reznikmm / gnat-llvm

LLVM based GNAT compiler

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 bitcode 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.

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

GNAT LLVM has been built successfully on GNU/Linux and Mac OS Mojave x86_64 native targets, using LLVM 9.0.1. Do not hesitate to report success on other configurations.

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:

  $ 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, GCC 8 or GCC 9.

• Build/install LLVM and Clang 9.0.1

  You can use an existing LLVM and clang 9.0.1 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 9.0.1 from sources. One possible way, assuming you have cmake version >= 3.7.2 in your path, is to do:

  $ 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 LLVMStructBAAPatch.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.