NEON implementation for Adler32

third_party/zlib/neon_adler32.patch

+commit e7e8afea42721f13a8c7f9bd7cc836a8612d5d10
+Author: Adenilson Cavalcanti <adenilson.cavalcanti@arm.com>
+Date:   Mon Jan 30 15:30:38 2017 -0800
+
+    NEON implementation for Adler32
+    
+    The checksum is calculated in the uncompressed PNG data
+    and can be made much faster by using SIMD.
+    
+    Tests in ARMv8 yielded an improvement of about 3x
+    (e.g. walltime was 350ms x 125ms for a 4096x4096 bytes
+    executed 30 times).
+
+diff --git a/third_party/zlib/BUILD.gn b/third_party/zlib/BUILD.gn
+index 5086563..09dfa5f 100644
+--- a/third_party/zlib/BUILD.gn
++++ b/third_party/zlib/BUILD.gn
+@@ -73,6 +73,11 @@ static_library("zlib") {
+ 
+   if (!is_ios && (current_cpu == "x86" || current_cpu == "x64")) {
+     sources += [ "x86.c" ]
++  } else if (current_cpu == "arm" || current_cpu == "arm64") {
++    sources += [
++      "neon_adler32.c",
++      "neon_adler32.h",
++    ]
+   }
+ 
+   configs -= [ "//build/config/compiler:chromium_code" ]
+diff --git a/third_party/zlib/adler32.c b/third_party/zlib/adler32.c
+index d0be438..26dad16 100644
+--- a/third_party/zlib/adler32.c
++++ b/third_party/zlib/adler32.c
+@@ -6,6 +6,9 @@
+ /* @(#) $Id$ */
+ 
+ #include "zutil.h"
++#ifdef __ARM_NEON__
++#include "neon_adler32.h"
++#endif
+ 
+ local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2));
+ 
+@@ -65,6 +68,12 @@ uLong ZEXPORT adler32_z(adler, buf, len)
+     const Bytef *buf;
+     z_size_t len;
+ {
++#ifdef __ARM_NEON__
++    if (len > 31) {
++      return NEON_adler32(adler, buf, len);
++    }
++#endif
++
+     unsigned long sum2;
+     unsigned n;
+ 
+diff --git a/third_party/zlib/neon_adler32.c b/third_party/zlib/neon_adler32.c
+new file mode 100644
+index 0000000..8356842
+--- /dev/null
++++ b/third_party/zlib/neon_adler32.c
+@@ -0,0 +1,122 @@
++/* Copyright 2017 The Chromium Authors. All rights reserved.
++ * Use of this source code is governed by a BSD-style license that can be
++ * found in the LICENSE file.
++*/
++
++#include "neon_adler32.h"
++#ifdef __ARM_NEON__
++#include <arm_neon.h>
++
++static void NEON_accum32(uint32_t *s, const unsigned char *buf,
++                         unsigned int len)
++{
++  static const uint8_t taps[32] = {
++    32, 31, 30, 29, 28, 27, 26, 25,
++    24, 23, 22, 21, 20, 19, 18, 17,
++    16, 15, 14, 13, 12, 11, 10, 9,
++    8, 7, 6, 5, 4, 3, 2, 1 };
++
++  uint8x16_t t0 = vld1q_u8(taps), t1 = vld1q_u8(taps + 16);
++
++  uint32x4_t adacc = vdupq_n_u32(0), s2acc = vdupq_n_u32(0);
++  adacc = vsetq_lane_u32(s[0], adacc, 0);
++  s2acc = vsetq_lane_u32(s[1], s2acc, 0);
++
++  while (len >= 2) {
++    uint8x16_t d0 = vld1q_u8(buf), d1 = vld1q_u8(buf + 16);
++    uint16x8_t adler, sum2;
++    s2acc = vaddq_u32(s2acc, vshlq_n_u32(adacc, 5));
++    adler = vpaddlq_u8(       d0);
++    adler = vpadalq_u8(adler, d1);
++    sum2 = vmull_u8(      vget_low_u8(t0), vget_low_u8(d0));
++    sum2 = vmlal_u8(sum2, vget_high_u8(t0), vget_high_u8(d0));
++    sum2 = vmlal_u8(sum2, vget_low_u8(t1), vget_low_u8(d1));
++    sum2 = vmlal_u8(sum2, vget_high_u8(t1), vget_high_u8(d1));
++    adacc = vpadalq_u16(adacc, adler);
++    s2acc = vpadalq_u16(s2acc, sum2);
++    len -= 2;
++    buf += 32;
++  }
++
++
++  while (len > 0) {
++    uint8x16_t d0 = vld1q_u8(buf);
++    uint16x8_t adler, sum2;
++    s2acc = vaddq_u32(s2acc, vshlq_n_u32(adacc, 4));
++    adler = vpaddlq_u8(d0);
++    sum2 = vmull_u8(      vget_low_u8(t1), vget_low_u8(d0));
++    sum2 = vmlal_u8(sum2, vget_high_u8(t1), vget_high_u8(d0));
++    adacc = vpadalq_u16(adacc, adler);
++    s2acc = vpadalq_u16(s2acc, sum2);
++    buf += 16;
++    len--;
++  }
++
++  {
++    uint32x2_t adacc2 = vpadd_u32(vget_low_u32(adacc), vget_high_u32(adacc));
++    uint32x2_t s2acc2 = vpadd_u32(vget_low_u32(s2acc), vget_high_u32(s2acc));
++    uint32x2_t as = vpadd_u32(adacc2, s2acc2);
++    s[0] = vget_lane_u32(as, 0);
++    s[1] = vget_lane_u32(as, 1);
++  }
++}
++
++static void NEON_handle_tail(uint32_t *pair, const unsigned char *buf,
++                             unsigned int len)
++{
++  /* Oldie K&R code integration. */
++  unsigned int i;
++  for (i = 0; i < len; ++i) {
++    pair[0] += buf[i];
++    pair[1] += pair[0];
++  }
++}
++
++unsigned long NEON_adler32(unsigned long adler, const unsigned char *buf,
++                           const unsigned int len)
++{
++  /* The largest prime smaller than 65536. */
++  const uint32_t M_BASE = 65521;
++  /* This is the threshold where doing accumulation may overflow. */
++  const int M_NMAX = 5552;
++
++  unsigned long sum2;
++  uint32_t pair[2];
++  int n = M_NMAX;
++  unsigned int done = 0;
++  /* Oldie K&R code integration. */
++  unsigned int i;
++
++  /* Split Adler-32 into component sums, it can be supplied by
++   * the caller sites (e.g. in a PNG file).
++   */
++  sum2 = (adler >> 16) & 0xffff;
++  adler &= 0xffff;
++  pair[0] = adler;
++  pair[1] = sum2;
++
++  for (i = 0; i < len; i += n) {
++    if ((i + n) > len)
++      n = len - i;
++
++    if (n < 16)
++      break;
++
++    NEON_accum32(pair, buf + i, n / 16);
++    pair[0] %= M_BASE;
++    pair[1] %= M_BASE;
++
++    done += (n / 16) * 16;
++  }
++
++  /* Handle the tail elements. */
++  if (done < len) {
++    NEON_handle_tail(pair, (buf + done), len - done);
++    pair[0] %= M_BASE;
++    pair[1] %= M_BASE;
++  }
++
++  /* D = B * 65536 + A, see: https://en.wikipedia.org/wiki/Adler-32. */
++  return (pair[1] << 16) | pair[0];
++}
++#endif
+diff --git a/third_party/zlib/neon_adler32.h b/third_party/zlib/neon_adler32.h
+new file mode 100644
+index 0000000..3043e3d
+--- /dev/null
++++ b/third_party/zlib/neon_adler32.h
+@@ -0,0 +1,12 @@
++/* Copyright 2017 The Chromium Authors. All rights reserved.
++ * Use of this source code is governed by a BSD-style license that can be
++ * found in the LICENSE file.
++*/
++#ifndef __NEON_ADLER32__
++#define __NEON_ADLER32__
++
++#ifdef __ARM_NEON__
++unsigned long NEON_adler32(unsigned long adler, const unsigned char *buf,
++                           const unsigned int len);
++#endif
++#endif