351 lines
11 KiB
Rust
351 lines
11 KiB
Rust
// Copyright 2019 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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use bitmap;
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use std::cmp;
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use std::collections::HashMap;
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struct Ranges {
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ranges: Vec<std::ops::Range<usize>>,
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}
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impl Ranges {
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fn new() -> Self {
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Ranges { ranges: Vec::new() }
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}
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fn add(&mut self, start: usize, end: usize) {
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let (start, end) = (cmp::min(start, end), cmp::max(start, end) + 1);
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self.ranges.push(std::ops::Range { start, end });
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}
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fn contains(&self, start: usize, end: usize) -> bool {
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let (start, end) = (cmp::min(start, end), cmp::max(start, end));
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(start..=end).any(|v| self.ranges.iter().any(|r| r.contains(&v)))
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}
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fn contains_range(&self, range: &std::ops::Range<usize>) -> bool {
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self.contains(range.start, range.end)
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}
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fn range_sum(&self) -> usize {
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self.ranges.iter().map(|r| r.end - r.start).sum()
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}
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}
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#[derive(Copy, Clone, PartialEq, Debug)]
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pub enum ChannelState {
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Free,
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// Occupied means no connection. This is the same as a constant false.
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Occupied,
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// Constant true.
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Constant,
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Net(usize),
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}
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pub type ChannelLayout = [ChannelState];
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impl ChannelState {
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pub fn is_free(&self) -> bool {
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self == &ChannelState::Free
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}
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pub fn contains_net(&self) -> bool {
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match self {
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ChannelState::Net(_) => true,
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_ => false,
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}
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}
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pub fn is_constant_on(&self) -> bool {
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match self {
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ChannelState::Constant => true,
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_ => false,
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}
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}
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}
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#[derive(Copy, Clone, PartialEq, Debug)]
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pub enum ChannelOp {
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Move,
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Copy,
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}
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#[derive(Debug, Clone)]
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pub struct WireConnection {
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pub from: usize,
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pub to: Vec<usize>,
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pub mode: ChannelOp,
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}
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#[derive(Debug)]
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pub struct ChannelSubState {
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pub wires: Vec<WireConnection>,
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pub occupancy_map: bitmap::Bitmap<Vec<usize>, bitmap::OneBit>,
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}
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#[derive(Debug)]
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struct Task {
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net: usize,
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from: usize,
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to: Vec<usize>,
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}
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impl Task {
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fn channel_range_required(&self) -> std::ops::Range<usize> {
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let from = [self.from];
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let min = self.to.iter().chain(&from).min().unwrap();
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let max = self.to.iter().chain(&from).max().unwrap();
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std::ops::Range {
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start: *min,
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end: max + 1,
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}
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}
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fn channel_width_required(&self) -> usize {
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let r = self.channel_range_required();
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r.end - r.start
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}
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fn occupied_target_pins(&self, layout: &ChannelLayout) -> Vec<usize> {
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let mut occupied = Vec::new();
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for &idx in &self.to {
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if layout[idx].contains_net() && layout[idx] != ChannelState::Net(self.net) {
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occupied.push(idx);
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}
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}
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occupied
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}
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// Returns how 'good' a new 'from' position is for this task (when evicting)
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// so that we can prefer nice spots.
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fn eviction_cost(&self, new_pos: usize) -> usize {
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let min = self.to.iter().min().unwrap();
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let max = self.to.iter().max().unwrap();
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let dist = (self.from as isize - new_pos as isize).abs() as usize;
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if new_pos > *max {
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2 * (new_pos - *max) + dist
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} else if new_pos < *min {
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2 * (*min - new_pos) + dist
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} else {
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dist
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}
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}
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}
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#[derive(Default)]
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struct RouteTasks {
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// source idx -> vec<target idx>
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tasks: HashMap<usize, Vec<usize>>,
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}
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impl RouteTasks {
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fn add(&mut self, from: usize, to: usize) {
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if let Some(k) = self.tasks.get_mut(&from) {
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k.push(to);
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} else {
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self.tasks.insert(from, vec![to]);
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}
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}
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fn into_tasks(mut self, src: &ChannelLayout) -> Vec<Task> {
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self.tasks
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.drain()
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.map(|(k, v)| {
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let net = match src[k] {
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ChannelState::Net(i) => i,
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_ => unreachable!(),
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};
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Task {
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net,
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from: k,
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to: v,
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}
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})
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.collect::<Vec<_>>()
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}
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}
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pub fn route_channel(start: &ChannelLayout, end: &ChannelLayout) -> Vec<ChannelSubState> {
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let mut state = start.to_owned();
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// Expand the state to be at least end.len() wide.
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while state.len() < end.len() {
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state.push(ChannelState::Free);
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}
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let mut tasks = RouteTasks::default();
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for end_idx in 0..end.len() {
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if !end[end_idx].contains_net() || end[end_idx] == state[end_idx] {
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continue;
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}
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let state_idx = state
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.iter()
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.position(|v| v == &end[end_idx])
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.unwrap_or_else(|| panic!("Required field '{:?}' not found", end[end_idx]));
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tasks.add(state_idx, end_idx);
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}
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let mut tasks = tasks.into_tasks(&state);
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// Order by how much of the channel this task occupies.
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tasks.sort_by(|a, b| a.channel_width_required().cmp(&b.channel_width_required()));
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let mut steps: Vec<ChannelSubState> = Vec::new();
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loop {
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// Ranges of the channel that is currently occupied.
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let mut ranges = Ranges::new();
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// Instruction on how to connect pins in the current part of the channel.
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let mut wires = Vec::new();
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// To detect if we were unable to do anything due to blocked pins.
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let old_task_len = tasks.len();
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tasks = tasks
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.drain(0..tasks.len())
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.filter(|task| {
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// Speed things up by only 'enforcing' 50% channel utilization.
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if ranges.range_sum() > (cmp::max(state.len(), end.len()) / 2) {
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return true;
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}
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// Do we have the required part of the channel available?
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if ranges.contains_range(&task.channel_range_required()) {
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return true;
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}
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let blocking_pins = task.occupied_target_pins(&state);
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if blocking_pins.is_empty() {
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// Targets are free, directly move (or copy) it there.
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let keep = if task.from >= end.len() || state[task.from] != end[task.from] {
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state[task.from] = ChannelState::Free;
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false
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} else {
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true
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};
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wires.push(WireConnection {
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from: task.from,
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to: task.to.clone(),
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mode: if keep {
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ChannelOp::Copy
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} else {
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ChannelOp::Move
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},
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});
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let r = task.channel_range_required();
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// -1 here since .add() + channel_range_required() will do +1.
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ranges.add(r.start, r.end - 1);
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for &to in &task.to {
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state[to] = ChannelState::Net(task.net);
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}
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// We successfully handled this one.
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return false;
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}
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true
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})
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.collect::<Vec<_>>();
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// We were unable to handle any tasks -> we need to evict some channels.
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if old_task_len == tasks.len() {
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// Find available positions where we can evict to.
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let mut free_positions = state
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.iter()
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.enumerate()
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.filter(|(_, v)| !v.contains_net())
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.map(|(k, _)| k)
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.filter(|&k| k >= end.len() || !end[k].contains_net())
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.collect::<Vec<_>>();
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if free_positions.is_empty() {
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println!("[!] No free positions found, expanding channel");
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// Make sure that we have some room, scaling with the number of
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// remaining tasks as a random tradeoff.
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for _ in 0..(tasks.len() / 10 + 1) {
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state.push(ChannelState::Free);
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free_positions.push(state.len() - 1);
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}
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}
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for task_idx in 0..tasks.len() {
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let blocking_pins = tasks[task_idx].occupied_target_pins(&state);
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for to_evict in blocking_pins {
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// Find corresponding task.
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let task_idx_to_evict = tasks
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.iter()
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.position(|t| t.from == to_evict)
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.unwrap_or_else(|| panic!("Could not find task blocking {}", to_evict));
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// Find a good place for this task to evict to.
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free_positions.sort_by(|&a, &b| {
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// Comparing in the opposite order on purpose here so
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// that we can use pop() later.
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tasks[task_idx_to_evict]
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.eviction_cost(b)
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.cmp(&tasks[task_idx_to_evict].eviction_cost(a))
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});
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let from = tasks[task_idx_to_evict].from;
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let new_pos = *free_positions.last().unwrap();
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// Check whether the space is actually available.
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let req_range = std::ops::Range {
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start: cmp::min(from, new_pos),
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end: cmp::max(from, new_pos) + 1,
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};
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if !ranges.contains_range(&req_range) {
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free_positions.pop();
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ranges.add(from, new_pos);
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wires.push(WireConnection {
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from,
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to: vec![new_pos],
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mode: ChannelOp::Move,
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});
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tasks[task_idx_to_evict].from = new_pos;
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state[new_pos] = ChannelState::Net(tasks[task_idx_to_evict].net);
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state[to_evict] = ChannelState::Free;
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}
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}
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}
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}
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let mut bitmap =
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bitmap::Bitmap::from_storage(state.len(), (), vec![0; (state.len() + 63) / 64])
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.unwrap();
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for idx in state
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.iter()
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.enumerate()
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.filter(|(_, v)| v.contains_net())
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.map(|(k, _)| k)
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{
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bitmap.set(idx, 1);
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}
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steps.push(ChannelSubState {
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wires,
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occupancy_map: bitmap,
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});
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if tasks.is_empty() {
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return steps;
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}
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}
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}
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