wha

hblang/src/codegen.rs

@@ -0,0 +1,592 @@
+use std::{iter::Cycle, ops::Range, usize};
+
+use crate::{
+    lexer::{self, Ty},
+    parser::{Exp, Function, Item, Literal, Struct, Type},
+};
+
+type Reg = u8;
+type Offset = i32;
+type Pushed = bool;
+type SlotIndex = usize;
+type Label = usize;
+type Data = usize;
+type Size = usize;
+
+//| Register   | Description         | Saver  |
+//|:-----------|:--------------------|:-------|
+//| r0         | Hard-wired zero     | N/A    |
+//| r1 - r2    | Return values       | Caller |
+//| r2 - r11   | Function parameters | Caller |
+//| r12 - r30  | General purpose     | Caller |
+//| r31        | Return address      | Caller |
+//| r32 - r253 | General purpose     | Callee |
+//| r254       | Stack pointer       | Callee |
+//| r255       | Thread pointer      | N/A    |
+
+struct RegAlloc {
+    pub regs:        Box<[Option<usize>; 256]>,
+    pub used:        Box<[bool; 256]>,
+    pub spill_cycle: Cycle<Range<u8>>,
+}
+
+impl RegAlloc {
+    const STACK_POINTER: Reg = 254;
+    const ZERO: Reg = 0;
+    const RETURN_ADDRESS: Reg = 31;
+
+    fn alloc_general(&mut self, slot: usize) -> Option<Reg> {
+        self.regs[32..254]
+            .iter_mut()
+            .zip(&mut self.used[32..254])
+            .position(|(reg, used)| {
+                if reg.is_none() {
+                    *reg = Some(slot);
+                    *used = true;
+                    true
+                } else {
+                    false
+                }
+            })
+            .map(|reg| reg as Reg + 32)
+    }
+
+    fn free(&mut self, reg: Reg) {
+        assert!(self.regs[reg as usize].take().is_some());
+    }
+
+    fn is_used(&self, reg: Reg) -> bool {
+        self.regs[reg as usize].is_some()
+    }
+
+    fn spill(&mut self, for_slot: usize) -> (Reg, Option<usize>) {
+        let to_spill = self.spill_cycle.next().unwrap();
+        let slot = self.spill_specific(to_spill, for_slot);
+        (to_spill as Reg + 32, slot)
+    }
+
+    fn spill_specific(&mut self, reg: Reg, for_slot: usize) -> Option<usize> {
+        self.regs[reg as usize].replace(for_slot)
+    }
+
+    fn restore(&mut self, reg: Reg, slot: usize) -> usize {
+        self.regs[reg as usize].replace(slot).unwrap()
+    }
+
+    fn alloc_specific(&mut self, reg: u8, to: usize) {
+        assert!(self.regs[reg as usize].replace(to).is_none());
+    }
+
+    fn alloc_specific_in_reg(&mut self, reg: InReg, to: usize) {
+        match reg {
+            InReg::Single(r) => self.alloc_specific(r, to),
+            InReg::Pair(r1, r2) => {
+                self.alloc_specific(r1, to);
+                self.alloc_specific(r2, to);
+            }
+        }
+    }
+}
+
+pub struct ParamAlloc {
+    reg_range: Range<Reg>,
+    stack:     Offset,
+}
+
+impl ParamAlloc {
+    fn for_params() -> Self {
+        Self {
+            stack:     8, // return adress is in callers stack frame
+            reg_range: 2..12,
+        }
+    }
+
+    fn for_returns() -> Self {
+        Self {
+            stack:     0,
+            reg_range: 0..2,
+        }
+    }
+
+    fn alloc(&mut self, size: usize) -> SlotValue {
+        match self.try_alloc_regs(size) {
+            Some(reg) => reg,
+            None => {
+                let stack = self.stack;
+                self.stack += size as Offset;
+                SlotValue::Stack(stack)
+            }
+        }
+    }
+
+    fn try_alloc_regs(&mut self, size: usize) -> Option<SlotValue> {
+        let mut needed = size.div_ceil(8);
+        if needed > 2 {
+            needed = 1; // passed by ref
+        }
+
+        if self.reg_range.len() < needed {
+            return None;
+        }
+
+        match needed {
+            1 => {
+                let reg = self.reg_range.start;
+                self.reg_range.start += 1;
+                Some(SlotValue::Reg(InReg::Single(reg)))
+            }
+            2 => {
+                let reg = self.reg_range.start;
+                self.reg_range.start += 2;
+                Some(SlotValue::Reg(InReg::Pair(reg, reg + 1)))
+            }
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl Default for RegAlloc {
+    fn default() -> Self {
+        Self {
+            regs:        Box::new([None; 256]),
+            used:        Box::new([false; 256]),
+            spill_cycle: (32..254).cycle(),
+        }
+    }
+}
+
+struct Variable {
+    name:     String,
+    location: usize,
+}
+
+#[derive(Clone, Copy)]
+struct SlotId {
+    // index into slot stack
+    index:  SlotIndex,
+    // temorary offset carried over when eg. accessing fields
+    offset: Offset,
+    // this means we can mutate the value as part of computation
+    owned:  bool,
+}
+
+impl SlotId {
+    fn base(location: usize) -> Self {
+        Self {
+            index:  location,
+            offset: 0,
+            owned:  true,
+        }
+    }
+
+    fn borrowed(self) -> Self {
+        Self {
+            owned: false,
+            ..self
+        }
+    }
+}
+
+struct Slot {
+    ty:    Type,
+    value: SlotValue,
+}
+
+#[repr(transparent)]
+struct InstBuffer {
+    buffer: Vec<u8>,
+}
+
+impl InstBuffer {
+    fn new(vec: &mut Vec<u8>) -> &mut Self {
+        unsafe { &mut *(vec as *mut Vec<u8> as *mut Self) }
+    }
+}
+
+impl hbbytecode::Buffer for InstBuffer {
+    fn reserve(&mut self, bytes: usize) {
+        self.buffer.reserve(bytes);
+    }
+
+    unsafe fn write(&mut self, byte: u8) {
+        self.buffer.push(byte);
+    }
+}
+
+#[derive(Clone, Copy)]
+enum InReg {
+    Single(Reg),
+    // if one of the registes is allocated, the other is too, ALWAYS
+    // with the same slot
+    Pair(Reg, Reg),
+}
+
+#[derive(Clone, Copy)]
+enum Spill {
+    Reg(InReg),
+    Stack(Offset), // relative to frame end (rsp if nothing was pushed)
+}
+
+#[derive(Clone, Copy)]
+enum SlotValue {
+    Reg(InReg),
+    Stack(Offset), // relative to frame start (rbp)
+    Imm(u64),
+    Spilled(Spill, SlotIndex),
+}
+
+pub struct Value {
+    store:  ValueStore,
+    offset: Offset,
+}
+
+#[derive(Clone, Copy)]
+enum ValueStore {
+    Reg(InReg),
+    Stack(Offset, Pushed),
+    Imm(u64),
+}
+
+impl From<SlotValue> for ValueStore {
+    fn from(value: SlotValue) -> Self {
+        match value {
+            SlotValue::Reg(reg) => ValueStore::Reg(reg),
+            SlotValue::Stack(offset) => ValueStore::Stack(offset, false),
+            SlotValue::Imm(imm) => ValueStore::Imm(imm),
+            SlotValue::Spilled(spill, _) => match spill {
+                Spill::Reg(reg) => ValueStore::Reg(reg),
+                Spill::Stack(offset) => ValueStore::Stack(offset, true),
+            },
+        }
+    }
+}
+
+pub struct LabelReloc {
+    pub label:  Label,
+    pub offset: usize,
+}
+
+pub struct DataReloc {
+    pub data:   Data,
+    pub offset: usize,
+}
+
+#[must_use]
+pub struct Frame {
+    pub slot_count: usize,
+    pub var_count:  usize,
+}
+
+enum Instr {
+    BinOp(lexer::Op, Value, Value),
+    Move(Size, Value, Value),
+    Push(Reg),
+    Jump(Label),
+    Call(String),
+    JumpIfZero(Value, Label),
+}
+
+#[derive(Default)]
+pub struct Generator<'a> {
+    ast: &'a [Item],
+
+    func_labels: Vec<(String, Label)>,
+
+    stack_size:  Offset,
+    pushed_size: Offset,
+
+    regs:      RegAlloc,
+    variables: Vec<Variable>,
+    slots:     Vec<Slot>,
+
+    labels:       Vec<Option<usize>>,
+    label_relocs: Vec<LabelReloc>,
+
+    data:        Vec<Option<usize>>,
+    data_relocs: Vec<DataReloc>,
+
+    code_section: Vec<u8>,
+    data_section: Vec<u8>,
+
+    instrs: Vec<Instr>,
+}
+
+impl<'a> Generator<'a> {
+    fn generate(mut self) -> Vec<u8> {
+        for item in self.ast {
+            let Item::Function(f) = item else { continue };
+            self.generate_function(f);
+        }
+
+        self.link()
+    }
+
+    fn generate_function(&mut self, f: &Function) {
+        let frame = self.push_frame();
+
+        let mut param_alloc = ParamAlloc::for_params();
+
+        for param in f.args.iter() {
+            let param_size = self.size_of(&param.ty);
+            let value = param_alloc.alloc(param_size);
+            let slot = self.add_slot(param.ty.clone(), value);
+            if let SlotValue::Reg(reg) = value {
+                self.regs.alloc_specific_in_reg(reg, slot);
+            }
+            self.add_variable(param.name.clone(), slot);
+        }
+
+        for stmt in f.body.iter() {
+            assert!(self
+                .generate_expr(Some(Type::Builtin(Ty::Void)), stmt)
+                .is_none());
+        }
+
+        self.pop_frame(frame);
+    }
+
+    fn generate_expr(&mut self, expected: Option<Type>, expr: &Exp) -> Option<SlotId> {
+        let value = match expr {
+            Exp::Literal(lit) => SlotId::base(match lit {
+                Literal::Int(i) => self.add_slot(expected.clone().unwrap(), SlotValue::Imm(*i)),
+                Literal::Bool(b) => {
+                    self.add_slot(Type::Builtin(Ty::Bool), SlotValue::Imm(*b as u64))
+                }
+            }),
+            Exp::Variable(ident) => {
+                SlotId::base(self.lookup_variable(ident).unwrap().location).borrowed()
+            }
+            Exp::Call { name, args } => self.generate_call(expected.clone(), name, args),
+            Exp::Ctor { name, fields } => todo!(),
+            Exp::Index { base, index } => todo!(),
+            Exp::Field { base, field } => todo!(),
+            Exp::Unary { op, exp } => todo!(),
+            Exp::Binary { op, left, right } => todo!(),
+            Exp::If { cond, then, else_ } => todo!(),
+            Exp::Let { name, ty, value } => todo!(),
+            Exp::For {
+                init,
+                cond,
+                step,
+                block,
+            } => todo!(),
+            Exp::Block(_) => todo!(),
+            Exp::Return(_) => todo!(),
+            Exp::Break => todo!(),
+            Exp::Continue => todo!(),
+        };
+
+        if let Some(expected) = expected {
+            let actual = self.slots[value.index].ty.clone();
+            assert_eq!(expected, actual);
+        }
+
+        Some(value)
+    }
+
+    fn generate_call(&mut self, expected: Option<Type>, name: &str, args: &[Exp]) -> SlotId {
+        let frame = self.push_frame();
+        let func = self.lookup_function(name);
+
+        let mut ret_alloc = ParamAlloc::for_returns();
+        let ret_size = self.size_of(&func.ret);
+        let ret_slot = ret_alloc.alloc(ret_size);
+
+        let mut arg_alloc = ParamAlloc::for_params();
+        for (arg, param) in args.iter().zip(&func.args) {
+            let arg_slot = self.generate_expr(Some(param.ty.clone()), arg).unwrap();
+            let arg_size = self.size_of(&param.ty);
+            let param_slot = arg_alloc.alloc(arg_size);
+            self.set_temporarly(arg_slot, param_slot);
+        }
+
+        self.instrs.push(Instr::Call(name.to_owned()));
+
+        todo!()
+    }
+
+    fn set_temporarly(&mut self, from: SlotId, to: SlotValue) {
+        let to = self.make_mutable(to, from.index);
+        let to_slot = self.add_slot(self.slots[from.index].ty.clone(), to);
+        self.emit_move(from, SlotId::base(to_slot));
+    }
+
+    fn make_mutable(&mut self, target: SlotValue, by: SlotIndex) -> SlotValue {
+        match target {
+            SlotValue::Reg(in_reg) => {
+                self.regs.alloc_specific_in_reg(in_reg, by);
+                target
+            }
+            SlotValue::Spilled(Spill::Reg(in_reg), slot) => {
+                let new_val = SlotValue::Spilled(
+                    match in_reg {
+                        InReg::Single(reg) => Spill::Stack(self.emmit_push(reg)),
+                        InReg::Pair(r1, r2) => {
+                            self.emmit_push(r2);
+                            Spill::Stack(self.emmit_push(r1))
+                        }
+                    },
+                    slot,
+                );
+                let new_slot = self.add_slot(self.slots[slot].ty.clone(), new_val);
+                SlotValue::Spilled(Spill::Reg(in_reg), new_slot)
+            }
+            _ => unreachable!(),
+        }
+    }
+
+    fn emmit_push(&mut self, reg: Reg) -> Offset {
+        self.pushed_size += 8;
+        self.instrs.push(Instr::Push(reg));
+        self.pushed_size
+    }
+
+    fn emit_move(&mut self, from: SlotId, to: SlotId) {
+        let size = self.size_of(&self.slots[from.index].ty);
+        let other_size = self.size_of(&self.slots[to.index].ty);
+        assert_eq!(size, other_size);
+
+        self.instrs.push(Instr::Move(
+            size,
+            self.slot_to_value(from),
+            self.slot_to_value(to),
+        ));
+    }
+
+    fn slot_to_value(&self, slot: SlotId) -> Value {
+        let slot_val = &self.slots[slot.index];
+        Value {
+            store:  slot_val.value.into(),
+            offset: slot.offset,
+        }
+    }
+
+    fn size_of(&self, ty: &Type) -> Size {
+        match ty {
+            Type::Builtin(ty) => match ty {
+                Ty::U8 | Ty::I8 | Ty::Bool => 1,
+                Ty::U16 | Ty::I16 => 2,
+                Ty::U32 | Ty::I32 => 4,
+                Ty::U64 | Ty::I64 => 8,
+                Ty::Void => 0,
+            },
+            Type::Struct(name) => self
+                .lookup_struct(name)
+                .fields
+                .iter()
+                .map(|field| self.size_of(&field.ty))
+                .sum(),
+            Type::Pinter(_) => 8,
+        }
+    }
+}
+
+impl<'a> Generator<'a> {
+    fn add_variable(&mut self, name: String, location: usize) {
+        self.variables.push(Variable { name, location });
+    }
+
+    fn add_slot(&mut self, ty: Type, value: SlotValue) -> usize {
+        let slot = self.slots.len();
+        self.slots.push(Slot { ty, value });
+        slot
+    }
+
+    fn link(mut self) -> Vec<u8> {
+        for reloc in self.label_relocs {
+            let label = self.labels[reloc.label].unwrap();
+            let offset = reloc.offset;
+            let target = label - offset;
+            let target_bytes = u64::to_le_bytes(target as u64);
+            self.code_section[offset..offset + 8].copy_from_slice(&target_bytes);
+        }
+
+        for reloc in self.data_relocs {
+            let data = self.data[reloc.data].unwrap();
+            let offset = reloc.offset;
+            let target = data;
+            let target_bytes = u64::to_le_bytes((target + self.code_section.len()) as u64);
+            self.data_section[offset..offset + 8].copy_from_slice(&target_bytes);
+        }
+
+        self.code_section.extend_from_slice(&self.data_section);
+        self.code_section
+    }
+
+    fn lookup_func_label(&mut self, name: &str) -> Label {
+        if let Some(label) = self.func_labels.iter().find(|(n, _)| n == name) {
+            return label.1;
+        }
+
+        panic!("Function not found: {}", name);
+    }
+
+    fn declare_label(&mut self) -> Label {
+        self.labels.push(None);
+        self.labels.len() - 1
+    }
+
+    fn define_label(&mut self, label: Label) {
+        self.labels[label] = Some(self.code_section.len());
+    }
+
+    fn declare_data(&mut self) -> Data {
+        self.data.push(None);
+        self.data.len() - 1
+    }
+
+    fn define_data(&mut self, data: Data, bytes: &[u8]) {
+        self.data[data] = Some(self.data.len());
+        self.data_section.extend_from_slice(bytes);
+    }
+
+    fn lookup_struct(&self, name: &str) -> &Struct {
+        self.lookup_item(name)
+            .map(|item| match item {
+                Item::Struct(s) => s,
+                _ => panic!("Not a struct: {}", name),
+            })
+            .expect("Struct not found")
+    }
+
+    fn lookup_function(&self, name: &str) -> &'a Function {
+        self.lookup_item(name)
+            .map(|item| match item {
+                Item::Function(f) => f,
+                _ => panic!("Not a function: {}", name),
+            })
+            .expect("Function not found")
+    }
+
+    fn lookup_item(&self, name: &str) -> Option<&'a Item> {
+        self.ast.iter().find(|item| match item {
+            Item::Import(_) => false,
+            Item::Struct(s) => s.name == name,
+            Item::Function(f) => f.name == name,
+        })
+    }
+
+    fn lookup_variable(&self, name: &str) -> Option<&Variable> {
+        self.variables.iter().find(|variable| variable.name == name)
+    }
+
+    fn push_frame(&mut self) -> Frame {
+        Frame {
+            slot_count: self.slots.len(),
+            var_count:  self.variables.len(),
+        }
+    }
+
+    fn pop_frame(&mut self, frame: Frame) {
+        self.slots.truncate(frame.slot_count);
+        self.variables.truncate(frame.var_count);
+    }
+}
+
+pub fn generate(ast: &[Item]) -> Vec<u8> {
+    Generator {
+        ast,
+        ..Default::default()
+    }
+    .generate()
+}