Verified compilation of open modules (i.e., modules whose functionality depends on other modules) provides a foundation for end-to-end verification of modular programs ubiquitous in contemporary software. However, despite intensive investigation in this topic for decades, the proposed approaches are still difficult to use in practice as they rely on assumptions about the internal working of compilers which make it difficult for external users to apply the verification results. We propose an approach to verified compositional compilation without such assumptions in the setting of verifying compilation of heterogeneous modules written in first-order languages supporting global memory and pointers. Our approach is based on the memory model of CompCert and a new discovery that a Kripke relation with a notion of memory protection can serve as a uniform and composable semantic interface for the compiler passes. By absorbing the rely-guarantee conditions on memory evolution for all compiler passes into this Kripke Memory Relation and by piggybacking requirements on compiler optimizations onto it, we get compositional correctness theorems for realistic optimizing compilers as refinements that directly relate native semantics of open modules and that are ignorant of intermediate compilation processes. Such direct refinements support all the compositionality and adequacy properties essential for verified compilation of open modules. We have applied this approach to the full compilation chain of CompCert with its Clight source language and demonstrated that our compiler correctness theorem is open to composition and intuitive to use with reduced verification complexity through end-to-end verification of non-trivial heterogeneous modules that may freely invoke each other (e.g., mutually recursively).

翻译：开放模块（即功能依赖其他模块的模块）的已验证编译为现代软件中普遍存在的模块化程序端到端验证提供了基础。然而，尽管该主题已历经数十年深入研究，现有方法在实际应用中仍存在困难——它们依赖于编译器内部工作机制的假设，使得外部用户难以运用验证结果。针对采用支持全局内存与指针的一阶语言编写的异构模块的编译验证场景，本文提出一种无需此类假设的已验证组合编译方法。该方法基于CompCert内存模型，并发现具有内存保护概念的克里普克关系可作为编译器遍次的统一可组合语义接口。通过将编译器所有遍次关于内存演化的依赖-保证条件吸收至克里普克内存关系，并将编译器优化需求附加其上，我们为实际优化编译器推导出以直接精化形式呈现的组合正确性定理——该定理直接关联开放模块原生语义且对中间编译过程透明。此类直接精化支持开放模块已验证编译所需的所有组合性与充分性属性。我们已将该方法应用于包含Clight源语言的CompCert完整编译链，并通过非平凡异构模块（例如相互递归调用）的端到端验证，证明我们的编译器正确性定理开放组合、直观易用，且显著降低了验证复杂度。