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llilc-faq.md

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LLILC FAQ

  • Q: What is LLILC?
    A: LLILC is an MSIL code generator based on LLVM. Today LLILC can produce a JIT compiler that can be used with CoreCLR, but our over-arching aim is to allow easier porting of managed languages to any platform while supporting a spectrum of compilation strategies.

  • Q: What targets will LLILC generate code for?
    A: Initially x64. In future: any target that LLVM supports is possible (x86, ARM-64, ...)

  • Q: What platforms will LLILC target?
    A: LLILC targets the same platforms as CoreCLR: Linux, MAC OS X and Windows

  • Q: How does the LLILC JIT compiler relate to the CoreCLR RyuJIT compiler?
    A: Their aims are different: RyuJIT is a high-performance, custom JIT, in that it implements its own optimizatons and codegen, specific to C#. It matches the high throughput required by the CoreCLR runtime. LLILC, by contrast, uses the LLVM framework, which provides industrial-strength optimizations, leveraged by the Clang C++ compiler. It thereby offers a familiar environment within which developers can implement low-level, ‘backend’ tools, such as code analyzers, obfuscators, verifiers, etc.

  • Q: How do I get started?
    A: See the Welcome Document

  • Q: Are there any demos?
    A: Not as yet. We need to extend the JIT to handle more tests first.

  • Q: How does LLILC differ from Roslyn in the features it provides for building software tools?
    A: Roslyn provides frontend support, whilst LLILC (via LLVM) provides backend support:

    • Roslyn exposes the data structures of a frontend – so it’s ideal for building tools such as IDEs, with syntax coloring, warning squiggles, use/definition lookup, refactoring, etc; or translators that convert C# to some other language; or pretty-print formatters; or analyzers that check conformance with coding guidelines (think FxCop).

    • LLILC, via LLVM, exposes the data structures of a backend – so it’s ideal for building tools that inject extra code (eg: performance profiler, code tracer, debugger, parallelism analyzer, race detector); or super-optimizing code (eg: auto-vectorizer, auto-parallelizer); or test-case reduction.

  • Q: When will the LLILC AOT (Ahead-Of-Time) compiler be ready?
    A: At the moment, CoreCLR does not include an AOT. We envisage that the LLILC AOT will work in two kinds of environment – those that allow runtime codegen, and those where the entire code is converted to native binary.

  • Q: How does LLILC relate to the .NET Native work?
    A: .NET Native provides a broad tool-chain, targeting Windows. The LLILC AOT could be used as the compiler component of .NET Native to target other platforms.