From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnout Vandecappelle Date: Thu, 17 Mar 2016 23:34:16 +0100 Subject: [Buildroot] [PATCH 02/16] arch/arm: Cortex-M3 provides only Thumb-2 In-Reply-To: <20160317213630.54f60dd6@free-electrons.com> References: <1458164602-16983-1-git-send-email-thomas.petazzoni@free-electrons.com> <1458164602-16983-3-git-send-email-thomas.petazzoni@free-electrons.com> <56E9E177.5000606@mind.be> <20160317213630.54f60dd6@free-electrons.com> Message-ID: <56EB30E8.2010008@mind.be> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net On 03/17/16 21:36, Thomas Petazzoni wrote: > Hello, > > On Wed, 16 Mar 2016 23:43:03 +0100, Arnout Vandecappelle wrote: >> On 03/16/16 22:43, Thomas Petazzoni wrote: >>> The Cortex-M cores only support Thumb-2, not Thumb. In fact, Thumb-2 >>> is a superset of Thumb, >> >> If thumb2 is a superset of thumb, then CPU_HAS_THUMB2 should select >> CPU_HAS_THUMB. And according to [1], it really is a superset. > > Thinking more about this, I don't see the point. > > Even if Thumb2 is strictly speaking a superset of Thumb1, there is no > gcc flag or mechanism that will allow you to generate Thumb1 code on a > Thumb2-capable core. > > Therefore, it IMO doesn't bring any benefit to select CPU_HAS_THUMB > from CPU_HAS_THUMB2. Well, my idea was that a package that needs a specific config option to use some thumb assembly (in an otherwise arm build) could just have a .mk condition on CPU_HAS_THUMB instead of CPU_HAS_THUMB or CPU_HAS_THUMB2. But that's not a situation we have at the moment anyway. Regards, Arnout -- Arnout Vandecappelle arnout at mind be Senior Embedded Software Architect +32-16-286500 Essensium/Mind http://www.mind.be G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle GPG fingerprint: 7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF