SPIRV

SPIR-V is a binary intermediate language designed by the Khronos Group to serve as a portable, cross-API representation for vertex, geometry, fragment, compute, and other shader stages. It is produced by front-end compilers from higher-level shading languages (such as GLSL and HLSL) and consumed by GPU drivers, notably in Vulkan and, with extensions, in OpenGL and OpenGL ES.

The format is a low-level, strongly typed, word-based intermediate representation. A SPIR-V module starts with a header and contains a sequence of instructions that reference types, constants, variables, and functions by unique identifiers. The module can declare capabilities, extensions, imports, a memory model, execution modes, and decorations to describe how code should be handled by the hardware and the driver. Its design emphasizes validation, optimization, and offline tooling, enabling safer and more predictable shader compilation pipelines.

A mature ecosystem surrounds SPIR-V tooling. The Khronos SPIR-V Tools project offers utilities such as an assembler (spirv-as), a disassembler (spirv-dis), a validator (spirv-val), a linker, and an optimizer (spirv-opt). Front-end compilers like glslang translate GLSL to SPIR-V, while other languages can also target SPIR-V through appropriate compilers or translation layers. SPIR-V modules are then interpreted by Vulkan drivers and, where supported, by OpenGL/OpenGL ES stacks.

Historically introduced in the mid-2010s, SPIR-V has evolved through multiple revisions to support new capabilities and hardware. It provides portability across GPU vendors, potential for pre-compilation and optimization, and decouples front-end language design from driver-specific implementations, at the cost of requiring tooling for inspection and validation.