diff --git a/src/headers/tomcrypt_cfg.h b/src/headers/tomcrypt_cfg.h
index f7ad3cc..cc3b6df 100644
--- a/src/headers/tomcrypt_cfg.h
+++ b/src/headers/tomcrypt_cfg.h
@@ -128,6 +128,22 @@ LTC_EXPORT int   LTC_CALL XSTRCMP(const char *s1, const char *s2);
    #define ENDIAN_NEUTRAL
 #endif
 
+/* gcc 4.3 and up has a bswap builtin; detect it by gcc version.
+ * clang also supports the bswap builtin, and although clang pretends
+ * to be gcc (macro-wise, anyway), clang pretends to be a version
+ * prior to gcc 4.3, so we can't detect bswap that way.  Instead,
+ * clang has a __has_builtin mechanism that can be used to check
+ * for builtins:
+ * http://clang.llvm.org/docs/LanguageExtensions.html#feature_check */
+#ifndef __has_builtin
+   #define __has_builtin(x) 0
+#endif
+#if !defined(LTC_NO_BSWAP) && defined(__GNUC__) &&                      \
+   ((__GNUC__ * 100 + __GNUC_MINOR__ >= 403) ||                         \
+    (__has_builtin(__builtin_bswap32) && __has_builtin(__builtin_bswap64)))
+   #define LTC_HAVE_BSWAP_BUILTIN
+#endif
+
 #endif
 
 
diff --git a/src/headers/tomcrypt_macros.h b/src/headers/tomcrypt_macros.h
index 732ec3c..86156cc 100644
--- a/src/headers/tomcrypt_macros.h
+++ b/src/headers/tomcrypt_macros.h
@@ -67,7 +67,17 @@
 
 #ifdef ENDIAN_LITTLE
 
-#if !defined(LTC_NO_BSWAP) && (defined(INTEL_CC) || (defined(__GNUC__) && (defined(__DJGPP__) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__i386__) || defined(__x86_64__))))
+#ifdef LTC_HAVE_BSWAP_BUILTIN
+
+#define STORE32H(x, y)                          \
+   { ulong32 __t = __builtin_bswap32 ((x));     \
+      XMEMCPY ((y), &__t, 4); }
+
+#define LOAD32H(x, y)                           \
+   { XMEMCPY (&(x), (y), 4);                    \
+      (x) = __builtin_bswap32 ((x)); }
+
+#elif !defined(LTC_NO_BSWAP) && (defined(INTEL_CC) || (defined(__GNUC__) && (defined(__DJGPP__) || defined(__CYGWIN__) || defined(__MINGW32__) || defined(__i386__) || defined(__x86_64__))))
 
 #define STORE32H(x, y)           \
 asm __volatile__ (               \
@@ -96,9 +106,7 @@ asm __volatile__ (             \
 
 #endif
 
-/* gcc 4.3 and up has a bswap builtin */
-#if !defined(LTC_NO_BSWAP) && \
-   (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ >= 403))
+#ifdef LTC_HAVE_BSWAP_BUILTIN
 
 #define STORE64H(x, y)                          \
    { ulong64 __t = __builtin_bswap64 ((x));     \
diff --git a/src/misc/crypt/crypt.c b/src/misc/crypt/crypt.c
index 1298397..e1b1ce0 100644
--- a/src/misc/crypt/crypt.c
+++ b/src/misc/crypt/crypt.c
@@ -286,7 +286,9 @@ const char *crypt_build_settings =
 #if defined(_MSC_VER)
     "   MSVC compiler detected.\n"
 #endif
-#if defined(__GNUC__)
+#if defined(__clang_version__)
+    "   Clang compiler " __clang_version__ ".\n"
+#elif defined(__GNUC__)         /* clang also defines __GNUC__ */
     "   GCC compiler detected.\n"
 #endif
 #if defined(INTEL_CC)