scryer-prolog 0.8.34

use prolog_parser::ast::*;

use prolog::forms::*;
use prolog::instructions::*;
use prolog::iterators::*;

use std::cell::Cell;
use std::collections::{BTreeMap, BTreeSet, HashMap};
use std::collections::btree_map::{IntoIter, IterMut, Values};
use std::mem::swap;
use std::rc::Rc;
use std::vec::Vec;

// labeled with chunk numbers.
pub enum VarStatus {
    Perm(usize), Temp(usize, TempVarData) // Perm(chunk_num) | Temp(chunk_num, _)
}

pub type OccurrenceSet = BTreeSet<(GenContext, usize)>;

// Perm: 0 initially, a stack register once processed.
// Temp: labeled with chunk_num and temp offset (unassigned if 0).
pub enum VarData {
    Perm(usize), Temp(usize, usize, TempVarData)
}

impl VarData {
    pub fn as_reg_type(&self) -> RegType {
        match self {
            &VarData::Temp(_, r, _) => RegType::Temp(r),
            &VarData::Perm(r) => RegType::Perm(r)
        }
    }
}

pub struct TempVarData {
    pub last_term_arity: usize,
    pub use_set: OccurrenceSet,
    pub no_use_set: BTreeSet<usize>,
    pub conflict_set: BTreeSet<usize>
}

impl TempVarData {
    pub fn new(last_term_arity: usize) -> Self {
        TempVarData {
            last_term_arity: last_term_arity,
            use_set: BTreeSet::new(),
            no_use_set: BTreeSet::new(),
            conflict_set: BTreeSet::new()
        }
    }

    pub fn uses_reg(&self, reg: usize) -> bool {
        for &(_, nreg) in self.use_set.iter() {
            if reg == nreg {
                return true;
            }
        }

        return false;
    }

    pub fn populate_conflict_set(&mut self) {
        if self.last_term_arity > 0 {
            let arity = self.last_term_arity;
            let mut conflict_set : BTreeSet<usize> = (1..arity).collect();

            for &(_, reg) in self.use_set.iter() {
                conflict_set.remove(&reg);
            }

            self.conflict_set = conflict_set;
        }
    }
}

type VariableFixture<'a> = (VarStatus, Vec<&'a Cell<VarReg>>);
pub struct VariableFixtures<'a>(BTreeMap<Rc<Var>, VariableFixture<'a>>);

impl<'a> VariableFixtures<'a>
{
    pub fn new() -> Self {
        VariableFixtures(BTreeMap::new())
    }

    pub fn insert(&mut self, var: Rc<Var>, vs: VariableFixture<'a>) {
        self.0.insert(var, vs);
    }

    // computes no_use and conflict sets for all temp vars.
    pub fn populate_restricting_sets(&mut self)
    {
        // three stages:
        // 1. move the use sets of each variable to a local HashMap, use_set
        // (iterate mutably, swap mutable refs).
        // 2. drain use_set. For each use set of U, add into the
        // no-use sets of appropriate variables T =/= U.
        // 3. Move the use sets back to their original locations in the fixture.
        // Compute the conflict set of u.

        // 1.
        let mut use_sets: HashMap<Rc<Var>, OccurrenceSet> = HashMap::new();

        for (var, &mut (ref mut var_status, _)) in self.iter_mut() {
            if let &mut VarStatus::Temp(_, ref mut var_data) = var_status {
                let mut use_set = OccurrenceSet::new();

                swap(&mut var_data.use_set, &mut use_set);
                use_sets.insert((*var).clone(), use_set);
            }
        }

        for (u, use_set) in use_sets.drain() {
            // 2.
            for &(term_loc, reg) in use_set.iter() {
                if let GenContext::Last(cn_u) = term_loc {
                    for (ref t, &mut (ref mut var_status, _)) in self.iter_mut() {
                        if let &mut VarStatus::Temp(cn_t, ref mut t_data) = var_status {
                            if cn_u == cn_t && *u != ***t {
                                if !t_data.uses_reg(reg) {
                                    t_data.no_use_set.insert(reg);
                                }
                            }
                        }
                    }
                }
            }

            // 3.
            match self.get_mut(u).unwrap() {
                &mut (VarStatus::Temp(_, ref mut u_data), _) => {
                    u_data.use_set = use_set;
                    u_data.populate_conflict_set();
                },
                _ => {}
            };
        }
    }

    fn get_mut(&mut self, u: Rc<Var>) -> Option<&mut VariableFixture<'a>> {
        self.0.get_mut(&u)
    }

    fn iter_mut(&mut self) -> IterMut<Rc<Var>, VariableFixture<'a>> {
        self.0.iter_mut()
    }

    fn record_temp_info(&mut self,
                        tvd: &mut TempVarData,
                        arg_c: usize,
                        term_loc: GenContext)
    {
        match term_loc {
            GenContext::Head | GenContext::Last(_) => {
                tvd.use_set.insert((term_loc, arg_c));
            },
            _ => {}
        };
    }

    pub fn vars_above_threshold(&self, index: usize) -> usize
    {
        let mut var_count = 0;

        for &(ref var_status, _) in self.values() {
            if let &VarStatus::Perm(i) = var_status {
                if i > index {
                    var_count += 1;
                }
            }
        }

        var_count
    }

    pub fn mark_vars_in_chunk<I>(&mut self, iter: I, lt_arity: usize, term_loc: GenContext)
        where I: Iterator<Item=TermRef<'a>>
    {
        let chunk_num = term_loc.chunk_num();
        let mut arg_c = 1;

        for term_ref in iter {
            if let &TermRef::Var(lvl, cell, ref var) = &term_ref {
                let mut status = self.0.remove(var)
                    .unwrap_or((VarStatus::Temp(chunk_num, TempVarData::new(lt_arity)),
                                Vec::new()));

                status.1.push(cell);

                match status.0 {
                    VarStatus::Temp(cn, ref mut tvd) if cn == chunk_num =>
                        if let Level::Shallow = lvl {
                            self.record_temp_info(tvd, arg_c, term_loc);
                        },
                    _ => status.0 = VarStatus::Perm(chunk_num)
                };

                self.0.insert(var.clone(), status);
            }

            if let Level::Shallow = term_ref.level() {
                arg_c += 1;
            }
        }
    }

    pub fn into_iter(self) -> IntoIter<Rc<Var>, VariableFixture<'a>> {
        self.0.into_iter()
    }

    fn values(&self) -> Values<Rc<Var>, VariableFixture<'a>> {
        self.0.values()
    }

    pub fn size(&self) -> usize {
        self.0.len()
    }

    pub fn set_perm_vals(&self, has_deep_cuts: bool)
    {
        let mut values_vec : Vec<_> = self.values()
            .filter_map(|ref v| {
                match &v.0 {
                    &VarStatus::Perm(i) => Some((i, &v.1)),
                    _ => None
                }
            })
            .collect();

        values_vec.sort_by_key(|ref v| v.0);

        let offset = has_deep_cuts as usize;

        for (i, (_, cells)) in values_vec.into_iter().rev().enumerate() {
            for cell in cells {
                cell.set(VarReg::Norm(RegType::Perm(i + 1 + offset)));
            }
        }
    }
}

pub struct UnsafeVarMarker {
    pub unsafe_vars: HashMap<RegType, bool>
}

impl UnsafeVarMarker {
    pub fn new() -> Self {
        UnsafeVarMarker {
            unsafe_vars: HashMap::new()
        }
    }

    pub fn record_unsafe_vars(&mut self, fixtures: &VariableFixtures) {
        for &(_, ref cb) in fixtures.values() {
            if let Some(index) = cb.first() {
                if !self.unsafe_vars.contains_key(&index.get().norm()) {
                    self.unsafe_vars.insert(index.get().norm(), false);
                }
            }
        }
    }

    pub fn mark_safe_vars(&mut self, query_instr: &mut QueryInstruction) {
        match query_instr {
            &mut QueryInstruction::PutVariable(RegType::Temp(r), _) =>
                if let Some(found) = self.unsafe_vars.get_mut(&RegType::Temp(r)) {
                    *found = true;
                },
            &mut QueryInstruction::SetVariable(reg) =>
                if let Some(found) = self.unsafe_vars.get_mut(&reg) {
                    *found = true;
                },
            _ => {}
        }
    }

    pub fn mark_unsafe_vars(&mut self, query_instr: &mut QueryInstruction)
    {
        match query_instr {
            &mut QueryInstruction::PutValue(RegType::Perm(i), arg) =>
                if let Some(found) = self.unsafe_vars.get_mut(&RegType::Perm(i)) {
                    if !*found {
                        *found = true;
                        *query_instr = QueryInstruction::PutUnsafeValue(i, arg);
                    }
                },
            &mut QueryInstruction::SetValue(reg) =>
                if let Some(found) = self.unsafe_vars.get_mut(&reg) {
                    if !*found {
                        *found = true;
                        *query_instr = QueryInstruction::SetLocalValue(reg);
                    }
                },
            _ => {}
        }
    }
}