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https://github.com/vhiribarren/llvm-tuto-kaleidoscope-golang

LLVM Kaleidoscope tutorial in Go, toy project.
https://github.com/vhiribarren/llvm-tuto-kaleidoscope-golang

go golang llvm toy-project tutorial

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LLVM Kaleidoscope tutorial in Go, toy project.

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# LLVM Kaleidoscope Tutorial in Go



_**Warning: WORK IN PROGRESS**_



This is a toy project to test LLVM and manipulate other tools (Go, YACC, ...). It

works, but I do not necessarily follow all the best practices and the code is

not necessarily robust against some errors.



It follows the tutorial: https://llvm.org/docs/tutorial/index.html



Here what is currently done, with some differences with the original tutorial:



- Step1: Lexer

    - https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl01.html

    - Usage of Go instead of C++ for the whole tutorial

    - Lexing is manually done (no usage of Go `Scanner`, ...)



- Step 2: Parser and AST

    - https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl02.html

    - Parsing done using YACC / GoYACC



- Step 3: Intermediate Representation (IR) code generation

    - https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl03.html

    - Usage of a Visitor pattern to analyze the abstract syntax tree

    - Usage of official LLVM v12 Go binding (based on LLVM C binding)



- Step 4: JIT and Optimizer support

    - https://llvm.org/docs/tutorial/MyFirstLanguageFrontend/LangImpl04.html

    - JIT: I did not found the symbol used in the default `KaleidoscopeJIT.h`

      file in the Go bindings, so I rewrote minimal JIT functions ; current

      used Go bindings provide the MCJIT executing engine



## How to run



You must have working/compiled LLVM v12 libraries on your system.



Launch tests:



    go test ./...



If changed, some files may need to be regenerated:



    go generate ./...



Launch:



    go run .



## Note on LLVM



I had issue in adding LLVM bindings as a Go module. For me, adding the

`github.com/llvm/llvm-project/llvm/bindings/go/llvm` or 

`github.com/llvm/llvm-project/tree/main/llvm/bindings/go/llvm` either created

some `no matching versions for query "latest"` issues or some zip file creation issues.



I tried to use an alternative - https://github.com/llir/llvm - however it does

not really provide bindings with LLVM, it is a lite wrapper to generate IR code

without optimization, etc.



So... I did manually copy files from

`https://github.com/llvm/llvm-project/tree/llvmorg-12.0.0/llvm/bindings/go`,

and added a `go.mod` file to mark it as a Go module.



A working LLVM installation is anyway needed.



To use with LLVM 12 on MacOS 11.2.2, with HomeBrew:



```bash

brew install llvm@12

brew install libffi

```



Before compiling the files, path to LLVM and FFI must be declared.

In my case, if using HomeBrew:



```bash

export CGO_CPPFLAGS="`/usr/local/Cellar/llvm/12.0.0/bin/llvm-config --cppflags` -fvisibility=hidden"

export CGO_CXXFLAGS=-std=c++14

export CGO_LDFLAGS="`/usr/local/Cellar/llvm/12.0.0/bin/llvm-config --ldflags --libs --system-libs all` -L/usr/local/Cellar/libffi/3.3_3/lib -lffi"

export CGO_LDFLAGS_ALLOW='-Wl,(-search_paths_first|-headerpad_max_install_names)'

```

Then, the Go program can be compiled.



Note that the `-fvisibility=hidden` flag was added to solve this warning message I had:



    ld: warning: direct access in function 'llvm::LLParser::parseMDTuple(llvm::MDNode*&, bool)'

    from file '/usr/local/Cellar/llvm/12.0.0/lib/libLLVMAsmParser.a(LLParser.cpp.o)' to global

    weak symbol 'llvm::MDTuple::get(llvm::LLVMContext&, llvm::ArrayRef)'

    from file '/var/folders/zy/n1jdlb2j08v2mwbf94z700800000gn/T/go-link-465421937/000016.o' means

    the weak symbol cannot be overridden at runtime. This was likely caused by different translation

    units being compiled with different visibility settings.