Rule 8.24

An exported @compute entry is called from host code as entry(bindings, workgroups). bindings has one property for each binding the entry reaches through its calls, and no other, each the binding’s host value (Rule 8.21); workgroups is the workgroup count, n or [x, y?, z?], dispatched as written with no bound added; the call returns a promise, and when it resolves every storage binding the entry wrote has been read back into the caller’s value in place, or stays on the device in the Resident passed for it (Rule 11.8). It runs on WebGPU where there is a device, the device of the runtime configure({ runtime }) names or else the one the call layer requests and the default program runtime shares (Rule 11.11), and otherwise on the CPU tier (Rule 11.7), in the order configure sets (Rule 11.8), every invocation of every workgroup in turn, z, then y, then x, with the workgroup memory zeroed for each workgroup; an entry that reaches a barrier needs WebGPU, and where there is none the call is refused with a TypeError naming the barrier and its line. In vite dev, and in a production build whose plugin says console: 'always', an entry’s WGSL records its console.* calls (Rule 11.9), and the runtime prints the decoded events to the host’s console after the dispatch or the draw, in the CPU tier’s order; console: 'never' records in neither, and the default, 'dev', records in vite dev alone. Each printed line, from the GPU or the CPU tier, starts with its tier, the call’s file and line, and the invocation when the event has one, in the format string, with the event’s arguments after it and its method kept. An exported @fragment entry that reads no builtin but position and front_facing and writes one @location(0) vec4 (its result, or a struct of that one field) is drawn as entry(target, bindings): one frame, with a full-screen triangle, into target, an HTMLCanvasElement or an OffscreenCanvas, filling its width by height; the draw returns a promise that resolves when the frame is submitted, and reads nothing back. It draws on WebGPU, then WebGL2 (the entry’s GLSL ES 3.00 fragment program, its rows copied so the first is the canvas’s top, as WGSL’s position counts them), then the CPU tier, pixel by pixel; the first draw into a canvas decides its tier, since a canvas keeps the first kind of context it hands out, and every later draw into it uses that tier; the frame is opaque on every tier. An entry the CPU tier cannot run (one that reaches a texture, or a call only a GPU computes) needs a GPU tier, and where it has none the call or the draw is refused with a TypeError naming why. An entry that reaches a binding with no host value (a storage texture, a depth texture, a texture of another dimension, an emulated f64), a fragment entry that reads what a vertex entry writes, and a vertex entry stay never in the host view, naming the work that adds it.