core: Add ARM64 FJCVTZS instruction optimization for f64 to i32

Author: CrazyboyQCD

core/Cargo.toml

@@ -92,6 +92,7 @@ egui = ["dep:egui", "dep:egui_extras", "png"]
 jpegxr = ["dep:jpegxr", "lzma"]
 default_font = []
 serde = ["serde/derive"]
+aarch64_jsconv = []
 
 [build-dependencies]
 build_playerglobal = { path = "build_playerglobal" }

core/src/ecma_conversions.rs

@@ -40,9 +40,44 @@ pub fn f64_to_wrapping_u32(n: f64) -> u32 {
 /// Converts an `f64` to an `i32` with ECMAScript `ToInt32` wrapping behavior.
 /// The value will be wrapped in the range [-2^31, 2^31).
 pub fn f64_to_wrapping_i32(n: f64) -> i32 {
+    #[cfg(feature = "aarch64_jsconv")]
+    {
+        #[cfg(all(target_arch = "aarch64", target_feature = "jsconv"))]
+        unsafe {
+            f64_to_wrapping_int32_aarch64(n)
+        }
+        #[cfg(not(all(target_arch = "aarch64", target_feature = "jsconv")))]
+        f64_to_wrapping_i32_generic(n)
+    }
+    #[cfg(not(feature = "aarch64_jsconv"))]
+    f64_to_wrapping_i32_generic(n)
+}
+
+#[allow(unused)]
+fn f64_to_wrapping_i32_generic(n: f64) -> i32 {
     f64_to_wrapping_u32(n) as i32
 }
 
+#[allow(unused)]
+#[cfg(feature = "aarch64_jsconv")]
+#[cfg(target_arch = "aarch64")]
+#[target_feature(enable = "jsconv")]
+/// Converts an `f64` to an `i32` with ECMAScript `ToInt32` wrapping behavior.
+/// The value will be wrapped in the range [-2^31, 2^31).
+/// Optimized for aarch64 cpu with the fjcvtzs instruction.
+unsafe fn f64_to_wrapping_int32_aarch64(number: f64) -> i32 {
+    let ret: i32;
+    // SAFETY: fjcvtzs instruction is available under jsconv feature.
+    unsafe {
+        std::arch::asm!(
+            "fjcvtzs {dst:w}, {src:d}",
+            src = in(vreg) number,
+            dst = out(reg) ret,
+        );
+    }
+    ret
+}
+
 /// Implements the IEEE-754 "Round to nearest, ties to even" rounding rule.
 /// (e.g., both 1.5 and 2.5 will round to 2).
 /// This also clamps out-of-range values and NaN to `i32::MIN`.