llvm dev - Feb 2015 - [LLVMdev] value tracking

I would like to know what API i can use to tell that x cant be negative. I
looked through the value tracking analysis API, nothing seems immediate.

int divBy4(int x) {
  if (x < 0) abort();
  return x/4;

}

http://llvm.org/docs/doxygen/html/ValueTracking_8h.html

Thanks,
Trent
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Hi Xin Tong,

On Thu, Feb 5, 2015 at 7:46 AM, Xin Tong <trent.tong at gmail.com>
wrote:
> I would like to know what API i can use to tell that x cant be negative. I
> looked through the value tracking analysis API, nothing seems immediate.
>
> int divBy4(int x) {
>   if (x < 0) abort();
>   return x/4;
>
> }
>
> http://llvm.org/docs/doxygen/html/ValueTracking_8h.html
  How about llvm::ComputeSignBit? I think you can tell it's negative
by the sign bit, right?

Regards,
chenwj