Make int_compare avoid overflow
Make int_compare avoid overflow

Summary:
Change int_compare to avoid overflow, without generating a call to a C
function or any branch instructions.

Reviewed By: cristianoc

Differential Revision: D3417671

fbshipit-source-id: e4c5d7b

ryoon/infer,blzq/infer,jsachs/infer,jvillard/infer,jsachs/infer,jsachs/infer,ropas/infer,jvillard/infer,blzq/infer,ropas/infer,facebook/infer,jvillard/infer,xennygrimmato/infer,kageiit/infer,facebook/infer,jsachs/infer,ropas/infer,blzq/infer,ryoon/infer,jsachs/infer,kageiit/infer,facebook/infer,facebook/infer,ryoon/infer,kageiit/infer,ropas/infer,jvillard/infer,jvillard/infer,facebook/infer,blzq/infer,xennygrimmato/infer,kageiit/infer,facebook/infer,jsachs/infer,jvillard/infer,ropas/infer,facebook/infer,xennygrimmato/infer,xennygrimmato/infer,xennygrimmato/infer,kageiit/infer,xennygrimmato/infer,ryoon/infer,blzq/infer,kageiit/infer,kageiit/infer,xennygrimmato/infer,ropas/infer,blzq/infer,ryoon/infer,ryoon/infer,jvillard/infer