#!/usr/bin/env python3
###########################################
## CacheSim.py
##
## Written: lserafini@hmc.edu
## Created: 27 March 2023
## Modified: 12 April 2023
##
## Purpose: Simulate a L1 D$ or I$ for comparison with Wally
##
## A component of the CORE-V-WALLY configurable RISC-V project.
## https://github.com/openhwgroup/cvw
##
## Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
##
## SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
##
## Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file
## except in compliance with the License, or, at your option, the Apache License version 2.0. You
## may obtain a copy of the License at
##
## https:##solderpad.org/licenses/SHL-2.1/
##
## Unless required by applicable law or agreed to in writing, any work distributed under the
## License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
## either express or implied. See the License for the specific language governing permissions
## and limitations under the License.
################################################################################################
# how to invoke this simulator:
# CacheSim.py <number of lines> <number of ways> <length of physical address> <length of tag> -f <log file> (-v)
# so the default invocation for rv64gc is 'CacheSim.py 64 4 56 44 -f <log file>'
# the log files to run this simulator on can be generated from testbench.sv
# by setting I_CACHE_ADDR_LOGGER and/or D_CACHE_ADDR_LOGGER to 1 before running tests.
# I (Lim) recommend logging a single set of tests (such as wally64priv) at a time.
# This helps avoid unexpected logger behavior.
# With verbose mode off, the simulator only reports mismatches between its and Wally's behavior.
# With verbose mode on, the simulator logs each access into the cache.
# Add -p or --perf to report the hit/miss ratio.
# Add -d or --dist to report the distribution of loads, stores, and atomic ops.
# These distributions may not add up to 100; this is because of flushes or invalidations.
import sys
import math
import argparse
import os
class CacheLine:
def __init__(self):
self.tag = 0
self.valid = False
self.dirty = False
def __str__(self):
string = "(V: " + str(self.valid) + ", D: " + str(self.dirty)
string += ", Tag: " + str(hex(self.tag)) + ")"
return string
def __repr__(self):
return self.__str__()
class Cache:
def __init__(self, numsets, numways, addrlen, taglen):
self.numways = numways
self.numsets = numsets
self.addrlen = addrlen
self.taglen = taglen
self.setlen = int(math.log(numsets, 2))
self.offsetlen = self.addrlen - self.taglen - self.setlen
self.ways = []
for i in range(numways):
self.ways.append([])
for j in range(numsets):
self.ways[i].append(CacheLine())
self.pLRU = []
for i in range(self.numsets):
self.pLRU.append([0]*(self.numways-1))
# flushes the cache by setting all dirty bits to False
def flush(self):
for way in self.ways:
for line in way:
line.dirty = False
# invalidates the cache by setting all valid bits to False
def invalidate(self):
for way in self.ways:
for line in way:
line.valid = False
# resets the pLRU to a fresh 2-D array of 0s
def clear_pLRU(self):
self.pLRU = []
for i in range(self.numsets):
self.pLRU.append([0]*(self.numways-1))
# splits the given address into tag, set, and offset
def splitaddr(self, addr):
# no need for offset in the sim, but it's here for debug
tag = addr >> (self.setlen + self.offsetlen) & int('1'*self.taglen, 2)
setnum = (addr >> self.offsetlen) & int('1'*self.setlen, 2)
offset = addr & int('1'*self.offsetlen, 2)
return tag, setnum, offset
# performs a cache access with the given address.
# returns a character representing the outcome:
# H/M/E/D - hit, miss, eviction, or eviction with writeback
def cacheaccess(self, addr, write=False):
tag, setnum, _ = self.splitaddr(addr)
# check our ways to see if we have a hit
for waynum in range(self.numways):
line = self.ways[waynum][setnum]
if line.tag == tag and line.valid:
line.dirty = line.dirty or write
self.update_pLRU(waynum, setnum)
return 'H'
# we didn't hit, but we may not need to evict.
# check for an empty way line.
for waynum in range(self.numways):
line = self.ways[waynum][setnum]
if not line.valid:
line.tag = tag
line.valid = True
line.dirty = write
self.update_pLRU(waynum, setnum)
return 'M'
# we need to evict. Select a victim and overwrite.
victim = self.getvictimway(setnum)
line = self.ways[victim][setnum]
prevdirty = line.dirty
line.tag = tag
line.valid = True # technically redundant
line.dirty = write
self.update_pLRU(victim, setnum)
return 'D' if prevdirty else 'E'
# updates the psuedo-LRU tree for the given set
# with an access to the given way
def update_pLRU(self, waynum, setnum):
if self.numways == 1:
return
tree = self.pLRU[setnum]
bottomrow = (self.numways - 1)//2
index = (waynum // 2) + bottomrow
tree[index] = int(not (waynum % 2))
while index > 0:
parent = (index-1) // 2
tree[parent] = index % 2
index = parent
# uses the psuedo-LRU tree to select
# a victim way from the given set
# returns the victim way as an integer
def getvictimway(self, setnum):
if self.numways == 1:
return 0
tree = self.pLRU[setnum]
index = 0
bottomrow = (self.numways - 1) // 2 #first index on the bottom row of the tree
while index < bottomrow:
if tree[index] == 0:
# Go to the left child
index = index*2 + 1
else: #tree[index] == 1
# Go to the right child
index = index*2 + 2
victim = (index - bottomrow)*2
if tree[index] == 1:
victim += 1
return victim
def __str__(self):
string = ""
for i in range(self.numways):
string += "Way " + str(i) + ": "
for line in self.ways[i]:
string += str(line) + ", "
string += "\n\n"
return string
def __repr__(self):
return self.__str__()
if __name__ == "__main__":
parser = argparse.ArgumentParser(description="Simulates a L1 cache.")
parser.add_argument('numlines', type=int, help="The number of lines per way (a power of 2)", metavar="L")
parser.add_argument('numways', type=int, help="The number of ways (a power of 2)", metavar='W')
parser.add_argument('addrlen', type=int, help="Length of the address in bits (a power of 2)", metavar="A")
parser.add_argument('taglen', type=int, help="Length of the tag in bits", metavar="T")
parser.add_argument('-f', "--file", required=True, help="Log file to simulate from")
parser.add_argument('-v', "--verbose", action='store_true', help="verbose/full-trace mode")
parser.add_argument('-p', "--perf", action='store_true', help="Report hit/miss ratio")
parser.add_argument('-d', "--dist", action='store_true', help="Report distribution of operations")
args = parser.parse_args()
cache = Cache(args.numlines, args.numways, args.addrlen, args.taglen)
extfile = os.path.expanduser(args.file)
nofails = True
if args.perf:
hits = 0
misses = 0
if args.dist:
loads = 0
stores = 0
atoms = 0
totalops = 0
with open(extfile, "r") as f:
for ln in f:
ln = ln.strip()
lninfo = ln.split()
if len(lninfo) < 3: #non-address line
if len(lninfo) > 0 and (lninfo[0] == 'BEGIN' or lninfo[0] == 'TRAIN'):
# currently BEGIN and END traces aren't being recorded correctly
# trying TRAIN clears instead
cache.invalidate() # a new test is starting, so 'empty' the cache
cache.clear_pLRU()
if args.verbose:
print("New Test")
else:
if args.dist:
totalops += 1
if lninfo[1] == 'F':
cache.flush()
if args.verbose:
print("F")
elif lninfo[1] == 'I':
cache.invalidate()
if args.verbose:
print("I")
else:
addr = int(lninfo[0], 16)
iswrite = lninfo[1] == 'W' or lninfo[1] == 'A'
result = cache.cacheaccess(addr, iswrite)
if args.verbose:
tag, setnum, offset = cache.splitaddr(addr)
print(hex(addr), hex(tag), hex(setnum), hex(offset), lninfo[2], result)
if args.perf:
if result == 'H':
hits += 1
else:
misses += 1
if args.dist:
if lninfo[1] == 'R':
loads += 1
elif lninfo[1] == 'W':
stores += 1
elif lninfo[1] == 'A':
atoms += 1
if not result == lninfo[2]:
print("Result mismatch at address", lninfo[0]+ ". Wally:", lninfo[2]+", Sim:", result)
nofails = False
if args.dist:
percent_loads = str(round(100*loads/totalops))
percent_stores = str(round(100*stores/totalops))
percent_atoms = str(round(100*atoms/totalops))
print("This log had", percent_loads+"% loads,", percent_stores+"% stores, and", percent_atoms+"% atomic operations.")
if args.perf:
ratio = round(hits/misses,3)
print("There were", hits, "hits and", misses, "misses. The hit/miss ratio was", str(ratio)+".")
if nofails:
print("SUCCESS! There were no mismatches between Wally and the sim.")