apu: Add new DSP56300 emulator with JIT execution engine

[mborgerson]

• Fixes a few bugs in the existing C interpreter
• Adds a state abstraction layer to switch between engines at runtime and maintain snapshot compatibility

TODO:

• Fix xemu test cases
• Fix macOS Build (target arch specification)
• Fix Windows build (Rust toolchain)
• Add dsp56300 license details to xemu's license gen script
• Pin version

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly upgrades the DSP56300 emulation by integrating a high-performance JIT engine alongside the existing C interpreter. The core architecture has been redesigned to support seamless runtime switching between these engines, preserving VM state and snapshot compatibility. This enhancement aims to improve audio processing efficiency and accuracy, while also providing users with control over the chosen DSP execution method through new configuration options.

Highlights

• New DSP56300 JIT Emulator: A new Just-In-Time (JIT) execution engine has been added for the DSP56300 emulator, offering potentially faster processing for audio.
• DSP Engine Abstraction: An abstraction layer was introduced to allow dynamic switching between the existing C interpreter and the new JIT engine at runtime, ensuring snapshot compatibility across engine changes.
• C Interpreter Bug Fixes and Refinements: Several bugs in the existing C interpreter were addressed, and its internal structure was refactored to align with the new abstraction, including changes to interrupt handling and peripheral access.
• Improved APU Thread Utilization Metrics: The APU thread's utilization calculation was refined to more accurately measure time spent building frames, replacing the previous sleep-based metric.
• UI Integration: New UI toggles have been added to enable or disable the DSP JIT engine and control real-time DSP processing.

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[gemini-code-assist]

Code Review

This pull request introduces a new DSP JIT (Just-In-Time) compilation engine for improved audio processing performance, configurable via a new use_dsp_jit option. The DSP emulation architecture has been refactored to support multiple backends (C interpreter and JIT) through a common DSPOps interface and a unified DspCoreState structure for VM state synchronization. This includes updating APU state tracking to use microseconds and a frame_work_acc_us metric, abstracting DSP cache invalidation, and integrating DSP state synchronization with VM save/load operations. Debugging macros have been removed, and the DSP DMA logic has been enhanced to include dma_read_count for more accurate DMA completion timing. The C interpreter's DSP core has been simplified by removing unused interrupt types and debug-related fields from its state, while the JIT backend provides a Rust-based implementation with memory region mapping and state synchronization logic.

[Triticum0]

Once available for test
TODO:

• Benchmark Interpreter vs JIT compiler on game which use DSP heavily.
• Test egde cases from Meta: Audio Issues  #904
• Test game that have dps cycle count tide to frame-rate Meta: Real Time DSP Required Games #2124
• Test for desync behaviours when hotswapping renders/Audio renders. (Still occurs)

[Triticum0]

Audio Loop that happens in Night Caster series and other games still occurs on the JIT engine

[Triticum0]

Midi behaviour also not improved seem less heavy that interpreter but still causes broken audio and games to lock up #579

[Triticum0]

From my preliminary tested performance improvements range from about 60% to 100% based on utilization metrics. and maxing utilization doesn't seem to be a concern based on my hardware. Will do some testing on low end hardware but couldn't see any regressions from what I tested. Also audio crackling seem way less to mostly fixed but only anecdotal to take with pinch of salt.

[Triticum0]

Doesn't Improve #2372 or #2600

[Triticum0]

JIT engine seem to use less GP Cycles compared to Interperter on Sega Online

JIT
GP Cycles (- 37.1%)
EP Cycles (- 46%)

Interperter

[Triticum0]

From 20+ games I tested only game which doesn't run at full speed with JIT was Sega GT Online. Also using Savestates for sega GT Online while another disk is loaded caused an assertion.
../hw/xbox/mcpx/apu/dsp/gp_ep.c:60: void scatter_gather_rw(MCPXAPUState *, hwaddr, unsigned int, uint8_t *, uint32_t, size_t, _Bool): Assertion page_entry <= max_sge' failed.
Doesn't occur if sega GT Online is mounted already.

[Triticum0]

Also had performance issues in v-rally 3. not sure what cause it high utilisation even with Jit engine after a while performance stablized but need to be look at as some reason performance dropped to single digits.

[Triticum0]

I recorded so gameplay comparison but not sure if I post it TLDR:

Fixes performance slowdown due to dsp.

• Burnout 2
• Freaky Flyers
• Quantum Redshift Chou Kousoku Kuukan Battle Race
• Racing Evoluzione
• V-rally 3

Fixes Audio Utilization crackling

• Quantum Redshift Chou Kousoku Kuukan Battle Race
• Racing Evoluzione

Doesn't fix cracking issues on ea games which seems to be tide to frame-rate, which based on regression issues #2790 and #2096

Other than performance improvements didn't fix any outstanding audio assertion/bug

Lastly do you recent performance regression some game weren't included do regression make comparison not useful, as well so of the performance differences might been due to recent regression.