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Bruno De Backer

Bruno De Backer

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    automemcpy: A framework for automatic generation of fundamental memory operations
    Sam Xi
    Proceedings of the 2021 ACM SIGPLAN International Symposium on Memory Management (ISMM '21), June 22, 2021, Virtual, Canada (to appear)
    Preview abstract Memory manipulation primitives (memcpy, memset, memcmp) are used by virtually every application, from high performance computing to user interfaces. They often consume a significant portion of CPU cycles. Because they are so ubiquitous and critical, they are provided by language runtimes and in particular by libc, the C standard library. These implementations are heavily optimized, typically written in hand-tuned assembly for each target architecture. In this article, we propose a principled alternative to hand-tuning these functions: (1) we profile the calls to these functions in their production environment and use this data to drive the important high-level algorithmic decisions, (2) we use a high-level language for the implementation, delegate the job of tuning the generated code to the compiler, and (3) we use constraint programming and automatic benchmarks to select the optimal high-level structure of the functions. We compile our memfunctions implementations using the same compiler toolchain that we use for application code, which allows leveraging the compiler further by allowing whole-program optimization. We have evaluated our approach by applying it to the fleet of one of the largest computing enterprises in the world. This work increased the performance of the fleet by 1%. View details
    Preview abstract Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for providing code security with variable-length instruction encoding. An aspect may include encoding instructions according to a set of rules. Such encoding may delimit the beginning of instructions using a specific bit, delimit the beginning of a basic block using another specific bit, enable handling of variable length constants that code size, and make code validation decidable and deterministic. Accordingly, code may be scanned once to verify that the code can be decoded into actual instruction, non-computed branches can be validated, and computed branches may trap if they branch to other places than the beginning of a basic starting block. View details
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