On 08/02/2019 16:19, Olivier Hainque wrote: > Hi Wilco, > >> On 8 Feb 2019, at 15:49, Wilco Dijkstra <wilco.dijks...@arm.com> wrote: >> >> Hi Olivier, >> >>> Below is a description of a very annoying bug we are witnessing >>> on ARM. >> ... >>> compiled with -Og -mapcs >> >> Do you know -mapcs has been deprecated for more than 4 years now? >> Is there a reason you are still using it? It was deprecated since -mapcs >> is both extremely inefficient and buggy. I would strongly suggest to stop >> using this option completely in all your software. > > Sorry, I had -mapcs-frame in mind. The investigation I described was > conducted with the default settings of the VxWorks port (no particular option) > and thought it might be of greater potential interest if exposed with a bare > eabi compiler. The conditions of interest are guarded with > > IS_NESTED (arm_current_func_type ()) > && ((TARGET_APCS_FRAME && frame_pointer_needed && TARGET_ARM) > > Turns out that the arm-eabi code with -mapcs-frame is very slightly > different than the vxworks one, which I missed on the first reading. > > Let me double check again ... > >> It's useful to create a bug report with the details, however it might not be >> worth fixing if the issue cannot be reproduced without -mapcs. -mapcs >> was never meant to support a static chain, especially not spills of the >> static chain. > > Understood. I'll start by examining the differences > between the vxworks and the eabi+aapcs-frame configurations > more closely, and I'll report back.
Olivier, while you are here could you also document the choices made by the vxworks port in terms of the ABI and how it differs from EABI ? It would certainly help with patch review. regards Ramana > > Thanks for your feedback! >
