LLJIT

This is a minimal interface to the JIT capability of LLVM, exposed via a Cython module. It allows you to load either LLVM assembly code or LLVM bitcode and execute it via LLVM's ExecutionEngine. (i.e., JIT).

Motivation

A much more complete interface to llvm exists, called llvm-py. However, at the time of this writing (LLVM 3.0) the LLVM API has changed enough that updating llvm-py is a non-trivial project.

Building

You'll need LLVM 3.0+ to build. It probably wouldn't be difficult to make this work with an older LLVM but I haven't bothered to try.

You may need to change the path of an include file in lljit/llvm.pxd, see the comments if you get this error:

lljit/lljit.cpp:238:39: fatal error: llvm/Support/TargetSelect.h: No such file or directory

The LLVM API is a moving target!

Build/install:

1. $ python setup.py build
2. $ sudo python setup.py install

Sample Usage

Lo,:

import lljit

# calling an external function...

asm = """
declare i32 @getpid()
define i32 @thing (i32 %x) {
  %1 = sub nsw i32 %x, 1
  %2 = call i32 @getpid()
  %3 = add i32 %2, %1
  ret i32 %3
}"""

m = lljit.module (asm, 0)
f = m.function ('thing')

print f(3)
print f(5)
print f(10)

Bitcode

I've included a module for parsing bitcode files. There are still problems, it is interpreting the insn sequences incorrectly, but the major difficulty of parsing the bit stream correctly has been cracked. I may eventually add an ability to write bitcode (e.g., for the backend of a compiler).

LLVM Hints

If you're new to LLVM, here are some quick hints to get you started.

Compile a C file to llvm assembly:

$ clang -emit-llvm -S t.c
[or]
$ llvm-gcc -emit-llvm -S t.c

Optimize some llvm assembly:

$ opt -std-compile-opts t.s -S

Compile to native code:

$ cat t.s | opt -std-compile-opts | llc

Compile to a different architecture:

$ cat t.s | opt -std-compile-opts | llc -march=arm