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/*
* Copyright (c) 2020 Collabora, Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* Authors (Collabora):
* Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
*/
/* Index buffer min/max cache. We need to calculate the min/max for arbitrary
* slices (start, start + count) of the index buffer at drawtime. As this can
* be quite expensive, we cache. Conceptually, we just use a hash table mapping
* the key (start, count) to the value (min, max). In practice, mesa's hash
* table implementation is higher overhead than we would like and makes
* handling memory usage a little complicated. So we use this data structure
* instead. Searching is O(n) to the size, but the size is capped at the
* PANFROST_MINMAX_SIZE constant (so this is a tradeoff between cache hit/miss
* ratio and cache search speed). Note that keys are adjacent so we get cache
* line alignment benefits. Insertion is O(1) and in-order until the cache
* fills up, after that it evicts the oldest cached value in a ring facilitated
* by index.
*/
#include "pan_minmax_cache.h"
bool
panfrost_minmax_cache_get(struct panfrost_minmax_cache *cache, unsigned start, unsigned count,
unsigned *min_index, unsigned *max_index)
{
uint64_t ht_key = (((uint64_t)count) << 32) | start;
bool found = false;
if (!cache)
return false;
for (unsigned i = 0; i < cache->size; ++i) {
if (cache->keys[i] == ht_key) {
uint64_t hit = cache->values[i];
*min_index = hit & 0xffffffff;
*max_index = hit >> 32;
found = true;
break;
}
}
return found;
}
void
panfrost_minmax_cache_add(struct panfrost_minmax_cache *cache, unsigned start, unsigned count,
unsigned min_index, unsigned max_index)
{
uint64_t ht_key = (((uint64_t)count) << 32) | start;
uint64_t value = min_index | (((uint64_t)max_index) << 32);
unsigned index = 0;
if (!cache)
return;
if (cache->size == PANFROST_MINMAX_SIZE) {
index = cache->index++;
cache->index = cache->index % PANFROST_MINMAX_SIZE;
} else {
index = cache->size++;
}
cache->keys[index] = ht_key;
cache->values[index] = value;
}
/* If we've been caching min/max indices and we update the index
* buffer, that may invalidate the min/max. Check what's been cached vs
* what we've written, and throw out invalid entries. */
void
panfrost_minmax_cache_invalidate(struct panfrost_minmax_cache *cache, struct pipe_transfer *transfer)
{
/* Ensure there is a cache to invalidate and a write */
if (!cache)
return;
if (!(transfer->usage & PIPE_TRANSFER_WRITE))
return;
unsigned valid_count = 0;
for (unsigned i = 0; i < cache->size; ++i) {
uint64_t key = cache->keys[i];
uint32_t start = key & 0xffffffff;
uint32_t count = key >> 32;
/* 1D range intersection */
bool invalid = MAX2(transfer->box.x, start) < MIN2(transfer->box.x + transfer->box.width, start + count);
if (!invalid) {
cache->keys[valid_count] = key;
cache->values[valid_count] = cache->values[i];
valid_count++;
}
}
cache->size = valid_count;
cache->index = 0;
}
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