GNAT LLVM

This is an Ada compiler based on LLVM, connecting the GNAT front-end to the LLVM code generator to generate LLVM bitcode for Ada and to open the LLVM ecosystem to Ada.

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.

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

• For more information on LLVM, see llvm.org.
• For more information on GNAT, see adacore.com.

Building

To build GNAT LLVM from sources, follow these steps:

• First do a checkout of this repository and go to this directory:

  $ git clone https://github.com/AdaCore/gnat-llvm.git
  $ cd gnat-llvm
  

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

  $ git clone git://gcc.gnu.org/git/gcc.git llvm-interface/gcc
  

  then under non Windows systems:

  $ ln -s gcc/gcc/ada llvm-interface/gnat_src
  

  under Windows systems:

  $ mv llvm-interface/gcc/gcc/ada llvm-interface/gnat_src
  

• Install (and put in your PATH) a recent GNAT, e.g GNAT Community 2021 or GCC 11.

• Install LLVM and Clang 16.0.x

  The recommended way to build GNAT LLVM is to use an existing LLVM and clang package installed via e.g. "brew install llvm" on Mac OS or "sudo apt-get install llvm-dev" on Ubuntu. You can also build llvm yourself with the options that suit your needs. After installing/building, make sure the llvm bin directory containing llvm-config and clang is in your PATH.

  An alternative only suitable for core GNAT LLVM development on x86 native configurations is to use the following command, assuming you have cmake version >= 3.13.4 in your path:

  $ make llvm
  

  Note that there's currently a bug in LLVM's aliasing handling. We check for it and generate slightly pessimized code in that case, but a patch to be applied to LLVM's lib/Analyze directory is in the file llvm/patches/LLVMStructTBAAPatch.diff.

• 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

• If you want in addition to generate bitcode for the GNAT runtime, you can do:

  $ make gnatlib-bc
  

  This will generate libgnat.bc and libgnarl.bc in the adalib directory, along with libgnat.a and libgnarl.a.

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 bitcode (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.