lamina-codegen 0.1.1

//! Stack frame layout for AArch64 code generation.
//!
//! This module provides frame mapping for virtual registers to stack slots.

use lamina_mir::{Function, Register};
use std::collections::{HashMap, HashSet};

/// Maps virtual registers to stack slot offsets.
pub struct FrameMap {
    pub slots: HashMap<Register, i32>,
    pub frame_size: i32,
}

impl FrameMap {
    /// Creates a frame map from a function, assigning stack slots to all virtual registers.
    pub fn from_function(f: &Function) -> Self {
        let mut regs: HashSet<Register> = HashSet::new();
        for p in &f.sig.params {
            regs.insert(p.reg.clone());
        }
        for b in &f.blocks {
            for ins in &b.instructions {
                if let Some(d) = ins.def_reg() {
                    regs.insert(d.clone());
                }
                for u in ins.use_regs() {
                    regs.insert(u.clone());
                }
            }
        }

        let mut reg_vec: Vec<Register> = regs.into_iter().collect();
        reg_vec.sort_by(|a, b| format!("{:?}", a).cmp(&format!("{:?}", b)));

        let mut slots = HashMap::new();
        let mut offset: i32 = -8;
        for r in reg_vec {
            if matches!(r, Register::Virtual(_)) {
                slots.insert(r, offset);
                offset -= 8;
            }
        }
        let mut frame_size = -offset - 8;
        if frame_size < 0 {
            frame_size = 0;
        }
        frame_size = (frame_size + 15) & !15;
        Self { slots, frame_size }
    }

    /// Returns the stack slot offset for a register, if it has one.
    pub fn slot_of(&self, r: &Register) -> Option<i32> {
        self.slots.get(r).copied()
    }
}