From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aneesh V Date: Mon, 06 Feb 2012 18:52:21 +0530 Subject: [U-Boot] [RFC PATCH 0/4] Enable Thumb build for ARM platforms In-Reply-To: <4F2FC6E2.8080209@ti.com> References: <1328528248-20872-1-git-send-email-aneesh@ti.com> <4F2FC6E2.8080209@ti.com> Message-ID: <4F2FD40D.8060807@ti.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Monday 06 February 2012 05:56 PM, Aneesh V wrote: > On Monday 06 February 2012 05:07 PM, Aneesh V wrote: >> Thumb is an alternate instruction set available in many >> ARM processors. Below is a detailed description from ARM >> specs: >> >> "The Thumb instruction set is a re-encoded subset of the >> ARM instruction set. Thumb instructions execute in their >> own processor state, with the architecture defining the >> mechanisms required to transition between ARM and Thumb >> states. The key difference is that Thumb instructions are >> half the size of ARM instructions(16 bits compared with 32 >> bits). Greater code density can usually be achieved by using >> the Thumb instruction set in preference to the ARM instruction >> set, at a cost of some reduction in performance" >> >> "In ARMv6T2, Thumb-2 technology is introduced. This technology >> makes it possible to extend the original Thumb instruction set >> with many 32-bit instructions. The range of 32-bit Thumb instructions >> included in ARMv6T2 permits Thumb code to achieve performance >> similar to ARM code, with code density better than that of earlier >> Thumb code. From ARMv6T2, the ARM and Thumb instruction sets provide >> almost identical functionality" >> >> This series adds Thumb support in U-Boot and enables it for >> OMAP4. It also fixes issues faced while booting OMAP4 with >> Thumb-2 images of U-Boot and SPL. >> >> Thumb mode is becoming increasingly relevant for U-Boot with >> the advent of SPL. It's very important to keep SPL size smaller >> considering the internal RAM size constraints on many platforms. >> On OMAP4 the size reduction enables us to use SPL on secure devices >> that have smaller internal RAM available for non-secure world. >> >> I would request all who are interested in this feature to test it >> and give feedback. To make that easier I have pushed my patches >> here (along with the timer patch from Nicolas that fixes boot on >> OMAP4): >> >> git at github.com:aneeshv/u-boot.git >> branch: thumb >> >> To enable support for new platforms you just need to add >> CONFIG_SYS_THUMB_BUILD in your config file. > > Some statistics: > > Code-size reduction: > Image ARM build Thumb build % Reduction > u-boot.bin 190408 144676 24.01% > u-boot-spl.bin 33200 25096 24.40% > > Performance(timestamp just before the main loop): > ARM build Thumb build % Reduction > 898510us 878247us -2.25% > > That is, performance actually improved marginally for the Thumb > build, maybe because of the reduced image sizes. Oops! I missed details about the tool-chains I used. I succcessfully tried the following tool-chains for the Thumb build. 1. Sourcery G++ Lite 2010q1-202 arm-none-linux-gnueabi-gcc (Sourcery G++ Lite 2010q1-202) 4.4.1 GNU ld (Sourcery G++ Lite 2010q1-202) - binutils 2.19.51.20090709 2. Linaro 4.6-2012.01 arm-linux-gnueabi-gcc (crosstool-NG linaro-1.13.1-2012.01-20120125 - Linaro GCC 2012.01) 4.6.3 20120105 (prerelease) GNU ld (crosstool-NG linaro-1.13.1-2012.01-20120125 - Linaro GCC 2012.01) 2.22 Test reports with different tool-chains will be greatly appreciated! best regards, Aneesh