Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -107,10 +107,18 @@
 #ifdef __GNUC__
 # define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
 #else
 # define GCC_VERSION 0
 #endif
+
+/* What version of CLANG is being used.  0 means GCC is not being used */
+#ifdef __clang__
+# define CLANG_VERSION \
+            (__clang_major__*1000000+__clang_minor__*1000+__clang_patchlevel__)
+#else
+# define CLANG_VERSION 0
+#endif
 
 /* Needed for various definitions... */
 #if defined(__GNUC__) && !defined(_GNU_SOURCE)
 # define _GNU_SOURCE
 #endif
@@ -231,11 +239,11 @@
 /*
 ** The SQLITE_ATOMIC_STATUS_DOWN macro is defined if and only if
 ** the sqlite3StatusDown() function is threadsafe.
 */
 #if !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=4004000
+    && (GCC_VERSION>=4004000 || CLANG_VERSION>=3000000)
 # define SQLITE_ATOMIC_STATUS_DOWN 1
 #endif
 
 /*
 ** Make sure that the compiler intrinsics we desire are enabled when

Index: src/status.c
==================================================================
--- src/status.c
+++ src/status.c
@@ -100,11 +100,11 @@
 void sqlite3StatusDown(int op, int N){
   wsdStatInit;
   assert( N>=0 );
   assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
 #if !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=4004000
+    && (GCC_VERSION>=4004000 || CLANG_VERSION>=3000000)
   (void)__sync_fetch_and_sub(&wsdStat.nowValue[op], N);
 #else
   assert( op>=0 && op<ArraySize(statMutex) );
   assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
                                            : sqlite3MallocMutex()) );

Index: src/util.c
==================================================================
--- src/util.c
+++ src/util.c
@@ -1139,11 +1139,11 @@
 #if SQLITE_BYTEORDER==4321
   u32 x;
   memcpy(&x,p,4);
   return x;
 #elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=4003000
+    && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
   u32 x;
   memcpy(&x,p,4);
   return __builtin_bswap32(x);
 #elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
     && defined(_MSC_VER) && _MSC_VER>=1300
@@ -1157,11 +1157,11 @@
 }
 void sqlite3Put4byte(unsigned char *p, u32 v){
 #if SQLITE_BYTEORDER==4321
   memcpy(p,&v,4);
 #elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=4003000
+    && (GCC_VERSION>=4003000 || CLANG_VERSION>=3000000)
   u32 x = __builtin_bswap32(v);
   memcpy(p,&x,4);
 #elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
     && defined(_MSC_VER) && _MSC_VER>=1300
   u32 x = _byteswap_ulong(v);
@@ -1278,11 +1278,11 @@
 ** Return 0 on success.  Or if the operation would have resulted in an
 ** overflow, leave *pA unchanged and return 1.
 */
 int sqlite3AddInt64(i64 *pA, i64 iB){
 #if !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=5004000
+    && (GCC_VERSION>=5004000 || CLANG_VERSION>=4000000)
   return __builtin_add_overflow(*pA, iB, pA);
 #else
   i64 iA = *pA;
   testcase( iA==0 ); testcase( iA==1 );
   testcase( iB==-1 ); testcase( iB==0 );
@@ -1299,11 +1299,11 @@
   return 0; 
 #endif
 }
 int sqlite3SubInt64(i64 *pA, i64 iB){
 #if !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=5004000
+    && (GCC_VERSION>=5004000 || CLANG_VERSION>=4000000)
   return __builtin_sub_overflow(*pA, iB, pA);
 #else
   testcase( iB==SMALLEST_INT64+1 );
   if( iB==SMALLEST_INT64 ){
     testcase( (*pA)==(-1) ); testcase( (*pA)==0 );
@@ -1315,11 +1315,11 @@
   }
 #endif
 }
 int sqlite3MulInt64(i64 *pA, i64 iB){
 #if !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=5004000
+    && (GCC_VERSION>=5004000 || CLANG_VERSION>=4000000)
   return __builtin_mul_overflow(*pA, iB, pA);
 #else
   i64 iA = *pA;
   if( iB>0 ){
     if( iA>LARGEST_INT64/iB ) return 1;