2026-08-19 - The first guest instruction, translated and executed

Done. A TDD cycle, red through green, on v_mov_b32 with an inline constant source.

• orbistoun-translate::predicated: a register file as a private array, per-instruction emission, and an epilogue that copies the low registers into the storage buffer so a test can assert on them.
• Three tests that say what the instruction should do and are settled by a GPU.

Verified. Gate green, and the gate says executed against a real device. The translated module validates under spirv-val and produces the right register values on hardware: v_mov_b32 v3, 9 leaves 9 in v3 and zero everywhere else, and a later move beats an earlier one.

Surprises.

• The driver answered a malformed module with an access violation. Not a validation error, not a rejected shader - a hard crash of the test process. create_shader_module had accepted it. The fault was mine and small: the buffer is a struct containing one array, so an access chain into it takes two indices - the member, always zero, then the element - and I passed the register number for both. In bounds for register zero, out of bounds for every other, and the first test to exercise a non-zero register brought the process down.

  spirv-val named it in one line. Without the validator wired up first this would have been a debugger session against a crashing GPU driver, which is exactly the afternoon D099 was written to avoid - and the vindication arrived within the hour.

• The register file needed an explicit null initialiser. A private variable is undefined at entry, so "an untouched register reads zero" would have been an assertion about whatever the driver happened to leave in memory. It would have passed on this machine and meant nothing.

Not done. One instruction of a few hundred. No arithmetic, no memory access, no control flow - and control flow is where the predicated strategy earns its name, since none of the execution-mask machinery exists yet. The register file is a plain array with no mask applied to writes.