Add SSSE3 implementation for Adler32.

adler32_ssse3.c

@@ -0,0 +1,159 @@
+/* adler32_simd.c
+ *
+ * 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 Chromium source repository LICENSE file.
+ *
+ * Per http://en.wikipedia.org/wiki/Adler-32 the adler32 A value (aka s1) is
+ * the sum of N input data bytes D1 ... DN,
+ *
+ *   A = A0 + D1 + D2 + ... + DN
+ *
+ * where A0 is the initial value.
+ *
+ * SSE2 _mm_sad_epu8() can be used for byte sums (see http://bit.ly/2wpUOeD,
+ * for example) and accumulating the byte sums can use SSE shuffle-adds (see
+ * the "Integer" section of http://bit.ly/2erPT8t for details). Arm NEON has
+ * similar instructions.
+ *
+ * The adler32 B value (aka s2) sums the A values from each step:
+ *
+ *   B0 + (A0 + D1) + (A0 + D1 + D2) + ... + (A0 + D1 + D2 + ... + DN) or
+ *
+ *       B0 + N.A0 + N.D1 + (N-1).D2 + (N-2).D3 + ... + (N-(N-1)).DN
+ *
+ * B0 being the initial value. For 32 bytes (ideal for garden-variety SIMD):
+ *
+ *   B = B0 + 32.A0 + [D1 D2 D3 ... D32] x [32 31 30 ... 1].
+ *
+ * Adjacent blocks of 32 input bytes can be iterated with the expressions to
+ * compute the adler32 s1 s2 of M >> 32 input bytes [1].
+ *
+ * As M grows, the s1 s2 sums grow. If left unchecked, they would eventually
+ * overflow the precision of their integer representation (bad). However, s1
+ * and s2 also need to be computed modulo the adler BASE value (reduced). If
+ * at most NMAX bytes are processed before a reduce, s1 s2 _cannot_ overflow
+ * a uint32_t type (the NMAX constraint) [2].
+ *
+ * [1] the iterative equations for s2 contain constant factors; these can be
+ * hoisted from the n-blocks do loop of the SIMD code.
+ *
+ * [2] zlib adler32_z() uses this fact to implement NMAX-block-based updates
+ * of the adler s1 s2 of uint32_t type (see adler32.c).
+ */
+
+#if defined(__x86_64__) || defined(__amd64) || defined(_M_AMD64) || defined(_M_X64) || defined(__I386__) ||            \
+    defined(__i386__) || defined(__THW_INTEL) || defined(_M_IX86)
+
+#include <stdint.h>
+#include <tmmintrin.h>
+
+#include "library.h"
+#include "adler32.h"
+
+void adler32_ssse3(uint16_t* sum1, uint16_t* sum2, const unsigned char* buf, size_t len)
+{
+    uint32_t s1 = *sum1;
+    uint32_t s2 = *sum2;
+
+    /*
+     * Process the data in blocks.
+     */
+    const unsigned BLOCK_SIZE = 1 << 5;
+    size_t         blocks     = len / BLOCK_SIZE;
+    len -= blocks * BLOCK_SIZE;
+    while(blocks)
+    {
+        unsigned n = NMAX / BLOCK_SIZE; /* The NMAX constraint. */
+        if(n > blocks) n = (unsigned)blocks;
+        blocks -= n;
+        const __m128i tap1 = _mm_setr_epi8(32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17);
+        const __m128i tap2 = _mm_setr_epi8(16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1);
+        const __m128i zero = _mm_setr_epi8(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
+        const __m128i ones = _mm_set_epi16(1, 1, 1, 1, 1, 1, 1, 1);
+        /*
+         * Process n blocks of data. At most NMAX data bytes can be
+         * processed before s2 must be reduced modulo BASE.
+         */
+        __m128i v_ps = _mm_set_epi32(0, 0, 0, s1 * n);
+        __m128i v_s2 = _mm_set_epi32(0, 0, 0, s2);
+        __m128i v_s1 = _mm_set_epi32(0, 0, 0, 0);
+        do {
+            /*
+             * Load 32 input bytes.
+             */
+            const __m128i bytes1 = _mm_loadu_si128((__m128i*)(buf));
+            const __m128i bytes2 = _mm_loadu_si128((__m128i*)(buf + 16));
+            /*
+             * Add previous block byte sum to v_ps.
+             */
+            v_ps = _mm_add_epi32(v_ps, v_s1);
+            /*
+             * Horizontally add the bytes for s1, multiply-adds the
+             * bytes by [ 32, 31, 30, ... ] for s2.
+             */
+            v_s1               = _mm_add_epi32(v_s1, _mm_sad_epu8(bytes1, zero));
+            const __m128i mad1 = _mm_maddubs_epi16(bytes1, tap1);
+            v_s2               = _mm_add_epi32(v_s2, _mm_madd_epi16(mad1, ones));
+            v_s1               = _mm_add_epi32(v_s1, _mm_sad_epu8(bytes2, zero));
+            const __m128i mad2 = _mm_maddubs_epi16(bytes2, tap2);
+            v_s2               = _mm_add_epi32(v_s2, _mm_madd_epi16(mad2, ones));
+            buf += BLOCK_SIZE;
+        } while(--n);
+        v_s2 = _mm_add_epi32(v_s2, _mm_slli_epi32(v_ps, 5));
+        /*
+         * Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
+         */
+#define S23O1 _MM_SHUFFLE(2, 3, 0, 1) /* A B C D -> B A D C */
+#define S1O32 _MM_SHUFFLE(1, 0, 3, 2) /* A B C D -> C D A B */
+        v_s1 = _mm_add_epi32(v_s1, _mm_shuffle_epi32(v_s1, S23O1));
+        v_s1 = _mm_add_epi32(v_s1, _mm_shuffle_epi32(v_s1, S1O32));
+        s1 += _mm_cvtsi128_si32(v_s1);
+        v_s2 = _mm_add_epi32(v_s2, _mm_shuffle_epi32(v_s2, S23O1));
+        v_s2 = _mm_add_epi32(v_s2, _mm_shuffle_epi32(v_s2, S1O32));
+        s2   = _mm_cvtsi128_si32(v_s2);
+#undef S23O1
+#undef S1O32
+        /*
+         * Reduce.
+         */
+        s1 %= ADLER_MODULE;
+        s2 %= ADLER_MODULE;
+    }
+    /*
+     * Handle leftover data.
+     */
+    if(len)
+    {
+        if(len >= 16)
+        {
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            s2 += (s1 += *buf++);
+            len -= 16;
+        }
+        while(len--) { s2 += (s1 += *buf++); }
+        if(s1 >= ADLER_MODULE) s1 -= ADLER_MODULE;
+        s2 %= ADLER_MODULE;
+    }
+    /*
+     * Return the recombined sums.
+     */
+    *sum1 = s1 & 0xFFFF;
+    *sum2 = s2 & 0xFFFF;
+}
+
+#endif