[jonathanstrange]

I once implemented a VM in Ada and just used a large switch. I extensively benchmarked it and it was blazingly fast at -O3.

However, it was only fast when I used packages very sparingly. In contrast to the usual advice given in the Ada community, splitting up the implementation into several packages slowed down the main loop tremendously. I suspect this wouldn't happen with whole-program optimization in C, but believe that the version of gcc I was using didn't support that for Ada. Also, my Green Threads were slower than a single thread, no matter which tricks I tried.

It's an abandoned project now, since the accompanying assembler was hacked together in Racket and at some point I simply lost track of what was going on where :O

[henrikeh]

FYI: I believe you have to use the flag -gnatn or -gnatN to inline packages with GNAT.

Optimizing your project: https://www.pegasoft.ca/resources/boblap/7.html

GNAT: Alphabetical list of all switches: https://gcc.gnu.org/onlinedocs/gcc-8.2.0/gnat_ugn/Alphabetic...

[TimJYoung]

Object Pascal (Delphi) also optimizes case statements, depending upon the nature of the statement:

https://stackoverflow.com/a/2548425

I tested this recently (Delphi XE6), and it definitely is as-described: you get straight jump instructions with enough case statement branches, and it is very fast.

Barry Kelly worked on the Delphi compiler, and I believe he comments here on Hacker News occasionally.

[vardump]

> you get straight jump instructions with enough case statement branches, and it is very fast

That's what pretty much any half-decent compiler does nowadays. It'd be much more surprising if it didn't.

[TimJYoung]

The interesting part to me was the variations in the emitted instructions, based upon the source. IOW, it would be easy to mistakenly think that you weren't going to get jumps if you only used a few case branches to test things out.