From 8d33659b93f8136505b89a34dcbc350c1ac4654d Mon Sep 17 00:00:00 2001
From: Nick Lewycky
This intrinsic indicates that before this point in the code, the value of the memory pointed to by ptr is dead. This means that it is known to - never be used and has an undefined value. A load from the pointer that is - preceded by this intrinsic can be replaced with + never be used and has an undefined value. A load from the pointer that + precedes this intrinsic can be replaced with 'undef'.
-- 2.11.0