[Bug ld/17212] Tag_CPU_name merging produces wrong tag for ARM.

[Bug ld/17212] Tag_CPU_name merging produces wrong tag for ARM.

[Maxim Ostapenko]

Hi,

I tried to compile a binary optimized for ARM Cortex-A15 with ARM 
Cortex-A8 cross-toolchain (host is x86_64-pc-linux-gnu), but 
Tag_CPU_name appears to be "Cortex-A8" for the binary instead of 
"Cortex-A15". The example session follows:

$ arm-v7a8-linux-gnueabi-gcc -O2 -mcpu=cortex-a15 divtest.c -o divtest.a15

$ readelf -A divtest.a15

Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-A8"
Tag_CPU_arch: v7
................................................
Tag_DIV_use: Allowed in v7-A with integer division extension

After some investigation I found out, that Tag_CPU_name merging based on 
Tag_CPU_arch. Since the first file to appear during linking is crt1.o, 
which has Tag_CPU_name: "Cortex-A8" for A8 toolchain, the result 
binary's Tag_CPU_name is also "Cortex-A8". Is this expected behavior of 
ld, or maybe tags should be merged to a more specific "Cortex-A15"? 
Perhaps we should use Tag_DIV_use when merging names?

-Maxim

Tag_CPU_name merging produces wrong tag for ARM.

[Maxim Ostapenko]

Add Andrew Stubbs  and Nick Clifton as author and reviewer of ARM 
attributes merging patch ( 
https://sourceware.org/ml/binutils/2009-01/msg00156.html).

-------- Original Message --------
Subject: 	[Bug ld/17212] Tag_CPU_name merging produces wrong tag for ARM.
Date: 	Tue, 02 Sep 2014 13:19:20 +0400
From: 	Maxim Ostapenko <m.ostapenko@partner.samsung.com>
To: 	binutils@sourceware.org
CC: 	Yury Gribov <y.gribov@samsung.com>, Slava Garbuzov 
<v.garbuzov@samsung.com>



Hi,

I tried to compile a binary optimized for ARM Cortex-A15 with ARM
Cortex-A8 cross-toolchain (host is x86_64-pc-linux-gnu), but
Tag_CPU_name appears to be "Cortex-A8" for the binary instead of
"Cortex-A15". The example session follows:

$ arm-v7a8-linux-gnueabi-gcc -O2 -mcpu=cortex-a15 divtest.c -o divtest.a15

$ readelf -A divtest.a15

Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-A8"
Tag_CPU_arch: v7
................................................
Tag_DIV_use: Allowed in v7-A with integer division extension

After some investigation I found out, that Tag_CPU_name merging based on
Tag_CPU_arch. Since the first file to appear during linking is crt1.o,
which has Tag_CPU_name: "Cortex-A8" for A8 toolchain, the result
binary's Tag_CPU_name is also "Cortex-A8". Is this expected behavior of
ld, or maybe tags should be merged to a more specific "Cortex-A15"?
Perhaps we should use Tag_DIV_use when merging names?

-Maxim

[Ping] Tag_CPU_name merging produces wrong tag for ARM.

[Maxim Ostapenko]

Ping.
On 09/02/2014 02:45 PM, Maxim Ostapenko wrote:
> Add Andrew Stubbs  and Nick Clifton as author and reviewer of ARM 
> attributes merging patch 
> (https://sourceware.org/ml/binutils/2009-01/msg00156.html).
>
> -------- Original Message --------
> Subject:     [Bug ld/17212] Tag_CPU_name merging produces wrong tag 
> for ARM.
> Date:     Tue, 02 Sep 2014 13:19:20 +0400
> From:     Maxim Ostapenko <m.ostapenko@partner.samsung.com>
> To:     binutils@sourceware.org
> CC:     Yury Gribov <y.gribov@samsung.com>, Slava Garbuzov 
> <v.garbuzov@samsung.com>
>
>
>
> Hi,
>
> I tried to compile a binary optimized for ARM Cortex-A15 with ARM
> Cortex-A8 cross-toolchain (host is x86_64-pc-linux-gnu), but
> Tag_CPU_name appears to be "Cortex-A8" for the binary instead of
> "Cortex-A15". The example session follows:
>
> $ arm-v7a8-linux-gnueabi-gcc -O2 -mcpu=cortex-a15 divtest.c -o 
> divtest.a15
>
> $ readelf -A divtest.a15
>
> Attribute Section: aeabi
> File Attributes
> Tag_CPU_name: "Cortex-A8"
> Tag_CPU_arch: v7
> ................................................
> Tag_DIV_use: Allowed in v7-A with integer division extension
>
> After some investigation I found out, that Tag_CPU_name merging based on
> Tag_CPU_arch. Since the first file to appear during linking is crt1.o,
> which has Tag_CPU_name: "Cortex-A8" for A8 toolchain, the result
> binary's Tag_CPU_name is also "Cortex-A8". Is this expected behavior of
> ld, or maybe tags should be merged to a more specific "Cortex-A15"?
> Perhaps we should use Tag_DIV_use when merging names?
>
> -Maxim
>
>
>

Re: Tag_CPU_name merging produces wrong tag for ARM.

[Andrew Stubbs]

On 02/09/14 11:45, Maxim Ostapenko wrote:
> I tried to compile a binary optimized for ARM Cortex-A15 with ARM
> Cortex-A8 cross-toolchain (host is x86_64-pc-linux-gnu), but
> Tag_CPU_name appears to be "Cortex-A8" for the binary instead of
> "Cortex-A15". The example session follows:

I'm not sure what the correct behaviour would be. I did know a lot about 
this stuff a few years ago, but my memory has faded, and I'm too busy to 
research this much.

I suggest you find the proper document at http://infocentre.arm.com, and 
compare the expected behaviour with what actually happens. Then we'll 
know how to fix it.

I remember putting in some specific rules for particular tags, but 
basically the merging just happens by type, and there's no automatic way 
to merge strings.

Andrew