Keil Logo

Arm Compiler Migration and Compatibility Guide

Arm® Compiler Migration and Compatibility Guide

Version 6.16

Table of Contents

About this book
Using this book
Typographic conventions
Other information
1 Configuration and Support Information
1.1 Support level definitions
1.2 Compiler configuration information
2 Migrating from Arm® Compiler 5 to Arm® Compiler 6
2.1 Migration overview
2.2 Toolchain differences
2.3 Default differences
2.4 Optimization differences
2.5 Backwards compatibility issues
2.6 Diagnostic messages
2.7 Migration example
3 Migrating from armcc to armclang
3.1 Migration of compiler command-line options from Arm® Compiler 5 to Arm® Compiler 6
3.2 Arm® Compiler 5 and Arm® Compiler 6 stack protection behavior
3.3 Command-line options for preprocessing assembly source code
3.4 Inline assembly with Arm® Compiler 6
3.5 Migrating architecture and processor names for command-line options
3.6 Preprocessing a scatter file when linking with armlink
3.7 Migrating predefined macros
4 Compiler Source Code Compatibility
4.1 Language extension compatibility: keywords
4.2 Language extension compatibility: attributes
4.3 Language extension compatibility: pragmas
4.4 Language extension compatibility: intrinsics
4.5 Diagnostics for pragma compatibility
4.6 C and C++ implementation compatibility
4.7 Compatibility of C++ objects
5 Migrating from armasm to the armclang Integrated Assembler
5.1 Migration of assembler command-line options from armasm to the armclang integrated assembler
5.2 Overview of differences between armasm and GNU syntax assembly code
5.4 Labels
5.5 Numeric local labels
5.6 Functions
5.7 Sections
5.8 Symbol naming rules
5.9 Numeric literals
5.10 Operators
5.11 Alignment
5.12 PC-relative addressing
5.13 A32 and T32 instruction substitutions
5.14 A32 and T32 pseudo-instructions
5.15 Conditional directives
5.16 Data definition directives
5.17 Instruction set directives
5.18 Miscellaneous directives
5.19 Symbol definition directives
5.20 Migration of armasm macros to integrated assembler macros
6 Changes Between Different Versions of Arm® Compiler 6
6.1 Summary of changes between Arm® Compiler 6.15 and Arm® Compiler 6.16
6.2 Summary of changes between Arm® Compiler 6.14 and Arm® Compiler 6.15
6.3 Summary of changes between Arm® Compiler 6.13 and Arm® Compiler 6.14
6.4 Summary of changes between Arm® Compiler 6.12 and Arm® Compiler 6.13
6.5 Summary of changes between Arm® Compiler 6.11 and Arm® Compiler 6.12
6.6 Summary of changes between Arm® Compiler 6.10 and Arm® Compiler 6.11
6.7 Summary of changes between Arm® Compiler 6.9 and Arm® Compiler 6.10
6.8 Summary of changes between Arm® Compiler 6.8 and Arm® Compiler 6.9
6.9 Summary of changes between Arm® Compiler 6.7 and Arm® Compiler 6.8
6.10 Summary of changes between Arm® Compiler 6.6 and Arm® Compiler 6.7
6.11 Summary of changes between Arm® Compiler 6.5 and Arm® Compiler 6.6
6.12 Compiling with -mexecute-only generates an empty .text section
A Code Examples
A.1 Example startup code for Arm® Compiler 5 project
A.2 Example startup code for Arm® Compiler 6 project
B Licenses
B.1 Apache License
C Arm® Compiler Migration and Compatibility Guide Changes
C.1 Changes for the Arm® Compiler Migration and Compatibility Guide

Release Information

Document History
Issue Date Confidentiality Change
A 14 March 2014 Non-Confidential Arm Compiler v6.00 Release
B 15 December 2014 Non-Confidential Arm Compiler v6.01 Release
C 30 June 2015 Non-Confidential Arm Compiler v6.02 Release
D 18 November 2015 Non-Confidential Arm Compiler v6.3 Release
E 24 February 2016 Non-Confidential Arm Compiler v6.4 Release
F 29 June 2016 Non-Confidential Arm Compiler v6.5 Release
G 04 November 2016 Non-Confidential Arm Compiler v6.6 Release
0607-00 05 April 2017 Non-Confidential Arm Compiler v6.7 Release. Document numbering scheme has changed.
0608-00 30 July 2017 Non-Confidential Arm Compiler v6.8 Release.
0609-00 25 October 2017 Non-Confidential Arm Compiler v6.9 Release.
0610-00 14 March 2018 Non-Confidential Arm Compiler v6.10 Release.
0611-00 25 October 2018 Non-Confidential Arm Compiler v6.11 Release.
0612-00 27 February 2019 Non-Confidential Arm Compiler v6.12 Release.
0613-00 09 October 2019 Non-Confidential Arm Compiler v6.13 Release.
0614-00 26 February 2020 Non-Confidential Arm Compiler v6.14 Release.
0615-00 07 October 2020 Non-Confidential Arm Compiler v6.15 Release.
0615-01 14 December 2020 Non-Confidential Documentation update 1 for Arm Compiler v6.15 Release.
0616-00 03 March 2021 Non-Confidential Arm Compiler v6.16 Release.
0616-01 12 March 2021 Non-Confidential Documentation update 1 for Arm Compiler v6.16 Release.

Non-Confidential Proprietary Notice

This document is protected by copyright and other related rights and the practice or implementation of the information contained in this document may be protected by one or more patents or pending patent applications. No part of this document may be reproduced in any form by any means without the express prior written permission of Arm. No license, express or implied, by estoppel or otherwise to any intellectual property rights is granted by this document unless specifically stated.

Your access to the information in this document is conditional upon your acceptance that you will not use or permit others to use the information for the purposes of determining whether implementations infringe any third party patents.

THIS DOCUMENT IS PROVIDED “AS IS”. ARM PROVIDES NO REPRESENTATIONS AND NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY, SATISFACTORY QUALITY, NON-INFRINGEMENT OR FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO THE DOCUMENT. For the avoidance of doubt, Arm makes no representation with respect to, and has undertaken no analysis to identify or understand the scope and content of, third party patents, copyrights, trade secrets, or other rights.

This document may include technical inaccuracies or typographical errors.


This document consists solely of commercial items. You shall be responsible for ensuring that any use, duplication or disclosure of this document complies fully with any relevant export laws and regulations to assure that this document or any portion thereof is not exported, directly or indirectly, in violation of such export laws. Use of the word “partner” in reference to Arm’s customers is not intended to create or refer to any partnership relationship with any other company. Arm may make changes to this document at any time and without notice.

If any of the provisions contained in these terms conflict with any of the provisions of any click through or signed written agreement covering this document with Arm, then the click through or signed written agreement prevails over and supersedes the conflicting provisions of these terms. This document may be translated into other languages for convenience, and you agree that if there is any conflict between the English version of this document and any translation, the terms of the English version of the Agreement shall prevail.

The Arm corporate logo and words marked with ® or ™ are registered trademarks or trademarks of Arm Limited (or its subsidiaries) in the US and/or elsewhere. All rights reserved. Other brands and names mentioned in this document may be the trademarks of their respective owners. Please follow Arm’s trademark usage guidelines at

Copyright © 2014–2021 Arm Limited (or its affiliates). All rights reserved.

Arm Limited. Company 02557590 registered in England.

110 Fulbourn Road, Cambridge, England CB1 9NJ.


Confidentiality Status

This document is Non-Confidential. The right to use, copy and disclose this document may be subject to license restrictions in accordance with the terms of the agreement entered into by Arm and the party that Arm delivered this document to.

Unrestricted Access is an Arm internal classification.

Product Status

The information in this document is Final, that is for a developed product.

Web Address

Progressive terminology commitment

Arm values inclusive communities. Arm recognizes that we and our industry have used terms that can be offensive. Arm strives to lead the industry and create change.

We believe that this document contains no offensive terms. If you find offensive terms in this document, please contact

Non-ConfidentialPDF file icon PDF version100068_0616_01_en
Copyright © 2014–2021 Arm Limited or its affiliates. All rights reserved. 
  Arm logo
Important information

This site uses cookies to store information on your computer. By continuing to use our site, you consent to our cookies.

Change Settings

Privacy Policy Update

Arm’s Privacy Policy has been updated. By continuing to use our site, you consent to Arm’s Privacy Policy. Please review our Privacy Policy to learn more about our collection, use and transfers
of your data.