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NEON implementation for Adler32 #251
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Using ARMv8 CRC32 specific instruction
CRC32 affects performance for both image decompression (PNG) as also in general browsing while accessing websites that serve content using compression (i.e. Content-Encoding: gzip). This first patch implements an optimized CRC32 function using the dedicated instruction available in ARMv8. It should be between 6x (A53: 116ms X 22ms for a 4Kx4Kx4 buffer) to 10x faster (A72: 91ms x 9ms) than the C implementation currently used by zlib. Details: https://bugs.chromium.org/p/chromium/issues/detail?id=709716 Change-Id: I069408ebc06c49a3c2be4ba3253319e025ee09d7
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| /* Copyright (C) 1995-2011, 2016 Mark Adler | ||
| * Copyright (C) 2017 ARM Holdings Inc. | ||
| * Authors: Adenilson Cavalcanti <[email protected]> | ||
| * Yang Zhang <[email protected]> | ||
| * This software is provided 'as-is', without any express or implied | ||
| * warranty. In no event will the authors be held liable for any damages | ||
| * arising from the use of this software. | ||
| * Permission is granted to anyone to use this software for any purpose, | ||
| * including commercial applications, and to alter it and redistribute it | ||
| * freely, subject to the following restrictions: | ||
| * 1. The origin of this software must not be misrepresented; you must not | ||
| * claim that you wrote the original software. If you use this software | ||
| * in a product, an acknowledgment in the product documentation would be | ||
| * appreciated but is not required. | ||
| * 2. Altered source versions must be plainly marked as such, and must not be | ||
| * misrepresented as being the original software. | ||
| * 3. This notice may not be removed or altered from any source distribution. | ||
| */ | ||
| #include <arm_acle.h> | ||
| // Depending on the compiler flavor, size_t may be defined in | ||
| // one or the other header. See: | ||
| // http://stackoverflow.com/questions/26410466/gcc-linaro-compiler-throws-error-unknown-type-name-size-t | ||
| #include <stdint.h> | ||
| #include <stddef.h> | ||
|
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| uint32_t armv8_crc32_little(uint32_t crc, | ||
| const unsigned char *buf, | ||
| size_t len) { | ||
| uint32_t c; | ||
| const uint32_t *buf4; | ||
|
|
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| c = crc; | ||
| c = ~c; | ||
| while (len && ((ptrdiff_t)buf & 3)) { | ||
| c = __crc32b(c, *buf++); | ||
| len--; | ||
| } | ||
|
|
||
| buf4 = (const uint32_t *)(const void *)buf; | ||
|
|
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| while (len >= 32) { | ||
| c = __crc32w(c, *buf4++); | ||
| c = __crc32w(c, *buf4++); | ||
| c = __crc32w(c, *buf4++); | ||
| c = __crc32w(c, *buf4++); | ||
| c = __crc32w(c, *buf4++); | ||
| c = __crc32w(c, *buf4++); | ||
| c = __crc32w(c, *buf4++); | ||
| c = __crc32w(c, *buf4++); | ||
| len -= 32; | ||
| } | ||
|
|
||
| while (len >= 4) { | ||
| c = __crc32w(c, *buf4++); | ||
| len -= 4; | ||
| } | ||
|
|
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| buf = (const unsigned char *)buf4; | ||
| if (len) { | ||
| do { | ||
| c = __crc32b(c, *buf++); | ||
| } while (--len); | ||
| } | ||
|
|
||
| c = ~c; | ||
| return c; | ||
| } | ||
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In a second thought, this should handle the case of buf == Z_NULL.