--- /dev/null
+/* Adler32 for POWER8 using VSX instructions.
+ * Copyright (C) 2020 IBM Corporation
+ * Author: Rogerio Alves <rcardoso@linux.ibm.com>
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ *
+ * Calculate adler32 checksum for 16 bytes at once using POWER8+ VSX (vector)
+ * instructions.
+ *
+ * If adler32 do 1 byte at time on the first iteration s1 is s1_0 (_n means
+ * iteration n) is the initial value of adler - at start _0 is 1 unless
+ * adler initial value is different than 1. So s1_1 = s1_0 + c[0] after
+ * the first calculation. For the iteration s1_2 = s1_1 + c[1] and so on.
+ * Hence, for iteration N, s1_N = s1_(N-1) + c[N] is the value of s1 on
+ * after iteration N.
+ *
+ * Therefore, for s2 and iteration N, s2_N = s2_0 + N*s1_N + N*c[0] +
+ * N-1*c[1] + ... + c[N]
+ *
+ * In a more general way:
+ *
+ * s1_N = s1_0 + sum(i=1 to N)c[i]
+ * s2_N = s2_0 + N*s1 + sum (i=1 to N)(N-i+1)*c[i]
+ *
+ * Where s1_N, s2_N are the values for s1, s2 after N iterations. So if we
+ * can process N-bit at time we can do this at once.
+ *
+ * Since VSX can support 16-bit vector instructions, we can process
+ * 16-bit at time using N = 16 we have:
+ *
+ * s1 = s1_16 = s1_(16-1) + c[16] = s1_0 + sum(i=1 to 16)c[i]
+ * s2 = s2_16 = s2_0 + 16*s1 + sum(i=1 to 16)(16-i+1)*c[i]
+ *
+ * After the first iteration we calculate the adler32 checksum for 16 bytes.
+ *
+ * For more background about adler32 please check the RFC:
+ * https://www.ietf.org/rfc/rfc1950.txt
+ */
+
+#ifdef POWER8_VSX_ADLER32
+
+#include <altivec.h>
+#include "zbuild.h"
+#include "zutil.h"
+#include "adler32_p.h"
+
+#define DO1(s1,s2,buf,i) {(s1) += buf[(i)]; (s2) += (s1);}
+#define DO2(s1,s2,buf,i) {DO1(s1,s2,buf,i); DO1(s1,s2,buf,i+1);}
+#define DO4(s1,s2,buf,i) {DO2(s1,s2,buf,i); DO2(s1,s2,buf,i+2);}
+#define DO8(s1,s2,buf,i) {DO4(s1,s2,buf,i); DO4(s1,s2,buf,i+4);}
+#define DO16(s1,s2,buf) {DO8(s1,s2,buf,0); DO8(s1,s2,buf,8);}
+
+/* Vector across sum unsigned int (saturate). */
+inline vector unsigned int vec_sumsu(vector unsigned int __a, vector unsigned int __b) {
+ __b = vec_sld(__a, __a, 8);
+ __b = vec_add(__b, __a);
+ __a = vec_sld(__b, __b, 4);
+ __a = vec_add(__a, __b);
+
+ return __a;
+}
+
+uint32_t adler32_power8(uint32_t adler, const unsigned char* buf, size_t len) {
+ uint32_t s1 = adler & 0xffff;
+ uint32_t s2 = (adler >> 16) & 0xffff;
+
+ /* in case user likes doing a byte at a time, keep it fast */
+ if (UNLIKELY(len == 1))
+ return adler32_len_1(s1, buf, s2);
+
+ /* If buffer is empty or len=0 we need to return adler initial value. */
+ if (UNLIKELY(buf == NULL))
+ return 1;
+
+ /* This is faster than VSX code for len < 64. */
+ if (len < 64) {
+ while (len >= 16) {
+ len -= 16;
+ DO16(s1,s2,buf);
+ buf += 16;
+ }
+ } else {
+ /* Use POWER VSX instructions for len >= 64. */
+ const vector unsigned int v_zeros = { 0 };
+ const vector unsigned char v_mul = {16, 15, 14, 13, 12, 11, 10, 9, 8, 7,
+ 6, 5, 4, 3, 2, 1};
+ const vector unsigned char vsh = vec_splat_u8(4);
+ const vector unsigned int vmask = {0xffffffff, 0x0, 0x0, 0x0};
+ vector unsigned int vs1 = { 0 };
+ vector unsigned int vs2 = { 0 };
+ vector unsigned int vs1_save = { 0 };
+ vector unsigned int vsum1, vsum2;
+ vector unsigned char vbuf;
+ int n;
+
+ vs1[0] = s1;
+ vs2[0] = s2;
+
+ /* Do length bigger than NMAX in blocks of NMAX size. */
+ while (len >= NMAX) {
+ len -= NMAX;
+ n = NMAX / 16;
+ do {
+ vbuf = vec_xl(0, (unsigned char *) buf);
+ vsum1 = vec_sum4s(vbuf, v_zeros); /* sum(i=1 to 16) buf[i]. */
+ /* sum(i=1 to 16) buf[i]*(16-i+1). */
+ vsum2 = vec_msum(vbuf, v_mul, v_zeros);
+ /* Save vs1. */
+ vs1_save = vec_add(vs1_save, vs1);
+ /* Accumulate the sums. */
+ vs1 = vec_add(vsum1, vs1);
+ vs2 = vec_add(vsum2, vs2);
+
+ buf += 16;
+ } while (--n);
+ /* Once each block of NMAX size. */
+ vs1 = vec_sumsu(vs1, vsum1);
+ vs1_save = vec_sll(vs1_save, vsh); /* 16*vs1_save. */
+ vs2 = vec_add(vs1_save, vs2);
+ vs2 = vec_sumsu(vs2, vsum2);
+
+ /* vs1[0] = (s1_i + sum(i=1 to 16)buf[i]) mod 65521. */
+ vs1[0] = vs1[0] % BASE;
+ /* vs2[0] = s2_i + 16*s1_save +
+ sum(i=1 to 16)(16-i+1)*buf[i] mod 65521. */
+ vs2[0] = vs2[0] % BASE;
+
+ vs1 = vec_and(vs1, vmask);
+ vs2 = vec_and(vs2, vmask);
+ vs1_save = v_zeros;
+ }
+
+ /* len is less than NMAX one modulo is needed. */
+ if (len >= 16) {
+ while (len >= 16) {
+ len -= 16;
+
+ vbuf = vec_xl(0, (unsigned char *) buf);
+
+ vsum1 = vec_sum4s(vbuf, v_zeros); /* sum(i=1 to 16) buf[i]. */
+ /* sum(i=1 to 16) buf[i]*(16-i+1). */
+ vsum2 = vec_msum(vbuf, v_mul, v_zeros);
+ /* Save vs1. */
+ vs1_save = vec_add(vs1_save, vs1);
+ /* Accumulate the sums. */
+ vs1 = vec_add(vsum1, vs1);
+ vs2 = vec_add(vsum2, vs2);
+
+ buf += 16;
+ }
+ /* Since the size will be always less than NMAX we do this once. */
+ vs1 = vec_sumsu(vs1, vsum1);
+ vs1_save = vec_sll(vs1_save, vsh); /* 16*vs1_save. */
+ vs2 = vec_add(vs1_save, vs2);
+ vs2 = vec_sumsu(vs2, vsum2);
+ }
+ /* Copy result back to s1, s2 (mod 65521). */
+ s1 = vs1[0] % BASE;
+ s2 = vs2[0] % BASE;
+ }
+
+ /* Process tail (len < 16).and return */
+ return adler32_len_16(s1, buf, len, s2);
+}
+
+#endif /* POWER8_VSX_ADLER32 */
projects / thirdparty / zlib-ng.git / commitdiff
