[llvm-dev] [RFC] Tensilica Xtensa (ESP32) backend

[Roman Lebedev via llvm-dev]

Is this target the one interested in `alignof(char) != sizeof(char)`,
`alignof(char) == 4`?  https://reviews.llvm.org/D58811

On Thu, Mar 7, 2019 at 4:13 PM Andrei Safronov via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> Hello,
>
> Thank you for your interest. We are planning to add support for ESP8266
> in the near future.
>
> Best regards,
> Andrey Safronov
> 07.03.2019 0:42, Dan Kortschak пишет:
> > This is welcome news to me.
> >
> > We use ESP8266 (yes, not ESP32, but your future plans include the older
> > MCU) for an IOT system in conjunction with RPi machines. The language
> > that we target in preference is Go, but obviously currently use C++ for
> > the ESPs. We'd like to use Go for the ESPs via the tinygo.org project,
> > but this depends on clang/llvm support of the MCU target.
> >
> > thanks
> > Dan Kortschak
> >
> > I recently asked here about the prior work https://lists.llvm.org/piper
> > mail/llvm-dev/2019-February/130169.html.
> >
> > On Wed, 2019-03-06 at 14:29 +0300, Andrei Safronov via llvm-dev wrote:
> >> Hello,
> >>
> >> I'm from Espressif Systems company, software department. Our company
> >> develops processors based on Xtensa architecture like ESP32 and
> >> ESP8266.
> >> We propose the integration of a backend targeting Xtensa
> >> architecture.
> >>
> >> We started to develop LLVM Xtensa backend almost a year ago. The
> >> reason
> >> was that we saw a demand from our large developers community.
> >> Currently
> >> only GNU compiler supports Xtensa architecture. The company has
> >> approved
> >> me to develop and maintain Xtensa backend.
> >>
> >> We already have the initial version of the Xtensa backend, based on
> >> LLVM
> >> Compiler Infrastructure, release 6.0.0. It was successfully tested
> >> using
> >> GCC torture testsuite and multiple applications.
> >>
> >> These are the links to LLVM and Clang repositories.
> >>
> >> https://github.com/espressif/llvm-xtensa
> >> https://github.com/espressif/clang-xtensa
> >>
> >> Current version can generate Xtensa assembly code as output, not
> >> object
> >> files yet, and has to be used together with GNU Binutils and GCC-
> >> built
> >> libraries to create object and binary files.
> >>
> >> Xtensa backend features implemented:
> >>
> >> - Xtensa target description(Xtnesa.td, XtensaTargetMachine.cpp,
> >> XtensaSubTarget.cpp)
> >> - ISA desciption (XtensaInstrInfo.td, XtensaInstrFormats.td,
> >> XtensaREgisterInfo.td)
> >> - Xtensa Call ABI (XtensaCallingConv.td, XtensaFrameLowering.cpp)
> >> - ASM printer/parser(XtesaAsmPrinter.cpp, XtensaInstrPrinter.cpp,
> >> XtensaAsmParser.cpp)
> >>
> >> Xtensa architecture features implemented in compiler:
> >>
> >> - Xtensa Core Architecture instructions
> >> - Code Density option
> >> - Windowed Register option
> >> - Floating-Point Coprocessor option
> >> - Boolean option (only a subset of instructions)
> >> - Thread Pointer option
> >> - atomic operations
> >>
> >> Current Xtensa target list:
> >>
> >> - support Xtensa LX6 target (ESP32) by default
> >>
> >> Compiler optimization levels include O0/O1/O2/O3/Os options.
> >>
> >> With LLVM community approval, my next plans will be
> >>
> >> - rebasing on the upstream version of LLVM.
> >> - object code generation (XtensaMC package)
> >> - implement test cases
> >> - support for LX106 target (ESP8266)
> >> - improvements of generated code performance
> >> - support for zero-overhead loop option
> >> - MAC16 option
> >>
> >> There were some discussions about implementation of the Xtensa
> >> backend
> >> and attempt to implement it:
> >> http://lists.llvm.org/pipermail/llvm-dev/2018-July/124789.html
> >> http://lists.llvm.org/pipermail/llvm-dev/2018-April/122676.html
> >>
> >> Also there were attempts to implement a LLVM Xtensa backend, but
> >> recently I found only one actual link:
> >> https://github.com/jdiez17/llvm-xtensa
> >>
> >> All comments and suggesions are welcome!
> >>
> >> Andrei Safronov
> >>
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> llvm-dev at lists.llvm.org
> >> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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