diff --git a/compiler/gen_dev/src/generic64/aarch64.rs b/compiler/gen_dev/src/generic64/aarch64.rs
index 194346358a..bbf5fb60c2 100644
--- a/compiler/gen_dev/src/generic64/aarch64.rs
+++ b/compiler/gen_dev/src/generic64/aarch64.rs
@@ -307,6 +307,16 @@ impl Assembler<AArch64GPReg> for AArch64Assembler {
         }
     }
 
+    #[inline(always)]
+    fn sub_reg64_reg64_reg64(
+        _buf: &mut Vec<'_, u8>,
+        _dst: AArch64GPReg,
+        _src1: AArch64GPReg,
+        _src2: AArch64GPReg,
+    ) {
+        unimplemented!("registers subtractions not implemented yet for AArch64");
+    }
+
     #[inline(always)]
     fn ret(buf: &mut Vec<'_, u8>) {
         ret_reg64(buf, AArch64GPReg::LR)
diff --git a/compiler/gen_dev/src/generic64/mod.rs b/compiler/gen_dev/src/generic64/mod.rs
index 5166a5aeb6..0432aa8a58 100644
--- a/compiler/gen_dev/src/generic64/mod.rs
+++ b/compiler/gen_dev/src/generic64/mod.rs
@@ -51,6 +51,7 @@ pub trait Assembler<GPReg: GPRegTrait> {
     fn mov_reg64_stack32(buf: &mut Vec<'_, u8>, dst: GPReg, offset: i32);
     fn mov_stack32_reg64(buf: &mut Vec<'_, u8>, offset: i32, src: GPReg);
     fn sub_reg64_reg64_imm32(buf: &mut Vec<'_, u8>, dst: GPReg, src1: GPReg, imm32: i32);
+    fn sub_reg64_reg64_reg64(buf: &mut Vec<'_, u8>, dst: GPReg, src1: GPReg, src2: GPReg);
     fn ret(buf: &mut Vec<'_, u8>);
 }
 
@@ -194,6 +195,19 @@ impl<'a, GPReg: GPRegTrait, ASM: Assembler<GPReg>, CC: CallConv<GPReg>> Backend<
         Ok(())
     }
 
+    fn build_num_sub_i64(
+        &mut self,
+        dst: &Symbol,
+        src1: &Symbol,
+        src2: &Symbol,
+    ) -> Result<(), String> {
+        let dst_reg = self.claim_gp_reg(dst)?;
+        let src1_reg = self.load_to_reg(src1)?;
+        let src2_reg = self.load_to_reg(src2)?;
+        ASM::sub_reg64_reg64_reg64(&mut self.buf, dst_reg, src1_reg, src2_reg);
+        Ok(())
+    }
+
     fn load_literal(&mut self, sym: &Symbol, lit: &Literal<'a>) -> Result<(), String> {
         match lit {
             Literal::Int(x) => {
diff --git a/compiler/gen_dev/src/generic64/x86_64.rs b/compiler/gen_dev/src/generic64/x86_64.rs
index b9471f9780..2f43ac920b 100644
--- a/compiler/gen_dev/src/generic64/x86_64.rs
+++ b/compiler/gen_dev/src/generic64/x86_64.rs
@@ -310,6 +310,22 @@ impl Assembler<X86_64GPReg> for X86_64Assembler {
         }
     }
     #[inline(always)]
+    fn sub_reg64_reg64_reg64(
+        buf: &mut Vec<'_, u8>,
+        dst: X86_64GPReg,
+        src1: X86_64GPReg,
+        src2: X86_64GPReg,
+    ) {
+        if dst == src1 {
+            sub_reg64_reg64(buf, dst, src2);
+        } else if dst == src2 {
+            sub_reg64_reg64(buf, dst, src1);
+        } else {
+            mov_reg64_reg64(buf, dst, src1);
+            sub_reg64_reg64(buf, dst, src2);
+        }
+    }
+    #[inline(always)]
     fn ret(buf: &mut Vec<'_, u8>) {
         ret(buf);
     }
@@ -379,6 +395,16 @@ fn add_reg64_reg64(buf: &mut Vec<'_, u8>, dst: X86_64GPReg, src: X86_64GPReg) {
     buf.extend(&[rex, 0x01, 0xC0 + dst_mod + src_mod]);
 }
 
+/// `SUB r/m64,r64` -> Sub r64 to r/m64.
+#[inline(always)]
+fn sub_reg64_reg64(buf: &mut Vec<'_, u8>, dst: X86_64GPReg, src: X86_64GPReg) {
+    let rex = add_rm_extension(dst, REX_W);
+    let rex = add_reg_extension(src, rex);
+    let dst_mod = dst as u8 % 8;
+    let src_mod = (src as u8 % 8) << 3;
+    buf.extend(&[rex, 0x29, 0xC0 + dst_mod + src_mod]);
+}
+
 /// `CMOVL r64,r/m64` -> Move if less (SF≠ OF).
 #[inline(always)]
 fn cmovl_reg64_reg64(buf: &mut Vec<'_, u8>, dst: X86_64GPReg, src: X86_64GPReg) {
diff --git a/compiler/gen_dev/src/lib.rs b/compiler/gen_dev/src/lib.rs
index a4df102b59..e3a80567e1 100644
--- a/compiler/gen_dev/src/lib.rs
+++ b/compiler/gen_dev/src/lib.rs
@@ -24,7 +24,7 @@ pub struct Env<'a> {
 }
 
 // INLINED_SYMBOLS is a set of all of the functions we automatically inline if seen.
-const INLINED_SYMBOLS: [Symbol; 2] = [Symbol::NUM_ABS, Symbol::NUM_ADD];
+const INLINED_SYMBOLS: [Symbol; 3] = [Symbol::NUM_ABS, Symbol::NUM_ADD, Symbol::NUM_SUB];
 
 // These relocations likely will need a length.
 // They may even need more definition, but this should be at least good enough for how we will use elf.
@@ -130,6 +130,10 @@ where
                                 // Instead of calling the function, just inline it.
                                 self.build_run_low_level(sym, &LowLevel::NumAdd, arguments, layout)
                             }
+                            Symbol::NUM_SUB => {
+                                // Instead of calling the function, just inline it.
+                                self.build_run_low_level(sym, &LowLevel::NumSub, arguments, layout)
+                            }
                             x => Err(format!("the function, {:?}, is not yet implemented", x)),
                         }
                     }
@@ -172,6 +176,15 @@ where
                     x => Err(format!("layout, {:?}, not implemented yet", x)),
                 }
             }
+            LowLevel::NumSub => {
+                // TODO: when this is expanded to floats. deal with typecasting here, and then call correct low level method.
+                match layout {
+                    Layout::Builtin(Builtin::Int64) => {
+                        self.build_num_sub_i64(sym, &args[0], &args[1])
+                    }
+                    x => Err(format!("layout, {:?}, not implemented yet", x)),
+                }
+            }
             x => Err(format!("low level, {:?}. is not yet implemented", x)),
         }
     }
@@ -180,7 +193,7 @@ where
     /// It only deals with inputs and outputs of i64 type.
     fn build_num_abs_i64(&mut self, dst: &Symbol, src: &Symbol) -> Result<(), String>;
 
-    /// build_num_add_i64 stores the absolute value of src into dst.
+    /// build_num_add_i64 stores the sum of src1 and src2 into dst.
     /// It only deals with inputs and outputs of i64 type.
     fn build_num_add_i64(
         &mut self,
@@ -189,6 +202,15 @@ where
         src2: &Symbol,
     ) -> Result<(), String>;
 
+    /// build_num_sub_i64 stores the `src1 - src2` difference  into dst.
+    /// It only deals with inputs and outputs of i64 type.
+    fn build_num_sub_i64(
+        &mut self,
+        dst: &Symbol,
+        src1: &Symbol,
+        src2: &Symbol,
+    ) -> Result<(), String>;
+
     /// literal_map gets the map from symbol to literal, used for lazy loading and literal folding.
     fn literal_map(&mut self) -> &mut MutMap<Symbol, Literal<'a>>;
 
diff --git a/compiler/gen_dev/tests/gen_num.rs b/compiler/gen_dev/tests/gen_num.rs
index 24be18721f..eb23442e8f 100644
--- a/compiler/gen_dev/tests/gen_num.rs
+++ b/compiler/gen_dev/tests/gen_num.rs
@@ -40,6 +40,19 @@ mod gen_num {
         );
     }
 
+    #[test]
+    fn gen_sub_i64() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                    1 - 2 - 3
+                "#
+            ),
+            -4,
+            i64
+        );
+    }
+
     #[test]
     fn i64_force_stack() {
         // This claims 33 registers. One more than Arm and RISC-V, and many more than x86-64.