6.6. Instructions to reverse bytes in a
general-purpose register
When an application or device driver has to interface to memory-mapped
peripheral registers or shared-memory structures that are not the
same endianness as that of the internal data structures, or the
endianness of the Operating System, an efficient way of being able
to explicitly transform the endianness of the data is required.
The following new instructions are added to the ARM and Thumb instruction
sets to provide this functionality:
reverse word (4 bytes) register, for
transforming big and little-endian 32-bit representations
reverse halfword and sign-extend, for transforming
signed 16-bit representations
reverse packed halfwords in a register for transforming
big- and little-endian 16-bit representations.
These instructions are described in About the architecture.
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