Without VK_EXT_shader_stencil_export (NVIDIA), stencil reference exports
are emulated by replaying the draw once per value. An export the prover
could not bound to at most 16 values was refused. The replay shader
compares the export's low eight bits, so an unbounded export now
replays all 256 values, and proven values are reduced to their low
eight bits as the comparison sees them.
Refs #4276
Co-Authored-By: Claude Opus 5.5 <[email protected]>
With DB_SHADER_CONTROL.STENCIL_OP_VAL_EXPORT_ENABLE the pixel shader
supplies the value that REPLACE_OP and the add and subtract operations
use in place of DB_STENCILREFMASK.STENCILOPVAL. The bit was refused as a
whole, which stopped Onimusha: Way of the Sword (PPSA27836) at a
DB_SHADER_CONTROL 0x45 draw with DB_STENCIL_CONTROL 0x40040 (REPLACE_OP
on depth pass, both faces), write mask 0xff and compare ALWAYS.
The export is accepted with the 32_GR and 32_ABGR Z formats. When no
reachable operation through a non-zero write mask reads the value, it
cannot change the result and is ignored. Without a test value export, a
reachable REPLACE_OP becomes REPLACE with the exported value as
FragStencilRefEXT (or the bounded replay on devices without the
extension), provided both faces compare without the test value and use
no ONES or REPLACE_TEST; early tests throw. The add and subtract
operations, and REPLACE_OP with a test value export, still throw.
The value is read from bits 8-15 of the second MRTZ channel: the
title's pixel shader shifts it left by 8 right before exp mrtz
(v_lshlrev_b32 v0, 8, v0). That is the only evidence for the layout and
it is listed as technical debt. The pixel stage info carries the new
flag into the cache key, the draw keys and request serialization
version 31.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
Preserve instance and triangle order with one dynamic-reference shader pipeline. Require bounded references, complete export coverage, replay-safe mask control and resources; refuse unsupported side effects and feedback.
Co-Authored-By: Codex <[email protected]>
