[Buildroot] libgcc erroneously built as armv5 for arm920t(armv4t)

adam hussein(!) kryme76 at yahoo.com
Thu Nov 21 14:56:10 UTC 2013


Hi Thomas,

Sorry for going quiet for so long; a lot of change going on here.

Thanks for the patch; much tidier!

I'm
 not in a position to work on this board now, the project taking a 
different direction altogether; however, I have found time for a sneaky 
test of the patch using the internal toolchain, and it seems fine.

The objdump showing that udivsi3 no longer has CLZ instructions.

arm-buildroot-linux-uclibcgnueabi-objdump -d u-boot | grep "20126c1c:" -A 10
20126c1c:    e2512001     subs    r2, r1, #1
20126c20:    012fff1e     bxeq    lr
20126c24:    3a000036     bcc    20126d04 <__udivsi3+0xe8>
20126c28:    e1500001     cmp    r0, r1
20126c2c:    9a000022     bls    20126cbc <__udivsi3+0xa0>
20126c30:    e1110002     tst    r1, r2
20126c34:    0a000023     beq    20126cc8 <__udivsi3+0xac>
20126c38:    e311020e     tst    r1, #-536870912    ; 0xe0000000
20126c3c:    01a01181     lsleq    r1, r1, #3
20126c40:    03a03008     moveq    r3, #8
20126c44:    13a03001     movne    r3, #1

Selecting Sourcery CodeBench 2013.05 external toolchain had the buildroot make attempt end with:

  LD      vmlinux
  SYSMAP  System.map
  SYSMAP  .tmp_System.map
  OBJCOPY arch/arm/boot/Image
  Kernel: arch/arm/boot/Image is ready
  AS      arch/arm/boot/compressed/head.o
arch/arm/boot/compressed/head.S: Assembler messages:
arch/arm/boot/compressed/head.S:936: Error: selected processor does not support ARM mode `clz r5,r4'

And using it for u-boot gave me:

arm-none-linux-gnueabi-objdump -d u-boot | grep "20126bc0:" -A 10
20126bc0:    e2512001     subs    r2, r1, #1
20126bc4:    012fff1e     bxeq    lr
20126bc8:    3a000074     bcc    20126da0 <__udivsi3+0x1e0>
20126bcc:    e1500001     cmp    r0, r1
20126bd0:    9a00006b     bls    20126d84 <__udivsi3+0x1c4>
20126bd4:    e1110002     tst    r1, r2
20126bd8:    0a00006c     beq    20126d90 <__udivsi3+0x1d0>
20126bdc:    e16f3f10     clz    r3, r0
20126be0:    e16f2f11     clz    r2, r1


I hope this tells you what you wanted to know, in spite of not being able to run on the hardware.


Adam





----- Original Message -----
From: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
To: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Cc: adam hussein(!) <kryme76 at yahoo.com>; "buildroot at busybox.net" <buildroot at busybox.net>
Sent: Thursday, November 7, 2013 7:31 PM
Subject: Re: [Buildroot] libgcc erroneously built as armv5 for arm920t(armv4t)

Adam,

Did you had the opportunity to test the proposed patch?


On Sat, 2 Nov 2013 16:39:06 +0100, Thomas Petazzoni wrote:
> Dear adam hussein\(!\),
> 
> On Thu, 26 Sep 2013 08:34:53 -0700 (PDT), adam hussein\(!\) wrote:
> 
> > I've been building the at91rm9200ek configuration of buildroot to get a toolchain I can use to build u-boot with some board specific configuration.
> > 
> > This is an ARM920T core chip with ARMv4T architecture  - later ARM9 series have ARMv5TE architecture (http://en.wikipedia.org/wiki/ARM9)
> > 
> > When gcc is built, or perhaps specifically libgcc only, it seems the selection of 920t/v4 architecture gets lost and v5 is used instead.
> > This means that when I use it to build u-boot, I find it has the __udivsi3 function using the illegal (to v4) instruction CLZ (count leading zeros).
> > 
> > The easiest workaround for me is to specify arm7tdmi and be done with it, but I'd like to try contributing a proper fix if possible.
> 
> Can you try the attached patch? Ideally, it would be nice if you could
> try it with two configurations:
> 
>  * With the internal toolchain backend
>  * With the Sourcery CodeBench 2013.05 external toolchain
> 
> and run it on real hardware.
> 
> Thanks a lot for your testing!
> 
> Thomas



-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com


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