Hoist proto_version load. #121
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Before this commit, we loaded a closure's `proto_version` on every iteration of the loop, which leads to a guard in every opcode in a trace. This commit hoists that load out to the only point where that value can change -- the `startfunc`/`return` label(s). These are where a new closure is dealt with (e.g. as a result of `OP_CALL`). Although we still have to call `yk_promote` for every opcode, the trace optimiser has a much easier job, because this tends to stay in a variable -- in general it can now remove 1 guard for all but the first opcode. Across several benchmarks I've looked at, this leads to a 2-6% increase.
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Before this commit, we loaded a closure's
proto_versionon every iteration of the loop, which leads to a guard in every opcode in a trace.This commit hoists that load out to the only point where that value can change -- the
startfunc/returnlabel(s). These are where a new closure is dealt with (e.g. as a result ofOP_CALL). Although we still have to callyk_promotefor every opcode, the trace optimiser has a much easier job, because this tends to stay in a variable -- in general it can now remove 1 guard for all but the first opcode. Across several benchmarks I've looked at, this leads to a 2-6% increase.