[llvm-dev] How to add new AVR targets?
Wilhelm Meier via llvm-dev
llvm-dev at lists.llvm.org
Mon Mar 30 23:09:41 PDT 2020
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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