Implement ARM __ssat and __usat functions

Author: eduardosm

crates/core_arch/src/arm/mod.rs

@@ -11,8 +11,7 @@
 mod sat;
 
 #[cfg(any(target_feature = "v6", doc))]
-// Remove warning because this module is currently empty.
-#[allow(unused_imports)]
+#[unstable(feature = "stdarch_arm_sat", issue = "none")]
 pub use self::sat::*;
 
 // Supported arches: 5TE, 7E-M. See Section 10.1 of ACLE (e.g. QADD)

crates/core_arch/src/arm/sat.rs

@@ -1,8 +1,62 @@
 //! # References:
 //!
 //! - Section 8.4 "Saturating intrinsics"
-//!
-//! Intrinsics that could live here:
-//!
-//! - __ssat
-//! - __usat
+
+#[cfg(test)]
+use stdarch_test::assert_instr;
+
+/// Saturates a 32-bit signed integer to a signed integer with a given
+/// bit width.
+#[unstable(feature = "stdarch_arm_sat", issue = "none")]
+#[inline]
+#[cfg_attr(test, assert_instr("ssat", WIDTH = 8))]
+#[rustc_legacy_const_generics(1)]
+pub unsafe fn __ssat<const WIDTH: u32>(x: i32) -> i32 {
+    static_assert!(matches!(WIDTH, 1..=32));
+    arm_ssat(x, WIDTH as i32)
+}
+
+/// Saturates a 32-bit signed integer to an unsigned integer with a given
+/// bit width.
+#[unstable(feature = "stdarch_arm_sat", issue = "none")]
+#[inline]
+#[cfg_attr(test, assert_instr("usat", WIDTH = 8))]
+#[rustc_legacy_const_generics(1)]
+pub unsafe fn __usat<const WIDTH: u32>(x: i32) -> u32 {
+    static_assert!(matches!(WIDTH, 1..=32));
+    arm_usat(x, WIDTH as i32)
+}
+
+extern "unadjusted" {
+    #[link_name = "llvm.arm.ssat"]
+    fn arm_ssat(x: i32, y: i32) -> i32;
+
+    #[link_name = "llvm.arm.usat"]
+    fn arm_usat(x: i32, y: i32) -> u32;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use stdarch_test::simd_test;
+
+    #[test]
+    fn test_ssat() {
+        unsafe {
+            assert_eq!(__ssat::<8>(1), 1);
+            assert_eq!(__ssat::<8>(1000), 127);
+            assert_eq!(__ssat::<8>(-1), -1);
+            assert_eq!(__ssat::<8>(-1000), -128);
+        }
+    }
+
+    #[test]
+    fn test_usat() {
+        unsafe {
+            assert_eq!(__usat::<8>(1), 1);
+            assert_eq!(__usat::<8>(1000), 255);
+            assert_eq!(__usat::<8>(-1), 0);
+            assert_eq!(__usat::<8>(-1000), 0);
+        }
+    }
+}

crates/stdarch-verify/tests/arm.rs

@@ -449,6 +449,7 @@ fn verify_all_signatures() {
                 // TODO: we still need to verify these intrinsics or find a
                 // reference for them, need to figure out where though!
                 if !rust.file.ends_with("dsp.rs\"")
+                    && !rust.file.ends_with("sat.rs\"")
                     && !rust.file.ends_with("simd32.rs\"")
                     && !rust.file.ends_with("v6.rs\"")
                     && !rust.file.ends_with("v7.rs\"")