[Buildroot] PowerPC64 toolchain not building
Sam Bobroff
sam.bobroff at au1.ibm.com
Fri Jan 29 00:55:30 UTC 2016
On Thu, Jan 28, 2016 at 10:20:44AM +0100, Thomas Petazzoni wrote:
> Hello,
>
> On Thu, 28 Jan 2016 09:17:42 +0100, Thomas Petazzoni wrote:
>
> > I've restarted a build on my laptop, which has a more modern distro,
> > I'll let you know the results.
>
> The following defconfig:
>
> BR2_powerpc64=y
> BR2_powerpc_power8=y
>
> fails to build on my machine, with the same error:
>
> /tmp/ccZgjbrm.s: Assembler messages:
> /tmp/ccZgjbrm.s:19: Error: operand out of domain (7 is not a multiple of 2)
>
> Here is the offending assembly file:
>
> .file "exch_n.c"
> .section ".toc","aw"
> .section ".text"
> .align 2
> .globl libat_exchange_16
> .hidden libat_exchange_16
> .section ".opd","aw"
> .align 3
> libat_exchange_16:
> .quad .L.libat_exchange_16,.TOC. at tocbase,0
> .previous
> .type libat_exchange_16, @function
> .L.libat_exchange_16:
> sync
> mr 9,3
> mr 11,5
> mr 10,4
> .L2:
> lqarx 7,0,9
> mr 3,7
> mr 4,8
> stqcx. 10,0,9
> bne- 0,.L2
> isync
> blr
> .long 0
> .byte 0,0,0,0,0,0,0,0
> .size libat_exchange_16,.-.L.libat_exchange_16
> .globl __atomic_exchange_16
> .set __atomic_exchange_16,libat_exchange_16
> .ident "GCC: (Buildroot 2016.02-git-00995-g390d559) 4.9.3"
>
> So the instruction "lqarx 7,0,9" is at fault.
>
> Best regards,
>
> Thomas
I've managed to replicate your problem!
The key to reproducing it seems to be to optimise for size: I compared your
compile line to mine, and the only difference was -Os vs. -O3 :-)
So try optimizing for speed instead: this obviously works around it for me ;-)
And yes, it's the lqarx instruction causing the problem: it's first argument must
be even but it's 7, so this looks like a bug in gcc.
I did some searching around and it looks like this has been a problem in the
past and it's been fixed, but it looks like optimizing for size causes it to
re-appear. There's a bit of related info here:
http://comments.gmane.org/gmane.comp.gcc.bugs/388637
Would you like to raise it on https://gcc.gnu.org/bugzilla/ ?
Alternativly, it's no problem for me handle it if you like (I work on PowerKVM
:-).
Cheers,
Sam.
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