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|
use rustv::isa;
use rustv::memory::{MemoryInterface, Result, SharedMemory};
/// A cache that can be used as two separate caches or one
/// set-associative cache.
pub struct ShareableCache<'a> {
core_id: usize,
primary: SharedMemory<'a>,
secondary: SharedMemory<'a>,
secondary_enabled: bool,
use_secondary: bool,
}
impl<'a> ShareableCache<'a> {
pub fn new(core_id: usize,
cache1: SharedMemory<'a>, cache2: SharedMemory<'a>)
-> ShareableCache<'a> {
ShareableCache {
core_id: core_id,
primary: cache1.clone(),
secondary: cache2.clone(),
secondary_enabled: false,
use_secondary: false,
}
}
pub fn enable_secondary(&mut self) {
self.secondary_enabled = true;
self.use_secondary = true;
}
pub fn disable_secondary(&mut self) {
self.secondary_enabled = false;
}
fn address_accessible(&self, address: isa::Address) -> (bool, bool) {
// Use scopes to make sure these borrows end before the
// branches of the if statement begin
let primary_accessible = {
self.primary.borrow().is_address_accessible(address)
};
let secondary_accessible = {
self.secondary.borrow().is_address_accessible(address)
};
(primary_accessible, secondary_accessible)
}
fn snoop(cache: &mut SharedMemory<'a>,
address: isa::Address, value: isa::Word) {
// Cache snooping: update all cache lines when a write is made
if cache.borrow().is_address_accessible(address) {
// Depends on invariant: write_word completes instantly
// when the address is accessible (in-cache)
cache.borrow_mut().write_word(address, value);
}
}
}
impl<'a> MemoryInterface for ShareableCache<'a> {
fn latency(&self) -> u32 {
self.primary.borrow().latency()
}
fn step(&mut self) {
// We only step the primary cache. The idea is that the
// secondary cache should be the primary cache of another
// ShareableCache.
self.primary.borrow_mut().step();
}
fn is_address_accessible(&self, address: isa::Address) -> bool {
self.primary.borrow().is_address_accessible(address) ||
(self.secondary_enabled &&
self.secondary.borrow().is_address_accessible(address))
}
fn read_word(&mut self, address: isa::Address) -> Result<isa::Word> {
if self.secondary_enabled {
let (primary_accessible, secondary_accessible) =
self.address_accessible(address);
if primary_accessible {
self.primary.borrow_mut().read_word(address)
}
else if secondary_accessible {
self.secondary.borrow_mut().read_word(address)
}
else {
self.use_secondary = !self.use_secondary;
if self.use_secondary {
self.secondary.borrow_mut().read_word(address)
}
else {
self.primary.borrow_mut().read_word(address)
}
}
}
else {
self.primary.borrow_mut().read_word(address)
}
}
fn write_word(&mut self, address: isa::Address, value: isa::Word) -> Result<()> {
if self.secondary_enabled {
let (primary_accessible, secondary_accessible) =
self.address_accessible(address);
if primary_accessible {
ShareableCache::snoop(&mut self.secondary, address, value);
self.primary.borrow_mut().write_word(address, value)
}
else if secondary_accessible {
ShareableCache::snoop(&mut self.primary, address, value);
self.secondary.borrow_mut().write_word(address, value)
}
else {
self.use_secondary = !self.use_secondary;
if self.use_secondary {
ShareableCache::snoop(&mut self.primary, address, value);
self.secondary.borrow_mut().write_word(address, value)
}
else {
ShareableCache::snoop(&mut self.secondary, address, value);
self.primary.borrow_mut().write_word(address, value)
}
}
}
else {
ShareableCache::snoop(&mut self.secondary, address, value);
self.primary.borrow_mut().write_word(address, value)
}
}
}
|
