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A Provably Sound TAL for Back-end Optimization

Juan Chen, Dinghao Wu, Andrew Appel, and Hai Fang

Abstract

Typed assembly languages provide a way to generate machinecheckable safety proofs for machine-language programs. But the soundness proofs of most existing typed assembly languages are hand-written and cannot be machine-checked, which is worrisome for such large calculi. We have designed and implemented a low-level typed assembly language (LTAL) with a semantic model and established its soundness from the model. Compared to existing typed assembly languages, LTAL is more scalable and more secure; it has no macro instructions that hinder low-level optimizations such as instruction scheduling; its type constructors are expressive enough to capture data flow information, support the compiler's choice of data representations and permit typed position-independent code; and its type-checking algorithm is completely syntax-directed.

We have built a prototype system, based on Standard ML of New Jersey, that compiles most of core ML to Sparc code. We explain how we were able to make the untyped back end in SML/NJ preserve types during instruction selection and register allocation, without restricting low-level optimizations and without knowledge of any type system pervading the instruction selector and register allocator.

Details

Publication typeInproceedings
Published inACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI 03)
PublisherAssociation for Computing Machinery, Inc.
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