From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Wed, 17 Jul 2013 17:58:38 +0200 Subject: [Buildroot] [PATCH] arch/arm: add support for thumb(1) mode In-Reply-To: <1374075555-9599-1-git-send-email-gustavo@zacarias.com.ar> References: <1374075555-9599-1-git-send-email-gustavo@zacarias.com.ar> Message-ID: <20130717175838.2fc2831e@skate> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Dear Gustavo Zacarias, On Wed, 17 Jul 2013 12:39:15 -0300, Gustavo Zacarias wrote: > +config BR2_ARM_INSTRUCTIONS_THUMB > + bool "Thumb" > + depends on BR2_ARM_CPU_HAS_THUMB > + help > + This option instructions the compiler to generate Thumb > + instructions, which allows to mix 16 bits instructions and > + 32 bits instructions. This generally provides a much smaller > + compiled binary size. I think this is misleading: Thumb doesn't allow to mix 16 bits and 32 bits instructions like Thumb2 does. IIRC, with Thumb, a particular function needs to be either completely Thumb (16 bits) or completely ARM (32 bits), and there is the thumb-interworking mechanism between the two. Which leads me to this question: is adding Thumb support as simple as what you're adding? Aren't there some additional thumb-interworking complexities to handle? Thanks! Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com