Add support for IAR compiler (#5347)

include/flatbuffers/base.h

@@ -55,6 +55,10 @@
 
 #include "flatbuffers/stl_emulation.h"
 
+#if defined(__ICCARM__)
+#include <intrinsics.h>
+#endif
+
 // Note the __clang__ check is needed, because clang presents itself
 // as an older GNUC compiler (4.2).
 // Clang 3.3 and later implement all of the ISO C++ 2011 standard.
@@ -117,7 +121,7 @@
   #define FLATBUFFERS_LITTLEENDIAN 0
 #endif // __s390x__
 #if !defined(FLATBUFFERS_LITTLEENDIAN)
-  #if defined(__GNUC__) || defined(__clang__)
+  #if defined(__GNUC__) || defined(__clang__) || defined(__ICCARM__)
     #if (defined(__BIG_ENDIAN__) || \
          (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__))
       #define FLATBUFFERS_LITTLEENDIAN 0
@@ -303,6 +307,11 @@ template<typename T> T EndianSwap(T t) {
     #define FLATBUFFERS_BYTESWAP16 _byteswap_ushort
     #define FLATBUFFERS_BYTESWAP32 _byteswap_ulong
     #define FLATBUFFERS_BYTESWAP64 _byteswap_uint64
+  #elif defined(__ICCARM__)
+    #define FLATBUFFERS_BYTESWAP16 __REV16
+    #define FLATBUFFERS_BYTESWAP32 __REV
+    #define FLATBUFFERS_BYTESWAP64(x) \
+       ((__REV(static_cast<uint32_t>(x >> 32U))) | (static_cast<uint64_t>(__REV(static_cast<uint32_t>(x)))) << 32U)
   #else
     #if defined(__GNUC__) && __GNUC__ * 100 + __GNUC_MINOR__ < 408 && !defined(__clang__)
       // __builtin_bswap16 was missing prior to GCC 4.8.

include/flatbuffers/flatbuffers.h

@@ -2475,7 +2475,7 @@ inline int LookupEnum(const char **names, const char *name) {
   #define FLATBUFFERS_STRUCT_END(name, size) \
     __pragma(pack()) \
     static_assert(sizeof(name) == size, "compiler breaks packing rules")
-#elif defined(__GNUC__) || defined(__clang__)
+#elif defined(__GNUC__) || defined(__clang__) || defined(__ICCARM__)
   #define FLATBUFFERS_MANUALLY_ALIGNED_STRUCT(alignment) \
     _Pragma("pack(1)") \
     struct __attribute__((aligned(alignment)))