The resurrected LLVM "C Backend", with improvements.
GOAL OF THIS FORK
My primary goal is to have a backend I can use for this project:
The LLVM frontend for the D programming language, aka LDC, generates valid bitcode that JuliaComputing/llvm-cbe can't process (it generates uncompilable C code). (It seems that the JuliaComputing/llvm-cbe was only tested with bitcode inputs that were generated by clang)
Moreover, the project in its current state needs a lot of cleaning, its merely consists of one huge source file and uses heavy C++ syntax that isn't required anymore, and the test suite is hard to use.
So my goal here is to have a codebase:
- that has no bugs blocking the dscripten project.
- that works with a recent version of LLVM (at the moment 3.9, vs JuliaComputing/llvm-cbe which requires LLVM 3.7)
- that can be compiled out of the LLVM tree (as long as there's one llvm-config in the PATH).
- that has a trustable suite of tests which directly feed llvm-cbe with deterministic LLVM bitcode (instead of relying on clang code generation, as JuliaComputing/llvm-cbe does).
- that don't require compromises on code cleanliness.
- whose output is standard ISO C99 code, instead of relying on the specifics of some compilers.
This version of the LLVM-CBE library works with LLVM 3.9. You will have to compile this version of LLVM before you try to use LLVM-CBE. This guide will walk you through the compilation and installation of both tools and show usage statements to verify that the LLVM-CBE library is compiled correctly.
The library is known to compile on various Linux versions (Redhat, Mageia, Ubuntu, Debian), Mac OS X, and Windows (Mingw-w64).
Step 1a: Installing LLVM manually
LLVM-CBE currently requires LLVM 3.9 to be installed somewhere on your system, and that the corresponding "llvm-config" be in your PATH. (only LLVM is needed, not clang).
The first step is to compile LLVM on your machine:
$ cd $HOME $ git clone https://github.com/llvm-mirror/llvm $ cd llvm $ git checkout release_39 $ ./configure $ make $ make install
At this point, you should have llvm-config in your path:
$ llvm-config --version 3.9.1
Step 1b: Install LLVM from repositories
Alternatively, a LLVM installed some other way can be used, e.g. installing the Debian packages. Be aware that some distributions will suffix the 'llvm-config' program with LLVM version, e.g 'llvm-config-3.9'. In this case, you will need to set the environment variable LLVM_CONFIG so the makefile knows which program to call. Example:
$ export LLVM_CONFIG=llvm-config-3.9
Step 2: Compiling LLVM-CBE
Next, download and compile llvm-cbe:
$ cd $HOME $ git clone https://github.com/JuliaComputing/llvm-cbe.git llvm-cbe $ cd llvm-cbe
Step 3: Usage Examples
Once llvm-cbe is compiled, you can run it with the following command.
$ bin/llvm-cbe main.ll -o=main.cbe.c $ gcc -w main.cbe.c -o main.exe $ ./main.exe
Run the test suite
This will trigger the build and run the tests.