llgo/README.md

llgo - A Go compiler based on LLVM
=====

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This is a Go compiler based on LLVM in order to better integrate Go with the C ecosystem including Python. It's a subproject of [the Go+ project](https://github.com/goplus/gop).

## C standard libary support

```go
package main

import "github.com/goplus/llgo/c"

func main() {
	c.Printf(c.Str("Hello world\n"))
}
```

This is a simple example of calling the C `printf` function to print `Hello world`. Here, `c.Str` is not a function for converting a Go string to a C string, but a built-in instruction supported by llgo for generating a C string constant.

See [github.com/goplus/llgo/c](https://pkg.go.dev/github.com/goplus/llgo/c) for more detials.


## Python support

You can import a Python library in llgo! For example:

```go
package main

import (
	"github.com/goplus/llgo/c"
	"github.com/goplus/llgo/py"
	"github.com/goplus/llgo/py/math"
)

func main() {
	x := math.Sqrt(py.Float(2))
	c.Printf(c.Str("sqrt(2) = %f\n"), x.Float64())
}
```

Here, We call `py.Float(2)` to create a Python floating point number 2, and pass it to Python’s `math.sqrt` to get `x`. Then use `x.Float64()` to convert the Python object to Go's `float64` type, and finally we print the value through C `printf`.


## Other frequently used libraries

TODO


## How to install

Follow these steps to generate the `llgo` command (its usage is the same as the `go` command):

### on macOS

```sh
brew update  # execute if needed
brew install llvm@17
go install -v ./...
```

### on Linux

```sh
echo 'deb http://apt.llvm.org/focal/ llvm-toolchain-focal-17 main' | sudo tee /etc/apt/sources.list.d/llvm.list
wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
sudo apt-get update  # execute if needed
sudo apt-get install --no-install-recommends llvm-17-dev
go install -v ./...
```

### on Windows

TODO


## Demo

The `_demo` directory contains our demos (it start with `_` to prevent the `go` command from compiling it):

* [hello](_demo/hello/hello.go): call C printf to print `Hello world`
* [concat](_demo/concat/concat.go): call C fprintf with stderr, and Go variadic function
* [qsort](_demo/qsort/qsort.go): call C function with a callback (eg. qsort)
* [genints](_demo/genints/genints.go): various forms of closure usage (including C function, recv.method and anonymous function)
* [llama2-c](_demo/llama2-c): inference Llama 2 (It's the first llgo AI example)

And the `_pydemo` directory contains python related demos:

* [callpy](_pydemo/callpy/callpy.go): call Python standard library function `math.sqrt`


### How to run demos

To run the demos in directory `_demo`:

```sh
cd <demo-directory>  # eg. cd _demo/genints
llgo run .
```

To run the demos in directory `_pydemo`, you need to set the `LLGO_LIB_PYTHON` environment variable first. Assuming you use Python 3.12, and the `libpython3.12.so` (or `libpython3.12.dylib` or `python3.12.lib`) file is in the /foo/bar directory, then you need to set `LLGO_LIB_PYTHON` to:

```sh
export LLGO_LIB_PYTHON=/foo/bar/python3.12
```

For example, `/opt/homebrew/Frameworks/Python.framework/Versions/3.12/libpython3.12.dylib` is a typical python lib location under macOS. So we should set it like this:

```sh
export LLGO_LIB_PYTHON=/opt/homebrew/Frameworks/Python.framework/Versions/3.12/python3.12
```

Then you can run the demos in directory `_pydemo`:

```sh
cd <demo-directory>  # eg. cd _pydemo/callpy
llgo run .
```