mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-26 02:11:36 -04:00
Matthew Stanley
e28c2a0ff9
The universal fix for the idle-freeze host-stack leak (RECURSION_BUG.md §25): make
the recompiler emit guest calls as TAIL-TRANSFERS driven by the trampoline + the
guest's own $ra/$sp, instead of nesting one psx_dispatch_impl per guest call frame.
This makes the host stack incapable of mirroring unbounded guest re-entrancy — the
architectural root of the leak — for ANY game. Perf cost accepted ("right before
fast").
Stage 1 (full_function_emitter.cpp), GATED behind gen-time env PSX_CPS:
- jal/jalr (orphaned-delay + pending-delay paths): emit `cpu->pc=target; return;`
(tail-transfer) + register the return address as a dispatchable continuation,
instead of nested psx_dispatch + psx_call_contract. JALR captures the target reg
BEFORE the link write (rd==rs alias-safe).
- jr $ra (all 3 sites): publish `cpu->pc = cpu->gpr[31]; return;` under CPS so the
trampoline dispatches the caller's continuation (legacy `return;` relied on the
nested-dispatch C-return). Required — without it the BIOS exits at frame 0.
GATING PROVEN SAFE: regen+build WITHOUT PSX_CPS boots Tomba normally — default
codegen byte-unaffected; CPS fully opt-in.
OPEN (CPS path only): with PSX_CPS=1 the BIOS boots main() then exits at frame 0
(execution completed, PC=0). Root cause (high confidence): the trampoline must
dispatch mid-function continuation addresses, but the dispatch table holds only
function entries → a return to a continuation misses → psx_unknown_dispatch →
pc=0 → exit. NEXT: add registered continuations to the dispatch table (map
continuation_addr → containing func), then re-regen PSX_CPS=1 and run the §25 gate
(ce_profile flat + oracle-identical + 15-min soak + dwarf->overworld). Stages 2
(interp interp_enter_compiled surface) + 3 (sljit/overlay parity) follow.
Safe revert point for the whole feature: commit ae47e69.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>