1 files changed, 29 insertions, 0 deletions
diff --git a/library/stdarch/crates/core_arch/src/x86_64/bswap.rs b/library/stdarch/crates/core_arch/src/x86_64/bswap.rs
new file mode 100644
index 000000000..90a209ce3
--- /dev/null
+++ b/library/stdarch/crates/core_arch/src/x86_64/bswap.rs
@@ -0,0 +1,29 @@
+//! Byte swap intrinsics.
+
+#![allow(clippy::module_name_repetitions)]
+
+#[cfg(test)]
+use stdarch_test::assert_instr;
+
+/// Returns an integer with the reversed byte order of x
+///
+/// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_bswap64)
+#[inline]
+#[cfg_attr(test, assert_instr(bswap))]
+#[stable(feature = "simd_x86", since = "1.27.0")]
+pub unsafe fn _bswap64(x: i64) -> i64 {
+    x.swap_bytes()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_bswap64() {
+        unsafe {
+            assert_eq!(_bswap64(0x0EADBEEFFADECA0E), 0x0ECADEFAEFBEAD0E);
+            assert_eq!(_bswap64(0x0000000000000000), 0x0000000000000000);
+        }
+    }
+}