[llvm] [X86] Faster truncf and roundf on x86 SSE2 (PR #226513)

[Michael Schmidt via llvm-commits]

RunDevelopment wrote:

Hi! Thank you both for working on this. I made the issue and would like to join the discussion here :) 

> Also for float, a better bound is `|x| >= 2^23`, and for double, `|x| >= 2^53`.

I talked about this in the issue. Any value between 2^23 and 2^31 (inclusive) works as a threshold for float32 (similar for float64). I suggested using a large threshold purely in hopes that it helps LLVM to remove the return-unchanged branch if it knows something about the range of the input. I.e. if it knows that the input is between 0 and 2^16, LLVM can remove the branch. So I would like to suggest using 2^31 and 2^63 again, as they may enable more optimizations down the line. 

Frankly, it's probably not going to make much of a huge difference, but having more optimization potential by picking a larger threshold seems like a no-brainer to me.

https://github.com/llvm/llvm-project/pull/226513