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by acuozzo 1553 days ago
> the switch statement is really just an “if” statement in disguise

If the switch is over a fixed set of strings, then can't the backend generate a perfect hash function ala gperf and then proceed to use the computed hash value to implement a jump table?

Also, FWIW, the only compiler backends I've ever seen blindly emit a jump table all died in the '80s. Jump tables aren't always the fastest choice: https://www.cipht.net/2017/10/03/are-jump-tables-always-fast...
2 comments
morelisp 1553 days ago
Go currently uses a binary search for integer switches (and I believe serial comparisons otherwise). Jump tables are in development and likely to appear around 1.19 or 1.20. As you say, there's a lot of edge cases to consider when figuring out whether a table or comparisons are the better choice.

https://go-review.googlesource.com/c/go/+/357330/

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MrDOS 1552 days ago
> can't the backend (...) implement a jump table?

Note that my example “switches” over two independent variables. Even if the Go compiler did generate a table, for this example it would really be generating two tables: and then we're back to the “how is this better than an `if`?” question.

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