[fpc-devel] about freepascal for mips

[Jeppe Græsdal Johansen]

Den 25-05-2012 13:54, Jonas Maebe skrev:
>
> Fuxin Zhang wrote on Fri, 25 May 2012:
>
>> And my progress and problems:
>>   I've got the source from subversion and tried to build it in ubuntu
>> 11.10 x86-64 machine. With the following patch and commands, I can get a
>> partly working ppcrossmipsel(it can at least build a helloworld and
>> runnable):
>> patch:
>>   Index: Makefile.fpc
>> ===================================================================
>> --- Makefile.fpc    (版本 21354)
>> +++ Makefile.fpc    (工作副本)
> [snip]
>> This is to fix various file not found errors. I am not sure whether 
>> it is
>> 'right' fix.
>
> No, definitely it's definitely not right. It's strange that you need 
> those changes, since the Linux RTL Makefile is used daily. Did you 
> need those changes even to compile it for i386?
>
>> commands:
>>   cd rtl/linux;
>>   patch Makefile.fpc; fpcmake -Ti386-linux,mipsel-linux
>
> It's better to use -Tall (since there are more Linux targets than just 
> i386 and mipsel).
>
>> /home/foxsen/fpc/rtl/units/mipsel-linux/sysutils.o: In function
>> `SYSUTILS_$$_finalize':
>> /home/foxsen/fpc/rtl/unix/sysutils.pp:1414: relocation truncated to fit:
>> R_MIPS_PC16 against
>> `SYSTEM$_$TINTERFACEDOBJECT_$__$$_QUERYINTERFACE$TGUID$formal$$LONGINT'
>> /home/foxsen/fpc/rtl/unix/sysutils.pp:1414: relocation truncated to fit:
>> R_MIPS_PC16 against `SYSTEM$_$TINTERFACEDOBJECT_$__$$__ADDREF$$LONGINT'
>> /home/foxsen/fpc/rtl/unix/sysutils.pp:1414: relocation truncated to fit:
>> R_MIPS_PC16 against `SYSTEM$_$TINTERFACEDOBJECT_$__$$__RELEASE$$LONGINT'
>> pp.pas(224,36) Error: Error while linking
>> pp.pas(224,36) Fatal: There were 1 errors compiling module, stopping
>> Fatal: Compilation aborted> make[1]: *** [ppcmipsel] 错误 1
>> make[1]:正在离开目录 `/home/foxsen/fpc/compiler'
>> make: *** [cycle] 错误 2
>>
>> I know it is related to mips branch offset overflow.
>
> A similar issue exists on PowerPC: conditional branches are limited to 
> 16 bit offsets, while unconditional branches can reach up to 26 bits 
> or so. As far as I can see, it's similar on MIPS (the B* opcodes 
> versus the J opcode). If so, you may be able to create a MIPS version 
> of the fixup_jmps procedure in compiler/ppcgen/aasmcpu.pas and add it 
> to compiler/mips/aasmcpu.pas (it's called from psub.pas, you'll have 
> to modify the ifdef there to also activate it for MIPS and MIPSEL).
>
> The actual errors you get are strange though. We never insert 
> conditional branches from one routine to another (in the above case: 
> from SYSUTILS_$$_finalize, or more likely from interface wrappers 
> following that symbol, to various other routines). Looking at the code 
> for tcgcpu.g_intf_wrapper in compiler/mips/cgcpu.pas, the code for 
> interface wrappers uses the "B" as opposed to the "J" instruction to 
> branch to the interface wrappers. Maybe that's a copy/paste error from 
> another platform. I'm not sure what "B" means though, I don't see it 
> listed at http://www.mrc.uidaho.edu/mrc/people/jff/digital/MIPSir.html
>
> Anyway, I guess this patch will solve the above error:
>
> Index: compiler/mips/cgcpu.pas
> ===================================================================
> --- compiler/mips/cgcpu.pas    (revision 21359)
> +++ compiler/mips/cgcpu.pas    (working copy)
> @@ -1722,7 +1722,7 @@
>      op_onr24methodaddr;
>    end
>    else
> -   
> list.concat(taicpu.op_sym(A_B,current_asmdata.RefAsmSymbol(procdef.mangledname)));
> +   
> list.concat(taicpu.op_sym(A_J,current_asmdata.RefAsmSymbol(procdef.mangledname)));
>    { Delay slot }
>    list.Concat(TAiCpu.Op_none(A_NOP));
>
>> After some
>> research,I've found that ppc code support -fPIC.
>
> PIC normally won't help with branch offset overflows.
>
>> But when I try to enable
>> it,the other issue appears:
>
> Yes, PIC requires cpu-specific support. It shouldn't be necessary to 
> get an initial port up and running though.
>
>
> Jonas
I wonder how you people managed to build anything at all.

When I tried to build from SVN trunk there would be an endless steam of 
internalerrors related to fpu registers, no matter if compiled with MIPS 
FPU or softfloat.

I managed to remove the errors with the following patch, such that 
everything compiled, but I haven't been able to test it: 
http://j-software.dk/fpc-mipsel.patch

Does anyone know if there's an easy way to set up an emulator for 
testing? Been fighting with qemu for the last half hour without results.

Regards,
Jeppe