Introducing Web High Level Shading Language (WHLSL): A graphics shading language for WebGPU

Yesterday, the W3C GPU for the Web Community Group introduced a new graphics shading language for the WebGPU API called Web High Level Shading Language (WHLSL, pronounced “whistle”). The language extends HLSL to provide better security and safety.

Last year, a W3C GPU for the Web Community Group was formed by the engineers from Apple, Mozilla, Microsoft, Google, and others. This group is working towards bringing in a low-level 3D graphics API to the Web called WebGPU.

WebGPU, just like other modern 3D graphics API, uses shaders. Shaders are programs that take advantage of the specialized architecture of GPUs. For instance, apps designed for Metal use the Metal Shading Language, apps designed for Direct3D 12 use HLSL, and apps designed for Vulkan use SPIR-V or GLSL. That’s why the WebKit team introduced WHLSL for the WebGPU API.

Here are some of the requirements WHLSL aims to fulfill:

Need for a safe shader language

Irrespective of what an application does, the shader should only be allowed to read or write data from the Web page’s domain. Without this safety insurance, malicious websites can run a shader that reads pixels out of other parts of the screen, even from native apps.

Well-specified language

To ensure interoperability between browsers, a shading language for the Web must be precisely specified. Also, often rendering teams write shaders in their own custom in-house language, and are later cross-compiled to whichever language is necessary. That is why the shader language should have a reasonably small set of unambiguous grammar and type checking rules that compiler writers can reference when emitting this language.

Translatable to other languages

As WebGPU is designed to work on top of Metal, Direct3D 12, and Vulkan, the shader should be translatable to Metal Shading Language, HLSL (or DXIL), and SPIR-V. There should be a provision to represent the shaders in a form that is acceptable to APIs other than WebGPU.

Performant language

To provide an overall improved performance the compiler needs to run quickly and programs produced by the compiler need to run efficiently on real GPUs.

Easy to read and write

The shader language should be easy to read and write for a developer. It should be familiar to both GPU and CPU programmers. GPU programmers are important clients as they have experience in writing shaders. As GPUs are now popularly being used in various fields other than rendering including machine learning, computer vision, and neural networks, the CPU programmers are also important clients.

To learn more in detail about WLHSL, check out WebKit’s post.

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