Handoff snapshot of the env-gated diagnostic scaffolding used across the
intro-video RE. Kept out of the milestone commits (645feb8..5573ac1) to keep
those clean; committed here so nothing is lost on handoff.
New — XENIA_PROFILE wall-time profiler (crates/xenia-gpu/src/prof.rs):
Coarse buckets attributing playback wall time to interpreter (step_block),
kernel HLE (call_export), block decode/cache (lookup_or_build), texture
decode, host draw, and present; prints periodic snapshots (every 500M guest
instr, or every 500 presents) + a clean-exit report. Hot path is gated on a
cached is_on() (one relaxed load) so it is zero-cost when XENIA_PROFILE is
unset. Call sites: main.rs run_superblock / parallel worker (step_block,
lookup_or_build, call_export), texture_cache ensure_cached, render.rs present
+ dispatch_xenos_draws.
First profile (movie playback, headless single-thread lockstep): effective
~35 MIPS; interpreter body ~40% @ ~95-102 MIPS; texture decode 0.3% (cache
works); present ~0%; the rest is per-block dispatch + scheduler plumbing
(~13 instr/block over 229M blocks). Overhead-bound, not interpreter-body
bound; the levers are coarser execution units (superblock chaining) and
ultimately a JIT.
Pre-existing read-only probe knobs (were uncommitted; env-gated, observe-only):
XENIA_RET_CAPTURE_PC/_REG/_MEM, LOG_RESUMES, LOG_WAITS, LOG_SIGNAL,
FORCE_TID, STARVE_LIMIT, INCUMBENT_PICK, INSTR_PER_MS, DUMP_FRAME,
DUMP_WGSL, BIND_LOG, CONST_LOG, DISPATCH_REC, AUDIT_PC_TRACE.
Tooling: sylph-run.sh (movie oracle loop, 180s default timeout),
zq.py (DuckDB disasm/xref helper).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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