Re: [uClinux-dev] Latest GCC toolchain for m68k

Thu, 17 May 2012 22:17:48 -0700 

Hi Luis,

On 18/05/12 00:21, Luis Alves wrote:

Yes, that file exists in the sources gcc-<version>/gcc/config/m68k/uclinux.h
I've changed those flags and it works (at least in a small test with
the first pass gcc).

But take a look at the comments in my bug report:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53386


Yeah, interesting discussion :-)



Someone says that it is related to the ABI change in gcc>= 4.3.x and
that I should use as target 'm68k-uclinuxoldabi' and
--with-cpu=m68000.

For now I've just changed the flags in the header file... maybe I'll
try building it with that weird target (m68k-uclinuxoldabi).


Well, I consider it a bug still (I will probably make some gcc people
unhappy :-(  The ABI change itself doesn't really have anything to do
with it. If you use "gcc -m68000" to generate code that cannot work
then it is a bug. I couldn't in good conscience call that a configuration
error (though we know you can fix it by changing the that STRICT_ALIGNMENT
setting).

But that is just my take on it.

Regards
Greg




On Thu, May 17, 2012 at 2:59 PM, Greg Ungerer<g...@snapgear.com>  wrote:

Hi Luis,


On 05/17/2012 08:29 PM, Luis Alves wrote:


A guy just posted a comment in my bug report. It happens that it is a
gcc configuration issue:


config/m68k/linux.h:
/* for 68k machines this only needs to be TRUE for the 68000 */

#undef STRICT_ALIGNMENT
#define STRICT_ALIGNMENT 0
#undef M68K_HONOR_TARGET_STRICT_ALIGNMENT
#define M68K_HONOR_TARGET_STRICT_ALIGNMENT 0




I don't know if this will affect the build for coldfire targets. If it
does then from now on the 68000 should be excluded from the coldfire
toolchains to avoid this issues.

I'll build a nice toolchain for the 68000 and then make some more tests.



Wow, that is interesting. I don't quite see why that should not
always be set, otherwise how does specifying "-m68000" work at all.

Is there a config/m68k/uclinux.h file? áI don't have the sources
handly right now to check.

Regards
Greg




On Thu, May 17, 2012 at 7:45 AM, Greg Ungerer<g...@snapgear.com>  áwrote:


Hi Luis,


On 05/17/2012 12:58 PM, Luis Alves wrote:



I've built a new toolchain using the latest tools and gcc-4.6.4
(gcc-4.7.0 is giving me compiler internal errors!).
But unfortunately the results are the same (bad assembly code - It
look it is producing 68020 code, since when I use the -m68020 flag,
the resulting assembly code is equal!)




That is bad...




I've downgraded gcc to 4.2.4 (the version I was using before this
toolchain quest) and it works (produces correct assembly code).
I don't know what is the latest working version for the 68000 targets.
Maybe I'll go one by one until I find the broken one...




Ouch, doesn't sound like much fun.




I guess this is related to gcc so I've reported it as a bug it in the
gcc bugzilla (Bug 53386).

Do you have any further suggestion?




The gcc compile options looked good to me. If you have -m68000 set
the you should be getting code that is good for 68000. I guess the
code generation is at least only using the correct set of 68000
instructions.

Choosing a different optimization level may change the instruction/
addressing modes used. But really that would just be a work around.

Otherwise I would suggest sticking with 4.2.4 if that works.

Regards
Greg





On Wed, May 16, 2012 at 9:42 PM, Luis Alves<lja...@gmail.com>  á├íwrote:



Hi Greg,



What are the compiler options supplied to gcc?
(If you make the kernel with V=1 then you get the full command
line trace)



Here is one:

m68k-uclinux-gcc -Wp,-MD,net/sunrpc/.sysctl.o.d Ôö£├¡-nostdinc -isystem
/usr/local/lib/gcc/m68k-uclinux/4.5.1/include
-I/root/m68k/20120401/uClinux-dist/linux-3.x/arch/m68k/include
-Iarch/m68k/include/generated -Iinclude Ôö£├¡-include


/root/m68k/20120401/uClinux-dist/linux-3.x/include/linux/kconfig.h
-D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common -Werror-implicit-function-declaration
-Wno-format-security -fno-delete-null-pointer-checks -O2 -m68000 -pipe
-DUTS_SYSNAME=\"uClinux\" -D__uClinux__ -Wframe-larger-than=1024
-fno-stack-protector -fomit-frame-pointer
-Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow
-fconserve-stack -DCC_HAVE_ASM_GOTO Ôö£├¡ Ôö£├¡-D"KBUILD_STR(s)=#s"


-D"KBUILD_BASENAME=KBUILD_STR(sysctl)"
-D"KBUILD_MODNAME=KBUILD_STR(sunrpc)" -c -o net/sunrpc/sysctl.o
net/sunrpc/sysctl.c

I guess the -m68000 should be enough, but it isn't.

I've compiled the same file with -m68020 and the output assembly is
exactly the same.





When ever i have the time I'll try to build a toolchain (maybe using
gcc 4.7) and check the generated code.
Maybe I also could try the code sourcery one, but there is no
reference for the 'legacy 68k' family on their download page (only
coldfire).





Any m68k targeted compiler should be able to generate code for any
family member with the right command line options. With the bundled
toolchains you may not have the libs generated for your specific
CPU member though.



I just confirmed and there is no support for non-coldfire cpu's in
code sourcery toolchain...


Regards
Greg



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Regards,
Luis Alves









--
------------------------------------------------------------------------
Greg Ungerer á-- áPrincipal Engineer á á á áEMAIL: 
á á
g...@snapgear.com
SnapGear Group, McAfee á á á á á á á á á 
á áPHONE: á á á
+61 7 3435 2888
8 Gardner Close, á á á á á á á á á á 
á á á áFAX: á á á
á +61 7 3891 3630
Milton, QLD, 4064, Australia á á á á á á á áWEB:
http://www.SnapGear.com








--
------------------------------------------------------------------------
Greg Ungerer á-- áPrincipal Engineer á á á áEMAIL: á á g...@snapgear.com
SnapGear Group, McAfee á á á á á á á á á á áPHONE: á á á +61 7 
3435 2888
8 Gardner Close, á á á á á á á á á á á á á áFAX: á á á á +61 
7 3891 3630
Milton, QLD, 4064, Australia á á á á á á á áWEB: http://www.SnapGear.com







--
------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     g...@snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close                             FAX:         +61 7 3217 5323
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com
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