Run-time feature detection for Aarch64 on Windows.

library/stdarch/crates/std_detect/src/detect/mod.rs

@@ -106,6 +106,9 @@ cfg_if! {
         mod aarch64;
         #[path = "os/freebsd/mod.rs"]
         mod os;
+    } else if #[cfg(all(target_os = "windows", target_arch = "aarch64"))] {
+        #[path = "os/windows/aarch64.rs"]
+        mod os;
     } else {
         #[path = "os/other.rs"]
         mod os;

library/stdarch/crates/std_detect/src/detect/os/windows/aarch64.rs

@@ -0,0 +1,55 @@
+//! Run-time feature detection for Aarch64 on Windows.
+
+use crate::detect::{cache, Feature};
+
+/// Try to read the features using IsProcessorFeaturePresent.
+pub(crate) fn detect_features() -> cache::Initializer {
+    type DWORD = u32;
+    type BOOL = i32;
+
+    const FALSE: BOOL = 0;
+    // The following Microsoft documents isn't updated for aarch64.
+    // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-isprocessorfeaturepresent
+    // These are defined in winnt.h of Windows SDK
+    const PF_ARM_NEON_INSTRUCTIONS_AVAILABLE: u32 = 19;
+    const PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE: u32 = 30;
+    const PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE: u32 = 31;
+
+    extern "system" {
+        pub fn IsProcessorFeaturePresent(ProcessorFeature: DWORD) -> BOOL;
+    }
+
+    let mut value = cache::Initializer::default();
+    {
+        let mut enable_feature = |f, enable| {
+            if enable {
+                value.set(f as u32);
+            }
+        };
+
+        // Some features such Feature::fp may be supported on current CPU,
+        // but no way to detect it by OS API.
+        // Also, we require unsafe block for the extern "system" calls.
+        unsafe {
+            enable_feature(
+                Feature::asimd,
+                IsProcessorFeaturePresent(PF_ARM_NEON_INSTRUCTIONS_AVAILABLE) != FALSE,
+            );
+            enable_feature(
+                Feature::crc,
+                IsProcessorFeaturePresent(PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE) != FALSE,
+            );
+            // PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE means aes, sha1, sha2 and
+            // pmull support
+            enable_feature(
+                Feature::crypto,
+                IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE) != FALSE,
+            );
+            enable_feature(
+                Feature::pmull,
+                IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE) != FALSE,
+            );
+        }
+    }
+    value
+}