[llvm-dev] How to add new AVR targets?
Wilhelm Meier via llvm-dev
llvm-dev at lists.llvm.org
Fri Apr 3 06:09:40 PDT 2020
Should I create an issue in bugzilla for this? Just to be reminded ...
Am 31.03.20 um 09:34 schrieb Wilhelm Meier via llvm-dev:
> Hi Dylan,
>
> looks ok now.
>
> One thing:
>
> the ISR is now:
>
> __vector_21: ; @__vector_21
> __vector_21$local:
> sei
> push r0
> push r1
> in r0, 63
> push r0
> clr r0
> push r24
> lds r24, v1
> sts v2, r24
> pop r24
> pop r0
> out 63, r0
> pop r1
> pop r0
> reti
>
> There are unneccessary push/pops of r1 and r0 too, since the clr is
> useless ... GCC had the same problem but they made improvements.
>
> Thanks.
>
>
> Am 31.03.20 um 08:09 schrieb Wilhelm Meier via llvm-dev:
>> Hi Dylan,
>>
>> thank you. I'll be back with a test ...
>>
>> Wilhelm
>>
>> Am 31.03.20 um 08:06 schrieb Dylan McKay:
>>> Hey Wilhelm,
>>>
>>> That's a bug, the "interrupt" attribute is not being recognized by the
>>> backend.
>>>
>>> I have fixed it in
>>> https://github.com/llvm/llvm-project/commit/339b34266c1b54a9b5ff2f83cfb1da9cd8c9d90a
>>>
>>> Pull the latest LLVM and it should be fixed.
>>>
>>>
>>> On Tue, Mar 31, 2020 at 8:00 AM Wilhelm Meier <wilhelm.meier at hs-kl.de
>>> <mailto:wilhelm.meier at hs-kl.de>> wrote:
>>>
>>> Hi Dylan,
>>>
>>> I used the following commandline:
>>>
>>> clang++ -Os -DF_OSC=20000000 -DF_CPU=20000000 --target=avr -I.
>>> -I../include0 -I../../include0 -I../../../include0 -I../../include0/std
>>> -I../include0/std -I../../../include0/std -I../../3rdparty/boost
>>> -I/usr/avr/include -mmcu=atmega328p
>>> /home/lmeier/Projekte/wmucpp/clang/bm00/bm00.cc -S -emit-llvm --output
>>> bm00.ir <http://bm00.ir>
>>>
>>> Please find the IR attached in the file bm00.ir <http://bm00.ir>
>>>
>>> Thanks,
>>> Wilhelm
>>>
>>>
>>> Am 30.03.20 um 13:44 schrieb Dylan McKay:
>>> > Hey Wilhelm,
>>> >
>>> > Could you post the LLVM IR generated from your C++ file?
>>> >
>>> > This can be achieved with 'clang -S -emit-llvm'
>>> >
>>> > Cheers
>>> >
>>> > On Sat, Mar 28, 2020 at 6:36 PM Wilhelm Meier
>>> <wilhelm.meier at hs-kl.de <mailto:wilhelm.meier at hs-kl.de>
>>> > <mailto:wilhelm.meier at hs-kl.de <mailto:wilhelm.meier at hs-kl.de>>>
>>> wrote:
>>> >
>>> > Answering partly to myself there was a extern "C" missing.
>>> >
>>> > But the register pushes ans reti are still missing.
>>> >
>>> > Whats wrong?
>>> >
>>> > Am 28.03.20 um 06:26 schrieb Wilhelm Meier via llvm-dev:
>>> > > Hi Dylan,
>>> > >
>>> > > the following code
>>> > >
>>> > > volatile uint8_t v1;
>>> > > volatile uint8_t v2;
>>> > >
>>> > > __attribute__((interrupt)) void __vector_21(void) {
>>> > > v2 = v1;
>>> > > }
>>> > >
>>> > > produces in C mode:
>>> > >
>>> > > 00000092 <__vector_21>:
>>> > > 92: 80 91 61 00 lds r24, 0x0061 ; 0x800061 <v1>
>>> > > 96: 80 93 60 00 sts 0x0060, r24 ; 0x800060
>>> <__data_end>
>>> > > 9a: 08 95 ret
>>> > >
>>> > > and in C++ mode:
>>> > >
>>> > > 00000074 <_Z11__vector_21v>:
>>> > > 74: 80 91 60 00 lds r24, 0x0060 ; 0x800060
>>> <__data_end>
>>> > > 78: 80 93 61 00 sts 0x0061, r24 ; 0x800061 <v2>
>>> > > 7c: 08 95 ret
>>> > >
>>> > > So, in C++ mode it is not recognized as ISR due to name
>>> mangling.
>>> > >
>>> > > Furthermore there are no register push/pos and no reti.
>>> > >
>>> > > Whats wrong?
>>> > >
>>> > > Thanks.
>>> > >
>>> > >
>>> > > Am 11.03.20 um 08:13 schrieb Dylan McKay:
>>> > >> Here you go Wilhelm,
>>> > >>
>>> > >> https://github.com/dylanmckay/clang-avr-libc-interrupt-example
>>> > >>
>>> > >>
>>> > >>
>>> > >> On Thu, Mar 5, 2020 at 4:05 AM Wilhelm Meier
>>> > <wilhelm.meier at hs-kl.de <mailto:wilhelm.meier at hs-kl.de>
>>> <mailto:wilhelm.meier at hs-kl.de <mailto:wilhelm.meier at hs-kl.de>>
>>> > >> <mailto:wilhelm.meier at hs-kl.de
>>> <mailto:wilhelm.meier at hs-kl.de> <mailto:wilhelm.meier at hs-kl.de
>>> <mailto:wilhelm.meier at hs-kl.de>>>>
>>> > wrote:
>>> > >>
>>> > >> Am 04.03.20 um 13:28 schrieb Dylan McKay:
>>> > >>
>>> > >> >
>>> > >> > * *The C/C++ function needs to be declared with either
>>> > the calling
>>> > >> > convention avr-interrupt or
>>> > avr-non-blocking-interrupt.* Skipping
>>> > >> > this step will cause regular ret instructions to be
>>> > emitted for
>>> > >> > return-from-subroutine, instead of the required reti
>>> > for interrupt
>>> > >> > handlers. ISRs also have stricter requirements on
>>> which
>>> > registers
>>> > >> > must not be clobbered after execution, which the
>>> > backend will
>>> > >> handle
>>> > >> > properly by restoring all clobbered registers in the
>>> > interrupt
>>> > >> > handler epilogue
>>> > >> > * *The symbol names of the ISR function handlers must
>>> > match those
>>> > >> > referred to in avr-libc/avr-libgcc/crt*. This is
>>> > because the ISR
>>> > >> > table is specified in assembly inside the GCC AVR
>>> CRT.
>>> > The way it
>>> > >> > works is that the external symbol references in
>>> the CRT
>>> > object
>>> > >> files
>>> > >> > are declared with an exotic linkage type that causes
>>> > the linker to
>>> > >> > skip linking of the symbols if they are undefined
>>> > references.
>>> > >> If you
>>> > >> > chose a custom ISR table in a custom CRT or runtime
>>> > library, you
>>> > >> > would be free to choose ISR names as you pleased.
>>> > >> >
>>> > >> Thank you for your explanation. But I suspect I didn't
>>> get it
>>> > right. Can
>>> > >> you please provide an example?
>>> > >>
>>> > >> Thanks
>>> > >>
>>> > > _______________________________________________
>>> > > LLVM Developers mailing list
>>> > > llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>>> <mailto:llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>>
>>> > > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>> > >
>>> >
>>>
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