This intrinsic inserts a REV instruction or an equivalent code sequence into the instruction stream generated by the compiler. It enables you to convert a 32-bit big-endian data value into a little-endian data value, or a 32-bit little-endian data value into a big-endian data value from within your C or C++ code.
The __rev intrinsic is available irrespective of the target processor or architecture you are compiling for. However, if the REV instruction is not available on the target, the compiler compensates with an alternative code sequence that could increase the number of instructions, effectively expanding the intrinsic into a function.
The compiler introduces REV automatically when it recognizes certain expressions.
unsigned int __rev(unsigned int val )
is an unsigned int .
The __rev intrinsic returns the value obtained from val by reversing its byte order.