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File zlib-1.2.12-adler32-vector-optimizations-for-power.patch of Package zlib (Revision f215c3ae08c05431d00f4f647091017e)

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From 772f4bd0f880c4c193ab7da78728f38821572a02 Mon Sep 17 00:00:00 2001
From: Rogerio Alves <rcardoso@linux.ibm.com>
Date: Mon, 9 Dec 2019 14:40:53 -0300
Subject: [PATCH] Adler32 vector optimization for Power.

This commit implements a Power (POWER8+) vector optimization for Adler32
checksum using VSX (vector) instructions. The VSX adler32 checksum is up
to 10x fast than the adler32 baseline code.

Author: Rogerio Alves <rcardoso@linux.ibm.com>
---
 CMakeLists.txt                   |   1 +
 Makefile.in                      |   8 ++
 adler32.c                        |  11 ++
 configure                        |   4 +-
 contrib/power/adler32_power8.c   | 196 +++++++++++++++++++++++++++++++
 contrib/power/adler32_resolver.c |  15 +++
 contrib/power/power.h            |   4 +-
 7 files changed, 236 insertions(+), 3 deletions(-)
 create mode 100644 contrib/power/adler32_power8.c
 create mode 100644 contrib/power/adler32_resolver.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 581e1fa6d..c6296ee68 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -185,6 +185,7 @@ if(CMAKE_COMPILER_IS_GNUCC)
             if(POWER8)
                 add_definitions(-DZ_POWER8)
                 set(ZLIB_POWER8
+                  contrib/power/adler32_power8.c
                   contrib/power/crc32_z_power8.c)
 
                 set_source_files_properties(
diff --git a/Makefile.in b/Makefile.in
index 16943044e..a0ffac860 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -165,6 +165,9 @@ minigzip64.o: $(SRCDIR)test/minigzip.c $(SRCDIR)zlib.h zconf.h
 adler32.o: $(SRCDIR)adler32.c
 	$(CC) $(CFLAGS) $(ZINC) -c -o $@ $(SRCDIR)adler32.c
 
+adler32_power8.o: $(SRCDIR)contrib/power/adler32_power8.c
+	$(CC) $(CFLAGS) -mcpu=power8 $(ZINC) -c -o $@ $(SRCDIR)contrib/power/adler32_power8.c
+
 crc32.o: $(SRCDIR)crc32.c
 	$(CC) $(CFLAGS) $(ZINC) -c -o $@ $(SRCDIR)crc32.c
 
@@ -216,6 +219,11 @@ adler32.lo: $(SRCDIR)adler32.c
 	$(CC) $(SFLAGS) $(ZINC) -DPIC -c -o objs/adler32.o $(SRCDIR)adler32.c
 	-@mv objs/adler32.o $@
 
+adler32_power8.lo: $(SRCDIR)contrib/power/adler32_power8.c
+	-@mkdir objs 2>/dev/null || test -d objs
+	$(CC) $(SFLAGS) -mcpu=power8 $(ZINC) -DPIC -c -o objs/adler32_power8.o $(SRCDIR)contrib/power/adler32_power8.c
+	-@mv objs/adler32_power8.o $@
+
 crc32.lo: $(SRCDIR)crc32.c
 	-@mkdir objs 2>/dev/null || test -d objs
 	$(CC) $(SFLAGS) $(ZINC) -DPIC -c -o objs/crc32.o $(SRCDIR)crc32.c
diff --git a/adler32.c b/adler32.c
index d0be4380a..4bde0fa18 100644
--- a/adler32.c
+++ b/adler32.c
@@ -131,6 +131,12 @@ uLong ZEXPORT adler32_z(adler, buf, len)
 }
 
 /* ========================================================================= */
+
+#ifdef Z_POWER_OPT
+/* Rename the default function to avoid naming conflicts */
+#define adler32 adler32_default
+#endif /* Z_POWER_OPT */
+
 uLong ZEXPORT adler32(adler, buf, len)
     uLong adler;
     const Bytef *buf;
@@ -139,6 +145,11 @@ uLong ZEXPORT adler32(adler, buf, len)
     return adler32_z(adler, buf, len);
 }
 
+#ifdef Z_POWER_OPT
+#undef adler32
+#include "contrib/power/adler32_resolver.c"
+#endif /* Z_POWER_OPT */
+
 /* ========================================================================= */
 local uLong adler32_combine_(adler1, adler2, len2)
     uLong adler1;
diff --git a/configure b/configure
index 914d9f4aa..810a7404d 100755
--- a/configure
+++ b/configure
@@ -879,8 +879,8 @@ if tryboth $CC -c $CFLAGS $test.c; then
 
   if tryboth $CC -c $CFLAGS -mcpu=power8 $test.c; then
     POWER8="-DZ_POWER8"
-    PIC_OBJC="${PIC_OBJC} crc32_z_power8.lo"
-    OBJC="${OBJC} crc32_z_power8.o"
+    PIC_OBJC="${PIC_OBJC} adler32_power8.lo crc32_z_power8.lo"
+    OBJC="${OBJC} adler32_power8.o crc32_z_power8.o"
     echo "Checking for -mcpu=power8 support... Yes." | tee -a configure.log
   else
     echo "Checking for -mcpu=power8 support... No." | tee -a configure.log
diff --git a/contrib/power/adler32_power8.c b/contrib/power/adler32_power8.c
new file mode 100644
index 000000000..473c39457
--- /dev/null
+++ b/contrib/power/adler32_power8.c
@@ -0,0 +1,196 @@
+/*
+ * Adler32 for POWER 8+ using VSX instructions.
+ *
+ * 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
+ *
+ * Copyright (C) 2019 Rogerio Alves <rcardoso@linux.ibm.com>, IBM
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ *
+ */
+
+#include "../../zutil.h"
+#include <altivec.h>
+
+/* Largest prime smaller than 65536.  */
+#define BASE 65521U
+#define NMAX 5552
+/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1.  */
+
+#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;
+}
+
+uLong ZLIB_INTERNAL _adler32_power8 (uLong adler, const Bytef* buf, uInt len)
+{
+  /* If buffer is empty or len=0 we need to return adler initial value.  */
+  if (buf == NULL)
+      return 1;
+
+  unsigned int s1 = adler & 0xffff;
+  unsigned int s2 = (adler >> 16) & 0xffff;
+
+  /* in case user likes doing a byte at a time, keep it fast */
+  if (len == 1) {
+      s1 += buf[0];
+      if (s1 >= BASE)
+          s1 -= BASE;
+      s2 += s1;
+      if (s2 >= BASE)
+          s2 -= BASE;
+      return (s2 << 16) | s1;
+  }
+
+  /* Keep it fast for short length buffers. */
+  if (len < 16) {
+      while (len--) {
+          s1 += *buf++;
+          s2 += s1;
+      }
+      if (s1 >= BASE)
+          s1 -= BASE;
+      s2 %= BASE;
+      return (s2 << 16) | s1;
+  }
+
+  /* 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 = vec_xl(0, &s1);
+      vector unsigned int vs2 = vec_xl(0, &s2);
+      vector unsigned int vs1_save = { 0 };
+      vector unsigned int vsum1, vsum2;
+      vector unsigned char vbuf;
+      int n;
+
+      /* Zeros the undefined values of vectors vs1, vs2.  */
+      vs1 = vec_and(vs1, vmask);
+      vs2 = vec_and(vs2, vmask);
+
+      /* 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).  */
+  while (len--) {
+      s1 += *buf++;
+      s2 += s1;
+  }
+  s1 %= BASE;
+  s2 %= BASE;
+
+  return (s2 << 16) | s1;
+}
diff --git a/contrib/power/adler32_resolver.c b/contrib/power/adler32_resolver.c
new file mode 100644
index 000000000..07a1a2cb2
--- /dev/null
+++ b/contrib/power/adler32_resolver.c
@@ -0,0 +1,15 @@
+/* Copyright (C) 2019 Rogerio Alves <rcardoso@linux.ibm.com>, IBM
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+#include "../gcc/zifunc.h"
+#include "power.h"
+
+Z_IFUNC(adler32) {
+#ifdef Z_POWER8
+    if (__builtin_cpu_supports("arch_2_07"))
+        return _adler32_power8;
+#endif
+
+    return adler32_default;
+}
diff --git a/contrib/power/power.h b/contrib/power/power.h
index 79123aa90..f57c76167 100644
--- a/contrib/power/power.h
+++ b/contrib/power/power.h
@@ -2,7 +2,9 @@
  *               2019 Rogerio Alves    <rogerio.alves@ibm.com>, IBM
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
-
 #include "../../zconf.h"
+#include "../../zutil.h"
+
+uLong _adler32_power8(uLong adler, const Bytef* buf, uInt len);
 
 unsigned long _crc32_z_power8(unsigned long, const Bytef *, z_size_t);

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