D31018: Handle boundry condition missed by r297682

[Artyom Skrobov via llvm-commits]

>> Do you have any suggestions as to how I could debug it?
> Are you configuring it the same way?  

Yes; but still no luck reproducing the hang.


> Strictly speaking, your patch has undefined behavior (negating INT_MIN); maybe try committing a version without the undefined behavior?

Sure, I'll try that; and will back it out again if it doesn't help.