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.
The target is a custom board based on Freescale/NXP mx6qsabresd (I'm not
ready to submit it to the main tree yet) so sabresd should produce the same
result. Just have IPU enabled.
---
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