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a7d7ff5019
* libguile/gc.h: * libguile/gc.c (scm_gc_pin_object): New function. (scm_gc_object_address): New function, to be used instead of SCM_UNPACK when an object's address is exposed, for example via hashq. * libguile/atomic.c: * libguile/cache-internal.h: * libguile/continuations.c: * libguile/dynstack.c: * libguile/dynstack.h: * libguile/ephemerons.c: * libguile/exceptions.c: * libguile/finalizers.c: * libguile/fluids-internal.h: * libguile/fluids.c: * libguile/foreign.c: * libguile/frames.c: * libguile/hash.c: * libguile/hashtab.c: * libguile/intrinsics.c: * libguile/memoize.c: * libguile/print.c: * libguile/programs.c: * libguile/smob.c: * libguile/struct.c: * libguile/struct.h: * libguile/variable.c: * libguile/vm.c: Use the new functions everywhere that is needed. Because they take a thread, sometimes we have to do some extra plumbing.
104 lines
2.9 KiB
C
104 lines
2.9 KiB
C
#ifndef SCM_CACHE_INTERNAL_H
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#define SCM_CACHE_INTERNAL_H
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/* Copyright 2016,2018,2025
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Free Software Foundation, Inc.
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This file is part of Guile.
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Guile is free software: you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published
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by the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Guile is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with Guile. If not, see
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<https://www.gnu.org/licenses/>. */
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#include <string.h>
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#include "libguile/gc.h"
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#include "libguile/hash.h"
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/* A simple cache with 8 entries. The cache entries are stored in a
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sorted vector. */
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struct scm_cache_entry
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{
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scm_t_bits key;
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scm_t_bits value;
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};
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#define SCM_CACHE_SIZE 16
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struct scm_cache
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{
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scm_t_bits eviction_cookie;
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struct scm_cache_entry entries[SCM_CACHE_SIZE];
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};
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static inline int
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scm_cache_full_p (struct scm_cache *cache)
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{
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return cache->entries[0].key != 0;
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}
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static inline void
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scm_cache_evict_1 (struct scm_cache *cache, struct scm_cache_entry *evicted)
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{
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size_t idx;
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cache->eviction_cookie = scm_ihashq (SCM_PACK (cache->eviction_cookie), -1);
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idx = cache->eviction_cookie & (SCM_CACHE_SIZE - 1);
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memcpy (evicted, cache->entries + idx, sizeof (*evicted));
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memmove (cache->entries + 1,
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cache->entries,
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sizeof (cache->entries[0]) * idx);
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cache->entries[0].key = 0;
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cache->entries[0].value = 0;
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}
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static inline struct scm_cache_entry*
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scm_cache_lookup (struct scm_cache *cache, SCM k)
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{
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scm_t_bits k_bits = SCM_UNPACK (k);
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struct scm_cache_entry *entry = cache->entries;
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/* Unrolled binary search, compiled to branchless cmp + cmov chain. */
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if (entry[8].key <= k_bits) entry += 8;
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if (entry[4].key <= k_bits) entry += 4;
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if (entry[2].key <= k_bits) entry += 2;
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if (entry[1].key <= k_bits) entry += 1;
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return entry;
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}
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static inline void
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scm_cache_insert (struct scm_thread *thr, struct scm_cache *cache, SCM k, SCM v,
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struct scm_cache_entry *evicted)
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{
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struct scm_cache_entry *entry;
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if (scm_cache_full_p (cache))
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scm_cache_evict_1 (cache, evicted);
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entry = scm_cache_lookup (cache, k);
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if (entry->key == SCM_UNPACK (k))
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{
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entry->value = SCM_UNPACK (v);
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return;
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}
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memmove (cache->entries,
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cache->entries + 1,
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(entry - cache->entries) * sizeof (*entry));
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// FIXME: Perhaps we should just reorder after a GC in which a fluid
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// is moved. For now, pin the key.
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entry->key = scm_gc_object_address (thr, k);
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entry->value = SCM_UNPACK (v);
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}
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#endif /* SCM_CACHE_INTERNAL_H */
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