
     1,68,0 { PATH_MAIN_SEPARATOR_STR }
     1,65,0 { LET_ELSE, POINTER_CAST_CONSTNESS }
     1,63,0 { CLONE_INTO }
-    1,62,0 { BOOL_THEN_SOME, DEFAULT_ENUM_ATTRIBUTE, CONST_EXTERN_FN }
+    1,62,0 { BOOL_THEN_SOME, DEFAULT_ENUM_ATTRIBUTE, CONST_EXTERN_C_FN }
     1,59,0 { THREAD_LOCAL_CONST_INIT }
     1,58,0 { FORMAT_ARGS_CAPTURE, PATTERN_TRAIT_CHAR_ARRAY, CONST_RAW_PTR_DEREF }
     1,56,0 { CONST_FN_UNION }
diff --git a/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs b/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs
index 052d738b2e7..859afe1b963 100644
--- a/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs
+++ b/src/tools/clippy/clippy_lints/src/missing_const_for_fn.rs
@@ -119,9 +119,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingConstForFn {
                     .iter()
                     .any(|param| matches!(param.kind, GenericParamKind::Const { .. }));
 
-                if already_const(header)
-                    || has_const_generic_params
-                    || !could_be_const_with_abi(cx, &self.msrv, header.abi)
+                if already_const(header) || has_const_generic_params || !could_be_const_with_abi(&self.msrv, header.abi)
                 {
                     return;
                 }
@@ -183,13 +181,13 @@ fn already_const(header: hir::FnHeader) -> bool {
     header.constness == Constness::Const
 }
 
-fn could_be_const_with_abi(cx: &LateContext<'_>, msrv: &Msrv, abi: Abi) -> bool {
+fn could_be_const_with_abi(msrv: &Msrv, abi: Abi) -> bool {
     match abi {
         Abi::Rust => true,
         // `const extern "C"` was stabilized after 1.62.0
-        Abi::C { unwind: false } => msrv.meets(msrvs::CONST_EXTERN_FN),
+        Abi::C { unwind: false } => msrv.meets(msrvs::CONST_EXTERN_C_FN),
         // Rest ABIs are still unstable and need the `const_extern_fn` feature enabled.
-        _ => cx.tcx.features().const_extern_fn,
+        _ => msrv.meets(msrvs::CONST_EXTERN_FN),
     }
 }
 
diff --git a/src/tools/clippy/tests/ui/arithmetic_side_effects.rs b/src/tools/clippy/tests/ui/arithmetic_side_effects.rs
index 9d06e14e88c..0838d064a5f 100644
--- a/src/tools/clippy/tests/ui/arithmetic_side_effects.rs
+++ b/src/tools/clippy/tests/ui/arithmetic_side_effects.rs
@@ -1,5 +1,8 @@
 //@aux-build:proc_macro_derive.rs
 
+#![feature(f128)]
+#![feature(f16)]
+
 #![allow(
     clippy::assign_op_pattern,
     clippy::erasing_op,
@@ -10,9 +13,6 @@
     arithmetic_overflow,
     unconditional_panic
 )]
-#![feature(const_mut_refs)]
-#![feature(f128)]
-#![feature(f16)]
 #![warn(clippy::arithmetic_side_effects)]
 
 extern crate proc_macro_derive;
diff --git a/src/tools/clippy/tests/ui/expect_tool_lint_rfc_2383.stderr b/src/tools/clippy/tests/ui/expect_tool_lint_rfc_2383.stderr
index f70d3408aa4..028e22ca724 100644
--- a/src/tools/clippy/tests/ui/expect_tool_lint_rfc_2383.stderr
+++ b/src/tools/clippy/tests/ui/expect_tool_lint_rfc_2383.stderr
@@ -14,6 +14,14 @@ LL |         #[expect(invalid_nan_comparisons)]
    |                  ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this lint expectation is unfulfilled
+  --> tests/ui/expect_tool_lint_rfc_2383.rs:36:18
+   |
+LL |         #[expect(invalid_nan_comparisons)]
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: this lint expectation is unfulfilled
   --> tests/ui/expect_tool_lint_rfc_2383.rs:107:14
    |
 LL |     #[expect(clippy::almost_swapped)]
@@ -37,5 +45,5 @@ error: this lint expectation is unfulfilled
 LL |     #[expect(clippy::overly_complex_bool_expr)]
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 6 previous errors
+error: aborting due to 7 previous errors
 
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/cant_be_const.rs b/src/tools/clippy/tests/ui/missing_const_for_fn/cant_be_const.rs
index 2c6e1e92da0..ca323dcf173 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/cant_be_const.rs
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/cant_be_const.rs
@@ -186,12 +186,6 @@ mod msrv {
     extern "C" fn c() {}
 }
 
-mod with_extern {
-    extern "C-unwind" fn c_unwind() {}
-    extern "system" fn system() {}
-    extern "system-unwind" fn system_unwind() {}
-}
-
 mod with_ty_alias {
     type Foo = impl std::fmt::Debug;
 
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.fixed b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.fixed
index f54503ada97..41b424a8e5d 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.fixed
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.fixed
@@ -1,6 +1,6 @@
 #![warn(clippy::missing_const_for_fn)]
 #![allow(incomplete_features, clippy::let_and_return, clippy::missing_transmute_annotations)]
-#![feature(const_mut_refs)]
+#![allow(unsupported_calling_conventions)]
 #![feature(const_trait_impl)]
 
 use std::mem::transmute;
@@ -204,3 +204,16 @@ mod with_ty_alias {
     // in this test.
     const fn alias_ty_is_projection(bar: <() as FooTrait>::Foo) {}
 }
+
+mod extern_fn {
+    const extern "C-unwind" fn c_unwind() {}
+    //~^ ERROR: this could be a `const fn`
+    const extern "system" fn system() {}
+    //~^ ERROR: this could be a `const fn`
+    const extern "system-unwind" fn system_unwind() {}
+    //~^ ERROR: this could be a `const fn`
+    pub const extern "stdcall" fn std_call() {}
+    //~^ ERROR: this could be a `const fn`
+    pub const extern "stdcall-unwind" fn std_call_unwind() {}
+    //~^ ERROR: this could be a `const fn`
+}
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.rs b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.rs
index 2c229068e4d..27593575a01 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.rs
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.rs
@@ -1,6 +1,6 @@
 #![warn(clippy::missing_const_for_fn)]
 #![allow(incomplete_features, clippy::let_and_return, clippy::missing_transmute_annotations)]
-#![feature(const_mut_refs)]
+#![allow(unsupported_calling_conventions)]
 #![feature(const_trait_impl)]
 
 use std::mem::transmute;
@@ -204,3 +204,16 @@ mod with_ty_alias {
     // in this test.
     fn alias_ty_is_projection(bar: <() as FooTrait>::Foo) {}
 }
+
+mod extern_fn {
+    extern "C-unwind" fn c_unwind() {}
+    //~^ ERROR: this could be a `const fn`
+    extern "system" fn system() {}
+    //~^ ERROR: this could be a `const fn`
+    extern "system-unwind" fn system_unwind() {}
+    //~^ ERROR: this could be a `const fn`
+    pub extern "stdcall" fn std_call() {}
+    //~^ ERROR: this could be a `const fn`
+    pub extern "stdcall-unwind" fn std_call_unwind() {}
+    //~^ ERROR: this could be a `const fn`
+}
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr
index fb4db703103..12d97b17119 100644
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr
+++ b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr
@@ -283,5 +283,60 @@ help: make the function `const`
 LL |     const fn alias_ty_is_projection(bar: <() as FooTrait>::Foo) {}
    |     +++++
 
-error: aborting due to 21 previous errors
+error: this could be a `const fn`
+  --> tests/ui/missing_const_for_fn/could_be_const.rs:209:5
+   |
+LL |     extern "C-unwind" fn c_unwind() {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function `const`
+   |
+LL |     const extern "C-unwind" fn c_unwind() {}
+   |     +++++
+
+error: this could be a `const fn`
+  --> tests/ui/missing_const_for_fn/could_be_const.rs:211:5
+   |
+LL |     extern "system" fn system() {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function `const`
+   |
+LL |     const extern "system" fn system() {}
+   |     +++++
+
+error: this could be a `const fn`
+  --> tests/ui/missing_const_for_fn/could_be_const.rs:213:5
+   |
+LL |     extern "system-unwind" fn system_unwind() {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function `const`
+   |
+LL |     const extern "system-unwind" fn system_unwind() {}
+   |     +++++
+
+error: this could be a `const fn`
+  --> tests/ui/missing_const_for_fn/could_be_const.rs:215:5
+   |
+LL |     pub extern "stdcall" fn std_call() {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function `const`
+   |
+LL |     pub const extern "stdcall" fn std_call() {}
+   |         +++++
+
+error: this could be a `const fn`
+  --> tests/ui/missing_const_for_fn/could_be_const.rs:217:5
+   |
+LL |     pub extern "stdcall-unwind" fn std_call_unwind() {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: make the function `const`
+   |
+LL |     pub const extern "stdcall-unwind" fn std_call_unwind() {}
+   |         +++++
+
+error: aborting due to 26 previous errors
 
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.fixed b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.fixed
deleted file mode 100644
index c103db536ab..00000000000
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.fixed
+++ /dev/null
@@ -1,14 +0,0 @@
-#![warn(clippy::missing_const_for_fn)]
-#![allow(unsupported_calling_conventions)]
-#![feature(const_extern_fn)]
-
-const extern "C-unwind" fn c_unwind() {}
-//~^ ERROR: this could be a `const fn`
-const extern "system" fn system() {}
-//~^ ERROR: this could be a `const fn`
-const extern "system-unwind" fn system_unwind() {}
-//~^ ERROR: this could be a `const fn`
-pub const extern "stdcall" fn std_call() {}
-//~^ ERROR: this could be a `const fn`
-pub const extern "stdcall-unwind" fn std_call_unwind() {}
-//~^ ERROR: this could be a `const fn`
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs
deleted file mode 100644
index 0f7020ae559..00000000000
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs
+++ /dev/null
@@ -1,14 +0,0 @@
-#![warn(clippy::missing_const_for_fn)]
-#![allow(unsupported_calling_conventions)]
-#![feature(const_extern_fn)]
-
-extern "C-unwind" fn c_unwind() {}
-//~^ ERROR: this could be a `const fn`
-extern "system" fn system() {}
-//~^ ERROR: this could be a `const fn`
-extern "system-unwind" fn system_unwind() {}
-//~^ ERROR: this could be a `const fn`
-pub extern "stdcall" fn std_call() {}
-//~^ ERROR: this could be a `const fn`
-pub extern "stdcall-unwind" fn std_call_unwind() {}
-//~^ ERROR: this could be a `const fn`
diff --git a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.stderr b/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.stderr
deleted file mode 100644
index 036094a367b..00000000000
--- a/src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.stderr
+++ /dev/null
@@ -1,59 +0,0 @@
-error: this could be a `const fn`
-  --> tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs:5:1
-   |
-LL | extern "C-unwind" fn c_unwind() {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `-D clippy::missing-const-for-fn` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::missing_const_for_fn)]`
-help: make the function `const`
-   |
-LL | const extern "C-unwind" fn c_unwind() {}
-   | +++++
-
-error: this could be a `const fn`
-  --> tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs:7:1
-   |
-LL | extern "system" fn system() {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: make the function `const`
-   |
-LL | const extern "system" fn system() {}
-   | +++++
-
-error: this could be a `const fn`
-  --> tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs:9:1
-   |
-LL | extern "system-unwind" fn system_unwind() {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: make the function `const`
-   |
-LL | const extern "system-unwind" fn system_unwind() {}
-   | +++++
-
-error: this could be a `const fn`
-  --> tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs:11:1
-   |
-LL | pub extern "stdcall" fn std_call() {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: make the function `const`
-   |
-LL | pub const extern "stdcall" fn std_call() {}
-   |     +++++
-
-error: this could be a `const fn`
-  --> tests/ui/missing_const_for_fn/could_be_const_with_const_extern_fn.rs:13:1
-   |
-LL | pub extern "stdcall-unwind" fn std_call_unwind() {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: make the function `const`
-   |
-LL | pub const extern "stdcall-unwind" fn std_call_unwind() {}
-   |     +++++
-
-error: aborting due to 5 previous errors
-
diff --git a/src/tools/miri/rust-version b/src/tools/miri/rust-version
index 58b6e1f49e3..eeff9ac8e38 100644
--- a/src/tools/miri/rust-version
+++ b/src/tools/miri/rust-version
@@ -1 +1 @@
-23b04c0513472f3728ad482398008e077979e5c4
+c16ff44537509ca911ffd3653b17c6187c71831d
diff --git a/src/tools/miri/src/concurrency/data_race.rs b/src/tools/miri/src/concurrency/data_race.rs
index b604fd868a0..b5b43f589f6 100644
--- a/src/tools/miri/src/concurrency/data_race.rs
+++ b/src/tools/miri/src/concurrency/data_race.rs
@@ -47,6 +47,7 @@ use std::{
 };
 
 use rustc_ast::Mutability;
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::{mir, ty::Ty};
@@ -1047,32 +1048,31 @@ impl VClockAlloc {
     ) -> InterpResult<'tcx> {
         let current_span = machine.current_span();
         let global = machine.data_race.as_ref().unwrap();
-        if global.race_detecting() {
-            let (index, mut thread_clocks) = global.active_thread_state_mut(&machine.threads);
-            let mut alloc_ranges = self.alloc_ranges.borrow_mut();
-            for (mem_clocks_range, mem_clocks) in
-                alloc_ranges.iter_mut(access_range.start, access_range.size)
+        if !global.race_detecting() {
+            return Ok(());
+        }
+        let (index, mut thread_clocks) = global.active_thread_state_mut(&machine.threads);
+        let mut alloc_ranges = self.alloc_ranges.borrow_mut();
+        for (mem_clocks_range, mem_clocks) in
+            alloc_ranges.iter_mut(access_range.start, access_range.size)
+        {
+            if let Err(DataRace) =
+                mem_clocks.read_race_detect(&mut thread_clocks, index, read_type, current_span)
             {
-                if let Err(DataRace) =
-                    mem_clocks.read_race_detect(&mut thread_clocks, index, read_type, current_span)
-                {
-                    drop(thread_clocks);
-                    // Report data-race.
-                    return Self::report_data_race(
-                        global,
-                        &machine.threads,
-                        mem_clocks,
-                        AccessType::NaRead(read_type),
-                        access_range.size,
-                        interpret::Pointer::new(alloc_id, Size::from_bytes(mem_clocks_range.start)),
-                        ty,
-                    );
-                }
+                drop(thread_clocks);
+                // Report data-race.
+                return Self::report_data_race(
+                    global,
+                    &machine.threads,
+                    mem_clocks,
+                    AccessType::NaRead(read_type),
+                    access_range.size,
+                    interpret::Pointer::new(alloc_id, Size::from_bytes(mem_clocks_range.start)),
+                    ty,
+                );
             }
-            Ok(())
-        } else {
-            Ok(())
         }
+        Ok(())
     }
 
     /// Detect data-races for an unsynchronized write operation. It will not perform
@@ -1090,33 +1090,129 @@ impl VClockAlloc {
     ) -> InterpResult<'tcx> {
         let current_span = machine.current_span();
         let global = machine.data_race.as_mut().unwrap();
-        if global.race_detecting() {
-            let (index, mut thread_clocks) = global.active_thread_state_mut(&machine.threads);
-            for (mem_clocks_range, mem_clocks) in
-                self.alloc_ranges.get_mut().iter_mut(access_range.start, access_range.size)
+        if !global.race_detecting() {
+            return Ok(());
+        }
+        let (index, mut thread_clocks) = global.active_thread_state_mut(&machine.threads);
+        for (mem_clocks_range, mem_clocks) in
+            self.alloc_ranges.get_mut().iter_mut(access_range.start, access_range.size)
+        {
+            if let Err(DataRace) =
+                mem_clocks.write_race_detect(&mut thread_clocks, index, write_type, current_span)
             {
-                if let Err(DataRace) = mem_clocks.write_race_detect(
-                    &mut thread_clocks,
-                    index,
-                    write_type,
-                    current_span,
-                ) {
-                    drop(thread_clocks);
-                    // Report data-race
-                    return Self::report_data_race(
-                        global,
-                        &machine.threads,
-                        mem_clocks,
-                        AccessType::NaWrite(write_type),
-                        access_range.size,
-                        interpret::Pointer::new(alloc_id, Size::from_bytes(mem_clocks_range.start)),
-                        ty,
-                    );
-                }
+                drop(thread_clocks);
+                // Report data-race
+                return Self::report_data_race(
+                    global,
+                    &machine.threads,
+                    mem_clocks,
+                    AccessType::NaWrite(write_type),
+                    access_range.size,
+                    interpret::Pointer::new(alloc_id, Size::from_bytes(mem_clocks_range.start)),
+                    ty,
+                );
             }
-            Ok(())
+        }
+        Ok(())
+    }
+}
+
+/// Vector clock state for a stack frame (tracking the local variables
+/// that do not have an allocation yet).
+#[derive(Debug, Default)]
+pub struct FrameState {
+    local_clocks: RefCell<FxHashMap<mir::Local, LocalClocks>>,
+}
+
+/// Stripped-down version of [`MemoryCellClocks`] for the clocks we need to keep track
+/// of in a local that does not yet have addressable memory -- and hence can only
+/// be accessed from the thread its stack frame belongs to, and cannot be access atomically.
+#[derive(Debug)]
+struct LocalClocks {
+    write: VTimestamp,
+    write_type: NaWriteType,
+    read: VTimestamp,
+}
+
+impl Default for LocalClocks {
+    fn default() -> Self {
+        Self { write: VTimestamp::ZERO, write_type: NaWriteType::Allocate, read: VTimestamp::ZERO }
+    }
+}
+
+impl FrameState {
+    pub fn local_write(&self, local: mir::Local, storage_live: bool, machine: &MiriMachine<'_>) {
+        let current_span = machine.current_span();
+        let global = machine.data_race.as_ref().unwrap();
+        if !global.race_detecting() {
+            return;
+        }
+        let (index, mut thread_clocks) = global.active_thread_state_mut(&machine.threads);
+        // This should do the same things as `MemoryCellClocks::write_race_detect`.
+        if !current_span.is_dummy() {
+            thread_clocks.clock.index_mut(index).span = current_span;
+        }
+        let mut clocks = self.local_clocks.borrow_mut();
+        if storage_live {
+            let new_clocks = LocalClocks {
+                write: thread_clocks.clock[index],
+                write_type: NaWriteType::Allocate,
+                read: VTimestamp::ZERO,
+            };
+            // There might already be an entry in the map for this, if the local was previously
+            // live already.
+            clocks.insert(local, new_clocks);
         } else {
-            Ok(())
+            // This can fail to exist if `race_detecting` was false when the allocation
+            // occurred, in which case we can backdate this to the beginning of time.
+            let clocks = clocks.entry(local).or_default();
+            clocks.write = thread_clocks.clock[index];
+            clocks.write_type = NaWriteType::Write;
+        }
+    }
+
+    pub fn local_read(&self, local: mir::Local, machine: &MiriMachine<'_>) {
+        let current_span = machine.current_span();
+        let global = machine.data_race.as_ref().unwrap();
+        if !global.race_detecting() {
+            return;
+        }
+        let (index, mut thread_clocks) = global.active_thread_state_mut(&machine.threads);
+        // This should do the same things as `MemoryCellClocks::read_race_detect`.
+        if !current_span.is_dummy() {
+            thread_clocks.clock.index_mut(index).span = current_span;
+        }
+        thread_clocks.clock.index_mut(index).set_read_type(NaReadType::Read);
+        // This can fail to exist if `race_detecting` was false when the allocation
+        // occurred, in which case we can backdate this to the beginning of time.
+        let mut clocks = self.local_clocks.borrow_mut();
+        let clocks = clocks.entry(local).or_default();
+        clocks.read = thread_clocks.clock[index];
+    }
+
+    pub fn local_moved_to_memory(
+        &self,
+        local: mir::Local,
+        alloc: &mut VClockAlloc,
+        machine: &MiriMachine<'_>,
+    ) {
+        let global = machine.data_race.as_ref().unwrap();
+        if !global.race_detecting() {
+            return;
+        }
+        let (index, _thread_clocks) = global.active_thread_state_mut(&machine.threads);
+        // Get the time the last write actually happened. This can fail to exist if
+        // `race_detecting` was false when the write occurred, in that case we can backdate this
+        // to the beginning of time.
+        let local_clocks = self.local_clocks.borrow_mut().remove(&local).unwrap_or_default();
+        for (_mem_clocks_range, mem_clocks) in alloc.alloc_ranges.get_mut().iter_mut_all() {
+            // The initialization write for this already happened, just at the wrong timestamp.
+            // Check that the thread index matches what we expect.
+            assert_eq!(mem_clocks.write.0, index);
+            // Convert the local's clocks into memory clocks.
+            mem_clocks.write = (index, local_clocks.write);
+            mem_clocks.write_type = local_clocks.write_type;
+            mem_clocks.read = VClock::new_with_index(index, local_clocks.read);
         }
     }
 }
@@ -1305,69 +1401,67 @@ trait EvalContextPrivExt<'tcx>: MiriInterpCxExt<'tcx> {
     ) -> InterpResult<'tcx> {
         let this = self.eval_context_ref();
         assert!(access.is_atomic());
-        if let Some(data_race) = &this.machine.data_race {
-            if data_race.race_detecting() {
-                let size = place.layout.size;
-                let (alloc_id, base_offset, _prov) = this.ptr_get_alloc_id(place.ptr(), 0)?;
-                // Load and log the atomic operation.
-                // Note that atomic loads are possible even from read-only allocations, so `get_alloc_extra_mut` is not an option.
-                let alloc_meta = this.get_alloc_extra(alloc_id)?.data_race.as_ref().unwrap();
-                trace!(
-                    "Atomic op({}) with ordering {:?} on {:?} (size={})",
-                    access.description(None, None),
-                    &atomic,
-                    place.ptr(),
-                    size.bytes()
-                );
+        let Some(data_race) = &this.machine.data_race else { return Ok(()) };
+        if !data_race.race_detecting() {
+            return Ok(());
+        }
+        let size = place.layout.size;
+        let (alloc_id, base_offset, _prov) = this.ptr_get_alloc_id(place.ptr(), 0)?;
+        // Load and log the atomic operation.
+        // Note that atomic loads are possible even from read-only allocations, so `get_alloc_extra_mut` is not an option.
+        let alloc_meta = this.get_alloc_extra(alloc_id)?.data_race.as_ref().unwrap();
+        trace!(
+            "Atomic op({}) with ordering {:?} on {:?} (size={})",
+            access.description(None, None),
+            &atomic,
+            place.ptr(),
+            size.bytes()
+        );
 
-                let current_span = this.machine.current_span();
-                // Perform the atomic operation.
-                data_race.maybe_perform_sync_operation(
-                    &this.machine.threads,
-                    current_span,
-                    |index, mut thread_clocks| {
-                        for (mem_clocks_range, mem_clocks) in
-                            alloc_meta.alloc_ranges.borrow_mut().iter_mut(base_offset, size)
-                        {
-                            if let Err(DataRace) = op(mem_clocks, &mut thread_clocks, index, atomic)
-                            {
-                                mem::drop(thread_clocks);
-                                return VClockAlloc::report_data_race(
-                                    data_race,
-                                    &this.machine.threads,
-                                    mem_clocks,
-                                    access,
-                                    place.layout.size,
-                                    interpret::Pointer::new(
-                                        alloc_id,
-                                        Size::from_bytes(mem_clocks_range.start),
-                                    ),
-                                    None,
-                                )
-                                .map(|_| true);
-                            }
-                        }
-
-                        // This conservatively assumes all operations have release semantics
-                        Ok(true)
-                    },
-                )?;
-
-                // Log changes to atomic memory.
-                if tracing::enabled!(tracing::Level::TRACE) {
-                    for (_offset, mem_clocks) in
-                        alloc_meta.alloc_ranges.borrow().iter(base_offset, size)
-                    {
-                        trace!(
-                            "Updated atomic memory({:?}, size={}) to {:#?}",
-                            place.ptr(),
-                            size.bytes(),
-                            mem_clocks.atomic_ops
-                        );
+        let current_span = this.machine.current_span();
+        // Perform the atomic operation.
+        data_race.maybe_perform_sync_operation(
+            &this.machine.threads,
+            current_span,
+            |index, mut thread_clocks| {
+                for (mem_clocks_range, mem_clocks) in
+                    alloc_meta.alloc_ranges.borrow_mut().iter_mut(base_offset, size)
+                {
+                    if let Err(DataRace) = op(mem_clocks, &mut thread_clocks, index, atomic) {
+                        mem::drop(thread_clocks);
+                        return VClockAlloc::report_data_race(
+                            data_race,
+                            &this.machine.threads,
+                            mem_clocks,
+                            access,
+                            place.layout.size,
+                            interpret::Pointer::new(
+                                alloc_id,
+                                Size::from_bytes(mem_clocks_range.start),
+                            ),
+                            None,
+                        )
+                        .map(|_| true);
                     }
                 }
+
+                // This conservatively assumes all operations have release semantics
+                Ok(true)
+            },
+        )?;
+
+        // Log changes to atomic memory.
+        if tracing::enabled!(tracing::Level::TRACE) {
+            for (_offset, mem_clocks) in alloc_meta.alloc_ranges.borrow().iter(base_offset, size) {
+                trace!(
+                    "Updated atomic memory({:?}, size={}) to {:#?}",
+                    place.ptr(),
+                    size.bytes(),
+                    mem_clocks.atomic_ops
+                );
             }
         }
+
         Ok(())
     }
 }
diff --git a/src/tools/miri/src/concurrency/thread.rs b/src/tools/miri/src/concurrency/thread.rs
index 306245a843b..4efe2beb155 100644
--- a/src/tools/miri/src/concurrency/thread.rs
+++ b/src/tools/miri/src/concurrency/thread.rs
@@ -530,7 +530,9 @@ impl<'tcx> ThreadManager<'tcx> {
     }
 
     /// Mutably borrow the stack of the active thread.
-    fn active_thread_stack_mut(&mut self) -> &mut Vec<Frame<'tcx, Provenance, FrameExtra<'tcx>>> {
+    pub fn active_thread_stack_mut(
+        &mut self,
+    ) -> &mut Vec<Frame<'tcx, Provenance, FrameExtra<'tcx>>> {
         &mut self.threads[self.active_thread].stack
     }
     pub fn all_stacks(
@@ -898,7 +900,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             // This allocation will be deallocated when the thread dies, so it is not in read-only memory.
             alloc.mutability = Mutability::Mut;
             // Create a fresh allocation with this content.
-            let ptr = this.allocate_raw_ptr(alloc, MiriMemoryKind::Tls.into())?;
+            let ptr = this.insert_allocation(alloc, MiriMemoryKind::Tls.into())?;
             this.machine.threads.set_thread_local_alloc(def_id, ptr);
             Ok(ptr)
         }
diff --git a/src/tools/miri/src/concurrency/vector_clock.rs b/src/tools/miri/src/concurrency/vector_clock.rs
index c3496bc1a0c..0968e10bbee 100644
--- a/src/tools/miri/src/concurrency/vector_clock.rs
+++ b/src/tools/miri/src/concurrency/vector_clock.rs
@@ -130,6 +130,9 @@ impl Ord for VTimestamp {
 /// also this means that there is only one unique valid length
 /// for each set of vector clock values and hence the PartialEq
 /// and Eq derivations are correct.
+///
+/// This means we cannot represent a clock where the last entry is a timestamp-0 read that occurs
+/// because of a retag. That's fine, all it does is risk wrong diagnostics in a extreme corner case.
 #[derive(PartialEq, Eq, Default, Debug)]
 pub struct VClock(SmallVec<[VTimestamp; SMALL_VECTOR]>);
 
@@ -137,6 +140,9 @@ impl VClock {
     /// Create a new vector-clock containing all zeros except
     /// for a value at the given index
     pub(super) fn new_with_index(index: VectorIdx, timestamp: VTimestamp) -> VClock {
+        if timestamp.time() == 0 {
+            return VClock::default();
+        }
         let len = index.index() + 1;
         let mut vec = smallvec::smallvec![VTimestamp::ZERO; len];
         vec[index.index()] = timestamp;
diff --git a/src/tools/miri/src/intrinsics/mod.rs b/src/tools/miri/src/intrinsics/mod.rs
index 0ab1b9dfb61..7acc99a8af0 100644
--- a/src/tools/miri/src/intrinsics/mod.rs
+++ b/src/tools/miri/src/intrinsics/mod.rs
@@ -3,11 +3,8 @@
 mod atomic;
 mod simd;
 
-use std::iter;
-
 use rand::Rng;
 use rustc_apfloat::{Float, Round};
-use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::{
     mir,
     ty::{self, FloatTy},
@@ -119,19 +116,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 this.copy_op(dest, &place)?;
             }
 
-            "write_bytes" | "volatile_set_memory" => {
+            "volatile_set_memory" => {
                 let [ptr, val_byte, count] = check_arg_count(args)?;
-                let ty = ptr.layout.ty.builtin_deref(true).unwrap();
-                let ty_layout = this.layout_of(ty)?;
-                let val_byte = this.read_scalar(val_byte)?.to_u8()?;
-                let ptr = this.read_pointer(ptr)?;
-                let count = this.read_target_usize(count)?;
-                // `checked_mul` enforces a too small bound (the correct one would probably be target_isize_max),
-                // but no actual allocation can be big enough for the difference to be noticeable.
-                let byte_count = ty_layout.size.checked_mul(count, this).ok_or_else(|| {
-                    err_ub_format!("overflow computing total size of `{intrinsic_name}`")
-                })?;
-                this.write_bytes_ptr(ptr, iter::repeat(val_byte).take(byte_count.bytes_usize()))?;
+                this.write_bytes_intrinsic(ptr, val_byte, count, "volatile_set_memory")?;
             }
 
             // Memory model / provenance manipulation
diff --git a/src/tools/miri/src/intrinsics/simd.rs b/src/tools/miri/src/intrinsics/simd.rs
index aa91b89d0ec..e22306ca82f 100644
--- a/src/tools/miri/src/intrinsics/simd.rs
+++ b/src/tools/miri/src/intrinsics/simd.rs
@@ -664,15 +664,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 let [left, right, index] = check_arg_count(args)?;
                 let (left, left_len) = this.project_to_simd(left)?;
                 let (right, right_len) = this.project_to_simd(right)?;
+                let (index, index_len) = this.project_to_simd(index)?;
                 let (dest, dest_len) = this.project_to_simd(dest)?;
 
-                // `index` is an array or a SIMD type
-                let (index, index_len) = match index.layout.ty.kind() {
-                    // FIXME: remove this once `index` must always be a SIMD vector.
-                    ty::Array(..) => (index.clone(), index.len(this)?),
-                    _ => this.project_to_simd(index)?,
-                };
-
                 assert_eq!(left_len, right_len);
                 assert_eq!(index_len, dest_len);
 
diff --git a/src/tools/miri/src/machine.rs b/src/tools/miri/src/machine.rs
index 76b4366476d..df55902decd 100644
--- a/src/tools/miri/src/machine.rs
+++ b/src/tools/miri/src/machine.rs
@@ -81,24 +81,42 @@ pub struct FrameExtra<'tcx> {
     /// an additional bit of "salt" into the cache key. This salt is fixed per-frame
     /// so that within a call, a const will have a stable address.
     salt: usize,
+
+    /// Data race detector per-frame data.
+    pub data_race: Option<data_race::FrameState>,
 }
 
 impl<'tcx> std::fmt::Debug for FrameExtra<'tcx> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         // Omitting `timing`, it does not support `Debug`.
-        let FrameExtra { borrow_tracker, catch_unwind, timing: _, is_user_relevant: _, salt: _ } =
-            self;
+        let FrameExtra {
+            borrow_tracker,
+            catch_unwind,
+            timing: _,
+            is_user_relevant,
+            salt,
+            data_race,
+        } = self;
         f.debug_struct("FrameData")
             .field("borrow_tracker", borrow_tracker)
             .field("catch_unwind", catch_unwind)
+            .field("is_user_relevant", is_user_relevant)
+            .field("salt", salt)
+            .field("data_race", data_race)
             .finish()
     }
 }
 
 impl VisitProvenance for FrameExtra<'_> {
     fn visit_provenance(&self, visit: &mut VisitWith<'_>) {
-        let FrameExtra { catch_unwind, borrow_tracker, timing: _, is_user_relevant: _, salt: _ } =
-            self;
+        let FrameExtra {
+            catch_unwind,
+            borrow_tracker,
+            timing: _,
+            is_user_relevant: _,
+            salt: _,
+            data_race: _,
+        } = self;
 
         catch_unwind.visit_provenance(visit);
         borrow_tracker.visit_provenance(visit);
@@ -1446,6 +1464,7 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> {
             timing,
             is_user_relevant: ecx.machine.is_user_relevant(&frame),
             salt: ecx.machine.rng.borrow_mut().gen::<usize>() % ADDRS_PER_ANON_GLOBAL,
+            data_race: ecx.machine.data_race.as_ref().map(|_| data_race::FrameState::default()),
         };
 
         Ok(frame.with_extra(extra))
@@ -1551,7 +1570,25 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> {
         res
     }
 
-    fn after_local_allocated(
+    fn after_local_read(ecx: &InterpCx<'tcx, Self>, local: mir::Local) -> InterpResult<'tcx> {
+        if let Some(data_race) = &ecx.frame().extra.data_race {
+            data_race.local_read(local, &ecx.machine);
+        }
+        Ok(())
+    }
+
+    fn after_local_write(
+        ecx: &mut InterpCx<'tcx, Self>,
+        local: mir::Local,
+        storage_live: bool,
+    ) -> InterpResult<'tcx> {
+        if let Some(data_race) = &ecx.frame().extra.data_race {
+            data_race.local_write(local, storage_live, &ecx.machine);
+        }
+        Ok(())
+    }
+
+    fn after_local_moved_to_memory(
         ecx: &mut InterpCx<'tcx, Self>,
         local: mir::Local,
         mplace: &MPlaceTy<'tcx>,
@@ -1559,9 +1596,17 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> {
         let Some(Provenance::Concrete { alloc_id, .. }) = mplace.ptr().provenance else {
             panic!("after_local_allocated should only be called on fresh allocations");
         };
+        // Record the span where this was allocated: the declaration of the local.
         let local_decl = &ecx.frame().body().local_decls[local];
         let span = local_decl.source_info.span;
         ecx.machine.allocation_spans.borrow_mut().insert(alloc_id, (span, None));
+        // The data race system has to fix the clocks used for this write.
+        let (alloc_info, machine) = ecx.get_alloc_extra_mut(alloc_id)?;
+        if let Some(data_race) =
+            &machine.threads.active_thread_stack().last().unwrap().extra.data_race
+        {
+            data_race.local_moved_to_memory(local, alloc_info.data_race.as_mut().unwrap(), machine);
+        }
         Ok(())
     }
 
diff --git a/src/tools/miri/src/shims/foreign_items.rs b/src/tools/miri/src/shims/foreign_items.rs
index 88ab012f978..67dc1476175 100644
--- a/src/tools/miri/src/shims/foreign_items.rs
+++ b/src/tools/miri/src/shims/foreign_items.rs
@@ -196,7 +196,7 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
         if size == 0 {
             throw_ub_format!("creating allocation with size 0");
         }
-        if i128::from(size) > this.tcx.data_layout.pointer_size.signed_int_max() {
+        if size > this.max_size_of_val().bytes() {
             throw_ub_format!("creating an allocation larger than half the address space");
         }
         if let Err(e) = Align::from_bytes(align) {
@@ -441,19 +441,34 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
             "malloc" => {
                 let [size] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let size = this.read_target_usize(size)?;
-                let res = this.malloc(size, /*zero_init:*/ false)?;
-                this.write_pointer(res, dest)?;
+                if size <= this.max_size_of_val().bytes() {
+                    let res = this.malloc(size, /*zero_init:*/ false)?;
+                    this.write_pointer(res, dest)?;
+                } else {
+                    // If this does not fit in an isize, return null and, on Unix, set errno.
+                    if this.target_os_is_unix() {
+                        let einval = this.eval_libc("ENOMEM");
+                        this.set_last_error(einval)?;
+                    }
+                    this.write_null(dest)?;
+                }
             }
             "calloc" => {
-                let [items, len] =
+                let [items, elem_size] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let items = this.read_target_usize(items)?;
-                let len = this.read_target_usize(len)?;
-                let size = items
-                    .checked_mul(len)
-                    .ok_or_else(|| err_ub_format!("overflow during calloc size computation"))?;
-                let res = this.malloc(size, /*zero_init:*/ true)?;
-                this.write_pointer(res, dest)?;
+                let elem_size = this.read_target_usize(elem_size)?;
+                if let Some(size) = this.compute_size_in_bytes(Size::from_bytes(elem_size), items) {
+                    let res = this.malloc(size.bytes(), /*zero_init:*/ true)?;
+                    this.write_pointer(res, dest)?;
+                } else {
+                    // On size overflow, return null and, on Unix, set errno.
+                    if this.target_os_is_unix() {
+                        let einval = this.eval_libc("ENOMEM");
+                        this.set_last_error(einval)?;
+                    }
+                    this.write_null(dest)?;
+                }
             }
             "free" => {
                 let [ptr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
@@ -465,8 +480,17 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let old_ptr = this.read_pointer(old_ptr)?;
                 let new_size = this.read_target_usize(new_size)?;
-                let res = this.realloc(old_ptr, new_size)?;
-                this.write_pointer(res, dest)?;
+                if new_size <= this.max_size_of_val().bytes() {
+                    let res = this.realloc(old_ptr, new_size)?;
+                    this.write_pointer(res, dest)?;
+                } else {
+                    // If this does not fit in an isize, return null and, on Unix, set errno.
+                    if this.target_os_is_unix() {
+                        let einval = this.eval_libc("ENOMEM");
+                        this.set_last_error(einval)?;
+                    }
+                    this.write_null(dest)?;
+                }
             }
 
             // Rust allocation
diff --git a/src/tools/miri/src/shims/unix/foreign_items.rs b/src/tools/miri/src/shims/unix/foreign_items.rs
index 273a99b3116..73f933264fd 100644
--- a/src/tools/miri/src/shims/unix/foreign_items.rs
+++ b/src/tools/miri/src/shims/unix/foreign_items.rs
@@ -363,14 +363,14 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 //
                 // Linux: https://www.unix.com/man-page/linux/3/reallocarray/
                 // FreeBSD: https://man.freebsd.org/cgi/man.cgi?query=reallocarray
-                match nmemb.checked_mul(size) {
+                match this.compute_size_in_bytes(Size::from_bytes(size), nmemb) {
                     None => {
                         let einval = this.eval_libc("ENOMEM");
                         this.set_last_error(einval)?;
                         this.write_null(dest)?;
                     }
                     Some(len) => {
-                        let res = this.realloc(ptr, len)?;
+                        let res = this.realloc(ptr, len.bytes())?;
                         this.write_pointer(res, dest)?;
                     }
                 }
diff --git a/src/tools/miri/tests/fail/data_race/local_variable_alloc_race.rs b/src/tools/miri/tests/fail/data_race/local_variable_alloc_race.rs
new file mode 100644
index 00000000000..751a308a399
--- /dev/null
+++ b/src/tools/miri/tests/fail/data_race/local_variable_alloc_race.rs
@@ -0,0 +1,57 @@
+//@compile-flags: -Zmiri-preemption-rate=0.0 -Zmiri-disable-weak-memory-emulation
+#![feature(core_intrinsics)]
+#![feature(custom_mir)]
+
+use std::intrinsics::mir::*;
+use std::sync::atomic::Ordering::*;
+use std::sync::atomic::*;
+use std::thread::JoinHandle;
+
+static P: AtomicPtr<u8> = AtomicPtr::new(core::ptr::null_mut());
+
+fn spawn_thread() -> JoinHandle<()> {
+    std::thread::spawn(|| {
+        while P.load(Relaxed).is_null() {
+            std::hint::spin_loop();
+        }
+        unsafe {
+            // Initialize `*P`.
+            let ptr = P.load(Relaxed);
+            *ptr = 127;
+            //~^ ERROR: Data race detected between (1) creating a new allocation on thread `main` and (2) non-atomic write on thread `unnamed-1`
+        }
+    })
+}
+
+fn finish(t: JoinHandle<()>, val_ptr: *mut u8) {
+    P.store(val_ptr, Relaxed);
+
+    // Wait for the thread to be done.
+    t.join().unwrap();
+
+    // Read initialized value.
+    assert_eq!(unsafe { *val_ptr }, 127);
+}
+
+#[custom_mir(dialect = "runtime", phase = "optimized")]
+fn main() {
+    mir! {
+        let t;
+        let val;
+        let val_ptr;
+        let _ret;
+        {
+            Call(t = spawn_thread(), ReturnTo(after_spawn), UnwindContinue())
+        }
+        after_spawn = {
+            // This races with the write in the other thread.
+            StorageLive(val);
+
+            val_ptr = &raw mut val;
+            Call(_ret = finish(t, val_ptr), ReturnTo(done), UnwindContinue())
+        }
+        done = {
+            Return()
+        }
+    }
+}
diff --git a/src/tools/miri/tests/fail/data_race/local_variable_alloc_race.stderr b/src/tools/miri/tests/fail/data_race/local_variable_alloc_race.stderr
new file mode 100644
index 00000000000..f46eb078a51
--- /dev/null
+++ b/src/tools/miri/tests/fail/data_race/local_variable_alloc_race.stderr
@@ -0,0 +1,20 @@
+error: Undefined Behavior: Data race detected between (1) creating a new allocation on thread `main` and (2) non-atomic write on thread `unnamed-ID` at ALLOC. (2) just happened here
+  --> $DIR/local_variable_alloc_race.rs:LL:CC
+   |
+LL |             *ptr = 127;
+   |             ^^^^^^^^^^ Data race detected between (1) creating a new allocation on thread `main` and (2) non-atomic write on thread `unnamed-ID` at ALLOC. (2) just happened here
+   |
+help: and (1) occurred earlier here
+  --> $DIR/local_variable_alloc_race.rs:LL:CC
+   |
+LL |             StorageLive(val);
+   |             ^^^^^^^^^^^^^^^^
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE (of the first span) on thread `unnamed-ID`:
+   = note: inside closure at $DIR/local_variable_alloc_race.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/fail/data_race/local_variable_read_race.rs b/src/tools/miri/tests/fail/data_race/local_variable_read_race.rs
new file mode 100644
index 00000000000..16a23f595ee
--- /dev/null
+++ b/src/tools/miri/tests/fail/data_race/local_variable_read_race.rs
@@ -0,0 +1,38 @@
+//@compile-flags: -Zmiri-preemption-rate=0.0 -Zmiri-disable-weak-memory-emulation
+use std::sync::atomic::Ordering::*;
+use std::sync::atomic::*;
+
+static P: AtomicPtr<u8> = AtomicPtr::new(core::ptr::null_mut());
+
+fn main() {
+    // Create the local variable, and initialize it.
+    let mut val: u8 = 0;
+
+    let t1 = std::thread::spawn(|| {
+        while P.load(Relaxed).is_null() {
+            std::hint::spin_loop();
+        }
+        unsafe {
+            // Initialize `*P`.
+            let ptr = P.load(Relaxed);
+            *ptr = 127;
+            //~^ ERROR: Data race detected between (1) non-atomic read on thread `main` and (2) non-atomic write on thread `unnamed-1`
+        }
+    });
+
+    // This read is not ordered with the store above, and thus should be reported as a race.
+    let _val = val;
+
+    // Actually generate memory for the local variable.
+    // This is the time its value is actually written to memory.
+    // If we just "pre-date" the write to the beginning of time (since we don't know
+    // when it actually happened), we'd miss the UB in this test.
+    // Also, the UB error should point at the write above, not the addr-of here.
+    P.store(std::ptr::addr_of_mut!(val), Relaxed);
+
+    // Wait for the thread to be done.
+    t1.join().unwrap();
+
+    // Read initialized value.
+    assert_eq!(val, 127);
+}
diff --git a/src/tools/miri/tests/fail/data_race/local_variable_read_race.stderr b/src/tools/miri/tests/fail/data_race/local_variable_read_race.stderr
new file mode 100644
index 00000000000..d14c2fb47ff
--- /dev/null
+++ b/src/tools/miri/tests/fail/data_race/local_variable_read_race.stderr
@@ -0,0 +1,20 @@
+error: Undefined Behavior: Data race detected between (1) non-atomic read on thread `main` and (2) non-atomic write on thread `unnamed-ID` at ALLOC. (2) just happened here
+  --> $DIR/local_variable_read_race.rs:LL:CC
+   |
+LL |             *ptr = 127;
+   |             ^^^^^^^^^^ Data race detected between (1) non-atomic read on thread `main` and (2) non-atomic write on thread `unnamed-ID` at ALLOC. (2) just happened here
+   |
+help: and (1) occurred earlier here
+  --> $DIR/local_variable_read_race.rs:LL:CC
+   |
+LL |     let _val = val;
+   |                ^^^
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE (of the first span) on thread `unnamed-ID`:
+   = note: inside closure at $DIR/local_variable_read_race.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/fail/data_race/local_variable_write_race.rs b/src/tools/miri/tests/fail/data_race/local_variable_write_race.rs
new file mode 100644
index 00000000000..7e00573146c
--- /dev/null
+++ b/src/tools/miri/tests/fail/data_race/local_variable_write_race.rs
@@ -0,0 +1,37 @@
+//@compile-flags: -Zmiri-preemption-rate=0.0 -Zmiri-disable-weak-memory-emulation
+use std::sync::atomic::Ordering::*;
+use std::sync::atomic::*;
+
+static P: AtomicPtr<u8> = AtomicPtr::new(core::ptr::null_mut());
+
+fn main() {
+    let t1 = std::thread::spawn(|| {
+        while P.load(Relaxed).is_null() {
+            std::hint::spin_loop();
+        }
+        unsafe {
+            // Initialize `*P`.
+            let ptr = P.load(Relaxed);
+            *ptr = 127;
+            //~^ ERROR: Data race detected between (1) non-atomic write on thread `main` and (2) non-atomic write on thread `unnamed-1`
+        }
+    });
+
+    // Create the local variable, and initialize it.
+    // This is not ordered with the store above, so it's definitely UB
+    // for that thread to access this variable.
+    let mut val: u8 = 0;
+
+    // Actually generate memory for the local variable.
+    // This is the time its value is actually written to memory.
+    // If we just "pre-date" the write to the beginning of time (since we don't know
+    // when it actually happened), we'd miss the UB in this test.
+    // Also, the UB error should point at the write above, not the addr-of here.
+    P.store(std::ptr::addr_of_mut!(val), Relaxed);
+
+    // Wait for the thread to be done.
+    t1.join().unwrap();
+
+    // Read initialized value.
+    assert_eq!(val, 127);
+}
diff --git a/src/tools/miri/tests/fail/data_race/local_variable_write_race.stderr b/src/tools/miri/tests/fail/data_race/local_variable_write_race.stderr
new file mode 100644
index 00000000000..d84db955a3d
--- /dev/null
+++ b/src/tools/miri/tests/fail/data_race/local_variable_write_race.stderr
@@ -0,0 +1,20 @@
+error: Undefined Behavior: Data race detected between (1) non-atomic write on thread `main` and (2) non-atomic write on thread `unnamed-ID` at ALLOC. (2) just happened here
+  --> $DIR/local_variable_write_race.rs:LL:CC
+   |
+LL |             *ptr = 127;
+   |             ^^^^^^^^^^ Data race detected between (1) non-atomic write on thread `main` and (2) non-atomic write on thread `unnamed-ID` at ALLOC. (2) just happened here
+   |
+help: and (1) occurred earlier here
+  --> $DIR/local_variable_write_race.rs:LL:CC
+   |
+LL |     let mut val: u8 = 0;
+   |                       ^
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE (of the first span) on thread `unnamed-ID`:
+   = note: inside closure at $DIR/local_variable_write_race.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/pass-dep/libc/libc-mem.rs b/src/tools/miri/tests/pass-dep/libc/libc-mem.rs
index aa383a99bc2..c399616b9ae 100644
--- a/src/tools/miri/tests/pass-dep/libc/libc-mem.rs
+++ b/src/tools/miri/tests/pass-dep/libc/libc-mem.rs
@@ -101,6 +101,10 @@ fn test_malloc() {
         let slice = slice::from_raw_parts(p3 as *const u8, 20);
         assert_eq!(&slice, &[0_u8; 20]);
 
+        // new size way too big (so this doesn't actually realloc).
+        let p_too_big = libc::realloc(p3, usize::MAX);
+        assert!(p_too_big.is_null());
+
         // old size > new size
         let p4 = libc::realloc(p3, 10);
         let slice = slice::from_raw_parts(p4 as *const u8, 10);
@@ -119,9 +123,13 @@ fn test_malloc() {
     unsafe {
         let p1 = libc::realloc(ptr::null_mut(), 20);
         assert!(!p1.is_null());
-
         libc::free(p1);
     }
+
+    unsafe {
+        let p_too_big = libc::malloc(usize::MAX);
+        assert!(p_too_big.is_null());
+    }
 }
 
 fn test_calloc() {
@@ -143,6 +151,9 @@ fn test_calloc() {
         let slice = slice::from_raw_parts(p4 as *const u8, 4 * 8);
         assert_eq!(&slice, &[0_u8; 4 * 8]);
         libc::free(p4);
+
+        let p_too_big = libc::calloc(usize::MAX / 4, 4);
+        assert!(p_too_big.is_null());
     }
 }
 
diff --git a/src/tools/miri/tests/pass/concurrency/data_race.rs b/src/tools/miri/tests/pass/concurrency/data_race.rs
index d31420380a5..34380dfa504 100644
--- a/src/tools/miri/tests/pass/concurrency/data_race.rs
+++ b/src/tools/miri/tests/pass/concurrency/data_race.rs
@@ -1,6 +1,6 @@
 //@compile-flags: -Zmiri-disable-weak-memory-emulation -Zmiri-preemption-rate=0
 
-use std::sync::atomic::{fence, AtomicUsize, Ordering};
+use std::sync::atomic::*;
 use std::thread::spawn;
 
 #[derive(Copy, Clone)]
@@ -112,9 +112,41 @@ pub fn test_simple_release() {
     }
 }
 
+fn test_local_variable_lazy_write() {
+    static P: AtomicPtr<u8> = AtomicPtr::new(core::ptr::null_mut());
+
+    // Create the local variable, and initialize it.
+    // This write happens before the thread is spanwed, so there is no data race.
+    let mut val: u8 = 0;
+
+    let t1 = std::thread::spawn(|| {
+        while P.load(Ordering::Relaxed).is_null() {
+            std::hint::spin_loop();
+        }
+        unsafe {
+            // Initialize `*P`.
+            let ptr = P.load(Ordering::Relaxed);
+            *ptr = 127;
+        }
+    });
+
+    // Actually generate memory for the local variable.
+    // This is the time its value is actually written to memory:
+    // that's *after* the thread above was spawned!
+    // This may hence look like a data race wrt the access in the thread above.
+    P.store(std::ptr::addr_of_mut!(val), Ordering::Relaxed);
+
+    // Wait for the thread to be done.
+    t1.join().unwrap();
+
+    // Read initialized value.
+    assert_eq!(val, 127);
+}
+
 pub fn main() {
     test_fence_sync();
     test_multiple_reads();
     test_rmw_no_block();
     test_simple_release();
+    test_local_variable_lazy_write();
 }
diff --git a/src/tools/miri/tests/pass/intrinsics/portable-simd.rs b/src/tools/miri/tests/pass/intrinsics/portable-simd.rs
index daf75fee8fe..4c0d6f52425 100644
--- a/src/tools/miri/tests/pass/intrinsics/portable-simd.rs
+++ b/src/tools/miri/tests/pass/intrinsics/portable-simd.rs
@@ -619,7 +619,6 @@ fn simd_intrinsics() {
             i32x4::from_array([10, 2, 10, 10])
         );
         assert_eq!(simd_shuffle_generic::<_, i32x4, { &[3, 1, 0, 2] }>(a, b), a,);
-        assert_eq!(simd_shuffle::<_, _, i32x4>(a, b, const { [3u32, 1, 0, 2] }), a,);
         assert_eq!(
             simd_shuffle::<_, _, i32x4>(a, b, const { u32x4::from_array([3u32, 1, 0, 2]) }),
             a,
@@ -629,10 +628,6 @@ fn simd_intrinsics() {
             i32x4::from_array([4, 2, 1, 10]),
         );
         assert_eq!(
-            simd_shuffle::<_, _, i32x4>(a, b, const { [7u32, 5, 4, 6] }),
-            i32x4::from_array([4, 2, 1, 10]),
-        );
-        assert_eq!(
             simd_shuffle::<_, _, i32x4>(a, b, const { u32x4::from_array([7u32, 5, 4, 6]) }),
             i32x4::from_array([4, 2, 1, 10]),
         );
diff --git a/src/tools/tidy/src/issues.txt b/src/tools/tidy/src/issues.txt
index 4627079a647..8197a1bd859 100644
--- a/src/tools/tidy/src/issues.txt
+++ b/src/tools/tidy/src/issues.txt
@@ -675,8 +675,6 @@ ui/consts/auxiliary/issue-17718-aux.rs
 ui/consts/auxiliary/issue-63226.rs
 ui/consts/const-eval/issue-100878.rs
 ui/consts/const-eval/issue-104390.rs
-ui/consts/const-eval/issue-114994-fail.rs
-ui/consts/const-eval/issue-114994.rs
 ui/consts/const-eval/issue-43197.rs
 ui/consts/const-eval/issue-44578.rs
 ui/consts/const-eval/issue-47971.rs