vhiribarren / llvm-tuto-kaleidoscope-golang

LLVM Kaleidoscope tutorial in Go, toy project.

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:

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:

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<llvm::Metadata*>)'
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.