diff --git a/library/stdarch/crates/intrinsic-test/src/arm/config.rs b/library/stdarch/crates/intrinsic-test/src/arm/config.rs
index 6faaf57d6c90..cee80374ae9d 100644
--- a/library/stdarch/crates/intrinsic-test/src/arm/config.rs
+++ b/library/stdarch/crates/intrinsic-test/src/arm/config.rs
@@ -21,6 +21,93 @@ pub const POLY128_OSTREAM_DEF: &str = r#"std::ostream& operator<<(std::ostream&
     return os;
 }"#;
 
+// Format f16 values (and vectors containing them) in a way that is consistent with C.
+pub const F16_FORMATTING_DEF: &str = r#"
+/// Used to continue `Debug`ging SIMD types as `MySimd(1, 2, 3, 4)`, as they
+/// were before moving to array-based simd.
+#[inline]
+fn debug_simd_finish<T: core::fmt::Debug, const N: usize>(
+    formatter: &mut core::fmt::Formatter<'_>,
+    type_name: &str,
+    array: &[T; N],
+) -> core::fmt::Result {
+    core::fmt::Formatter::debug_tuple_fields_finish(
+        formatter,
+        type_name,
+        &core::array::from_fn::<&dyn core::fmt::Debug, N, _>(|i| &array[i]),
+    )
+}
+
+#[repr(transparent)]
+struct Hex<T>(T);
+
+impl<T: DebugHexF16> core::fmt::Debug for Hex<T> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        <T as DebugHexF16>::fmt(&self.0, f)
+    }
+}
+
+fn debug_f16<T: DebugHexF16>(x: T) -> impl core::fmt::Debug {
+    Hex(x)
+}
+
+trait DebugHexF16 {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result;
+}
+
+impl DebugHexF16 for f16 {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(f, "{:#06x?}", self.to_bits())
+    }
+}
+
+impl DebugHexF16 for float16x4_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        let array = unsafe { core::mem::transmute::<_, [Hex<f16>; 4]>(*self) };
+        debug_simd_finish(f, "float16x4_t", &array)
+    }
+}
+
+impl DebugHexF16 for float16x8_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        let array = unsafe { core::mem::transmute::<_, [Hex<f16>; 8]>(*self) };
+        debug_simd_finish(f, "float16x8_t", &array)
+    }
+}
+
+impl DebugHexF16 for float16x4x2_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        debug_simd_finish(f, "float16x4x2_t", &[Hex(self.0), Hex(self.1)])
+    }
+}
+impl DebugHexF16 for float16x4x3_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        debug_simd_finish(f, "float16x4x3_t", &[Hex(self.0), Hex(self.1), Hex(self.2)])
+    }
+}
+impl DebugHexF16 for float16x4x4_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        debug_simd_finish(f, "float16x4x4_t", &[Hex(self.0), Hex(self.1), Hex(self.2), Hex(self.3)])
+    }
+}
+
+impl DebugHexF16 for float16x8x2_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        debug_simd_finish(f, "float16x8x2_t", &[Hex(self.0), Hex(self.1)])
+    }
+}
+impl DebugHexF16 for float16x8x3_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        debug_simd_finish(f, "float16x8x3_t", &[Hex(self.0), Hex(self.1), Hex(self.2)])
+    }
+}
+impl DebugHexF16 for float16x8x4_t {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        debug_simd_finish(f, "float16x8x4_t", &[Hex(self.0), Hex(self.1), Hex(self.2), Hex(self.3)])
+    }
+}
+ "#;
+
 pub const AARCH_CONFIGURATIONS: &str = r#"
 #![cfg_attr(target_arch = "arm", feature(stdarch_arm_neon_intrinsics))]
 #![cfg_attr(target_arch = "arm", feature(stdarch_aarch32_crc32))]
@@ -30,5 +117,6 @@ pub const AARCH_CONFIGURATIONS: &str = r#"
 #![cfg_attr(any(target_arch = "aarch64", target_arch = "arm64ec"), feature(stdarch_neon_sha3))]
 #![cfg_attr(any(target_arch = "aarch64", target_arch = "arm64ec"), feature(stdarch_neon_sm4))]
 #![cfg_attr(any(target_arch = "aarch64", target_arch = "arm64ec"), feature(stdarch_neon_ftts))]
+#![feature(fmt_helpers_for_derive)]
 #![feature(stdarch_neon_f16)]
 "#;
diff --git a/library/stdarch/crates/intrinsic-test/src/arm/intrinsic.rs b/library/stdarch/crates/intrinsic-test/src/arm/intrinsic.rs
index d86a590d883c..e408432bfaeb 100644
--- a/library/stdarch/crates/intrinsic-test/src/arm/intrinsic.rs
+++ b/library/stdarch/crates/intrinsic-test/src/arm/intrinsic.rs
@@ -87,7 +87,7 @@ impl IntrinsicDefinition<ArmIntrinsicType> for Intrinsic<ArmIntrinsicType> {
         )
     }
 
-    pub fn generate_loop_c(
+    fn generate_loop_c(
         &self,
         indentation: Indentation,
         additional: &str,
@@ -108,7 +108,7 @@ impl IntrinsicDefinition<ArmIntrinsicType> for Intrinsic<ArmIntrinsicType> {
         )
     }
 
-    pub fn generate_loop_rust(
+    fn generate_loop_rust(
         &self,
         indentation: Indentation,
         additional: &str,
diff --git a/library/stdarch/crates/intrinsic-test/src/arm/mod.rs b/library/stdarch/crates/intrinsic-test/src/arm/mod.rs
index 9e083a620932..9e089863b62b 100644
--- a/library/stdarch/crates/intrinsic-test/src/arm/mod.rs
+++ b/library/stdarch/crates/intrinsic-test/src/arm/mod.rs
@@ -13,7 +13,7 @@ use crate::common::gen_rust::compile_rust;
 use crate::common::intrinsic::{Intrinsic, IntrinsicDefinition};
 use crate::common::intrinsic_helpers::{BaseIntrinsicTypeDefinition, TypeKind};
 use crate::common::write_file::{write_c_testfiles, write_rust_testfiles};
-use config::{AARCH_CONFIGURATIONS, POLY128_OSTREAM_DEF, build_notices};
+use config::{AARCH_CONFIGURATIONS, F16_FORMATTING_DEF, POLY128_OSTREAM_DEF, build_notices};
 use json_parser::get_neon_intrinsics;
 
 pub struct ArmArchitectureTest {
@@ -91,6 +91,7 @@ impl SupportedArchitectureTest for ArmArchitectureTest {
                 .collect::<Vec<_>>(),
             final_target,
             &build_notices("// "),
+            F16_FORMATTING_DEF,
             AARCH_CONFIGURATIONS,
         );
 
diff --git a/library/stdarch/crates/intrinsic-test/src/common/gen_rust.rs b/library/stdarch/crates/intrinsic-test/src/common/gen_rust.rs
index 5c6a1efaec09..260ff1b010d3 100644
--- a/library/stdarch/crates/intrinsic-test/src/common/gen_rust.rs
+++ b/library/stdarch/crates/intrinsic-test/src/common/gen_rust.rs
@@ -7,6 +7,7 @@ use std::process::Command;
 
 pub fn generate_rust_program(
     notices: &str,
+    definitions: &str,
     configurations: &str,
     arch_definition: &str,
     arglists: &str,
@@ -17,7 +18,8 @@ pub fn generate_rust_program(
 #![feature(link_llvm_intrinsics)]
 #![feature(f16)]
 {configurations}
-#![allow(non_upper_case_globals)]
+{definitions}
+
 use core_arch::arch::{arch_definition}::*;
 
 fn main() {{
diff --git a/library/stdarch/crates/intrinsic-test/src/common/intrinsic.rs b/library/stdarch/crates/intrinsic-test/src/common/intrinsic.rs
index ace8dbf3a5db..05f4328d3ee6 100644
--- a/library/stdarch/crates/intrinsic-test/src/common/intrinsic.rs
+++ b/library/stdarch/crates/intrinsic-test/src/common/intrinsic.rs
@@ -202,7 +202,13 @@ where
         }
     }
 
-    fn generate_rust_program(&self, target: &str, notice: &str, cfg: &str) -> String {
+    fn generate_rust_program(
+        &self,
+        target: &str,
+        notice: &str,
+        definitions: &str,
+        cfg: &str,
+    ) -> String {
         let arguments = self.arguments();
         let constraints = arguments
             .iter()
@@ -212,6 +218,7 @@ where
         let indentation = Indentation::default();
         generate_rust_program(
             notice,
+            definitions,
             cfg,
             target,
             self.arguments()
diff --git a/library/stdarch/crates/intrinsic-test/src/common/write_file.rs b/library/stdarch/crates/intrinsic-test/src/common/write_file.rs
index adbf33397013..a8b62c7b6596 100644
--- a/library/stdarch/crates/intrinsic-test/src/common/write_file.rs
+++ b/library/stdarch/crates/intrinsic-test/src/common/write_file.rs
@@ -32,6 +32,7 @@ pub fn write_rust_testfiles<T: IntrinsicTypeDefinition>(
     intrinsics: Vec<&dyn IntrinsicDefinition<T>>,
     rust_target: &str,
     notice: &str,
+    definitions: &str,
     cfg: &str,
 ) -> Vec<String> {
     let intrinsics_name_list = intrinsics
@@ -41,7 +42,7 @@ pub fn write_rust_testfiles<T: IntrinsicTypeDefinition>(
     let filename_mapping = create_rust_filenames(&intrinsics_name_list);
 
     intrinsics.iter().for_each(|i| {
-        let rust_code = i.generate_rust_program(rust_target, notice, cfg);
+        let rust_code = i.generate_rust_program(rust_target, notice, definitions, cfg);
         match filename_mapping.get(&i.name()) {
             Some(filename) => write_file(filename, rust_code),
             None => {}
diff --git a/library/stdarch/crates/intrinsic-test/src/main.rs b/library/stdarch/crates/intrinsic-test/src/main.rs
index 686f750e32f1..054138a0dba1 100644
--- a/library/stdarch/crates/intrinsic-test/src/main.rs
+++ b/library/stdarch/crates/intrinsic-test/src/main.rs
@@ -1,4 +1,3 @@
-#![feature(slice_partition_dedup)]
 #[macro_use]
 extern crate log;