fn dav1d_get_cpu_flags_arm: Use `is_{arm,aarch64}_feature_detected!…

…` for CPU feature detection.

`is_arm_feature_detected!` is still unstable (rust-lang/rust#111190),
so we have to enable `#![feature(stdsimd)]` on `arm`,
though it doesn't look like this part of `stdsimd` is likely to change.

lib.rs

@@ -4,6 +4,7 @@
 #![feature(c_variadic)]
 #![feature(core_intrinsics)]
 #![feature(extern_types)]
+#![cfg_attr(target_arch = "arm", feature(stdsimd))]
 
 #[cfg(not(any(feature = "bitdepth_8", feature = "bitdepth_16")))]
 compile_error!("No bitdepths enabled. Enable one or more of the following features: `bitdepth_8`, `bitdepth_16`");

src/arm/cpu.rs

@@ -1,35 +1,25 @@
 use bitflags::bitflags;
-use cfg_if::cfg_if;
+use std::arch;
 use std::ffi::c_uint;
-use std::ffi::c_ulong;
 
 bitflags! {
     pub struct CpuFlags: c_uint {
         const NEON = 1 << 0;
     }
 }
 
-pub const NEON_HWCAP: c_ulong = 1 << 12;
-
 #[cold]
 pub unsafe fn dav1d_get_cpu_flags_arm() -> CpuFlags {
     let mut flags = CpuFlags::empty();
 
-    cfg_if! {
-        if #[cfg(any(
-            target_arch = "aarch64",
-            target_os = "windows",
-            target_os = "macos"
-        ))] {
-            flags |= CpuFlags::NEON;
-        } else if #[cfg(target_arch = "arm")] {
-            if (libc::getauxval(libc::AT_HWCAP) & NEON_HWCAP) != 0 {
-                flags |= CpuFlags::NEON;
-            }
-        } else if #[cfg(target_os = "android")] {
-            // TODO: Support Android by parsing `/proc/cpuinfo` the way the original C does.
-            todo!("Android is not yet supported")
-        }
+    #[cfg(target_arch = "arm")]
+    if arch::is_arm_feature_detected!("neon") {
+        flags |= CpuFlags::NEON;
+    }
+
+    #[cfg(target_arch = "aarch64")]
+    if arch::is_aarch64_feature_detected!("neon") {
+        flags |= CpuFlags::NEON;
     }
 
     flags