arch refactor + backend ir start

src/arch/x86_64/mod.rs

@@ -0,0 +1,25 @@
+mod asm;
+mod encode;
+mod reg;
+#[cfg(test)]
+mod test;
+
+use crate::{
+    arch::Arch,
+    backend::{LinkedProgram, Program},
+    io::CompilerMsg,
+};
+
+pub use asm::*;
+pub use encode::*;
+pub use reg::*;
+
+pub struct X86_64;
+
+impl Arch for X86_64 {
+    const NAME: &str = "x86_64";
+    type Asm = Asm;
+    fn compile(p: &Program<Self>) -> Result<LinkedProgram, CompilerMsg> {
+        encode_program(p)
+    }
+}