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40 lines
2.1 KiB
Plaintext
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Date: Wed, 31 Jan 2001 12:04:33 -0600
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From: Vikram S. Adve <vadve@cs.uiuc.edu>
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To: Chris Lattner <lattner@cs.uiuc.edu>
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Subject: another thought
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I have a budding idea about making LLVM a little more ambitious: a
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customizable runtime system that can be used to implement language-specific
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virtual machines for many different languages. E.g., a C vm, a C++ vm, a
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Java vm, a Lisp vm, ..
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The idea would be that LLVM would provide a standard set of runtime features
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(some low-level like standard assembly instructions with code generation and
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static and runtime optimization; some higher-level like type-safety and
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perhaps a garbage collection library). Each language vm would select the
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runtime features needed for that language, extending or customizing them as
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needed. Most of the machine-dependent code-generation and optimization
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features as well as low-level machine-independent optimizations (like PRE)
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could be provided by LLVM and should be sufficient for any language,
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simplifying the language compiler. (This would also help interoperability
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between languages.) Also, some or most of the higher-level
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machine-independent features like type-safety and access safety should be
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reusable by different languages, with minor extensions. The language
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compiler could then focus on language-specific analyses and optimizations.
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The risk is that this sounds like a universal IR -- something that the
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compiler community has tried and failed to develop for decades, and is
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universally skeptical about. No matter what we say, we won't be able to
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convince anyone that we have a universal IR that will work. We need to
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think about whether LLVM is different or if has something novel that might
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convince people. E.g., the idea of providing a package of separable
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features that different languages select from. Also, using SSA with or
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without type-safety as the intermediate representation.
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One interesting starting point would be to discuss how a JVM would be
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implemented on top of LLVM a bit more. That might give us clues on how to
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structure LLVM to support one or more language VMs.
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--Vikram
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