LLVA: A Low-level Virtual Instruction Set Architecture
Vikram Adve, Chris Lattner, Michael Brukman, Anand Shukla, and Brian Gaeke

Abstract:

A virtual instruction set architecture (V-ISA) implemented via a processor-specific software translation layer can provide great flexibility to processor designers. Recent examples such as Crusoe and DAISY, however, have used existing hardware instruction sets as virtual ISAs, which complicates translation and optimization. In fact, there has been little research on specific designs for a virtual ISA for processors. This paper proposes a novel virtual ISA (LLVA) and a translation strategy for implementing it on arbitrary hardware. The instruction set is typed, uses an infinite virtual register set in Static Single Assignment form, and provides explicit control-flow and dataflow information, and yet uses low-level operations closely matched to traditional hardware. It includes novel mechanisms to allow more flexible optimization of native code, including a flexible exception model and minor constraints on self-modifying code. We propose a translation strategy that enables offline translation and transparent offline caching of native code and profile information, while remaining completely OS-independent. It also supports optimizations directly on the representation at install-time, runtime, and offline between executions. We show experimentally that the virtual ISA is compact, it is closely matched to ordinary hardware instruction sets, and permits very fast code generation, yet has enough high-level information to permit sophisticated program analyses and optimizations.

Published:

"LLVA: A Low-level Virtual Instruction Set Architecture", Vikram Adve, Chris Lattner, Michael Brukman, Anand Shukla, and Brian Gaeke.
Proceedings of the 36th annual ACM/IEEE international symposium on Microarchitecture (MICRO-36), San Diego, California, Dec. 2003.

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BibTeX Entry:

  @InProceedings{ALBSG:MICRO36,
    author    = {Vikram Adve and Chris Lattner and Michael Brukman and Anand Shukla and Brian Gaeke},
    title     = "{LLVA: A Low-level Virtual Instruction Set Architecture}",
    booktitle = "{Proceedings of the 36th annual ACM/IEEE international symposium on Microarchitecture (MICRO-36)}",
    address   = {San Diego, California},
    month     = {Dec},
    year      = {2003}
  }