diff --git a/compiler/gen_dev/src/elf.rs b/compiler/gen_dev/src/elf.rs
index 3352d7853d..ffd924cbd7 100644
--- a/compiler/gen_dev/src/elf.rs
+++ b/compiler/gen_dev/src/elf.rs
@@ -59,9 +59,9 @@ pub fn build_module<'a>(
             }
 
             // Build procedures.
-            let mut backend: X86_64Backend = Backend::new();
+            let mut backend: X86_64Backend = Backend::new(env);
             for (proc_id, proc) in procs {
-                let proc_data = backend.build_proc(env, proc);
+                let proc_data = backend.build_proc(proc);
                 output.add_symbol_data(proc_id, text, proc_data, 16);
             }
             Ok(output)
diff --git a/compiler/gen_dev/src/lib.rs b/compiler/gen_dev/src/lib.rs
index 1650995746..8dfb7652c3 100644
--- a/compiler/gen_dev/src/lib.rs
+++ b/compiler/gen_dev/src/lib.rs
@@ -11,11 +11,11 @@
 // re-enable this when working on performance optimizations than have it block PRs.
 #![allow(clippy::large_enum_variant)]
 
-use bumpalo::Bump;
+use bumpalo::{collections::Vec, Bump};
 use object::write::Object;
 use roc_collections::all::{MutMap, MutSet};
 use roc_module::symbol::{Interns, Symbol};
-use roc_mono::ir::Proc;
+use roc_mono::ir::{Expr, Literal, Proc, Stmt};
 use roc_mono::layout::Layout;
 use target_lexicon::{BinaryFormat, Triple};
 
@@ -44,9 +44,11 @@ pub fn build_module<'a>(
     }
 }
 
-trait Backend {
+trait Backend<'a> {
     /// new creates a new backend that will output to the specific Object.
-    fn new() -> Self;
+    fn new(env: &'a Env) -> Self;
+
+    fn env(&self) -> &'a Env<'a>;
 
     /// reset resets any registers or other values that may be occupied at the end of a procedure.
     fn reset(&mut self);
@@ -54,12 +56,56 @@ trait Backend {
     /// build_proc creates a procedure and outputs it to the wrapped object writer.
     /// This will need to return the list of relocations because they have to be added differently based on file format.
     /// Also, assembly will of course be generated by individual calls on backend like may setup_stack.
-    fn build_proc<'a>(&mut self, env: &'a Env, _proc: Proc<'a>) -> &'a [u8] {
-        let mut out = bumpalo::vec![in env.arena; 0x55, 0x48, 0x89, 0xE5];
-        let body = [0xb8, 0x06, 0x00, 0x00, 0x00];
-        out.extend(body.iter());
-        out.push(0x5D);
-        out.push(0xC3);
-        out.into_bump_slice()
+    fn build_proc(&mut self, proc: Proc<'a>) -> &'a [u8] {
+        self.reset();
+        // TODO: let the backend know of all the arguments.
+        let mut buf = bumpalo::vec!(in self.env().arena);
+        self.build_stmt(&mut buf, &proc.body);
+        self.wrap_proc(buf).into_bump_slice()
     }
+
+    /// wrap_proc does any setup and cleanup that should happen around the procedure.
+    /// For example, this can store the frame pionter and setup stack space.
+    /// wrap_proc is run at the end of build_proc when all internal code is finalized.
+    /// wrap_proc returns a Vec because it is expected to prepend data.
+    fn wrap_proc(&mut self, buf: Vec<'a, u8>) -> Vec<'a, u8>;
+
+    /// build_stmt builds a statement and outputs at the end of the buffer.
+    fn build_stmt(&mut self, buf: &mut Vec<'a, u8>, stmt: &Stmt<'a>) {
+        match stmt {
+            Stmt::Let(sym, expr, layout, following) => {
+                self.build_expr(buf, sym, expr, layout);
+                self.build_stmt(buf, following);
+            }
+            Stmt::Ret(sym) => {
+                self.return_symbol(buf, sym);
+            }
+            x => unimplemented!("the statement, {:?}, is not yet implemented", x),
+        }
+    }
+
+    /// build_expr builds the expressions for the specified symbol.
+    /// The builder must keep track of the symbol because it may be refered to later.
+    /// In many cases values can be lazy loaded, like literals.
+    fn build_expr(
+        &mut self,
+        _buf: &mut Vec<'a, u8>,
+        sym: &Symbol,
+        expr: &Expr<'a>,
+        layout: &Layout<'a>,
+    ) {
+        match expr {
+            Expr::Literal(lit) => {
+                self.set_symbol_to_lit(sym, lit, layout);
+            }
+            x => unimplemented!("the expression, {:?}, is not yet implemented", x),
+        }
+    }
+
+    /// set_symbol_to_lit sets a symbol to be equal to a literal.
+    /// When the symbol is used, the literal should be loaded.
+    fn set_symbol_to_lit(&mut self, sym: &Symbol, lit: &Literal<'a>, layout: &Layout<'a>);
+
+    /// return_symbol moves a symbol to the correct return location for the backend.
+    fn return_symbol(&mut self, buf: &mut Vec<'a, u8>, sym: &Symbol);
 }
diff --git a/compiler/gen_dev/src/x86_64.rs b/compiler/gen_dev/src/x86_64.rs
index 0c10845f31..7378f270b4 100644
--- a/compiler/gen_dev/src/x86_64.rs
+++ b/compiler/gen_dev/src/x86_64.rs
@@ -1,23 +1,77 @@
-use crate::Backend;
+use crate::{Backend, Env};
+use bumpalo::collections::Vec;
+use roc_collections::all::MutMap;
+use roc_module::symbol::Symbol;
+use roc_mono::ir::Literal;
+use roc_mono::layout::Layout;
 
-pub struct X86_64Backend {
+pub struct X86_64Backend<'a> {
+    env: &'a Env<'a>,
+
+    // This will need to hold info a symbol is held in a register or on the stack as well.
+    symbols_map: MutMap<Symbol, (Literal<'a>, Layout<'a>)>,
     // This is gonna need to include a lot of data. Right now I can think of quite a few.
-// Registers order by priority with info of what data is stored in them.
-// Scope with knows were all variables are currently stored.X86_64Backend
+    // Registers order by priority with info of what data is stored in them.
+    // Scope with knows were all variables are currently stored.X86_64Backend
 
-// Since this is x86_64 the calling convetions is really just windows or linux/macos.
-// Hopefully this will be easy to extract into a trait somehow. Cause probably don't want if's everywhere.
-// Also, don't really want to build an x86_64-win backend specifically for it.
+    // Since this is x86_64 the calling convetions is really just windows or linux/macos.
+    // Hopefully this will be easy to extract into a trait somehow. Cause probably don't want if's everywhere.
+    // Also, don't really want to build an x86_64-win backend specifically for it.
 
-// function parameter registers listed by order. Need to know the float equivalent registers as well.
-// Probably need to encode stack parameter knowledge here too.
-// return parameter register. This includes dealing with multiple value returns.
+    // function parameter registers listed by order. Need to know the float equivalent registers as well.
+    // Probably need to encode stack parameter knowledge here too.
+    // return parameter register. This includes dealing with multiple value returns.
 }
 
-impl Backend for X86_64Backend {
-    fn new() -> Self {
-        X86_64Backend {}
+impl<'a> Backend<'a> for X86_64Backend<'a> {
+    fn new(env: &'a Env) -> Self {
+        X86_64Backend {
+            env,
+            symbols_map: MutMap::default(),
+        }
     }
 
-    fn reset(&mut self) {}
+    fn env(&self) -> &'a Env<'a> {
+        self.env
+    }
+
+    fn reset(&mut self) {
+        self.symbols_map.clear();
+    }
+
+    fn wrap_proc(&mut self, body: Vec<'a, u8>) -> Vec<'a, u8> {
+        // push rbp     (0x55)
+        // mov rbp, rsp (0x48, 0x89, 0xE5)
+        let mut out = bumpalo::vec![in self.env.arena; 0x55, 0x48, 0x89, 0xE5];
+        out.reserve(body.len() + 2);
+
+        // TODO: handle allocating and cleaning up data on the stack.
+
+        out.extend(body);
+
+        // pop rbp
+        out.push(0x5D);
+        // ret
+        out.push(0xC3);
+
+        out
+    }
+
+    fn set_symbol_to_lit(&mut self, sym: &Symbol, lit: &Literal<'a>, layout: &Layout<'a>) {
+        self.symbols_map
+            .insert(sym.clone(), (lit.clone(), layout.clone()));
+    }
+
+    fn return_symbol(&mut self, body: &mut Vec<'a, u8>, sym: &Symbol) {
+        //let body = bumpalo::vec![in env.arena; 0xb8, 0x06, 0x00, 0x00, 0x00];
+        match self.symbols_map.get(sym) {
+            Some((Literal::Int(x), _)) => {
+                // movabs rax, ...
+                body.extend(&[0x48, 0xB8]);
+                body.extend(&x.to_le_bytes());
+            }
+            Some(x) => unimplemented!("return value, {:?}, is not yet implemented", x),
+            None => panic!("Unknown return symbol: {}", sym),
+        }
+    }
 }
diff --git a/compiler/gen_dev/tests/gen_num.rs b/compiler/gen_dev/tests/gen_num.rs
index a28a4ffecb..aeb61b1769 100644
--- a/compiler/gen_dev/tests/gen_num.rs
+++ b/compiler/gen_dev/tests/gen_num.rs
@@ -15,7 +15,15 @@ mod gen_num {
 
     #[test]
     fn i64_values() {
-        assert_evals_to!("6", 6, i64);
+        assert_evals_to!("0", 0, i64);
+        assert_evals_to!("-0", 0, i64);
+        assert_evals_to!("-1", -1, i64);
+        assert_evals_to!("1", 1, i64);
+        assert_evals_to!("9_000_000_000_000", 9_000_000_000_000, i64);
+        assert_evals_to!("-9_000_000_000_000", -9_000_000_000_000, i64);
+        assert_evals_to!("0b1010", 0b1010, i64);
+        assert_evals_to!("0o17", 0o17, i64);
+        assert_evals_to!("0x1000_0000_0000_0000", 0x1000_0000_0000_0000, i64);
     }
     /*
     #[test]
@@ -44,12 +52,10 @@ mod gen_num {
         assert_evals_to!("Num.abs -4.7", 4.7, f64);
         assert_evals_to!("Num.abs 5.8", 5.8, f64);
     }
-    */
 
     #[test]
     fn i64_abs() {
         //assert_evals_to!("Num.abs -6", 6, i64);
-        /*
         assert_evals_to!("Num.abs 7", 7, i64);
         assert_evals_to!("Num.abs 0", 0, i64);
         assert_evals_to!("Num.abs -0", 0, i64);
@@ -57,10 +63,8 @@ mod gen_num {
         assert_evals_to!("Num.abs 1", 1, i64);
         assert_evals_to!("Num.abs 9_000_000_000_000", 9_000_000_000_000, i64);
         assert_evals_to!("Num.abs -9_000_000_000_000", 9_000_000_000_000, i64);
-        */
     }
 
-    /*
     #[test]
     fn gen_if_fn() {
         assert_evals_to!(