From b967b1449e0f6a9cd274cfec6dd3109e9ed0f821 Mon Sep 17 00:00:00 2001
From: Simon Hosie <simonhosie77+github@gmail.com>
Date: Fri, 6 Nov 2015 16:36:43 +0000
Subject: [PATCH] Add ARMv8 CRC32C support.

---
 README           |  8 +++++++-
 src/city-test.cc |  4 ++--
 src/city.cc      | 15 +++++++++++----
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/README b/README
index 0ec1917..ee576b8 100644
--- a/README
+++ b/README
@@ -99,12 +99,18 @@ On systems with gcc, we generally recommend:
 make all check CXXFLAGS="-g -O3"
 sudo make install
 
-Or, if your system has the CRC32 instruction, and you want to build everything:
+If your system has the SSE CRC32 instruction, and you want to build everything:
 
 ./configure --enable-sse4.2
 make all check CXXFLAGS="-g -O3 -msse4.2"
 sudo make install
 
+Or, for the ARMv8 CRC32C instruction:
+
+./configure --enable-sse4.2
+make all check CXXFLAGS="-g -O3 -march=armv8-a+crc"
+sudo make install
+
 Note that our build system doesn't try to determine the appropriate compiler
 flag for enabling SSE4.2.  For gcc it is "-msse4.2".  The --enable-sse4.2
 flag to the configure script controls whether citycrc.h is installed when
diff --git a/src/city-test.cc b/src/city-test.cc
index 06c9828..b94ab25 100644
--- a/src/city-test.cc
+++ b/src/city-test.cc
@@ -22,7 +22,7 @@
 #include <iostream>
 #include <string.h>
 #include "city.h"
-#ifdef __SSE4_2__
+#if defined __SSE4_2__ || defined __ARM_FEATURE_CRC32
 #include "citycrc.h"
 #endif
 
@@ -1279,7 +1279,7 @@ void Test(const uint64* expected, int offset, int len) {
   Check(expected[4], Uint128High64(u));
   Check(expected[5], Uint128Low64(v));
   Check(expected[6], Uint128High64(v));
-#ifdef __SSE4_2__
+#if defined __SSE4_2__ || defined __ARM_FEATURE_CRC32
   const uint128 y = CityHashCrc128(data + offset, len);
   const uint128 z = CityHashCrc128WithSeed(data + offset, len, kSeed128);
   uint64 crc256_results[4];
diff --git a/src/city.cc b/src/city.cc
index 41cd5ee..65d882f 100644
--- a/src/city.cc
+++ b/src/city.cc
@@ -512,9 +512,16 @@ uint128 CityHash128(const char *s, size_t len) {
       CityHash128WithSeed(s, len, uint128(k0, k1));
 }
 
-#ifdef __SSE4_2__
+#if defined __SSE4_2__ || defined __ARM_FEATURE_CRC32
 #include <citycrc.h>
+#ifdef __SSE4_2__
 #include <nmmintrin.h>
+#define crc32_u64 _mm_crc32_u64
+#endif
+#ifdef __ARM_FEATURE_CRC32
+#include <arm_acle.h>
+#define crc32_u64 __crc32cd
+#endif
 
 // Requires len >= 240.
 static void CityHashCrc256Long(const char *s, size_t len,
@@ -550,9 +557,9 @@ static void CityHashCrc256Long(const char *s, size_t len,
     g += e;                                     \
     e += z;                                     \
     g += x;                                     \
-    z = _mm_crc32_u64(z, b + g);                \
-    y = _mm_crc32_u64(y, e + h);                \
-    x = _mm_crc32_u64(x, f + a);                \
+    z = crc32_u64(z, b + g);                    \
+    y = crc32_u64(y, e + h);                    \
+    x = crc32_u64(x, f + a);                    \
     e = Rotate(e, r);                           \
     c += e;                                     \
     s += 40