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66 lines
2.4 KiB
C
66 lines
2.4 KiB
C
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/* Copyright 2018 The Chromium Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the Chromium source repository LICENSE file.
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*/
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#ifndef __SLIDE_HASH__NEON__
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#define __SLIDE_HASH__NEON__
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#include "deflate.h"
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#include <arm_neon.h>
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inline static void ZLIB_INTERNAL neon_slide_hash_update(Posf *hash,
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const uInt hash_size,
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const ush w_size)
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{
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/* NEON 'Q' registers allow to store 128 bits, so we can load 8x16-bits
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* values. For further details, check:
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* ARM DHT 0002A, section 1.3.2 NEON Registers.
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*/
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const size_t chunk = sizeof(uint16x8_t) / sizeof(uint16_t);
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/* Unrolling the operation yielded a compression performance boost in both
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* ARMv7 (from 11.7% to 13.4%) and ARMv8 (from 3.7% to 7.5%) for HTML4
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* content. For full benchmarking data, check: http://crbug.com/863257.
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*/
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const size_t stride = 2*chunk;
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const uint16x8_t v = vdupq_n_u16(w_size);
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for (Posf *end = hash + hash_size; hash != end; hash += stride) {
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uint16x8_t m_low = vld1q_u16(hash);
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uint16x8_t m_high = vld1q_u16(hash + chunk);
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/* The first 'q' in vqsubq_u16 makes these subtracts saturate to zero,
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* replacing the ternary operator expression in the original code:
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* (m >= wsize ? m - wsize : NIL).
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*/
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m_low = vqsubq_u16(m_low, v);
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m_high = vqsubq_u16(m_high, v);
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vst1q_u16(hash, m_low);
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vst1q_u16(hash + chunk, m_high);
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}
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}
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inline static void ZLIB_INTERNAL neon_slide_hash(Posf *head, Posf *prev,
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const unsigned short w_size,
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const uInt hash_size)
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{
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/*
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* SIMD implementation for hash table rebase assumes:
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* 1. hash chain offset (Pos) is 2 bytes.
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* 2. hash table size is multiple of 32 bytes.
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* #1 should be true as Pos is defined as "ush"
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* #2 should be true as hash_bits are greater than 7
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*/
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const size_t size = hash_size * sizeof(head[0]);
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Assert(sizeof(Pos) == 2, "Wrong Pos size.");
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Assert((size % sizeof(uint16x8_t) * 2) == 0, "Hash table size error.");
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neon_slide_hash_update(head, hash_size, w_size);
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#ifndef FASTEST
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neon_slide_hash_update(prev, w_size, w_size);
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#endif
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}
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#endif
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