ds_ordered_count adds the first active lane's value to a GDS counter and
returns the previous value, like ds_append adds the lane count. Waves are
not serialized in launch order: each still gets its own range. Ordered
swap and multi-dword counts stay refused. DISPATCH_DIRECT and
DISPATCH_INDIRECT accept ORDERED_APPEND_ENBL (bit 3) of the initiator.
Compute shaders of MXGP 26 (PPSA30839) use both.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
s_sethalt with SIMM16[0] clear is a no-op; s_sethalt 1, s_sendmsghalt, a reached s_code_end, s_rfe_b64, the ds_gws_* instructions and ds_ordered_count throw with the reason at translation. Linear decoding stops at s_code_end like at s_endpgm, so code padded with s_code_end after a final backward branch decodes. Encodings from LLVM SOPInstructions.td and DSInstructions.td, checked against the gfx10 MC tests; semantics from the RDNA 2 ISA guide.
