Chris Lattner wrote:
I'm a little further along now. I've started to put together a simple
driver for Elsa and LLVM that I'm calling "ellsif" (cute name, I think
The file being compiled is a "printf" function. Here are timing results
for optimized and unoptimized runs:
Cool, this is very nice!
Sorry to add noise to the list with this. I'm just very excited.
Again, my compliments to both the Elsa and LLVM teams. It says a lot
that I got this far in 19 days of part-time work.
This is a very cool hack, but I'm curious: what is your goal with this work? Are you just trying to see if it can be done, or does elsa provide an advantage over using the g++ parser with llvm?
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Well, primarily I'm doing it for fun.
My background is in compiler design and embedded systems programming, so I'm interested in both the front end and back end aspects.
I've build gcc many times over the years for different target processors and was never able to get my head around it internally. It is incredibly complex. I also didn't like the fact that I had to have N copies of gcc to support N processors.
I became interested in Elsa (via google) because I liked its extensible nature. I can drop in new syntax rules easily. It was also fairly easy to understand.
At first I looked into SUIF and started down that path. I wasn't entirely pleased with the results. Then I realized SUIF had been dead for about 5 years so I started looking around for alternatives and stumbled on LLVM.
It was easy to lower the Elsa AST to LLVM by using Elsa's extension capability.
I'm now at the point where I can see that compiling C with Elsa is a done deal. I have about 90% (or more) of basic C covered.
I decided that I wanted a cleaner way to move forward so I started writing the ellsif driver to automate the steps and make Elsa->LLVM look like a real tool.
Does Elsa provide an advantage over g++? For me, understanding it is a big plus. In addition, Elsa has a Berkeley-like license which I prefer.
I'll let you know if Elsa is a good choice after I get a little further along adding the C++ support.
Since I only have a few weeks invested in this project, I won't feel too bad if Elsa turns out to be a dead end. Along the way I found LLVM, which is definitely the way to go.
I'd like to get the Elsa stuff behind me because I'm itching to do an LLVM code generator for the Altera Nios2. I started by copying the MIPS sources and am studying them to get a feel for what's required.