calyx_opt/passes/sync/

compile_sync.rs

use crate::traversal::{Action, Named, VisResult, Visitor};
use calyx_ir::RRC;
use calyx_ir::{self as ir, GetAttributes};
use calyx_ir::{build_assignments, guard, structure};
use calyx_utils::{CalyxResult, Error};
use linked_hash_map::LinkedHashMap;
use std::collections::{HashMap, HashSet};
use std::rc::Rc;

#[derive(Default)]
/// 1. loop through all control statements under "par" block to find # barriers
///    needed and # members of each barrier
/// 2. add all cells and groups needed
/// 3. loop through all control statements, find the statements with @sync
///    attribute and replace them with
///     seq {
///       <stmt>;
///       incr_barrier_0_*;
///       write_barrier_0_*;
///       wait_*;
///       restore_*;
///     }
///    or
///     seq {
///       <stmt>;
///       incr_barrier_*_*;
///       write_barrier_*_*;
///       wait_*;
///       wait_restore_*;
///     }

pub struct CompileSync {
    barriers: BarrierMap,
}

/// the structure used to store cells and groups shared by one barrier
type BarrierMap = LinkedHashMap<u64, ([RRC<ir::Cell>; 2], [RRC<ir::Group>; 3])>;

impl Named for CompileSync {
    fn name() -> &'static str {
        "compile-sync"
    }

    fn description() -> &'static str {
        "Implement barriers for statements marked with @sync attribute"
    }
}

/// put into the count set the barrier indices appearing in the thread
fn count_barriers(
    s: &ir::Control,
    count: &mut HashSet<u64>,
) -> CalyxResult<()> {
    match s {
        ir::Control::Empty(_) => {
            if let Some(n) = s.get_attributes().get(ir::NumAttr::Sync) {
                count.insert(n);
            }
            Ok(())
        }
        ir::Control::Seq(seq) => {
            for stmt in seq.stmts.iter() {
                count_barriers(stmt, count)?;
            }
            Ok(())
        }
        ir::Control::While(ir::While { body, .. })
        | ir::Control::Repeat(ir::Repeat { body, .. }) => {
            count_barriers(body, count)?;
            Ok(())
        }
        ir::Control::If(i) => {
            count_barriers(&i.tbranch, count)?;
            count_barriers(&i.fbranch, count)?;
            Ok(())
        }
        ir::Control::Enable(e) => {
            if s.get_attributes().get(ir::NumAttr::Sync).is_some() {
                return Err(Error::malformed_control(
                    "Enable or Invoke controls cannot be marked with @sync"
                        .to_string(),
                )
                .with_pos(&e.attributes));
            }
            Ok(())
        }
        ir::Control::Invoke(i) => {
            if s.get_attributes().get(ir::NumAttr::Sync).is_some() {
                return Err(Error::malformed_control(
                    "Enable or Invoke controls cannot be marked with @sync"
                        .to_string(),
                )
                .with_pos(&i.attributes));
            }
            Ok(())
        }
        ir::Control::Par(_) => Ok(()),
        ir::Control::Static(_) => Ok(()),
    }
}

impl CompileSync {
    fn build_barriers(
        &mut self,
        builder: &mut ir::Builder,
        s: &mut ir::Control,
        count: &mut HashMap<u64, u64>,
    ) {
        match s {
            ir::Control::Empty(_) => {
                if let Some(ref n) = s.get_attributes().get(ir::NumAttr::Sync) {
                    if self.barriers.get(n).is_none() {
                        self.add_shared_structure(builder, n);
                    }
                    let (cells, groups) = &self.barriers[n];
                    let member_idx = count[n];

                    let mut new_s =
                        build_member(builder, cells, groups, &member_idx);
                    std::mem::swap(s, &mut new_s);
                }
            }
            ir::Control::Seq(seq) => {
                // go through each control statement
                // if @sync
                // see if we already have the set of shared primitives and groups
                // initialized
                // True -> generate the inidividual groups and buikld the seq stmt
                // False -> generate the shared groups, cells
                //          put the shared groups in the barriermap
                //          generate the individual groups
                //          build the seq stmt
                for stmt in seq.stmts.iter_mut() {
                    self.build_barriers(builder, stmt, count);
                }
            }
            ir::Control::While(w) => {
                self.build_barriers(builder, &mut w.body, count);
            }
            ir::Control::If(i) => {
                self.build_barriers(builder, &mut i.tbranch, count);
                self.build_barriers(builder, &mut i.fbranch, count);
            }
            _ => {}
        }
    }

    fn add_shared_structure(
        &mut self,
        builder: &mut ir::Builder,
        barrier_idx: &u64,
    ) {
        structure!(builder;
                let barrier = prim std_sync_reg(32);
                let eq = prim std_eq(32);
        );
        let restore = build_restore(builder, &barrier);
        let wait_restore = build_wait_restore(builder, &eq);
        let clear_barrier = build_clear_barrier(builder, &barrier);
        let shared_cells: [RRC<ir::Cell>; 2] = [barrier, eq];
        let shared_groups: [RRC<ir::Group>; 3] =
            [wait_restore, restore, clear_barrier];
        let info = (shared_cells, shared_groups);
        self.barriers.insert(*barrier_idx, info);
    }
}

//put together the group to read and increment the barrier
fn build_incr_barrier(
    builder: &mut ir::Builder,
    barrier: &RRC<ir::Cell>,
    save: &RRC<ir::Cell>,
    member_idx: &u64,
) -> RRC<ir::Group> {
    let group = builder.add_group("incr_barrier");
    structure!(builder;
        let incr = prim std_add(32);
        let cst_1 = constant(1, 1);
        let cst_2 = constant(1, 32););
    let read_done_guard = guard!(barrier[format!("read_done_{member_idx}")]);
    let assigns = build_assignments!(builder;
        // barrier_*.read_en_0 = 1'd1;
        barrier[format!("read_en_{member_idx}")] = ?cst_1["out"];
        //incr_*_*.left = barrier_*.out_*;
        incr["left"] = ? barrier[format!("out_{member_idx}")];
        // incr_*_*.right = 32'd1;
        incr["right"] = ? cst_2["out"];
        // save_*_*.in = barrier_*.read_done_*? incr_1.out;
        save["in"] = read_done_guard? incr["out"];
        // save_*_*.write_en = barrier_*.read_done_*;
        save["write_en"] = ? barrier[format!("read_done_{member_idx}")];
        // incr_barrier_*_*[done] = save_*_*.done;
        group["done"] = ?save["done"];
    );

    group.borrow_mut().assignments.extend(assigns);
    group
}

// put together the group to write to the barrier after incrementing
fn build_write_barrier(
    builder: &mut ir::Builder,
    barrier: &RRC<ir::Cell>,
    save: &RRC<ir::Cell>,
    member_idx: &u64,
) -> RRC<ir::Group> {
    let group = builder.add_group("write_barrier");
    structure!(builder;
    let cst_1 = constant(1, 1););
    let assigns = build_assignments!(builder;
        // barrier_*.write_en_* = 1'd1;
        barrier[format!("write_en_{member_idx}")] = ?cst_1["out"];
        // barrier_*.in_* = save_*_*.out;
        barrier[format!("in_{member_idx}")] = ?save["out"];
        // write_barrier_*_*[done] = barrier_*.write_done_*;
        group["done"] = ?barrier[format!("write_done_{member_idx}")];
    );
    group.borrow_mut().assignments.extend(assigns);
    group
}

// Put together the group to wait until the peek value reaches capacity.
// We don't actually care about the value being written to the register.
// We're only using it to make sure that the barrier has reached the expected
// value.
fn build_wait(builder: &mut ir::Builder, eq: &RRC<ir::Cell>) -> RRC<ir::Group> {
    let group = builder.add_group("wt");
    structure!(builder;
    let wait_reg = prim std_reg(1);
    let cst_1 = constant(1, 1););
    let eq_guard = guard!(eq["out"]);
    let assigns = build_assignments!(builder;
        // wait_reg_*.in = eq_*.out;
        // XXX(rachit): Since the value doesn't matter, can this just be zero?
        wait_reg["in"] = ?eq["out"];
        // wait_reg_*.write_en = eq_*.out? 1'd1;
        wait_reg["write_en"] = eq_guard? cst_1["out"];
        // wait_*[done] = wait_reg_*.done;
        group["done"] = ?wait_reg["done"];);
    group.borrow_mut().assignments.extend(assigns);
    group
}

// put together the group to empty out the sync reg before resetting it to 0
fn build_clear_barrier(
    builder: &mut ir::Builder,
    barrier: &RRC<ir::Cell>,
) -> RRC<ir::Group> {
    let group = builder.add_group("clear_barrier");
    structure!(builder;
    let cst_1 = constant(1, 1););
    let assigns = build_assignments!(builder;
    // barrier_*.read_en_0 = 1'd1;
    barrier["read_en_0"] = ?cst_1["out"];
    //clear_barrier_*[done] = barrier_1.read_done_0;
    group["done"] = ?barrier["read_done_0"];
    );
    group.borrow_mut().assignments.extend(assigns);
    group
}

// put together the group to restore the barrier to 0
fn build_restore(
    builder: &mut ir::Builder,
    barrier: &RRC<ir::Cell>,
) -> RRC<ir::Group> {
    let group = builder.add_group("restore");
    structure!(builder;
    let cst_1 = constant(1,1);
    let cst_2 = constant(0, 32););
    let assigns = build_assignments!(builder;
        // barrier_*.write_en_0 = 1'd1;
        barrier["write_en_0"] = ?cst_1["out"];
        // barrier_*.in_0 = 32'd0;
        barrier["in_0"] = ?cst_2["out"];
        // restore_*[done] = barrier_*.write_done_0;
        group["done"] = ?barrier["write_done_0"];
    );
    group.borrow_mut().assignments.extend(assigns);
    group
}

// Put together the group to wait for restorer to finish.
// Like the wait group, we don't care about the value in the register
// We just want to wait till the value in the barrier is set to 0.
fn build_wait_restore(
    builder: &mut ir::Builder,
    eq: &RRC<ir::Cell>,
) -> RRC<ir::Group> {
    let group = builder.add_group("wait_restore");
    structure!(builder;
    let wait_restore_reg = prim std_reg(1);
    let cst_1 = constant(1, 1););
    let eq_guard = !guard!(eq["out"]);
    let assigns = build_assignments!(builder;
    // wait_restore_reg_*.in = !eq_*.out? 1'd1;
    wait_restore_reg["in"] = eq_guard? cst_1["out"];
    // wait_restore_reg_*.write_en = !eq_*.out? 1'd1;
    wait_restore_reg["write_en"] = eq_guard? cst_1["out"];
    //wait_restore_*[done] = wait_restore_reg_*.done;
    group["done"] = ?wait_restore_reg["done"];
    );
    group.borrow_mut().assignments.extend(assigns);
    group
}

// put together the sequence of groups that a barrier member requires
fn build_member(
    builder: &mut ir::Builder,
    cells: &[RRC<ir::Cell>; 2],
    groups: &[RRC<ir::Group>; 3],
    member_idx: &u64,
) -> ir::Control {
    let mut stmts: Vec<ir::Control> = Vec::new();

    let barrier = Rc::clone(&cells[0]);
    let eq = Rc::clone(&cells[1]);
    let wait_restore = Rc::clone(&groups[0]);
    let restore = Rc::clone(&groups[1]);
    let clear_barrier = Rc::clone(&groups[2]);

    structure!(builder;
        let save = prim std_reg(32););
    let incr_barrier =
        build_incr_barrier(builder, &barrier, &save, &(member_idx - 1));
    let write_barrier =
        build_write_barrier(builder, &barrier, &save, &(member_idx - 1));
    let wait = build_wait(builder, &eq);

    stmts.push(ir::Control::enable(incr_barrier));
    stmts.push(ir::Control::enable(write_barrier));
    stmts.push(ir::Control::enable(wait));
    if member_idx == &1 {
        stmts.push(ir::Control::enable(clear_barrier));
        stmts.push(ir::Control::enable(restore));
    } else {
        stmts.push(ir::Control::enable(wait_restore));
    }
    ir::Control::seq(stmts)
}

impl Visitor for CompileSync {
    fn finish_par(
        &mut self,
        s: &mut ir::Par,
        comp: &mut ir::Component,
        sigs: &ir::LibrarySignatures,
        _comps: &[ir::Component],
    ) -> VisResult {
        let mut builder = ir::Builder::new(comp, sigs);
        let mut barrier_count: HashMap<u64, u64> = HashMap::new();
        for stmt in s.stmts.iter_mut() {
            let mut cnt: HashSet<u64> = HashSet::new();
            count_barriers(stmt, &mut cnt)?;
            for barrier in cnt {
                barrier_count
                    .entry(barrier)
                    .and_modify(|count| *count += 1)
                    .or_insert(1);
            }
            self.build_barriers(&mut builder, stmt, &mut barrier_count);
        }

        if self.barriers.is_empty() {
            return Ok(Action::Continue);
        }

        let mut init_barriers: Vec<ir::Control> = Vec::new();
        for (n, (cells, groups)) in self.barriers.iter() {
            let barrier = Rc::clone(&cells[0]);
            let eq = Rc::clone(&cells[1]);
            let restore = Rc::clone(&groups[1]);
            let n_members = barrier_count.get(n).unwrap();
            structure!(builder;
                let num_members = constant(*n_members, 32);
            );
            // add continuous assignments
            let assigns = build_assignments!(builder;
            // eq_*.left = barrier_*.peek;
            eq["left"] = ?barrier["peek"];
            // eq_*.right = 32'd* (number of members);
            eq["right"] = ?num_members["out"];
            );
            builder.component.continuous_assignments.extend(assigns);

            init_barriers.push(ir::Control::enable(restore));
        }

        // wrap the par stmt in a seq stmt so that barriers are initialized
        let mut changed_sequence: Vec<ir::Control> =
            vec![ir::Control::par(init_barriers)];
        let mut copied_par_stmts: Vec<ir::Control> = Vec::new();
        for con in s.stmts.drain(..) {
            copied_par_stmts.push(con);
        }
        changed_sequence.push(ir::Control::par(copied_par_stmts));

        Ok(Action::change(ir::Control::seq(changed_sequence)))
    }
}