CPU 20 SIMD on x86 SSE

Inside the book

This preview is derived from headings detected in the PDF’s opening pages.

• CPU Programming Series SIMD on x86: SSE AVX Practical Patterns Prepared by Ayman Alheraki simplifycpp.org February 2026 Contents Contents 2 Preface 15 Scope and Philosophy of This Booklet . . . . . . . . . . . . . . . . . . . . . . . . . 15 Why SIMD Still Matters on Modern x86 . . . . . . . . . . . . . . . . . . . . . . . . 16 What This Booklet Is Not . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Required Background and Assumptions . . . . . . . . . . . . . . . . . . . . . . . . 19 How to Read and Apply the Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . 20 1) Start with a scalar reference and a measurable baseline . . . . . . . . . . . . 21 2) Make data layout and loop shape SIMD-friendly . . . . . . . . . . . . . . . 21 3) Apply the SIMD pattern with a clear tail strategy . . . . . . . . . . . . . . . 21 4) Validate correctness with edge cases . . . . . . . . . . . . . . . . . . . . . . 22 5) Measure the right thing, the right way . . . . . . . . . . . . . . . . . . . . . 23 6) Keep maintainability: isolate SIMD and allow multiple backends . . . . . . 23 1 SIMD Fundamentals on x86 25 1.1 What SIMD Really Means at the Microarchitectural Level . . . . . . . . . . . 25 1.1.1 The canonical SIMD loop shape . . . . . . . . . . . . . . . . . . . . . 26 1.1.2 What the core “sees” . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.2 Vector Registers vs Scalar Execution . . . . . . . . . . . . . . . . . . . . . . . 27 2 3 1.2.1 Lane semantics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.2.2 Architectural width vs physica