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 9d39647f9e (part of #11183, but it was fine in e97d380437), 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.
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