D117 - A GPU ISA surface census

Status: decided Date: 2026-09-26

docs/GPU_SURFACE.md is generated by obscene-tool gpusurface from data/gpu-surface.tsv, which classifies each special-math operation by how obSCEne reaches it: covered, from GLSL, as a driver sequence, through hand-written SPIR-V, or not on this part. The in-repository table is the source; the LLVM intrinsic list, where available, only validates it.

Why: "probe every GPU operation" needs a statement of what every operation is. Generating from the table keeps the document reproducible on any machine; reachability is stated because a kernel cannot name an instruction.

Rejected: generating from the toolchain directly - not reproducible without LLVM installed.