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Why is PS3 emulation so fast: RPCS3 optimizations explained

8K views|1 months ago
💫 Short Summary

The video delves into optimizing floating point conversion for PlayStation 3 emulation, including handling unique formats inherited from PlayStation 2. It explores clamping input values for improved performance, utilizing SIMD instructions and AVX 512 for parallel operations. Emulating behavior through pshu B and shu B instructions in x86 assembly is discussed, along with AVX 512 path code for cryptographic acceleration. Benchmarking results show AVX 512's impact on game performance, with upcoming Zen 5 CPUs supporting these instructions. AMD and Intel have added efficient waiting instructions, with the speaker contributing to the rpcs3 project and planning more technical content.

✨ Highlights
📊 Transcript
Emulation of PlayStation 3 game code requires handling unique floating point format.
PlayStation 3 floating point format inherited from PlayStation 2 does not support infinity or NaN values.
Emulators need to implement additional instructions for compatibility with PS3 software.
Failure to properly emulate floating point format can lead to missing geometry in games like Ninja Gaiden and Sigma 2.
Clamping input values for PlayStation 2 and PlayStation 3 emulators.
V range PS instruction allows for positive and negative clamping with one instruction.
Behavior controlled by a constant value for accurate floating-point emulation.
V range PS instruction requires CPUs supporting AVX 512 instruction set.
Issues with Nan values in comparisons addressed with ordered and unordered comparisons for accuracy in PlayStation 3 comparison instructions.
Discussion on SIMD (Single Instruction Multiple Data) instructions and their efficiency in performing multiple operations in parallel.
SIMD instructions like VP blend and VP turn log can optimize bitwise operations and comparisons on data.
Mention of AVX 512 instruction set and its benefits.
Importance of optimized implementations for common instructions like ShuB (Shuffle bytes) and PshuB (Pack Shuffle bytes) in x86 programming.
Explanation of emulating behavior using pshu B and shu B instructions in x86 assembly.
The process involves shifting indices, indexing into special constants, XOR operations, and merging results.
Additional optimizations by LLVM include recognizing repeated calculations and simplifying code based on known bits analysis.
Optimizations for constant values, input vectors, and byte swapping are highlighted to improve code efficiency and execution speed for video games.
Overview of AVX 512 Path Code.
The instruction vg2 p8 apine QB operates on galwa fields with two elements for addition and multiplication modulo 2.
Background in mathematics is not required to understand the instruction, which functions as an exclusive or operation.
Intel provides examples showcasing the versatility of the instruction in applications such as bit shuffling and emulation.
The instruction's potential extends beyond cryptography, offering unique possibilities not found in x86 SIMD.
Optimization of the vperm2B function on Intel processors.
Inserting the second source vector into the upper 128 bits of the first source vector reduces the number of instructions required and improves performance significantly.
Benchmarking results show faster throughput for the latest AVX 512 path compared to previous versions.
AVX2 and AVX 512 instructions offer substantial speed improvements in game performance.
Selecting a CPU with AVX 512 support is emphasized for enhanced performance.
Overview of AVX1 and Zen 5 CPU features.
Zen 5 CPUs will support AVX 512 instructions, benefiting RPCS3.
Zen 5 offers doubled L1 and L2 bandwidth.
Memory access complexities on SPUs with limited local storage.
Game programming example involving sleep times on different operating systems.
AMD and Intel have added instructions for efficient waiting on a timer, resulting in performance and power draw improvements.
The speaker contributes to the rpcs3 project and focuses on technical subjects without covering basics.
Plans to create more videos, possibly unrelated to rpcs3, while in between jobs.
Encourages viewers to like, subscribe, and share the video, with intentions to continue creating content despite not aiming to be a full-time YouTuber.