Recompiler: a deferred compute shader is dispatched and aborts: s_swappc_b64 through a per-lane function table (Ratchet & Clank: Rift Apart) #3274

Title: Ratchet & Clank: Rift Apart (PPSA01474, content 01.005.003)
Where it stops: frame ~437, 1 of 1 runs with APS5_EAGER_WRITEBACK=1. Without it the title instead freezes at frame 456 (#3272) and never dispatches this shader. AnyPS5 f1ae427b plus local patches (listed in #3272). CachyOS, RTX 4090, driver 615.78.

The call site (described, not the game's code)

The shader is 0x5980 bytes and has one computed call. The block before it does this:

index  = v13 + v11                         ; per-lane table index
loop:
  id   = readfirstlane(index)
  exec = lanes where index == id
  desc = s_load_dwordx4  user_data[12:13] + 0x270     ; buffer descriptor
  rec  = s_buffer_load_dwordx4 desc, id * 16           ; {target_lo, target_hi, arg0, arg1}
  s[14:15] = rec.target ; s[16:17] = rec.args
  s_swappc_b64 s[14:15], s[14:15]                     ; link pair == target pair
  restore exec; repeat while lanes remain

• The target comes from guest memory through a descriptor read from user data, per lane. It is not s_getpc plus a constant, not a user-data pair, and not a code-resident jump table.
• The link pair is the target pair (s[14:15]), and the call returns with the callee's s_setpc_b64.
• The same shader also has three bounded s_call_b64 at 0x8ec, 0x4168 and 0x416c that share the link pair s[64:65]. Those may hit the one-call-per-link-pair limit once this one is handled.

What I don't know

• The table contents. I didn't capture the dispatch's user data, so I don't know how many distinct callees there are, or whether they are other registered shaders.
• I can dump APS5_TRACE_DISPATCH_IO/user data for this dispatch if that helps choose between a per-dispatch callee set and a registered-callee switch.

Related: #1817, #1836, #2062, #2749 (Stray, same message at many PCs), #2302 (closed: per-dispatch inlining).