Compiler Optimization & Load-Store Conflicts: A Performance Cliffhanger

This article details an unexpected performance issue: a simple geometry decoder shows massive performance variations across different compiler versions. The root cause? A little-known microarchitectural detail: load-store conflicts. GCC-14 cleverly vectorized the code, resulting in a performance boost. However, GCC-15 regressed significantly due to altered optimization strategies, leading to frequent load-store conflicts. Clang, surprisingly, excelled on ARM architectures by leveraging the load-store characteristics. This highlights that compiler optimization isn't a silver bullet; close attention to generated code and underlying hardware microarchitecture is crucial.