PPCCache: Update PLRU on any cache access #11559
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The previous code only updated the PLRU on cache misses, which made it so that the least recently inserted cache block was evicted, instead of the least recently used/hit one. This regressed in 9d39647 (part of dolphin-emu#11183, but it was fine in e97d380), although beforehand it was only implemented for the instruction cache, and the instruction cache hit extremely infrequently when the JIT or cached interpreter is in use, which generally keeps it from behaving correctly (the pure interpreter behaves correctly with it). I'm not aware of any games that are affected by this, though I did not do extensive testing.
AdmiralCurtiss
approved these changes
Feb 13, 2023
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For reference, the specific phrasing in https://fail0verflow.com/media/files/ppc_750cl.pdf is on page 141:
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The previous code only updated the PLRU on cache misses, which made it so that the least recently inserted cache block was evicted, instead of the least recently used/hit one.
This regressed in 9d39647 (part of #11183, but it was fine in e97d380), although beforehand it was only implemented for the instruction cache, and the instruction cache hit extremely infrequently when the JIT or cached interpreter is in use, which generally keeps it from behaving correctly (the pure interpreter behaves correctly with it).
I'm not aware of any games that are affected by this, though I did not do extensive testing.