The C++26 standard introduces std::simd for portable data parallelism. We present a complete implementation built on LLVM using a layered architecture: a minimal base layer interfaces with LLVM's SIMD capabilities, while higher-level features build on this foundation. Multi-target support emerges naturally by building upon LLVM's own architecture support, and a dispatch tag system isolates target-specific code to minimal locations. This design has proven particularly effective for x86, cleanly handling the many ISA variants (SSE, AVX, AVX-512, etc.), and should extend naturally to any SIMD target LLVM supports. As the compiler's support improves, the library improves too. We'll share our architectural patterns, performance results, and areas where LLVM could be enhanced to enable better code generation. The authors have been involved in the C++ standardisation process for this the library.