On Thu, Mar 24, 2016 at 12:49:54AM +0100, Marek Vasut wrote: > On 03/24/2016 12:47 AM, Sergey Kubushyn wrote: > > On Thu, 24 Mar 2016, Marek Vasut wrote: > > > >> On 03/24/2016 12:08 AM, Tom Rini wrote: > >>> On Wed, Mar 23, 2016 at 04:02:07PM -0700, Sergey Kubushyn wrote: > >>>> On Wed, 23 Mar 2016, Tom Rini wrote: > >>>> > >>>>> On Wed, Mar 23, 2016 at 06:08:45PM +0100, Albert ARIBAUD wrote: > >>>>>> Hello Tom, > >>>>>> > >>>>>> On Wed, 23 Mar 2016 09:22:38 -0400, Tom Rini <tr...@konsulko.com> > >>>>>> wrote: > >>>>>>> On Wed, Mar 23, 2016 at 01:53:35PM +0100, Albert ARIBAUD wrote: > >>>>>>>> Hello Marek, > >>>>>>>> > >>>>>>>> On Sun, 20 Mar 2016 17:15:34 +0100, Marek Vasut <ma...@denx.de> > >>>>>>>> wrote: > >>>>>>>>> This patch decouples U-Boot binary from the toolchain on > >>>>>>>>> systems where > >>>>>>>>> private libgcc is available. Instead of pulling in functions > >>>>>>>>> provided > >>>>>>>>> by the libgcc from the toolchain, U-Boot will use it's own set > >>>>>>>>> of libgcc > >>>>>>>>> functions. These functions are usually imported from Linux > >>>>>>>>> kernel, which > >>>>>>>>> also uses it's own libgcc functions instead of the ones > >>>>>>>>> provided by the > >>>>>>>>> toolchain. > >>>>>>>>> > >>>>>>>>> This patch solves a rather common problem. The toolchain can > >>>>>>>>> usually > >>>>>>>>> generate code for many variants of target architecture and > >>>>>>>>> often even > >>>>>>>>> different endianness. The libgcc on the other hand is usually > >>>>>>>>> compiled > >>>>>>>>> for one particular configuration and the functions provided by > >>>>>>>>> it may > >>>>>>>>> or may not be suited for use in U-Boot. This can manifest in > >>>>>>>>> two ways, > >>>>>>>>> either the U-Boot fails to compile altogether and linker will > >>>>>>>>> complain > >>>>>>>>> or, in the much worse case, the resulting U-Boot will build, > >>>>>>>>> but will > >>>>>>>>> misbehave in very subtle and hard to debug ways. > >>>>>>>> > >>>>>>>> I don't think using private libgcc by default is a good idea. > >>>>>>>> > >>>>>>>> U-Boot's private libgcc is not a feature of U-Boot, but a fix > >>>>>>>> for some > >>>>>>>> cases where a target cannot properly link with the libgcc > >>>>>>>> provided by > >>>>>>>> the (specific release of the) GCC toolchain in use. Using > >>>>>>>> private libgcc > >>>>>>>> to other cases than these does not fix or improve anything; those > >>>>>>>> other cases were working and did not require any fix in this > >>>>>>>> respect. > >>>>>>> > >>>>>>> This isn't true, exactly. If using clang for example everyone > >>>>>>> needs to > >>>>>>> enable this code. We're also using -fno-builtin -ffreestanding > >>>>>>> which > >>>>>>> should limit the amount of interference from the toolchain. And > >>>>>>> we get > >>>>>>> that. > >>>>>> > >>>>>> You mean clang does not produce self-sustained binaries? > >>>>> > >>>>> clang does not provide "libgcc", so there's no -lgcc providing all of > >>>>> the functions that are (today) in: > >>>>> _ashldi3.S _ashrdi3.S _divsi3.S _lshrdi3.S _modsi3.S _udivsi3.S > >>>>> _umodsi3.S div0.S _uldivmod.S > >>>>> which aside from __modsi3 and __umodsi3 are all __aeabi_xxx > >>>> > >>>> There is also _udivmoddi4 pulled from libgcc for 64-bit division > >>>> since we > >>>> switched to 64-bit all around ARM. It comes from clock calculations for > >>>> video, e.g. from drivers/video/ipu_common.c for i.MX6. > >>> > >>> Well, this is an example of why we both don't want libgcc ever nor do we > >>> want to overly expand what we do offer. In this case isn't it an > >>> example of something that should be using lldiv/do_div/etc? > >> > >> I haven't seen the _udivmoddi4 emitted in my tests. Linux's libgcc copy > >> also doesn't implement the function. Which toolchain do you use and > >> which target did you compile? > > > > I'm using my own armv7hl-linux-gnueabi toolchain built for hard float. > > Linux > > arm libgcc does have arch/arm/lib/div64.S file that provides __do_div64() > > function that is used by do_div() from include/asm/div64.h for 32-bit ARM > > platform. Sure, arm64 has neither div64.h nor div64.S. We _DO_ have div64.h > > (that is totally different from what Linux provides) but no div64.S in > > arch/arm/lib. > > In that case, we should just import div64.S from Linux on arm32 and be > done with it ? Since we now have all the necessary macros thanks to the > first four patches in this series, that should be trivial. > > What do you think? I can bake a patch real quick, so you can test it ?
Follow-up _series_ to re-sync our 64bit math stuff with the kernel. -- Tom
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