1 files changed, 67 insertions, 0 deletions
diff --git a/yjit/src/asm/arm64/inst/call.rs b/yjit/src/asm/arm64/inst/call.rs
new file mode 100644
index 0000000000..6f23acf9f5
--- /dev/null
+++ b/yjit/src/asm/arm64/inst/call.rs
@@ -0,0 +1,67 @@
+/// The struct that represents an A64 branch with link instruction that can be
+/// encoded.
+///
+/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
+/// | 31 30 29 28 | 27 26 25 24 | 23 22 21 20 | 19 18 17 16 | 15 14 13 12 | 11 10 09 08 | 07 06 05 04 | 03 02 01 00 |
+/// |  1  0  0  1    0  1                                                                                           |
+/// |                     imm26.................................................................................... |
+/// +-------------+-------------+-------------+-------------+-------------+-------------+-------------+-------------+
+///
+pub struct Call {
+    /// The PC-relative offset to jump to (which will be multiplied by 4).
+    imm26: i32
+}
+
+impl Call {
+    /// BL
+    /// https://developer.arm.com/documentation/ddi0596/2021-12/Base-Instructions/BL--Branch-with-Link-?lang=en
+    pub fn bl(imm26: i32) -> Self {
+        Self { imm26 }
+    }
+}
+
+/// https://developer.arm.com/documentation/ddi0602/2022-03/Index-by-Encoding/Branches--Exception-Generating-and-System-instructions?lang=en
+const FAMILY: u32 = 0b101;
+
+impl From<Call> for u32 {
+    /// Convert an instruction into a 32-bit value.
+    fn from(inst: Call) -> Self {
+        let imm26 = (inst.imm26 as u32) & ((1 << 26) - 1);
+
+        0
+        | (1 << 31)
+        | (FAMILY << 26)
+        | imm26
+    }
+}
+
+impl From<Call> for [u8; 4] {
+    /// Convert an instruction into a 4 byte array.
+    fn from(inst: Call) -> [u8; 4] {
+        let result: u32 = inst.into();
+        result.to_le_bytes()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_bl() {
+        let result: u32 = Call::bl(0).into();
+        assert_eq!(0x94000000, result);
+    }
+
+    #[test]
+    fn test_bl_positive() {
+        let result: u32 = Call::bl(256).into();
+        assert_eq!(0x94000100, result);
+    }
+
+    #[test]
+    fn test_bl_negative() {
+        let result: u32 = Call::bl(-256).into();
+        assert_eq!(0x97ffff00, result);
+    }
+}