[llvm-dev] [RFC] Tensilica Xtensa (ESP32) backend
Andrei Safronov via llvm-dev
llvm-dev at lists.llvm.org
Wed Mar 6 03:29:29 PST 2019
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.
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,
- ISA desciption (XtensaInstrInfo.td, XtensaInstrFormats.td,
- Xtensa Call ABI (XtensaCallingConv.td, XtensaFrameLowering.cpp)
- ASM printer/parser(XtesaAsmPrinter.cpp, XtensaInstrPrinter.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:
Also there were attempts to implement a LLVM Xtensa backend, but
recently I found only one actual link:
All comments and suggesions are welcome!
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