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gbarecomp v0.1.0 — Phase 2.8.D BIOS milestone

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@mstan mstan released this 25 May 03:20
· 252 commits to main since this release
v0.1.0
3f30288

gbarecomp v0.1.0

First tagged cut of the static GBA recompiler. Phase 2.8.D milestone:
the recompiled GBA BIOS executes via runtime_dispatch on the host C
stack with the interpreter strictly off the hot path. Minish Cap reaches
its title screen on top of this BIOS path (see MinishCapRecomp v0.0.1).

What you download

A single, fully-standalone gba.exe. No zip, no sidecar DLLs — SDL2,
libstdc++, libgcc, and libwinpthread are all statically linked into
the binary. The only DLLs it imports are stock Windows ones
(KERNEL32, USER32, GDI32, ole32, comdlg32, etc.) that ship with every
Windows install.

First launch

  1. Run gba.exe.
  2. A Windows file picker appears. Select your gba_bios.bin dump.
  3. The runtime hash-verifies the BIOS:
    • Match (SHA-1 300c20df...3492, CRC32 0x21A2AE0A) → BIOS canary
      runs.
    • Mismatch → warning dialog quoting the actual + expected hashes,
      then the canary runs anyway so you can validate atypical dumps.
  4. The validated path is saved in bios.cfg next to the .exe.

To pick a different BIOS later, delete bios.cfg or pass --bios
explicitly on the command line.

What's NOT in this release

  • No GBA BIOS image. The 16 KiB gba_bios.bin is copyrighted by
    Nintendo. You provide your own dump.
  • No game ROMs. Game runtimes (Minish Cap, etc.) ship separately.
  • No generated C. The recompiler output is regenerated from your
    BIOS dump at build time when you build from source.

Highlights since branch creation

  • arm_codegen pins ARMv4T edge cases: PC+12 reads for
    register-controlled shifts, S-bit LDM/STM with PC absent, LDMIA with
    base in list, empty-list with writeback, STMDB writeback with base
    not first in list.
  • Runtime: direct-call return idiom (host C-stack BLs with a
    return-stack predicate), always-on RuntimeTraceEntry ring buffer
    for post-mortem diagnostics, HALT idle pump that ticks PPU / timer /
    audio in cycle chunks until HALTCNT clears.
  • function_finder keys functions by (addr, mode) so ARM and THUMB
    can coexist at the same address, supports [[code_copy]]
    declarations for IWRAM / EWRAM copies whose source bytes live in
    ROM, and seeds fall-through after conditional indirect transfers
    (bxeq lr falls through to the next instruction when the condition
    fails).
  • BIOS TOML adds five new extra_func entries plus a 30-entry
    bios_intro_command jump table at 0x3738.
  • [[code_copy]] schema documented in docs/TOML_SCHEMA.md.
  • Asset picker module: Win32 file dialog + CRC32/SHA-1 validation +
    sidecar cache.
  • Static-release build flow: -DGBARECOMP_STATIC_RELEASE=ON plus
    CMAKE_EXE_LINKER_FLAGS=-static -static-libgcc -static-libstdc++
    produces a zero-dependency .exe.

Known issues

  • The picker's Win32 file dialog is Windows-only. On Linux / macOS,
    pass --bios explicitly until a portable dialog lands.
  • The interpreter inside gba.exe is a deliberate offline oracle (it
    is what the BIOS canary uses to step instructions, per
    PRINCIPLES.md). It is NOT used in any game runner's hot path.
  • See ISSUES.md for the deferred-bug list (audio sample drift,
    bios_intro_flawless ctest, etc.).
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