[swift-users] Why are Swift Loops slow?

[Andrew Trick]

> On Oct 12, 2016, at 9:05 AM, Joe Groff via swift-users <swift-users at swift.org> wrote:
> 
> It looks like LLVM does not recognize the overflow traps Swift emits on arithmetic operations as dead code, so that prevents it from completely eliminating the Swift loop.  That's a bug worth fixing in Swift, but unlikely to make a major difference in real, non-dead code. 

The traps aren’t dead if they are reachable. Eventually we will teach LLVM about less-strict trap semantics so they can be speculated and reordered. But for now we can do that sort of thing in SIL in the most important cases.

-Andy
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20161012/da15f454/attachment.html>