diff --git a/src/Makefile.am b/src/Makefile.am
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -207,6 +207,7 @@
   util.h \
   utilmoneystr.h \
   utiltime.h \
+  util/bitmanip.h \
   util/bytevectorhash.h \
   validation.h \
   validationinterface.h \
diff --git a/src/Makefile.test.include b/src/Makefile.test.include
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -42,6 +42,7 @@
   test/base58_tests.cpp \
   test/base64_tests.cpp \
   test/bip32_tests.cpp \
+  test/bitmanip_tests.cpp \
   test/blockchain_tests.cpp \
   test/blockcheck_tests.cpp \
   test/blockencodings_tests.cpp \
diff --git a/src/avalanche.cpp b/src/avalanche.cpp
--- a/src/avalanche.cpp
+++ b/src/avalanche.cpp
@@ -5,10 +5,10 @@
 #include <avalanche.h>
 
 #include <chain.h>
-#include <config/bitcoin-config.h>
 #include <netmessagemaker.h>
 #include <reverse_iterator.h>
 #include <scheduler.h>
+#include <util/bitmanip.h>
 #include <validation.h>
 
 #include <tuple>
@@ -23,23 +23,6 @@
  */
 static const size_t AVALANCHE_MAX_ELEMENT_POLL = 4096;
 
-static uint32_t countBits(uint32_t v) {
-#if HAVE_DECL___BUILTIN_POPCOUNT
-    return __builtin_popcount(v);
-#else
-    /**
-     * Computes the number of bits set in each group of 8bits then uses a
-     * multiplication to sum all of them in the 8 most significant bits and
-     * return these.
-     * More detailed explanation can be found at
-     * https://www.playingwithpointers.com/blog/swar.html
-     */
-    v = v - ((v >> 1) & 0x55555555);
-    v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
-    return (((v + (v >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
-#endif
-}
-
 bool VoteRecord::registerVote(NodeId nodeid, uint32_t error) {
     // We just got a new vote, so there is one less inflight request.
     clearInflightRequest();
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -55,6 +55,7 @@
 	base58_tests.cpp
 	base64_tests.cpp
 	bip32_tests.cpp
+	bitmanip_tests.cpp
 	blockchain_tests.cpp
 	blockcheck_tests.cpp
 	blockencodings_tests.cpp
diff --git a/src/test/bitmanip_tests.cpp b/src/test/bitmanip_tests.cpp
new file mode 100644
--- /dev/null
+++ b/src/test/bitmanip_tests.cpp
@@ -0,0 +1,60 @@
+// Copyright (c) 2019 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <test/test_bitcoin.h>
+#include <util/bitmanip.h>
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_FIXTURE_TEST_SUITE(bitmanip_tests, BasicTestingSetup)
+
+static void CheckBitCount(uint32_t value, uint32_t expected_count) {
+    // Count are rotation invariant.
+    for (int i = 0; i < 32; i++) {
+        BOOST_CHECK_EQUAL(countBits(value), expected_count);
+        value = (value << 1) | (value >> 31);
+    }
+}
+
+static uint32_t countBitsNaive(uint32_t value) {
+    uint32_t ret = 0;
+    while (value != 0) {
+        ret += (value & 0x01);
+        value >>= 1;
+    }
+
+    return ret;
+}
+
+#define COUNT 4096
+
+BOOST_AUTO_TEST_CASE(bit_count) {
+    // Check various known values.
+    CheckBitCount(0, 0);
+    CheckBitCount(1, 1);
+    CheckBitCount(0xffffffff, 32);
+    CheckBitCount(0x01234567, 12);
+    CheckBitCount(0x12345678, 13);
+    CheckBitCount(0xfedcba98, 20);
+    CheckBitCount(0x5a55aaa5, 16);
+    CheckBitCount(0xdeadbeef, 24);
+
+    for (uint32_t i = 2; i != 0; i <<= 1) {
+        // Check two bit set for all combinations.
+        CheckBitCount(i | 0x01, 2);
+    }
+
+    // Check many small values against a naive implementation.
+    for (uint32_t v = 0; v <= 0xfff; v++) {
+        CheckBitCount(v, countBitsNaive(v));
+    }
+
+    // Check random values against a naive implementation.
+    for (int i = 0; i < COUNT; i++) {
+        uint32_t v = InsecureRand32();
+        CheckBitCount(v, countBitsNaive(v));
+    }
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/util/bitmanip.h b/src/util/bitmanip.h
new file mode 100644
--- /dev/null
+++ b/src/util/bitmanip.h
@@ -0,0 +1,29 @@
+// Copyright (c) 2019 The Bitcoin developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_BITMANIP_H
+#define BITCOIN_UTIL_BITMANIP_H
+
+#include <config/bitcoin-config.h>
+
+#include <cstdint>
+
+inline uint32_t countBits(uint32_t v) {
+#if HAVE_DECL___BUILTIN_POPCOUNT
+    return __builtin_popcount(v);
+#else
+    /**
+     * Computes the number of bits set in each group of 8bits then uses a
+     * multiplication to sum all of them in the 8 most significant bits and
+     * return these.
+     * More detailed explanation can be found at
+     * https://www.playingwithpointers.com/blog/swar.html
+     */
+    v = v - ((v >> 1) & 0x55555555);
+    v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
+    return (((v + (v >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
+#endif
+}
+
+#endif // BITCOIN_UTIL_BITMANIP_H