diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index 47318d3c086f5..e7c58bce84259 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -1056,6 +1056,117 @@ impl CommandLineStep for StdarchVerify {
     }
 }
 
+/// Runs `core_arch`'s inline unit and `assert_instr` tests for the native
+/// targets rust already tests on (x86_64 / aarch64).
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct CoreArchTest {
+    build_compiler: Compiler,
+    host: TargetSelection,
+}
+
+impl CommandLineStep for CoreArchTest {
+    type Output = ();
+    const IS_HOST: bool = true;
+
+    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
+        run.alias("core-arch")
+    }
+
+    fn is_default_step(_builder: &Builder<'_>) -> bool {
+        true
+    }
+
+    fn make_run(run: RunConfig<'_>) {
+        run.builder.ensure(CoreArchTest {
+            build_compiler: get_compiler_to_test(run.builder, run.target),
+            host: run.target,
+        });
+    }
+
+    fn run(self, builder: &Builder<'_>) {
+        let host = self.host;
+        if !host.contains("x86_64-unknown-linux") && !host.contains("aarch64-unknown-linux") {
+            builder.info(&format!("Skipping core_arch tests, unsupported on {host}"));
+            return;
+        }
+
+        let build_compiler = self.build_compiler;
+        builder.std(build_compiler, host);
+        let record_failed_tests = builder.ensure(SetupFailedTestsFile);
+
+        let mut cargo = tool::prepare_tool_cargo(
+            builder,
+            build_compiler,
+            Mode::ToolStd,
+            host,
+            Kind::Test,
+            "library/stdarch/crates/core_arch",
+            SourceType::InTree,
+            &[],
+        );
+        cargo.env("TARGET", host.to_string().as_str());
+
+        let allowed_features = [
+            // tidy-alphabetical-start
+            "aarch64_unstable_target_feature",
+            "abi_unadjusted",
+            "abi_vectorcall",
+            "allow_internal_unstable",
+            "arm_target_feature",
+            "asm_experimental_arch",
+            "avx10_target_feature",
+            "clflushopt_target_feature",
+            "const_cmp",
+            "const_eval_select",
+            "const_trait_impl",
+            "core_intrinsics",
+            "custom_inner_attributes",
+            "decl_macro",
+            "doc_cfg",
+            "f16",
+            "fmt_helpers_for_derive",
+            "funnel_shifts",
+            "hexagon_target_feature",
+            "link_llvm_intrinsics",
+            "loongarch_target_feature",
+            "maybe_uninit_as_bytes",
+            "min_adt_const_params",
+            "mips_target_feature",
+            "movrs_target_feature",
+            "no_core",
+            "powerpc_target_feature",
+            "proc_macro_hygiene",
+            "repr_simd",
+            "riscv_target_feature",
+            "rtm_target_feature",
+            "rustc_attrs",
+            "simd_ffi",
+            "staged_api",
+            "stdarch_arm_feature_detection",
+            "stdarch_internal",
+            "stdarch_mips_feature_detection",
+            "stdarch_powerpc_feature_detection",
+            "stmt_expr_attributes",
+            "test",
+            "wasm_target_feature",
+            "x86_amx_intrinsics",
+            // tidy-alphabetical-end
+        ];
+        cargo.allow_features(&allowed_features.join(","));
+        cargo.rustflag("-Zmerge-functions=disabled");
+
+        run_cargo_test(
+            cargo,
+            &[],
+            &["core_arch".to_string()],
+            Some("core_arch"),
+            host,
+            builder,
+            record_failed_tests,
+        );
+    }
+}
+
 /// Runs stdarch's intrinsic-test binary crate to verify that Rust's `core::arch`
 /// SIMD intrinsics produce the same results as their C counterparts.
 ///
diff --git a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test.snap b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test.snap
index 32ed54050dc3d..0e4f2906c0d49 100644
--- a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test.snap
+++ b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test.snap
@@ -187,6 +187,9 @@ expression: test
 [Test] test::StdarchVerify
     targets: [x86_64-unknown-linux-gnu]
     - Set({library/stdarch/crates/stdarch-verify})
+[Test] test::CoreArchTest
+    targets: [x86_64-unknown-linux-gnu]
+    - Set({core-arch})
 [Test] test::RustdocJSStd
     targets: [x86_64-unknown-linux-gnu]
     - Suite(tests/rustdoc-js-std)
diff --git a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage.snap b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage.snap
index d1cdf81a14e08..996c3ba17438c 100644
--- a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage.snap
+++ b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage.snap
@@ -184,6 +184,9 @@ expression: test --skip=coverage
 [Test] test::StdarchVerify
     targets: [x86_64-unknown-linux-gnu]
     - Set({library/stdarch/crates/stdarch-verify})
+[Test] test::CoreArchTest
+    targets: [x86_64-unknown-linux-gnu]
+    - Set({core-arch})
 [Test] test::RustdocJSStd
     targets: [x86_64-unknown-linux-gnu]
     - Suite(tests/rustdoc-js-std)
diff --git a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_map.snap b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_map.snap
index df4b8a2ce1299..f24d8a9a11cd4 100644
--- a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_map.snap
+++ b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_map.snap
@@ -187,6 +187,9 @@ expression: test --skip=coverage-map
 [Test] test::StdarchVerify
     targets: [x86_64-unknown-linux-gnu]
     - Set({library/stdarch/crates/stdarch-verify})
+[Test] test::CoreArchTest
+    targets: [x86_64-unknown-linux-gnu]
+    - Set({core-arch})
 [Test] test::RustdocJSStd
     targets: [x86_64-unknown-linux-gnu]
     - Suite(tests/rustdoc-js-std)
diff --git a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_run.snap b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_run.snap
index 75992df8aa616..318433fc4568e 100644
--- a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_run.snap
+++ b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_run.snap
@@ -187,6 +187,9 @@ expression: test --skip=coverage-run
 [Test] test::StdarchVerify
     targets: [x86_64-unknown-linux-gnu]
     - Set({library/stdarch/crates/stdarch-verify})
+[Test] test::CoreArchTest
+    targets: [x86_64-unknown-linux-gnu]
+    - Set({core-arch})
 [Test] test::RustdocJSStd
     targets: [x86_64-unknown-linux-gnu]
     - Suite(tests/rustdoc-js-std)
diff --git a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests.snap b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests.snap
index 72839a9dddb10..1c10b30f723c3 100644
--- a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests.snap
+++ b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests.snap
@@ -148,6 +148,9 @@ expression: test --skip=tests
 [Test] test::StdarchVerify
     targets: [x86_64-unknown-linux-gnu]
     - Set({library/stdarch/crates/stdarch-verify})
+[Test] test::CoreArchTest
+    targets: [x86_64-unknown-linux-gnu]
+    - Set({core-arch})
 [Test] test::RustdocTheme
     targets: [x86_64-unknown-linux-gnu]
     - Set({src/tools/rustdoc-themes})
diff --git a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_coverage.snap b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_coverage.snap
index a44052fac41f9..d6336c14e0ae9 100644
--- a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_coverage.snap
+++ b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_coverage.snap
@@ -184,6 +184,9 @@ expression: test --skip=tests/coverage
 [Test] test::StdarchVerify
     targets: [x86_64-unknown-linux-gnu]
     - Set({library/stdarch/crates/stdarch-verify})
+[Test] test::CoreArchTest
+    targets: [x86_64-unknown-linux-gnu]
+    - Set({core-arch})
 [Test] test::RustdocJSStd
     targets: [x86_64-unknown-linux-gnu]
     - Suite(tests/rustdoc-js-std)
diff --git a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_etc.snap b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_etc.snap
index ee846481847cd..ea91c610295ca 100644
--- a/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_etc.snap
+++ b/src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_etc.snap
@@ -128,6 +128,9 @@ expression: test --skip=tests --skip=library --skip=tidyselftest
 [Test] test::RustcBook
     targets: [x86_64-unknown-linux-gnu]
     - Set({src/doc/rustc})
+[Test] test::CoreArchTest
+    targets: [x86_64-unknown-linux-gnu]
+    - Set({core-arch})
 [Test] test::RustdocTheme
     targets: [x86_64-unknown-linux-gnu]
     - Set({src/tools/rustdoc-themes})
diff --git a/src/bootstrap/src/core/builder/mod.rs b/src/bootstrap/src/core/builder/mod.rs
index 0bd0781133684..c9cea120dbd22 100644
--- a/src/bootstrap/src/core/builder/mod.rs
+++ b/src/bootstrap/src/core/builder/mod.rs
@@ -922,6 +922,7 @@ impl<'a> Builder<'a> {
                 test::Clippy,
                 test::CompiletestTest,
                 test::StdarchVerify,
+                test::CoreArchTest,
                 test::CrateRunMakeSupport,
                 test::CrateBuildHelper,
                 test::RustdocJSStd,
diff --git a/src/ci/docker/scripts/stage_2_test_set1.sh b/src/ci/docker/scripts/stage_2_test_set1.sh
index 62b3c2c051a40..e64d73e7c1309 100755
--- a/src/ci/docker/scripts/stage_2_test_set1.sh
+++ b/src/ci/docker/scripts/stage_2_test_set1.sh
@@ -20,8 +20,15 @@ if [ "$LLVM_VERSION" = "21" ]; then
   SKIP_INTRINSICS="--skip intrinsic-test"
 fi
 
+# Skip core-arch on LLVM < 23 to avoid CI failures.
+if [ -n "$LLVM_VERSION" ] && [ "$LLVM_VERSION" -lt 23 ]; then
+  echo "LLVM_VERSION < 23; skipping core-arch"
+  SKIP_CORE_ARCH="--skip core-arch"
+fi
+
 ../x.py --stage 2 test \
   ${SKIP_TIDY:+$SKIP_TIDY} \
   ${SKIP_INTRINSICS:+$SKIP_INTRINSICS} \
+  ${SKIP_CORE_ARCH:+$SKIP_CORE_ARCH} \
   --skip compiler \
   --skip src
diff --git a/src/ci/docker/scripts/stage_2_test_set2.sh b/src/ci/docker/scripts/stage_2_test_set2.sh
index c0cdc31011378..933ada10e1ff1 100755
--- a/src/ci/docker/scripts/stage_2_test_set2.sh
+++ b/src/ci/docker/scripts/stage_2_test_set2.sh
@@ -29,10 +29,17 @@ if [ "$LLVM_VERSION" = "21" ]; then
   SKIP_INTRINSICS="--skip intrinsic-test"
 fi
 
+# Skip core-arch on LLVM < 23 to avoid CI failures.
+if [ -n "$LLVM_VERSION" ] && [ "$LLVM_VERSION" -lt 23 ]; then
+  echo "LLVM_VERSION < 23; skipping core-arch"
+  SKIP_CORE_ARCH="--skip core-arch"
+fi
+
 ../x.py --stage 2 test \
   ${SKIP_TIDY:+$SKIP_TIDY} \
   ${SKIP_INTRINSICS:+$SKIP_INTRINSICS} \
   ${SKIP_RUST_ANALYZER:+$SKIP_RUST_ANALYZER} \
+  ${SKIP_CORE_ARCH:+$SKIP_CORE_ARCH} \
   --skip tests \
   --skip library \
   --skip tidyselftest