ARM: pxa/corgi: armv5te kernel 4.12 fails to decompress compiled with gcc7

[Petr Cvek]

Dne 17.10.2017 v 22:33 Aaro Koskinen napsal(a):
> Hi,
> 
Hi,

> On Mon, Oct 16, 2017 at 01:55:18PM +0200, Petr Cvek wrote:
>> Dne 15.10.2017 v 12:46 Aaro Koskinen napsal(a):
>>> This seems to be simpler to debug/reproduce using busybox. Compiling
>>> just busybox with GCC 7.2 and march=armv5te/mtune=xscale already
>>> produces failing xz decompression:
>>
>> Does it fail too when compiled with gcc 7.2 and with march=armv5t and/or
>> march=armv4t ?
> 
> At least armv4t seems to work.
> 

Are you sure you used gcc 7.2 and parameters march=armv5te + 
mtune=xscale? I've compiled the bugzilla code with these same parameters:

	-march=armv5te -mtune=xscale -marm -O2  -c strd.c

For me (on gcc 7.1.0) only mtune=xscale/iwmmxt doesn't generate STRD. 
Other mtune variants (arm1020e, arm926ej-s generate it). Here is a 
table, which was tested on a real hardware.

-march=armv5te -mtune=xscale	OK, code very long
-march=armv5te -mtune=iwmmxt	OK, same code as v5te/xscale
-march=iwmmxt			OK, same code as v5te/xscale
-march=armv5t			OK, less opcodes than v5te/xscale
-march=armv5			OK, same as armv5t
-march=armv5te			KO, unaligned STRD, alignment exception
-march=armv5tej			KO, unaligned STRD (PXA27x is only v5te)

BTW gcc 6.3.0 generates even longer code and it doesn't support armvtej. 
Perhaps your 7.2 has even more optimalizations even for mtune=xscale.

So I suppose compiling kernel and userspace with -match=armv5t or less 
should be fine for now (unless there is another similar problem due to 
7.x optimizations).

> 
>> I've just found my old gcc 6.3 compiled some code with a default armv4t.
> 
> You can set the default with compiling GCC using --with-arch=...

Yeah I know about that, it seems something probably override my settings 
(most likely my scripts for separate crosstool and buildroot).

> 
> BTW, the failing instruction seems to be STRD and there seems to be
> already a related bug report:
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82445

Big thanks for info.

> 
> A.
> 

Petr