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KG's Blog – KG's Blog · May 24, 2026

Tuning LLVM's SLP Vectorizer Cost Model

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Similar to my last post, this writeup covers how I solved a performance regression on LLVM by analyzing a benchmark from a RISCV target. TLDR A recent LLVM patch introduced ordered vector reductions to replace a chain of scalar fadds, but it triggered a performance regression on a benchmark by failing to account for cost of building the initial vector per iteration . This in turned caused…

Read on blog.kavin.me

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