diff --git a/src/Geno.cpp b/src/Geno.cpp
index 853a86a47ba5d7f422b9c4455ca3202685c9c641..77dc4a8a0ac1c51ea830795b8671c02b5114af35 100644
--- a/src/Geno.cpp
+++ b/src/Geno.cpp
@@ -43,6 +43,26 @@
 #include "submods/Pgenlib/PgenReader.h"
 #include <numeric>
 
+#if defined( __i386__ ) || defined(i386) || defined(_M_IX86)
+    /*
+     * __i386__ is defined by gcc and Intel compiler on Linux,
+     * _M_IX86 by VS compiler,
+     * i386 by Sun compilers on opensolaris at least
+     */
+    #define CPU_X86
+#elif defined(__x86_64__) || defined(__amd64__) || defined(__x86_64) || defined(_M_AMD64)
+    /*
+     * both __x86_64__ and __amd64__ are defined by gcc
+     * __x86_64 defined by sun compiler on opensolaris at least
+     * _M_AMD64 defined by MS compiler
+     */
+    #define CPU_AMD64
+#elif defined(__arm__) || defined(__aarch64__)
+    #define CPU_ARM
+#else
+    #error Unknown CPU
+#endif
+
 #ifdef _WIN64
   #include <intrin.h>
   uint32_t __inline CTZ64U(uint64_t value){
@@ -59,13 +79,13 @@
 #else
   //#define CTZU __builtin_ctz
   //#define CLZU __builtin_clz
-  #ifdef __linux__
+  #if defined(__linux__) && !defined(CPU_ARM)
   __attribute__((target("default")))
   #endif
   uint32_t CTZ64U(uint64_t value){
       return __builtin_ctzll(value);
   }
-  #ifdef __linux__
+  #if defined(__linux__) && !defined(CPU_ARM)
   __attribute__((target("popcnt")))
   uint32_t CTZ64U(uint64_t value){
       return __builtin_ctzll(value);
@@ -74,7 +94,7 @@
  
 #endif
 
-#ifdef __linux__
+#if defined(__linux__) && !defined(CPU_ARM)
 __attribute__((target("default")))
 #endif
 uint64_t fill_inter_zero(uint64_t x) {
@@ -91,7 +111,7 @@ uint64_t fill_inter_zero(uint64_t x) {
    x = x ^ t ^ (t << 1);
    return x;
 }
-#ifdef __linux__
+#if defined(__linux__) && !defined(CPU_ARM)
 #include <x86intrin.h>
 __attribute__((target("bmi2")))
 uint64_t fill_inter_zero(uint64_t x) {