Decoupled Control Flow and Data Access in RISC-V GPGPUs

Fuente: arXiv
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Autores principales: Sarda, Giuseppe M., Shah, Nimish, Nada, Abubakr, Bhattacharjee, Debjyoti, Verhelst, Marian
Formato: Preprint
Publicado: 2025
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author Sarda, Giuseppe M.
Shah, Nimish
Nada, Abubakr
Bhattacharjee, Debjyoti
Verhelst, Marian
author_facet Sarda, Giuseppe M.
Shah, Nimish
Nada, Abubakr
Bhattacharjee, Debjyoti
Verhelst, Marian
contents Vortex, a newly proposed open-source GPGPU platform based on the RISC-V ISA, offers a valid alternative for GPGPU research over the broadly-used modeling platforms based on commercial GPUs. Similarly to the push originating from the RISC-V movement for CPUs, Vortex can enable a myriad of fresh research directions for GPUs. However, as a young hardware platform, it currently lacks the performance competitiveness of commercial GPUs, which is crucial for widespread adoption. State-of-the-art GPUs, in fact, rely on complex architectural features, still unavailable in Vortex, to hide the micro-code overheads linked to control flow (CF) management and memory orchestration for data access. In particular, these components account for the majority of the dynamic instruction count in regular, memory-intensive kernels, such as linear algebra routines, which form the basis of many applications, including Machine Learning. To address these challenges with simple yet powerful micro-architecture modifications, this paper introduces decoupled CF and data access through 1.) a hardware CF manager to accelerate branching and predication in regular loop execution and 2.) decoupled memory streaming lanes to further hide memory latency with useful computation. The evaluation results for different kernels show 8$\times$ faster execution, 10$\times$ reduction in dynamic instruction count, and overall performance improvement from 0.35 to 1.63 $\mathrm{GFLOP/s/mm^2}$. Thanks to these enhancements, Vortex can become an ideal playground to enable GPGPU research for the next generation of Machine Learning.
format Preprint
id arxiv_https___arxiv_org_abs_2512_00032
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Decoupled Control Flow and Data Access in RISC-V GPGPUs
Sarda, Giuseppe M.
Shah, Nimish
Nada, Abubakr
Bhattacharjee, Debjyoti
Verhelst, Marian
Hardware Architecture
Vortex, a newly proposed open-source GPGPU platform based on the RISC-V ISA, offers a valid alternative for GPGPU research over the broadly-used modeling platforms based on commercial GPUs. Similarly to the push originating from the RISC-V movement for CPUs, Vortex can enable a myriad of fresh research directions for GPUs. However, as a young hardware platform, it currently lacks the performance competitiveness of commercial GPUs, which is crucial for widespread adoption. State-of-the-art GPUs, in fact, rely on complex architectural features, still unavailable in Vortex, to hide the micro-code overheads linked to control flow (CF) management and memory orchestration for data access. In particular, these components account for the majority of the dynamic instruction count in regular, memory-intensive kernels, such as linear algebra routines, which form the basis of many applications, including Machine Learning. To address these challenges with simple yet powerful micro-architecture modifications, this paper introduces decoupled CF and data access through 1.) a hardware CF manager to accelerate branching and predication in regular loop execution and 2.) decoupled memory streaming lanes to further hide memory latency with useful computation. The evaluation results for different kernels show 8$\times$ faster execution, 10$\times$ reduction in dynamic instruction count, and overall performance improvement from 0.35 to 1.63 $\mathrm{GFLOP/s/mm^2}$. Thanks to these enhancements, Vortex can become an ideal playground to enable GPGPU research for the next generation of Machine Learning.
title Decoupled Control Flow and Data Access in RISC-V GPGPUs
topic Hardware Architecture
url https://arxiv.org/abs/2512.00032