[fpc-devel] error target i386 -Cp80486

[J. Gareth Moreton]

Got it!  I would have solved this much sooner if I had just dived into 
the code instead of getting lost with git bisect!

https://gitlab.com/freepascal.org/fpc/source/-/merge_requests/655

It was an infinite loop in the "var13", "var14" and "var15" 
optimisations that don't trigger on the Pentium II (default option) and 
later.  They set the Result to True even if no changes were actually 
made and caused the compiler to check for the same optimisation over and 
over again without progressing.

Kit

P.S. Admittedly those optimisations could use some maintenance since I 
shouldn't need to set the operand sizes, but I'll save that for another day.

On 24/04/2024 05:08, J. Gareth Moreton via fpc-devel wrote:
> I've gotten back as far as here, and it's still bad:
>
> commit 7fbda0e0e8b1d071e72ccbc5e487dbb1c2173c63 (HEAD)
> Author: Jonas Maebe <jonas at freepascal.org>
> Date:   Wed Mar 24 14:33:09 2021 +0000
>
>       * support building with FPC 3.2.2
>
>     git-svn-id: trunk at 49045 -
>
> I can't check earlier without difficulty because 3.2.2 doesn't work.  
> However the hang (and also an eventual out of memory error) doesn't 
> occur if -OoNOPEEPHOLE is specified, meaning the problem is located in 
> the peephole optimizer.  So it looks like I'll have to try to debug 
> this the hard way!
>
> Kit
>
> On 23/04/2024 17:27, J. Gareth Moreton via fpc-devel wrote:
>> I've reproduced the hang doing "make clean all CPU_TARGET=i386 
>> OS_TARGET=win32 OPT="-Cp80486 -Op80486"" on my x86_64-win64 machine.
>>
>> So far I haven't found the bad commit - this problem has been here a 
>> while.
>>
>> Kit
>>
>> I still haven't found the bad commit!
>>
>> On 23/04/2024 12:46, J. Gareth Moreton via fpc-devel wrote:
>>> Absolutely I can.  I'll see what I can find.
>>>
>>> Gareth aka. Kit
>>>
>>> On 23/04/2024 12:09, Tomas Hajny via fpc-devel wrote:
>>>> On 2024-04-23 11:50, Marģers . via fpc-devel wrote:
>>>>> 1) does not work
>>>>> make clean singlezipinstall OS_TARGET=win32 CPU_TARGET=i386
>>>>> ALLOW_WARNINGS=1 OPT="  -O2 -vxitl -Cp80486 -Op80486"
>>>>>
>>>>> hangs on
>>>>> system.inc(421,2) Start reading includefile
>>>>> C:\Users\Lietotajs\Downloads\fora\a\486\gh\rtl\inc\generic.inc
>>>>  .
>>>>  .
>>>>
>>>> Indeed. This is clearly an issue related to optimizations. The 
>>>> important point missing here is that it happens when compiling with 
>>>> ppc1.exe. I just tried building a trunk compiler (make rtl_all 
>>>> compiler_all) with "OPT=-O- -Cp80486 -Op80486" and then started 
>>>> another compilation round with compiler built this way, but using 
>>>> -O2 this time, in order to make sure that it wasn't an optimization 
>>>> bug in the released 3.2.2 compiler. The new compilation round 
>>>> (using a non-optimized compiler) hangs at an exactly the same 
>>>> place, i.e. it's a bug (probably endless loop?) in the optimization 
>>>> code specific to the trunk compiler. @Gareth, could you please have 
>>>> a look at it?
>>>>
>>>> Tomas
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