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49 points Bogdanp | 1 comments | | HN request time: 0.201s | source
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nynx ◴[] No.44469206[source]
I must be missing something here. How would this help predict interpreter dispatch? Those won’t be a function of previous branch history or pc, which may very well be independent of the next opcode. They’d be a function of state in memory or registers.
replies(4): >>44469293 #>>44469360 #>>44469495 #>>44469524 #
1. dzaima ◴[] No.44469524[source]
If your interpreter is interpreting a program with unpredictable branches, of course no predictor will magically make your interpreter get branches better predicted than an equivalent compiled program will.

The question here is about all other branching the interpreter will do. i.e. even if you have a unpredictable `if (a+b < 0)`, there's still the dispatching to the "load-variable" and "add" and "load-constant" and "less-than" and "do-branch" opcodes, that still will benefit from being predicted, and they could very well if you have it repeated in a loop (despite still having a single unpredictable branch), or potentially even if you just have a common pattern in the language (e.g. comparison opcodes being followed by a branch opcode).