Beetle's ReadInstruction never fills an I-cache line for a fetch at
0xA0000000 or above: every such fetch costs +4 and clears the pending load
give-back. The dirty-RAM interpreter charges that by fetching at every PC.
Both static emitters emitted psx_icache_fetch only at cache-line leaders,
which is exact for cached code only. In OpenBIOS, 5,477 of the 9,592
in-place ROM (KSEG1) instruction sites were uncharged: 21,908 cycles short
per pass through that code, each also missing its give-back clear.
Both emitters now charge a fetch before every instruction whose runtime PC
is uncached. The predicate is psx_fetch_uncached in psx_instr_cost.h, which
psx_icache.c now uses too. The A0/B0/C0 call-vector native stubs charge one
fetch per executed word, so a KSEG1 call pays like the interpreter. Cached
code keeps the leader rule. R4's regenerated game C is byte-identical, and
the OpenBIOS diff is insertions only. psx_instr_cost.h joins the codegen
hash list, since the emitters fold it into emitted code.
Tests:
- ctest uncached_fetch_charge runs psxrecomp-bios on OpenBIOS and compares
per-instruction fetch charges three ways: the compiled fetches, the
interpreter's fetch path (psx_icache_fetch_interp) at every PC, and a
Beetle transcription.
- uncached_fetch_codegen_test checks the game emitter at KSEG1 and KSEG0.
Both tests fail on master. This closes bios-kseg1-fetch-charge in the
segment_aware_codegen ledger (#419).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Shokunin