In Thumb code, some instructions, for example a branch or
can be encoded as a 32-bit or 16-bit instruction. The assembler
chooses the size of the encoded instruction as described in Instruction
width selection in Thumb.
The assembler can issue warnings when an instruction is assembled to a 32-bit Thumb instruction where a 16-bit Thumb instruction could have been used. To enable this warning, use the following command line option when invoking the assembler:
armasm --diag_warning 1813