[LLVMdev] Why can't comparisons with negative zero be simplified?

[Matt Arsenault]

On 07/06/2015 03:06 PM, Sean Silva wrote:
> +Matt who is the one that originally committed this (r225265).
>
> -- Sean Silva
I think it's fine, but I was being extremely conservative with what it 
allows. This really should work in a lot more cases. Before my patch, it 
only worked for smaller integer types instead of considering the values. 
When I was working on this, I had it checking if the constant being 
compared could be represented by the integer type (e.g. fcmp eq with a 
fractional value -> false and also allow the non-equality compares). I 
think it was just disturbingly hard to break and I was afraid of 
breaking some edge case when the only real world cases I really cared 
about was eq/ne 0.

-Matt