diff options
Diffstat (limited to 'inc/cache.h')
| -rw-r--r-- | inc/cache.h | 119 |
1 files changed, 79 insertions, 40 deletions
diff --git a/inc/cache.h b/inc/cache.h index 0f15536..c9f7f66 100644 --- a/inc/cache.h +++ b/inc/cache.h @@ -1,79 +1,118 @@ +// Memory subsystem for the RISC-V[ECTOR] mini-ISA +// Copyright (C) 2025 Siddarth Suresh +// Copyright (C) 2025 bdunahu + +// This program is free software: you can redistribute it and/or modify +// it under the terms of the GNU General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. + +// This program is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License +// along with this program. If not, see <https://www.gnu.org/licenses/>. + #ifndef CACHE_H #define CACHE_H #include "definitions.h" #include "storage.h" #include <array> +#include <cmath> #include <functional> #include <ostream> +/** + * Parse an address into a tag, index into the cache table, and a line + * offset. + * @param the address to be parsed + * @param the resulting tag + * @param the resulting index + * @param the resulting offset + */ +// clang-format off +#define GET_FIELDS(a, t, i, o) \ + *(t) = GET_MID_BITS(a, this->size + LINE_SPEC - this->ways, MEM_WORD_SPEC); \ + *(i) = GET_MID_BITS(a, LINE_SPEC, this->size + LINE_SPEC - this->ways); \ + *(o) = GET_LS_BITS(a, LINE_SPEC) +// clang-format on + class Cache : public Storage { public: /** - * Constructor. +nn * Constructor. * @param The number of `lines` contained in memory. The total number of * words is this number multiplied by LINE_SIZE. * @param The next lowest level in storage. Methods from this object are * called in case of a cache miss. + * @param The number of bits required to specify a line in this level of cache. + * @param The number of ways this line of cache uses, or the number of data addresses stored for + * certain address index. * @param The number of clock cycles each access takes. * @return A new cache object. */ - Cache(Storage *lower, int delay); + Cache(Storage *lower, unsigned int size, unsigned int ways, int delay); ~Cache(); - int - write_word(void *, signed int, int) override; - int - write_line(void *, std::array<signed int, LINE_SIZE>, int) override; - int - read_line(void *, int, std::array<signed int, LINE_SIZE> &) override; - int - read_word(void *, int, signed int &) override; + int write_word(void *, signed int, int) override; + int write_line(void *, std::array<signed int, LINE_SIZE>, int) override; + int read_line(void *, int, std::array<signed int, LINE_SIZE> &) override; + int read_word(void *, int, signed int &) override; + private: + int process( + void *id, int address, std::function<void(int index, int offset)> request_handler) override; + /** + * Helper for process. + * Fetches `address` from a lower level of storage if it is not already + * present. The victim line is chosen/written back. + * @param the address that must be present in cache. + * @param 0 if the address is currently in cache, 1 if it is being fetched. + */ + int priming_address(int address); /** - * Getter for the meta attribute. - * TODO this doesn't seem like good object-oriented practice. - * @return this->meta + * Walks the ways in this set of ways. If none of the tags match, returns -1. Otherwise, returns + * the index the matching data is located. + * @param an index aligned to the set of ways in `this->data' + * @param the tag to be matched + * @return -1 if the tag is not present in this set of ways (not in cache), or the true index if + * the tag is present. */ - std::array<std::array<int, 2>, L1_CACHE_LINES> - get_meta() const; - - private: + int is_address_missing(int true_index, int tag); /** - * Helper for all access methods. - * Calls `request_handler` when `id` is allowed to complete its - * request cycle. - * @param the source making the request - * @param the address to write to - * @param the function to call when an access should be completed + * Converts an index into a set of ways into an index into `this->data', which is a + * 1D array. The next `this->ways' entries after the returned index represent the ways in the + * set for this index. + * @param an index to a set of ways + * @param an index aligned to the set of ways in `this->data' */ - int - process(void *id, int address, std::function<void(int index, int offset)> request_handler); + int get_true_index(int index); /** - * Returns OK if `id` is allowed to complete its request this cycle. - * Handles cache misses, wait times, and setting the current id this - * storage is serving. - * @param the id asking for a resource - * @return 1 if the access can be carried out this function call, 0 otherwise. + * Selects an index into the `data' and `meta' tables for write back using a random replacement + * policy. + * @param an index aligned to the set of ways in `this->data' + * @return an index aligned to the data line selected for eviction */ - int - is_access_cleared(void *id, int address); + int get_replacement_index(int index); /** - * Helper for is_access_cleared. - * Fetches `address` from a lower level of storage if it is not already - * present. The victim line is chosen/written back. - * @param the address that must be present in cache. - * @param 0 if the address is currently in cache, 1 if it is being fetched. + * The number of bits required to specify a line in this level of cache. + */ + unsigned int size; + /** + * The number of bits required to specify a way, or the number of data addresses stored for + * certain address index. */ - int - is_address_missing(int address); + unsigned int ways; /** * An array of metadata about elements in `data`. * If the first value of an element is negative, the corresponding * element in `data` is invalid. If the most second value of an element * is nonzero, the corresponding element in `data` is dirty. */ - std::array<std::array<int, 2>, L1_CACHE_LINES> meta; + std::vector<std::array<signed int, 3>> meta; }; #endif /* CACHE_H_INCLUDED */ |