Go 1.26 and 1.27 include experimental APIs for Single Instruction Multiple Data (SIMD) operations. SIMD is a native feature of many modern CPUs that allows software to perform uniform operations across vectors of data very quickly, such as adding 8 pairs of float64 values in a single instruction. It can significantly speed up many computationally-intensive tasks, ranging from cryptography to data processing to AI. In fact, Go’s Green Tea garbage collector even makes use of SIMD to accelerate scanning memory for live objects. Prior to these new experimental APIs, the only way to access this functionality from Go was by writing Go assembly.

Go 1.26 introduced a SIMD API for amd64, and Go 1.27 added APIs for arm64 (specifically NEON) and wasm. However, a basic challenge for a SIMD API is the enormous variation between platforms, not simply in what operations they support, but even in how vectors are represented. To provide full access to the breadth of these platforms, these APIs live in an architecture-dependent archsimd package.

But Go 1.27 goes beyond these architecture-dependent APIs and introduces an experimental, fully portable, platform- and size-agnostic SIMD interface, loosely based on Highway for C++. The goal is to support write-once near-asm-performance “simd” code on platforms with SIMD support, and to provide a competent emulation on those platforms that do not (yet) have SIMD support. The simd package currently supports AVX, AVX2, and AVX512 on amd64, NEON on arm64, and wasm’s SIMD instructions.

SIMD architectures vary in several dimensions, including vector sizes, masking approaches, and operation primitives. Each architecture provides its own primitives for rearranging vector elements and supports different crypto-related operations. Even basic arithmetic can have varying support; for example wasm lacks comparisons for vectors of 64-bit integers.