Add MTE intrinsics

Adds intrinsic functions to `core_arch::aarch64` for MTE, as per the
ACLE:
- __arm_mte_create_random_tag
- __arm_mte_increment_tag
- __arm_mte_exclude_tag
- __arm_mte_set_tag
- __arm_mte_get_tag
- __arm_mte_ptrdiff

These are unavailable without the `mte` target feature.

crates/core_arch/src/aarch64/mod.rs

@@ -6,6 +6,10 @@
 //! [arm_ref]: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0073a/IHI0073A_arm_neon_intrinsics_ref.pdf
 //! [arm_dat]: https://developer.arm.com/technologies/neon/intrinsics
 
+mod mte;
+#[unstable(feature = "stdarch_aarch64_mte", issue = "129010")]
+pub use self::mte::*;
+
 // NEON intrinsics are currently broken on big-endian, so don't expose them. (#1484)
 #[cfg(target_endian = "little")]
 mod neon;

crates/core_arch/src/aarch64/mte.rs

@@ -0,0 +1,171 @@
+//! AArch64 Memory tagging intrinsics
+//!
+//! [ACLE documentation](https://arm-software.github.io/acle/main/acle.html#markdown-toc-mte-intrinsics)
+
+extern "unadjusted" {
+    #[cfg_attr(
+        any(target_arch = "aarch64", target_arch = "arm64ec"),
+        link_name = "llvm.aarch64.irg"
+    )]
+    fn irg_(ptr: *const (), exclude: i64) -> *const ();
+    #[cfg_attr(
+        any(target_arch = "aarch64", target_arch = "arm64ec"),
+        link_name = "llvm.aarch64.gmi"
+    )]
+    fn gmi_(ptr: *const (), exclude: i64) -> i64;
+    #[cfg_attr(
+        any(target_arch = "aarch64", target_arch = "arm64ec"),
+        link_name = "llvm.aarch64.ldg"
+    )]
+    fn ldg_(ptr: *const (), tag_ptr: *const ()) -> *const ();
+    #[cfg_attr(
+        any(target_arch = "aarch64", target_arch = "arm64ec"),
+        link_name = "llvm.aarch64.stg"
+    )]
+    fn stg_(tagged_ptr: *const (), addr_to_tag: *const ());
+    #[cfg_attr(
+        any(target_arch = "aarch64", target_arch = "arm64ec"),
+        link_name = "llvm.aarch64.addg"
+    )]
+    fn addg_(ptr: *const (), value: i64) -> *const ();
+    #[cfg_attr(
+        any(target_arch = "aarch64", target_arch = "arm64ec"),
+        link_name = "llvm.aarch64.subp"
+    )]
+    fn subp_(ptr_a: *const (), ptr_b: *const ()) -> i64;
+}
+
+/// Return a pointer containing a randomly generated logical address tag.
+///
+/// `src`: A pointer containing an address.
+/// `mask`: A mask where each of the lower 16 bits specifies logical
+///         tags which must be excluded from consideration. Zero excludes no
+///         tags.
+///
+/// The returned pointer contains a copy of the `src` address, but with a
+/// randomly generated logical tag, excluding any specified by `mask`.
+///
+/// SAFETY: The pointer provided by this intrinsic will be invalid until the memory
+/// has been appropriately tagged with `__arm_mte_set_tag`. If using that intrinsic
+/// on the provided pointer is itself invalid, then it will be permanently invalid
+/// and Undefined Behavior to dereference it.
+#[inline]
+#[target_feature(enable = "mte")]
+#[unstable(feature = "stdarch_aarch64_mte", issue = "129010")]
+pub unsafe fn __arm_mte_create_random_tag<T>(src: *const T, mask: u64) -> *const T {
+    irg_(src as *const (), mask as i64) as *const T
+}
+
+/// Return a pointer with the logical address tag offset by a value.
+///
+/// `src`: A pointer containing an address and a logical tag.
+/// `OFFSET`: A compile-time constant value in the range [0, 15].
+///
+/// Adds offset to the logical address tag in `src`, wrapping if the result is
+/// outside of the valid 16 tags.
+///
+/// SAFETY: See `__arm_mte_create_random_tag`.
+#[inline]
+#[target_feature(enable = "mte")]
+#[unstable(feature = "stdarch_aarch64_mte", issue = "129010")]
+pub unsafe fn __arm_mte_increment_tag<const OFFSET: i64, T>(src: *const T) -> *const T {
+    addg_(src as *const (), OFFSET) as *const T
+}
+
+/// Add a logical tag to the set of excluded logical tags.
+///
+/// `src`: A pointer containing an address and a logical tag.
+/// `excluded`: A mask where the lower 16 bits each specify currently-excluded
+///             logical tags.
+///
+/// Adds the logical tag stored in `src` to the set in `excluded`, and returns
+/// the result.
+#[inline]
+#[target_feature(enable = "mte")]
+#[unstable(feature = "stdarch_aarch64_mte", issue = "129010")]
+pub unsafe fn __arm_mte_exclude_tag<T>(src: *const T, excluded: u64) -> u64 {
+    gmi_(src as *const (), excluded as i64) as u64
+}
+
+/// Store an allocation tag for the 16-byte granule of memory.
+///
+/// `tag_address`: A pointer containing an address and a logical tag, which
+///                must be 16-byte aligned.
+///
+/// SAFETY: `tag_address` must be 16-byte aligned. The tag will apply to the
+/// entire 16-byte memory granule.
+#[inline]
+#[target_feature(enable = "mte")]
+#[unstable(feature = "stdarch_aarch64_mte", issue = "129010")]
+pub unsafe fn __arm_mte_set_tag<T>(tag_address: *const T) {
+    stg_(tag_address as *const (), tag_address as *const ());
+}
+
+/// Load an allocation tag from memory, returning a new pointer with the
+/// corresponding logical tag.
+///
+/// `address`: A pointer containing an address from which allocation tag memory
+///            is read. This does not need to be 16-byte aligned.
+#[inline]
+#[target_feature(enable = "mte")]
+#[unstable(feature = "stdarch_aarch64_mte", issue = "129010")]
+pub unsafe fn __arm_mte_get_tag<T>(address: *const T) -> *const T {
+    ldg_(address as *const (), address as *const ()) as *const T
+}
+
+/// Calculate the difference between the address parts of two pointers, ignoring
+/// the tags, and sign-extending the result.
+#[inline]
+#[target_feature(enable = "mte")]
+#[unstable(feature = "stdarch_aarch64_mte", issue = "129010")]
+pub unsafe fn __arm_mte_ptrdiff<T, U>(a: *const T, b: *const U) -> i64 {
+    subp_(a as *const (), b as *const ())
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use stdarch_test::assert_instr;
+
+    #[cfg_attr(test, assert_instr(irg))]
+    #[allow(dead_code)]
+    #[target_feature(enable = "mte")]
+    pub unsafe fn __test_create_random_tag(src: *const (), mask: u64) -> *const () {
+        __arm_mte_create_random_tag(src, mask)
+    }
+
+    #[cfg_attr(test, assert_instr(addg))]
+    #[allow(dead_code)]
+    #[target_feature(enable = "mte")]
+    pub unsafe fn __test_increment_tag(src: *const ()) -> *const () {
+        __arm_mte_increment_tag::<1, _>(src)
+    }
+
+    #[cfg_attr(test, assert_instr(gmi))]
+    #[allow(dead_code)]
+    #[target_feature(enable = "mte")]
+    pub unsafe fn __test_exclude_tag(src: *const (), excluded: u64) -> u64 {
+        __arm_mte_exclude_tag(src, excluded)
+    }
+
+    #[cfg_attr(test, assert_instr(stg))]
+    #[allow(dead_code)]
+    #[target_feature(enable = "mte")]
+    pub unsafe fn __test_set_tag(src: *const ()) {
+        __arm_mte_set_tag(src)
+    }
+
+    #[cfg_attr(test, assert_instr(ldg))]
+    #[allow(dead_code)]
+    #[target_feature(enable = "mte")]
+    pub unsafe fn __test_get_tag(src: *const ()) -> *const () {
+        __arm_mte_get_tag(src)
+    }
+
+    #[cfg_attr(test, assert_instr(subp))]
+    #[allow(dead_code)]
+    #[target_feature(enable = "mte")]
+    pub unsafe fn __test_ptrdiff(a: *const (), b: *const ()) -> i64 {
+        __arm_mte_ptrdiff(a, b)
+    }
+}