It shouldn't be.

If the fastest way to implement a particular `switch` in assembly is with the equivalent of a set of `if`s, a reasonably smart compiler "should" be able to output the assembly to do that. And I thought that gcc and clang at least have actually been smart enough to do that for a while now.

But if the number of `if`s is high and the distribution sufficiently dense, where a jump table is better than a bunch of `if`s, then a `switch` should output that.

OTOH, a sufficiently smart compiler could theoretically turn a bunch of `if`s into a `switch`-like jump table - but it's much harder to reason that case through correctly than it is the other way, so I'm not sure any current compilers are sufficiently smart to do that.

On x64, GCC is supposed to use a a jump table with more than 4 cases when the cases are dense enough (gaps of 9 or less) to minimize wasted memory, otherwise it generates sequential comparisons. Testing on Godbolt, it looks like GCC 13.1 uses 10 cases as the jump table threshold for ARM64.

It shouldn't if the control flow is actually identical.

E.g. note how both the switch- and if-based functions generate the same code using a lookup table here:

https://godbolt.org/z/qoT3M7r5G