How does Static Recompilation differ from Emulation?

Summary

This video delves into the performance differences between RPCS3 and projects like Unleash Recompiled, focusing on why certain emulation strategies, such as static recompilation, yield better results. It compares the performance of games like Devil May Cry 4 and Yakuza 0, explaining the impact of PlayStation 3-specific optimizations and the challenges in emulating them. The video also explores how replacing low-level emulation with higher-level code can lead to faster performance, and discusses the complexities of patching game libraries to optimize gameplay. Finally, the video highlights the significant effort and optimizations that go into creating high-performance emulation for specific games.

Takeaways

• 😀 Unleash Recompiled is significantly faster than RPCS3 due to high-level emulation, bypassing lower-level game code and optimizing for a single game.
• 😀 RPCS3 uses static pre-compilation, but it doesn't recompile game-specific code with higher-level code like Unleash Recompiled does.
• 😀 The performance difference between RPCS3 and Unleash Recompiled is influenced by how the games were programmed, particularly how they use PlayStation 3 hardware features.
• 😀 Games like Devil May Cry 4, which don't utilize PlayStation 3's SPUs effectively, perform poorly in RPCS3 compared to games like Yakuza 0, which make better use of SPU optimizations.
• 😀 Unleash Recompiled focuses on a single game, allowing for game-specific optimizations, while RPCS3 aims for broad compatibility with thousands of games, limiting its ability to make similar optimizations.
• 😀 Post-process anti-aliasing (MLA) in games like Yakuza 0 causes performance issues in RPCS3, as emulating the PlayStation 3's SPU is slower than directly using the GPU for these effects.
• 😀 RPCS3's difficulty in handling SPU code and complex video decoding libraries contributes to slower performance in games that rely on these features, compared to simpler titles.
• 😀 High-level emulation of OS libraries in RPCS3 improves performance, but there’s potential for optimization by targeting game-specific libraries like the MLA library.
• 😀 Unleash Recompiled uses C++ code for certain operations (like division) to improve performance, whereas RPCS3 uses LLVM IR, which may be less efficient for specific tasks.
• 😀 The difference in performance between emulators and static recompilation projects highlights the trade-off between universal compatibility (RPCS3) and optimized performance for a single game (Unleash Recompiled).

Q & A

What is the main reason why 'Unleash Recompiled' is faster than RPCS3?

'Unleash Recompiled' is faster than RPCS3 because it uses static pre-compilation and optimizations specific to *Sonic Unleashed*, whereas RPCS3 uses general-purpose emulation that doesn’t fully optimize all aspects of every game.

How does 'Unleash Recompiled' differ from RPCS3 in terms of static pre-compilation?

While both use static pre-compilation, RPCS3 handles system-level emulation at a higher level, while 'Unleash Recompiled' performs deeper optimizations on the game-specific code, effectively turning game logic into higher-level code written in C++.

Why does 'Unleash Recompiled' perform better than RPCS3 when emulating games with SPU-heavy tasks?

'Unleash Recompiled' avoids the need for slow SPU emulation by recompiling and optimizing game code for modern systems, while RPCS3 still faces performance bottlenecks when dealing with SPU-heavy games due to the complexity of accurate emulation.

How does 'Unleash Recompiled' optimize for post-processing effects like MLA (Morphological Anti-Aliasing)?

'Unleash Recompiled' skips MLA entirely because, in the context of emulation, running MLA is slower due to the need for transferring images between GPU and memory multiple times. This is avoided in 'Unleash Recompiled,' leading to better performance.

What makes RPCS3 slower when emulating MLA in games like 'Yakuza 0'?

RPCS3 is slower with MLA because it must simulate the entire process, including copying images between GPU and memory, processing them, and then sending them back to the GPU. This results in a significant performance hit, even though the PS3’s GPU could handle it more efficiently.

What is the benefit of using high-level emulation of video decoding libraries in RPCS3?

High-level emulation of video decoding libraries in RPCS3 leads to better performance because it avoids emulating the complex, low-level SPU code responsible for video decoding. By hooking into existing high-level system libraries, RPCS3 can offload these tasks more efficiently.

Why does 'Unleash Recompiled' target the Xbox 360 version of *Sonic Unleashed* instead of the PS3 version?

'Unleash Recompiled' targets the Xbox 360 version because the Xbox 360’s architecture is more closely aligned with modern PC systems, making it easier to recompile the game and optimize performance compared to the PS3's unique hardware.

What specific advantages does 'Unleash Recompiled' have over RPCS3 when emulating PowerPC instructions?

'Unleash Recompiled' directly emits C++ code to emulate PowerPC instructions like division, using optimized intrinsics. RPCS3, on the other hand, emits LLVM IR and deals with extra challenges, such as handling undefined behaviors like division by zero, which can slow down performance.

How does the 'Unleash Recompiled' approach to optimizing game logic differ from RPCS3?

'Unleash Recompiled' optimizes game logic by reinterpreting specific instructions and operations with a tailored approach that suits only *Sonic Unleashed*, whereas RPCS3 uses more generic, reusable emulation techniques across multiple games.

What role does high-level recompilation play in projects like 'Zelda 64 Recompiled' compared to traditional emulation?

In 'Zelda 64 Recompiled,' high-level recompilation involves directly replacing game-specific code with optimized instructions, leading to better performance. While traditional emulation like in RPCS3 focuses on accurately replicating hardware behavior, high-level recompilation is more targeted and efficient for individual games.