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SPIR-V is catalyzing a revolution in the ecosystem for shader and kernel language compilers used for expressing parallel computation and GPU-based graphics. SPIR-V enables high-level language front-ends to emit programs in a standardized intermediate form to be ingested by Vulkan, OpenGL or OpenCL drivers. SPIR-V eliminates the need for high-level language front-end compilers in device drivers, significantly reducing driver complexity, enables a broad range of language and framework front-ends to run on diverse hardware architectures and encourages a vibrant ecosystem of open source analysis, porting, debug and optimization tools.
For developers, using SPIR-V means that kernel source code no longer has to be directly exposed, kernel load times can be accelerated, and developers can choose the use of a common language front-end compiler, improving kernel reliability and portability across multiple hardware implementations.
SPIR-V 1.5 has been released on September 13th, 2019 to accompany the launch of Vulkan 1.2
SPIR-V 1.5 expands developer conveniences, making SPIR-V easier for compilers and shader tool chains to target.
“We are excited to see the progress developers have made with the SPIR-V standardized IR. Developers are using the shader language of their choice and a variety of open source compilers to ship their games and applications. The Vulkan tools and ecosystem is evolving rapidly.” said David Neto, Shader compiler team lead at Google.
Learn more in the Vulkan 1.2 Press Release
SPIR (Standard Portable Intermediate Representation) was initially developed for use by OpenCL and SPIR versions 1.2 and 2.0 were based on LLVM. SPIR has now evolved into a cross-API intermediate language that is fully defined by Khronos with native support for shader and kernel features used by APIs such as Vulkan – called SPIR-V.
|SPIR 1.2||SPIR 2.0||SPIR-V 1.X|
|LLVM Interaction||Uses LLVM 3.2||Uses LLVM 3.4||100% Khronos defined Round-trip lossless conversion|
|Supported Language Feature Supported||OpenCL C 1.2||OpenCL C 1.2 OpenCL C 2.0||OpenCL C 1.2 / 2.X OpenCL C++ GLSL|
|OpenCL Ingestion||OpenCL 1.2 Extension||OpenCL 2.0 Extension||OpenCL 2.1/2.2 Core|
|Graphics API Ingestion||—||—||Vulkan 1.X and OpenGL 4.6 Core|
SPIR-V is the first open standard, cross-API intermediate language for natively representing parallel compute and graphics and is part of the core specifications of OpenCL 2.1, OpenCL 2.2, and the Vulkan GPU API. SPIR-V is also supported in an OpenGL 4.6 extension. SPIR–V does not use LLVM, and so is isolated from LLVM roadmap changes. Khronos has open sourced SPIR-V/LLVM conversion tools to enable construction of flexible toolchains that use both intermediate languages.
SPIR-V exposes the machine model for OpenCL 1.2, 2.0, 2.1, 2.2 and Vulkan - including full flow control, and graphics and parallel constructs not supported in LLVM. SPIR-V also supports OpenCL C and OpenCL C++ kernel languages as well as the GLSL shader language for Vulkan and OpenGL.
SPIR-V 1.1, launched in parallel with OpenCL 2.1, supported the kernel language features of OpenCL C++ in OpenCL 2.1, including initializer and finalizer function execution modes to support constructors and destructors. SPIR-V 1.1 also enhances the expressiveness of kernel programs by supporting named barriers, subgroup execution, and program scope pipes.
SPIR-V 1.2 launched in parallel with OpenCL 2.2 and fully supports the final OpenCL C++ kernel language and adds support for runtime specialization of key tuning parameters in OpenCL 2.2 such as workgroup size.
SPIR-V 1.3, launched in parallel with Vulkan 1.1, expands the capabilities of the Vulkan shader intermediate representation to support subgroup operations and enables enhanced compiler optimizations.
SPIR 2.0 is a mapping from the OpenCL C programming language into LLVM IR. This version of the SPIR is based on LLVM 3.2 and OpenCL C as defined in the OpenCL 2.0 specification. SPIR 2.0 supports all core features and KHR extensions for version 2.0 of OpenCL C