initial commit

library/compiler-builtins/src/lib.rs

@@ -0,0 +1,43 @@
+#![allow(unused_features)]
+#![cfg_attr(not(test), no_std)]
+#![feature(asm)]
+#![feature(core_intrinsics)]
+#![feature(naked_functions)]
+// TODO(rust-lang/rust#35021) uncomment when that PR lands
+// #![feature(rustc_builtins)]
+
+#[cfg(test)]
+extern crate core;
+
+use core::mem;
+
+#[cfg(target_arch = "arm")]
+pub mod arm;
+
+#[cfg(target_arch = "x86_64")]
+pub mod x86_64;
+
+#[cfg(test)]
+mod test;
+
+const CHAR_BITS: usize = 8;
+
+macro_rules! absv_i2 {
+    ($intrinsic:ident : $ty:ty) => {
+        #[no_mangle]
+        pub extern "C" fn $intrinsic(x: $ty) -> $ty {
+            let n = mem::size_of::<$ty>() * CHAR_BITS;
+            if x == 1 << (n - 1) {
+                panic!();
+            }
+            let y = x >> (n - 1);
+            (x ^ y) - y
+        }
+
+    }
+}
+
+absv_i2!(__absvsi2: i32);
+absv_i2!(__absvdi2: i64);
+// TODO(rust-lang/35118)?
+// absv_i2!(__absvti2, i128);