I am currently trying to speed up some of my C functions on a Cortex-M0 (Freescale KL25Z) using assembly. I get a problem with this minimal test program:
@.syntax unified .cpu cortex-m0 .text .global test .code 16 test: mov r0, #0 adds r0, r0, #1 bx lr
When I try to assemble my .s file to a .o file, I get this error
$ arm-none-eabi-as test.s -o test.o test.s: Assembler messages: test.s:8: Error: instruction not supported in Thumb16 mode -- `adds r0,r0,#1'
The error message doesn't make sense to me, ADDS is a valid instruction acording to this document. I found a possible answer on stackoverflow and added the line at the beginning of the program (".syntax unified" worked, like the second answer suggested). This resulted in fixing this problem, I can now use instructions like ADDS and ADCS, but I did get a new error:
$ arm-none-eabi-as test.s -o test.o test.s: Assembler messages: test.s:7: Error: cannot honor width suffix -- `mov r0,#0'
Some instructions using immediate values get this error. I am compiling on Mac OS 10.9.5. I can't find a solution to this via Google or Stackoverflow and have no idea how to get around these errors.
$ arm-none-eabi-gcc --version arm-none-eabi-gcc (GNU Tools for ARM Embedded Processors) 4.9.3 20150303 (release) [ARM/embedded-4_9-branch revision 221220] Copyright (C) 2014 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. $ arm-none-eabi-as --version GNU assembler (GNU Tools for ARM Embedded Processors) 18.104.22.16850304 Copyright 2013 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or later. This program has absolutely no warranty. This assembler was configured for a target of `arm-none-eabi'.