Mjolnir is a Clojure library designed to simplify native code generation. It is useful for writing on-the-fly high performance code, writing programming languages, or simply for exploring new how code performs on different platforms.

Internally, Mjolnir wraps the LLVM library. It then provides several layers of abstractions on top of LLVM. See the examples in the repository for indepth examples of the library at work.

NOTE: the real work lately has been going on in the datomic branch. See recent additions to that branch for up-to-date examples.

Constructors - various Clojure functions that wrap expressions and can emulate let, defn, etc. To use these, use the following pattern

(ns example
  (:require [mjolnir.constructors-init :as cinit])
  (:alias c mjolnir.constructors))

The alias line performs some magic that allows code like the following from within any clojure file:

(c/defn square [Int64 a -> Int64]
  (c/* a a))

Expressions - Constructors emit Mjolnir expressions. These live in mjolnir.types and mjolnir.expressions. These expressions are simply Clojure records that implement several common protocols. Once constructed, these expressions can be built via mjolnir.expressions/build. But most of the time this function will only be invoked against mjolnir.expressions/Module as this record contains alot of setup code that is neede for the other expressions to compile.

LLVMC - Expressions invoke the many functions found in mjolnir.llvmc. This namespace simply wraps the many functions found in LLVM. The wrapping is done via JNA.

LLVM-c - Internally, LLVM exposes the C++ api as a c library known as llvm-c.

LLVM - And finally, at the bottom we have the llvm library

Mjolnir supports a fairly basic, but powerful macro known as defnf. This macro acts much like Clojure's defn macro, but with C-like semantics:

(defnf fib [Int64 x -> Int64]
    (if (< x 2)
        x
        (+ (fib (- x 1))
           (fib (- x 2)))))

The code inside the macro will be translated to mjolnir constructors (via pre-fixing c- to a symbol if possible). Then the entire function will be type infered.

If a given variable is a struct, .- can be used to get a member:

(defnf myfn [Point* pnt -> Int64]
    (.-x pnt))  

In addition, pointer types support IFn, and when called, will create a cast operation:

(myfn (Point* (malloc (sizeof Point))))

At this time only OSX (64-bit) and NVidia PTX (on OSX) is supported. Adding new targets is easy, so if you want to add support for a platform, take a crack at it!.

FIXME

Copyright (c) 2012-2013 Timothy Baldridge

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