lots of refactoring

src/arch/x86_64/asm.rs

@@ -1,5 +1,5 @@
 use crate::{
-    arch::x86_64::{BitWidth, Reg, RegMode},
+    arch::x86_64::{Reg, RegH, RegWH, Width, WidthH},
     backend::Symbol,
 };
 
@@ -9,34 +9,42 @@ pub struct Asm {
 
 #[derive(Clone, Copy)]
 pub enum Instr {
-    Mov { dst: RegMode, src: RegImmMem },
+    Movr { dst: RegH, src: RegH, width: Width },
+    Movi { dst: RegWH, imm: u64 },
     // TODO: horrible
-    MemMov { reg: RegMode, offset: u64, val: u64 },
+    Movm { reg: RegWH, offset: u32, val: u32 },
     Int(u8),
     Call(Symbol),
-    CallMem(Symbol),
+    Callm(Symbol),
     Ret,
     Syscall,
-    Lea { dst: RegMode, sym: Symbol },
+    Lea { dst: RegWH, sym: Symbol },
-    Push(RegImm),
+    Pushr(Reg),
+    Pushi(u32),
     Pop(Reg),
     Sub,
 }
 
+#[derive(Clone, Copy)]
+pub struct Mem {
+    reg: Reg,
+    disp: u32,
+}
+
 #[derive(Clone, Copy)]
 pub enum RegImmMem {
-    Reg(RegMode),
+    Reg(RegWH),
     Imm(u64),
 }
 
 #[derive(Clone, Copy)]
-pub enum RegImm {
+pub enum RegImm<const WIDTH: u8> {
     Reg(Reg),
     Imm(u64),
 }
 
-impl From<RegMode> for RegImmMem {
+impl From<RegWH> for RegImmMem {
-    fn from(value: RegMode) -> Self {
+    fn from(value: RegWH) -> Self {
         Self::Reg(value)
     }
 }
@@ -60,31 +68,46 @@ impl From<i32> for RegImmMem {
 }
 
 mod fns {
+    use crate::io::CompilerMsg;
+
     use super::*;
-    pub fn mov(dst: RegMode, src: impl Into<RegImmMem>) -> Instr {
+    pub fn mov(dst: RegWH, src: impl Into<RegImmMem>) -> Result<Instr, CompilerMsg> {
-        Instr::Mov {
+        Ok(match src.into() {
-            dst,
+            RegImmMem::Reg(src) => {
+                if src.widthh.width() != dst.widthh.width() {
+                    return Err("src and dst are not same width".into());
+                }
+                Instr::Movr {
+                    dst: dst.into(),
                     src: src.into(),
+                    width: dst.widthh.into(),
                 }
             }
-
+            RegImmMem::Imm(imm) => Instr::Movi { dst, imm },
-    pub fn lea(dst: RegMode, sym: Symbol) -> Instr {
-        Instr::Lea { dst, sym }
-    }
-
-    pub fn push(reg: impl Into<RegImmMem>) -> Instr {
-        Instr::Push(match reg.into() {
-            RegImmMem::Reg(reg) => {
-                assert_eq!(reg.width, BitWidth::B64);
-                assert!(!reg.high);
-                RegImm::Reg(reg.reg)
-            }
-            RegImmMem::Imm(imm) => RegImm::Imm(imm),
         })
     }
 
-    pub fn pop(reg: RegMode) -> Instr {
+    pub fn lea(dst: RegWH, sym: Symbol) -> Instr {
-        assert!(reg.width == BitWidth::B64);
+        Instr::Lea { dst, sym }
+    }
+
+    pub fn push(reg: impl Into<RegImmMem>) -> Result<Instr, CompilerMsg> {
+        Ok(match reg.into() {
+            RegImmMem::Reg(reg) => {
+                if reg.widthh != WidthH::B64 {
+                    return Err("register must be 64 bit".into());
+                }
+                Instr::Pushr(reg.reg)
+            }
+            RegImmMem::Imm(imm) => match imm.try_into() {
+                Ok(imm) => Instr::Pushi(imm),
+                Err(_) => return Err("immediate must be 32 bit".into()),
+            },
+        })
+    }
+
+    pub fn pop(reg: RegWH) -> Instr {
+        assert!(reg.widthh == WidthH::B64);
         Instr::Pop(reg.reg)
     }
 }

src/arch/x86_64/encode.rs

@@ -2,6 +2,7 @@ use std::collections::HashMap;
 
 use super::*;
 use crate::backend::{LibImport, LinkedProgram, SymImport, SymTable, Symbol};
+use util::*;
 
 pub struct Encoder<'a> {
     pub data: Vec<u8>,
@@ -71,63 +72,42 @@ fn compile_instr(encoder: &mut Encoder, instr: &BInstr) -> Result<(), CompilerMs
 impl Encoder<'_> {
     // assembly
 
-    pub fn mov(&mut self, dst: RegMode, src: impl Into<RegImmMem>) -> Result<(), CompilerMsg> {
+    pub fn movi(&mut self, dst: RegWH, imm: u64) -> Result<(), CompilerMsg> {
-        let src = src.into();
+        if dst.widthh == WidthH::B16 {
-        let width = dst.width;
-        if width == BitWidth::B16 {
             self.data.push(0x66);
         }
-        let dst8 = dst.gt8();
+        if dst.requires_rex() {
-        let b64 = width == BitWidth::B64;
+            self.data.push(rex(dst.widthh, 0, 0, dst));
-        let b8 = width == BitWidth::B8;
-        let src8 = if let RegImmMem::Reg(src) = src {
-            src.gt8()
-        } else {
-            false
-        };
-        // special 64-bit / register 4-7 indicator
-        if dst8 || src8 || b64 || (dst.gt4() && !dst.high) {
-            self.data
-                .push(0x40 | dst8 as u8 | ((b64 as u8) << 3) | ((src8 as u8) << 2));
         }
-        match src {
+        if imm > dst.widthh.max() {
-            RegImmMem::Reg(src) => {
-                if dst.width != src.width {
-                    return Err("src and dst are not the same size".into());
-                }
-                self.data.push(0x88 | !b8 as u8);
-                let modrm = 0b11_000_000 | (src.base() << 3) | dst.base();
-                self.data.push(modrm);
-            }
-            RegImmMem::Imm(imm) => {
-                if imm > width.max() {
             return Err("immediate cannot fit in register".into());
         }
-                self.data.push(0xb0 | ((!b8 as u8) << 3) | dst.base());
+        let opcode = 0xb0 | ((dst.widthh.gt8() as u8) << 3);
-                self.data.extend(&imm.to_le_bytes()[..width.bytes()]);
+        self.data.push(opcode | dst.base());
-            }
+        self.data.extend(&imm.to_le_bytes()[..dst.widthh.bytes()]);
-        }
         Ok(())
     }
 
-    pub fn mem_mov(&mut self, reg: RegMode, offset: u64, val: u64) {
+    pub fn movr(&mut self, dst: RegH, src: RegH, width: Width) {
-        assert!(offset <= u8::MAX as u64);
+        if width == Width::B16 {
-        assert!(val <= u32::MAX as u64);
+            self.data.push(0x66);
-        self.data
-            .extend([0x48 | ((reg.gt8() as u8) << 2), 0xc7, 0x40 | reg.base()]);
-        if reg.reg == rsp.reg {
-            self.data.push(0x24)
         }
-        self.data.push(offset as u8);
+        if src.requires_rex(width) || dst.requires_rex(width) {
-        self.data.extend((val as u32).to_le_bytes());
+            self.data.push(rex(width, src, 0, dst));
+        }
+        self.data.push(0x88 | width.gt8() as u8);
+        self.data.push(modrm_regs(src, dst));
     }
 
-    pub fn lea(&mut self, dst: RegMode, sym: Symbol) {
+    pub fn movm(&mut self, reg: RegWH, offset: u32, val: u32) {
-        self.data.extend([
+        self.data.extend([rex(1, reg, 0, 0), 0xc7]);
-            0x48 | ((dst.gt8() as u8) << 2),
+        self.modrm_regdisp(reg, offset);
-            0x8d,
+        self.data.extend(val.to_le_bytes());
-            0x05 | (dst.base() << 3),
+    }
-        ]);
+
+    pub fn lea(&mut self, dst: RegWH, sym: Symbol) {
+        self.data
+            .extend([rex(1, dst, 0, 0), 0x8d, modrm_disp32(dst)]);
         self.sym_offset4(sym);
     }
 
@@ -144,7 +124,7 @@ impl Encoder<'_> {
         self.sym_offset4(sym);
     }
 
-    pub fn call_mem(&mut self, sym: Symbol) {
+    pub fn callm(&mut self, sym: Symbol) {
         self.data.extend([0xff, 0x15]);
         self.sym_offset4(sym);
     }
@@ -153,15 +133,15 @@ impl Encoder<'_> {
         self.data.push(0xc3);
     }
 
-    pub fn push(&mut self, reg: Reg) {
+    pub fn pushr(&mut self, reg: Reg) {
         if reg.gt8() {
             self.data.push(0x41);
         }
         self.data.push(0x50 | reg.base());
     }
 
-    pub fn push_imm(&mut self, imm: u64) {
+    pub fn pushi(&mut self, imm: u32) {
-        const U8: u64 = 2 << 8;
+        const U8: u32 = 2 << 8;
         if let 0..U8 = imm {
             self.data.push(0x6a);
             self.data.push(imm as u8);
@@ -195,30 +175,38 @@ impl Encoder<'_> {
 
     pub fn asm(&mut self, instr: Instr) -> Result<(), CompilerMsg> {
         match instr {
-            Instr::Mov { dst, src } => self.mov(dst, src)?,
+            Instr::Movr { dst, src, width } => self.movr(dst, src, width),
-            Instr::MemMov { reg, offset, val } => self.mem_mov(reg, offset, val),
+            Instr::Movi { dst, imm } => self.movi(dst, imm)?,
+            Instr::Movm { reg, offset, val } => self.movm(reg, offset, val),
             Instr::Int(code) => self.int(code),
             Instr::Syscall => self.syscall(),
             Instr::Lea { dst, sym } => self.lea(dst, sym),
             Instr::Call(sym) => self.call(sym),
+            Instr::Callm(sym) => self.callm(sym),
             Instr::Ret => self.ret(),
-            Instr::Push(val) => match val {
+            Instr::Pushr(reg) => self.pushr(reg),
-                RegImm::Reg(reg) => self.push(reg),
+            Instr::Pushi(imm) => self.pushi(imm),
-                RegImm::Imm(imm) => self.push_imm(imm),
-            },
             Instr::Pop(reg) => self.pop(reg),
-            Instr::CallMem(sym) => self.call_mem(sym),
             Instr::Sub => self.data.extend([0x48, 0x83, 0xec, 0x28]),
         }
         Ok(())
     }
-}
 
-/// assumes the next instruction is directly after
+    pub fn modrm_regdisp(&mut self, reg: impl Into<Reg>, disp: u32) {
-fn addr_offset(pos: usize, addr: u64) -> [u8; 4] {
+        let reg = reg.into();
-    let pos = (pos + 4) as i32;
+        let disp8 = disp < u8::MAX as u32;
-    let offset = addr as i32 - pos;
+        let mod_ = if disp8 { 0b01 } else { 0b10 };
-    offset.to_le_bytes()
+        self.data.push(modrm(mod_, 0, reg.base()));
+        if reg == rsp.reg {
+            // SIB
+            self.data.push(0x24);
+        }
+        if disp8 {
+            self.data.push(disp as u8);
+        } else {
+            self.data.extend(disp.to_le_bytes());
+        }
+    }
 }
 
 impl<'a> Encoder<'a> {

src/arch/x86_64/mod.rs

@@ -2,6 +2,7 @@ mod asm;
 mod encode;
 mod reg;
 mod test;
+mod util;
 
 use crate::{
     arch::Arch,

src/arch/x86_64/reg.rs

@@ -2,47 +2,35 @@
 pub struct Reg(u8);
 
 #[derive(Clone, Copy)]
-pub struct RegMode {
+pub struct RegH {
     pub reg: Reg,
-    pub width: BitWidth,
     pub high: bool,
 }
 
+#[derive(Clone, Copy)]
+pub struct RegWH {
+    pub reg: Reg,
+    pub widthh: WidthH,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq)]
-pub enum BitWidth {
+pub enum Width {
     B64,
     B32,
     B16,
     B8,
 }
 
-impl Reg {
+/// width that also specifies if high for 8 bit
-    pub fn base(&self) -> u8 {
+#[derive(Debug, Clone, Copy, PartialEq)]
-        self.0 & 0b111
+pub enum WidthH {
-    }
+    B64,
-    /// checks if register is not one of the first 8 (0-7)
+    B32,
-    pub fn gt8(&self) -> bool {
+    B16,
-        self.0 >= 0b1000
+    B8 { high: bool },
-    }
-    pub fn gt4(&self) -> bool {
-        self.0 >= 0b0100
-    }
 }
 
-impl RegMode {
+def_regs! { RegWH;
-    pub fn base(&self) -> u8 {
-        self.reg.base()
-    }
-    /// checks if register is not one of the first 8 (0-7)
-    pub fn gt8(&self) -> bool {
-        self.reg.gt8()
-    }
-    pub fn gt4(&self) -> bool {
-        self.reg.gt4()
-    }
-}
-
-def_regs! {
     0b0000 : rax eax ax al ah=spl,
     0b0001 : rcx ecx cx cl ch=bpl,
     0b0010 : rdx edx dx dl dh=sil,
@@ -63,13 +51,40 @@ def_regs! {
     0b1111 : r15 r15d r15w r15b,
 }
 
-impl BitWidth {
+impl Reg {
+    pub fn base(&self) -> u8 {
+        self.0 & 0b111
+    }
+    /// checks if register is not one of the first 8 (0-7)
+    pub fn gt8(&self) -> bool {
+        self.0 >= 0b1000
+    }
+    pub fn gt4(&self) -> bool {
+        self.0 >= 0b0100
+    }
+}
+
+impl RegWH {
+    pub fn requires_rex(&self) -> bool {
+        self.gt8()
+            || self.widthh == WidthH::B64
+            || (self.gt4() && self.widthh == WidthH::B8 { high: false })
+    }
+}
+
+impl RegH {
+    pub fn requires_rex(&self, width: Width) -> bool {
+        self.gt8() || width == Width::B64 || (self.gt4() && width == Width::B8 && !self.high)
+    }
+}
+
+impl WidthH {
     pub const fn max(&self) -> u64 {
         match self {
             Self::B64 => u64::MAX,
             Self::B32 => u32::MAX as u64,
             Self::B16 => u16::MAX as u64,
-            Self::B8 => u8::MAX as u64,
+            Self::B8 { .. } => u8::MAX as u64,
         }
     }
     pub const fn bytes(&self) -> usize {
@@ -77,28 +92,84 @@ impl BitWidth {
             Self::B64 => 8,
             Self::B32 => 4,
             Self::B16 => 2,
-            Self::B8 => 1,
+            Self::B8 { .. } => 1,
+        }
+    }
+    /// greater than 8 bits
+    pub const fn gt8(&self) -> bool {
+        !matches!(self, Self::B8 { .. })
+    }
+
+    pub const fn width(&self) -> Width {
+        match self {
+            WidthH::B64 => Width::B64,
+            WidthH::B32 => Width::B32,
+            WidthH::B16 => Width::B16,
+            WidthH::B8 { .. } => Width::B8,
+        }
+    }
+}
+
+impl Width {
+    /// greater than 8 bits
+    pub const fn gt8(&self) -> bool {
+        !matches!(self, Self::B8)
+    }
+}
+
+impl From<RegWH> for Reg {
+    fn from(value: RegWH) -> Self {
+        value.reg
+    }
+}
+
+impl From<RegH> for Reg {
+    fn from(value: RegH) -> Self {
+        value.reg
+    }
+}
+
+impl From<RegWH> for RegH {
+    fn from(value: RegWH) -> Self {
+        Self {
+            reg: value.reg,
+            high: if let WidthH::B8 { high } = value.widthh {
+                high
+            } else {
+                false
+            },
+        }
+    }
+}
+
+impl From<WidthH> for Width {
+    fn from(value: WidthH) -> Self {
+        match value {
+            WidthH::B64 => Self::B64,
+            WidthH::B32 => Self::B32,
+            WidthH::B16 => Self::B16,
+            WidthH::B8 { .. } => Self::B8,
         }
     }
 }
 
 macro_rules! def_regs {
-    ($($val:literal : $B64:ident $B32:ident $B16:ident $B8:ident $($B8H:ident=$hval:expr)?,)*) => {
+    ($Struct: ident; $($val:literal : $B64:ident $B32:ident $B16:ident $B8:ident $($B8H:ident=$hval:expr)?,)*) => {
         $(
         #[allow(non_upper_case_globals)]
-        pub const $B64: RegMode = RegMode { reg: Reg($val), width: BitWidth::B64, high: false };
+        pub const $B64: $Struct = $Struct { reg: Reg($val), widthh: WidthH::B64 };
         #[allow(non_upper_case_globals)]
-        pub const $B32: RegMode = RegMode { reg: Reg($val), width: BitWidth::B32, high: false };
+        pub const $B32: $Struct = $Struct { reg: Reg($val), widthh: WidthH::B32 };
         #[allow(non_upper_case_globals)]
-        pub const $B16: RegMode = RegMode { reg: Reg($val), width: BitWidth::B16, high: false };
+        pub const $B16: $Struct = $Struct { reg: Reg($val), widthh: WidthH::B16 };
         #[allow(non_upper_case_globals)]
-        pub const $B8 : RegMode = RegMode { reg: Reg($val), width: BitWidth::B8, high: false  };
+        pub const $B8 : $Struct = $Struct { reg: Reg($val), widthh: WidthH::B8 { high: false } };
         $(
         #[allow(non_upper_case_globals)]
-        pub const $B8H: RegMode = RegMode { reg: $hval.reg, width: BitWidth::B8, high: true };
+        pub const $B8H: $Struct = $Struct { reg: $hval.reg, widthh: WidthH::B8 { high: true } };
         )?
         )*
-        impl RegMode {
+        impl $Struct {
             pub fn parse(s: &str) -> Option<Self> {
                 Some(match s.to_lowercase().as_str() {
                     $(
@@ -116,4 +187,21 @@ macro_rules! def_regs {
         }
     };
 }
+
 use def_regs;
+
+impl std::ops::Deref for RegWH {
+    type Target = Reg;
+
+    fn deref(&self) -> &Self::Target {
+        &self.reg
+    }
+}
+
+impl std::ops::Deref for RegH {
+    type Target = Reg;
+
+    fn deref(&self) -> &Self::Target {
+        &self.reg
+    }
+}

src/arch/x86_64/test/bin.rs

@@ -5,11 +5,12 @@ use crate::{
 use std::{fs::OpenOptions, io::Write, os::unix::fs::OpenOptionsExt, process::Command};
 
 pub fn run() {
-    windows();
+    if let Err(err) = linux() {
-    // linux();
+        println!("{err:?}");
+    }
 }
 
-fn linux() {
+fn linux() -> Result<(), CompilerMsg> {
     let mut program = Program::<X86_64>::default();
     let text = b"Hello world!\n";
     let text_sym = program.ro_data("hello_en", text);
@@ -19,10 +20,10 @@ fn linux() {
         "hello2",
         [BInstr::Asm(Asm {
             instrs: vec![
-                mov(ax, 1),
+                mov(ax, 1)?,
-                mov(di, 1),
+                mov(di, 1)?,
                 lea(rsi, text_sym2),
-                mov(dx, text2.len() as u64),
+                mov(dx, text2.len() as u64)?,
                 Instr::Syscall,
                 Instr::Ret,
             ],
@@ -32,15 +33,15 @@ fn linux() {
         "main",
         [BInstr::Asm(Asm {
             instrs: vec![
-                mov(di, 39),
+                mov(di, 39)?,
-                push(rdi),
+                push(rdi)?,
-                mov(ax, 1),
+                mov(ax, 1)?,
-                mov(di, 1),
+                mov(di, 1)?,
                 lea(rsi, text_sym),
-                mov(dx, text.len() as u64),
+                mov(dx, text.len() as u64)?,
                 Instr::Syscall,
                 Instr::Call(hello2),
-                mov(ax, 0x3c),
+                mov(ax, 0x3c)?,
                 pop(rdi),
                 Instr::Syscall,
             ],
@@ -73,9 +74,10 @@ fn linux() {
     if let Some(code) = status.code() {
         std::process::exit(code);
     }
+    Ok(())
 }
 
-fn windows() {
+fn windows() -> Result<(), CompilerMsg> {
     let mut program = Program::<X86_64>::default();
     let [get_std_handle, write_file, exit_process] =
         program.external("KERNEL32.dll", ["GetStdHandle", "WriteFile", "ExitProcess"]);
@@ -88,22 +90,22 @@ fn windows() {
             instrs: vec![
                 Instr::Sub,
                 // stdout
-                mov(ecx, -11),
+                mov(ecx, -11)?,
-                Instr::CallMem(get_std_handle),
+                Instr::Callm(get_std_handle),
                 // write
-                mov(rcx, rax),
+                mov(rcx, rax)?,
                 lea(rdx, text_sym),
-                mov(r8d, text.len() as u64),
+                mov(r8d, text.len() as u64)?,
                 lea(r9, written),
-                Instr::MemMov {
+                Instr::Movm {
                     reg: rsp,
                     offset: 0x20,
                     val: 0,
                 },
-                Instr::CallMem(write_file),
+                Instr::Callm(write_file),
                 // exit
-                mov(ecx, 39),
+                mov(ecx, 39)?,
-                Instr::CallMem(exit_process),
+                Instr::Callm(exit_process),
             ],
         })],
     );
@@ -121,6 +123,7 @@ fn windows() {
     if let Some(code) = status.code() {
         std::process::exit(code);
     }
+    Ok(())
 }
 
 fn write(path: &str, binary: &[u8]) {

src/arch/x86_64/test/reg.rs

@@ -1,9 +1,15 @@
 use super::*;
 
-fn eq(expected: impl AsRef<[u8]>, asm: Instr) {
+fn eq(expected: impl AsRef<[u8]>, asm: Result<Instr, CompilerMsg>) {
     let expected = expected.as_ref();
     let program = Program::default();
     let mut encoder = Encoder::new(&program);
+    let asm = match asm {
+        Ok(v) => v,
+        Err(e) => {
+            panic!("expected {expected:x?}, failed to compile: {}", e.msg);
+        }
+    };
     if let Err(e) = encoder.asm(asm) {
         panic!("expected {expected:x?}, failed to compile: {}", e.msg);
     }
@@ -12,7 +18,7 @@ fn eq(expected: impl AsRef<[u8]>, asm: Instr) {
 }
 
 #[test]
-fn reg_reg() {
+fn mov_reg_reg() {
     // used objdump on some nasm compiled assembly
     eq([0x48, 0x89, 0xd8], mov(rax, rbx));
     eq([0x89, 0xd8], mov(eax, ebx));
@@ -34,10 +40,13 @@ fn reg_reg() {
     eq([0x4d, 0x89, 0xd1], mov(r9, r10));
 
     eq([0x4d, 0x89, 0xe0], mov(r8, r12));
+
+    eq([0x89, 0xe0], mov(eax, esp));
+    eq([0x89, 0xc4], mov(esp, eax));
 }
 
 #[test]
-fn reg_imm() {
+fn mov_reg_imm() {
     eq(
         [0x49, 0xbf, 0xf0, 0xde, 0xbc, 0x9a, 0x78, 0x56, 0x34, 0x12],
         mov(r15, 0x123456789abcdef0u64),

src/arch/x86_64/util.rs

@@ -0,0 +1,73 @@
+use super::*;
+
+pub trait RexBit {
+    fn val(self) -> bool;
+}
+
+impl RexBit for u8 {
+    fn val(self) -> bool {
+        self != 0
+    }
+}
+
+impl RexBit for bool {
+    fn val(self) -> bool {
+        self
+    }
+}
+
+impl RexBit for RegH {
+    fn val(self) -> bool {
+        self.gt8()
+    }
+}
+
+impl RexBit for RegWH {
+    fn val(self) -> bool {
+        self.gt8()
+    }
+}
+
+impl RexBit for WidthH {
+    fn val(self) -> bool {
+        self == WidthH::B64
+    }
+}
+
+impl RexBit for Width {
+    fn val(self) -> bool {
+        self == Width::B64
+    }
+}
+
+#[inline(always)]
+pub fn modrm_regs(reg: impl Into<Reg>, reg_rm: impl Into<Reg>) -> u8 {
+    modrm(0b11, reg.into().base(), reg_rm.into().base())
+}
+
+#[inline(always)]
+pub fn modrm_disp32(reg: impl Into<Reg>) -> u8 {
+    modrm(0b00, reg.into().base(), 0b101)
+}
+
+#[inline(always)]
+pub fn modrm(mod_: u8, reg: u8, rm: u8) -> u8 {
+    (mod_ << 6) | (reg << 3) | rm
+}
+
+#[inline(always)]
+pub fn rex(w: impl RexBit, r: impl RexBit, x: impl RexBit, b: impl RexBit) -> u8 {
+    0b0100_0000 | bit(w, 3) | bit(r, 2) | bit(x, 1) | bit(b, 0)
+}
+
+#[inline(always)]
+pub fn bit(val: impl RexBit, pos: u8) -> u8 {
+    (val.val() as u8) << pos
+}
+
+/// assumes the next instruction is directly after
+pub fn addr_offset(pos: usize, addr: u64) -> [u8; 4] {
+    let pos = (pos + 4) as i32;
+    let offset = addr as i32 - pos;
+    offset.to_le_bytes()
+}

src/parser/nodes/asm/x86_64.rs

@@ -17,7 +17,7 @@ impl Node for Asm {
                     let dst = parse_reg(ctx)?;
                     ctx.expect(Token::Comma)?;
                     let src = parse_rmi(ctx)?;
-                    instrs.push(Instr::Mov { dst, src });
+                    instrs.push(mov(dst, src)?);
                 }
                 "int" => {
                     ctx.next();
@@ -60,17 +60,17 @@ pub fn parse_rmi(ctx: &mut crate::parser::ParseCtx) -> Result<RegImmMem, Compile
     let next = ctx.expect_next()?;
     let err = || CompilerMsg::unexpected_token(&next, ctx.span, "a register or immediate");
     Ok(match &next {
-        Token::Ident(ident) => RegImmMem::Reg(RegMode::parse(ident).ok_or_else(err)?),
+        Token::Ident(ident) => RegImmMem::Reg(RegWH::parse(ident).ok_or_else(err)?),
         Token::Lit(LitTy::Number(num)) => RegImmMem::Imm(parse_imm(num, ctx.span)?),
         _ => return Err(err()),
     })
 }
 
-pub fn parse_reg(ctx: &mut crate::parser::ParseCtx) -> Result<RegMode, CompilerMsg> {
+pub fn parse_reg(ctx: &mut crate::parser::ParseCtx) -> Result<RegWH, CompilerMsg> {
     let next = ctx.expect_next()?;
     let err = || CompilerMsg::unexpected_token(&next, ctx.span, "a register");
     let Token::Ident(next) = &next else {
         return Err(err());
     };
-    RegMode::parse(next).ok_or_else(err)
+    RegWH::parse(next).ok_or_else(err)
 }