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LLVM based GNAT compiler
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README.md

GNAT LLVM

This is an experimental Ada compiler based on LLVM, connecting the GNAT front-end to the LLVM code generator.

This is a work-in-progress research project that's not meant for and shouldn't be used for industrial purposes. It's meant to show the feasibility of generating LLVM bit code for Ada and to open the LLVM ecosystem to Ada, including tools such as KLEE.

Note that we are not planning on replacing any existing GNAT port that's based on GCC: this project is meant to provide additional, not replacement, GNAT ports.

There are known bugs and limitations in this version.

Early users are welcome to experiment with this technology and provide feedback on successes, usages, limitations, pull requests, etc.

GNAT LLVM has been built successfully on GNU/Linux and Mac OS Mojave x86_64 native targets, using LLVM 9.0.0. Do not hesitate to report success on other configurations.

Building

To build GNAT LLVM from sources, follow these steps:

  • Obtain a check out of the GNAT sources from gcc.gnu.org under the llvm-interface directory:

    $ svn co svn://gcc.gnu.org/svn/gcc/trunk/gcc/ada llvm-interface/gnat_src
    
  • Install (and put in your PATH) a recent GNAT, e.g GNAT Community 2019 or GCC 8

  • Build/install LLVM and Clang 9.0.0

    You can use an existing LLVM and clang 9.0.0 package install via e.g. "brew install llvm" on Mac OS or "sudo apt-get install llvm-dev" on Ubuntu. Make sure the llvm bin directory containing llvm-config and clang is in your PATH.

    Alternatively, you can build LLVM and Clang 9.0.0 from sources. One possible way, assuming you have cmake version >= 3.7.2 in your path, is to do:

    $ make llvm
    
  • Finally build GNAT LLVM:

    $ make
    

This creates a "ready to use" set of directories "bin" and "lib" under llvm-interface which you can put in your PATH:

PATH=$PWD/llvm-interface/bin:$PATH

Usage

  • To run the compiler and produce a native object file:

    $ llvm-gcc -c file.adb
    
  • To debug the compiler:

    $ gdb -args llvm-gnat1 -c file.adb
    
  • To build a complete native executable:

    $ llvm-gnatmake main.adb
    
  • To build a whole project:

    $ gprbuild --target=llvm -Pprj ...
    
  • To generate LLVM bit code (will generate a .bc file):

    $ llvm-gcc -c -emit-llvm file.adb
    
  • To generate LLVM assembly (will generate a .ll file):

    $ llvm-gcc -c -S -emit-llvm file.adb
    
  • To generate native assembly file (will generate a .s file):

    $ llvm-gcc -S file.adb
    

License

The GNAT LLVM tool is licensed under the GNU General Public License version 3 or later; see file COPYING3 for details.

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