[PATCH] Enable ARM-V7R Big-Endian Multilib

[Jonathan Brandmeyer]

This patch enables a single additional big-endian multilib target which is compatible with the TMS570 Cortex-R processor. The diff should cleanly apply to the 2015 Q1 4.9 source release after unpacking the included tarballs.

Tested on the TI LAUNCHXL2-TMS57012 demo board from an Ubuntu 14.04 host.

Users have brought this issue up a few times, with various patches appearing in the Answers section. A promise was made in the past to incorporate an appropriate big-endian multilib target, but no action was taken and the user's patch suffered bitrot.

Please incorporate this patch and enable the big-endian target by default in the future.

[Thomas Preud'homme (thomas-preudhomme)]

Hi Jonathan,

There is two issues that prevented us from using big endian support patches into our GCC ARM embedded toolchain: (1) copyright assignment and (2) board for testing. The source code of the GCC distributed in our toolchain is maintained in a SVN branch on FSF repository. A consequence of this is that all patches we carry must have their copyright assigned to FSF which was not the case with previous patches. Regarding this patch, is it a rebasing of previous patches or did you write it from scratch? If the latter, did you sign a FSF copyright assignment form and got a confirmation from then?

The second issue is that we are dedicated to make high quality releases but don't have at present the hardware to test big endian support in the toolchain. Without this we cannot guarantee that this support works as intended when doing a release.

Best regards

[Jonathan Brandmeyer (jbrandmeyer-c)]

Regarding copyright assignment, the existing copyright assignment between my employer (Google, Inc) and the FSF applies. I have already obtained permission from my employer to release this patch under that existing agreement.

Regarding testing, a TMS570 launchpad dev board is pretty cheap :) I did need to modify some of the files in HALCOGEN to make it work with GCC, but I would be happy to share them.

[Thomas Preud'homme (thomas-preudhomme)]

Hi Jonathan,

That's good news. We shall be able to buy a board for testing indeed. Given the interest for this feature, we are interested in integrating this. We will review your patch (possibly once we have the board) and let you know of any feedback we might have.

Thanks for proposing this patch, it is much appreciated.

Best regards.

[jdobry (jdobry)]

Hello I thing that this patch is incomplete. It add BE support only for hardFPU not softfp. It miss 2 lines in MULTILIB_REQUIRED, 2 lines in MULTILIB_OSDIRNAMES and 2 lines in MULTILIB_REUSE
See to https://answers.launchpad.net/gcc-arm-embedded/+question/263922

PS: We are using similar patch over 2 years without problem

[JiriJ (jirij-0)]

Hello Jonathan and Thomas,

we(my colleague and me) can also offer support for preparing some test code for the TMS570 device. We have some experience with Hercules Development Kit (TMS570LS3137 chip).

Please let us know if we can help you somehow.

Best regards,
Jiri

[Jonathan Brandmeyer (jbrandmeyer-c)]

We did not have a need for a softfp target, so we did not add one. However, it is true that some very low-end family members of that processor line do not have the FPU enabled.

[jdobry (jdobry)]

Here is new version of the patch for the ARM GCC 6.2 2016q4

http://pastebin.com/z4AcpbDu

[jdobry (jdobry)]

New patch for ARM GCC 7 2018q2

https://pastebin.com/RcdDaydf

PS: We are waiting over 6 years for this.

[Tejas Belagod (belagod-tejas)]

Hi jdobry,

Unfortunately there's nothing we can do about this patch - you will need to submit this upstream on the gcc lists.

https://gcc.gnu.org/ml/gcc-patches/

Thanks,
Tejas.